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Scott Wordley
01-10-2003, 07:25 AM
I know there are still a lot of sceptics out there so I thought it would be a good time to devote a thread entirely to wings. Here at Monash we are completely convinced of the benefit of wings, even with the low speeds encountered in FSAE, but we'd love to hear everyone else's thoughts on the topic.

Regards,

Scott "Maverick" Wordley &
Roan "Goose" Lyddy-Meaney
MOnash FSAE Wingmen

Dominic Venieri
01-10-2003, 08:30 AM
Roan and I have spoken before about wings, so you know that we are also supporters of winged FSAE cars. Posts from late summer concerning the Solo II nationals from Dr. Woods, Ken Hassler, and the alumni from Cal Poly Pomona show their ideas about wings as well.

The trick is to get a winged car under 500 lbs. Our car and UTA were the first to have suspension mounted wings, theirs was over 500 lbs by a bit (530ish), ours was just under (497). The year before with chassis mounted wings, both our cars were under 500.

We don't have any wind tunnel data on our wings unfortunately, just CFD, but have driven with and without, and seen considerable differences in available grip.

www.formularpi.com (http://www.formularpi.com)

Scott Wordley
01-10-2003, 05:11 PM
Yeah, our car was a bit overweight at 270kg (594lb), so that's something we need to focus on for the new car.

But we found that the wings more than made up for all that extra weight.

Regards,

Scott "Maverick" Wordley &
Roan "Goose" Lyddy-Meaney
MOnash FSAE Wingmen

Charlie
01-10-2003, 05:58 PM
Personally, I think a winged car done right will be faster than a wingless. But it's very difficult and very time consuming to do wings the right way. I compare it to NA vs. turbo engines in the competition. Yes, you can make more low-end power with a turbo and that makes it better. However the complexity and time required to make everything click just right make it difficult to justify the project to teams trying to budget time effectively. I see wings as the same.

Auburn was one of the few teams running wings in the late 90's. In fact I think we were the only winged team in 1999. The 1999 car was a 2nd year car, except the 1998 version was wingless. The 1999 car was faster in the endurance event, probably helped by the wing (which was active, and electropneumatic). However the extra weight hurt all the other driving events, as well as design and cost.

I think a winged car can be faster in the endurance event easily. But it would have to be an excellent setup to overcome the problems in skidpad and acceleration (and in the US, autocross. Seems like the other autox events are a lot faster).

Add in the extra time involved, and that is why we don't have a winged car. But like turbos, I'd love to try it someday, and I think there are benefits to be had.

-Charlie Ping
Auburn University FSAE 1999-present
http://www.auburn.edu/~pingiii/2002FSAE/carblank.jpg

Scott Wordley
01-11-2003, 04:24 AM
Actually the Australian autocross track which we just competed at was one of the slowest tracks ever (according to Carroll Smith), yet we still managed to gain an advantage.

The only way to make wings work in this competition is to aim for the maximum possible downforce. The maximum possible area of the wings is limited by the rules, so the only possible way to increase downforce further is to increase the CL. The way to do this is to run multi element wings. I think that three elements is the minimum anyone should consider using. I still can't understand why teams like Cal Poly Pomona are using single element wings. It's not much more work to build multi-element wings and the gains from it are huge.

The quest for downforce doesn't stop after front and rear multi-element wings have been designed. The next logical step is to buld sidepod diffusers. The downforce from these is somewhat limited due to the small floorpan area for the negative pressure to act over, but every little bit counts. As well as the wings and the side diffusers we also ran a very large rear diffuser (first team ever worldwide to our knowledge).

Charlie, I had a look at your website to check out your winged cars and I am still struggling to understand the logic behind the design. Our rear wing alone was at least as big as your single wing and ours was a four element wing which gave us around half of our total downforce. And judging from the angle of the wing in the pictures it looks well and trully past the stall angle.

The only way to make wings work in this competition is to make them BIG.

Regards,

Scott "Maverick" Wordley &
Roan "Goose" Lyddy-Meaney
MOnash FSAE Wingmen

Charlie
01-11-2003, 06:20 AM
What was the fastest Austrailian Autocross time?

To answer your questions, I had nothing to do with the wing design as it was done in 1997. The same wing was used in 1999, with the pitch active (throttle position activated). I joined in 1999 after competition, and only 1 1999 member returned in 2000. So little knowledge was passed on.

Like I said, I believe that wings can be an overall benefit, but the time spent on them will likely be better spent on something else, depending on your team's situation of course. If you have the capability and workforce to work on wings it's a worthwhile project to look into.

Until then we will work on the basics, like weight, power, and refinement in all areas.

-Charlie Ping
Auburn University FSAE 1999-present
http://www.auburn.edu/~pingiii/2002FSAE/carblank.jpg

Charlie
01-11-2003, 09:49 AM
I checked the results, 39 second AutoX times. Detroit's best time was a 75. What was the length of the course in Australia?

-Charlie Ping
Auburn University FSAE 1999-present

Scott Wordley
01-12-2003, 03:38 PM
From memory the autocross track was about 450 metres. The fastest time was actually 34.89

Regards,

Scott "Maverick" Wordley &
Roan "Goose" Lyddy-Meaney
MOnash FSAE Wingmen

wingman
01-14-2003, 12:38 PM
Hey everyone,

Props to the boys down under for starting this thread.......
For what its worth, you guys answered your own questions about aero configurations.
In fact, you touched on the core question of the FSAE competition.
Mods such as forced induction, aero, composite chassis, engine (I could a had a V8) etc... are all worth it IF you can justify the performance improvement against time, resources, skills, and interest. Interest being the key here!! If you believe that something will work strongly enough, you can make time to gain skills and resources.

So lets compare what I currently see as the two ends of the aero spectrum: Cal Poly Pomona 2000 vs. UTA 2002. (BTW, I like MOnash's 02 car but don't know enough about it) Both teams shared intense interest in making aero work, and had VERY well established infrastructure and resource bases.

Specs:
Cal Poly
Ø Low Speed, High Lift, Single Element Wings (30 sq. ft. worth)
Ø Development Requirements: Undergrad (Junior) Level Research Project For Airfoil Selection, Wing Integration, and Construction
Ø Chassis Mounted design (total weight 50 lbs...ouch)
Ø Construction: fiberglass skin, foam core, vacuum bagged wings wood end plates, aluminum tube mounts. (all built in the lab on campus)
Ø Performance 250 to 350 pounds down force @ 60 mph (based on test data) increase of .25-.50 lateral Gs on endurance course in Detroit and sustained 2+ lateral Gs on SCCA courses
Ø Pros: simple design, simple construction, rapid prototype, simple to tune, better low speed performance
Ø Cons: dynamic sprung weight, lower efficiency, high CG, not as esthetically pleasing (i.e. design points)

UTA (Ken please chime in if I'm too far off on this)
Ø Multi Element front and rear wings with under body tunnels
Ø Development Requirements: Graduate Level development utilizing CFD for wing element placement and tunnel integration.
Ø Suspension Mounted design (total weight about 30 pounds...nice job)
Ø Construction: Carbon Fiber, Hollow Molded wings and under tray. Construction care of professional composite fabricator (gotta find and reel in those industry sponsors!!)
Ø Performance (according to UTA drivers) .3 g increase in cornering in Detroit .50 or more on faster courses (i.e. SCCA events)
Ø Pros: Downforce directly to tires, low CG, potentially more efficient, lighter, MUCH more aesthetically pleasing (i.e. design points)
Ø Cons: Highly Complex to develop, construct, and tune, questionable low speed performance.


So which car is a better design...IMO: UTAs 02 car was a better overall design than Cal Poly's 2000 car
The UTA car was lighter (70 pounds or more), smaller, better integrated, and better prepared when the two competed at SCCA Nationals in 2002.

On a side note, UTA did poorly in Detroit for 02 (the car broke) but beat the Cal Poly Car (3rd place in Detroit 2000) at Nationals in 02 after further development and tuning.

OK so there is a base line for all you up and comers out there, and in my opinion, a team should not even attempt aero unless they have a proven existing car design to build from, and DRIVERS, DRIVERS, DRIVERS!!!!!!!!! Without those things you will not be done with your car in time to practice and will not have the skills to drive it, let alone tune it, so you might as well stay home thus avoiding being laughed at in Detroit while your pushing your broken race car off the course after leading the endurance race..... (or so I've heard nudge, nudge, wink, wink, sob, sob)

My two cents on Aero implementation (and the car in general):
1. Keep It Simple (small steps grasshopper...) the difference in performance between the above examples was more about total weight, size, and engine performance than aero (UTAs Aero was better IMO but not enough better to discount Cal Poly's approach.) Unless you have the time and resources to design and VALIDATE a complex aero package, forget it!! A simple wing addition to the car can be just as effectively as tunnels, multi elements, suspension mounting bla bla bla.....
2. Make sure you understand the impact of performance upgrades to the car, whatever they may be. Unless you can justify your upgrade will allow your drivers to go faster (not make the car theoretically faster) don't do it. Therefore it's all about research and testing.
3. Don't reinvent the wheel, but worse yet, don't buy into what someone else has done as the absolute. Ultimately it comes down to the standard engineering answer to any technical question (usually from management or worse yet....marketing)
So in this case....Do Aerodynamics work on FSAE cars??????

"IT DEPENDS"

In Closing, I would like to ask UTA to post the G circle data from Nationals in 2000 and 2002 (i.e. wings vs. no wings on similar (BUT NOT THE SAME!!) car) Given the speeds at Nationals, I don't think this info is proprietary. BTW, the G circles for Cal Poly, UTA and one of the A-mod cars from 2000 Nationals are on the web somewhere....

Keep it up everyone, you help us old guys stay young

Cheers,
Wingman

Charlie
01-14-2003, 04:05 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Dominic Venieri:
Our car and UTA were the first to have suspension mounted wings, theirs was over 500 lbs by a bit (530ish), ours was just under (497). <HR></BLOCKQUOTE>

I just re-read this post, and I've got to add that Auburn University had a suspension mounted wing in 1997 and 1999. http://fsae.com/groupee_common/emoticons/icon_razz.gif

-Charlie Ping
Auburn University FSAE 1999-present

Scott Wordley
01-15-2003, 05:31 PM
Hi Wingman. Its good to see a few more people getting in on this discussion.

You mentioned that you used wing profiles designed for low speeds. I've had a lot of trouble finding any information on suitable profiles, so if you'd like to discuss this with me in more detail you can email me at roanl@hotmail.com.

We're gonna get our new website up soon (It was supposed to be done a year ago but got put on hold because of the wings) so you'll be able to check out a ton of photos of our car as well as video footage from the wind tunnel (smoke visualisation) and video of the car on track.

We constructed our wings using CNC wire cut foam profiles with a layer of wet lay up carbon fibre and vac bagged the whole thing. This seemed like an easy way to do it until we decided to coat the wings with a layer of resin to bring up the surface finish and then the work really began (I'll be happy if I never have to sand again in my life). For this years car we'll be making all our wings from moulds (and probably making a spare front wing this time). For the endplates we used nomex honeycomb with carbon skins. Diffusers were also carbon/nomex. There was four of us who did most of this work and none of us had any previous experience with composites. We learnt everything as we went along and did all the work in at Uni.

I agree that multi element wings are more complex to construct, but I don't agree that they are any more complex to design or tune. The two of us (both Undergrads) did all the design work with a couple of good books to guide us and no previous experience. We actually wrote a paper on the work which we did and Scott presented it at a Young Automotive and Transport Engineers conference. He won first prize which was a travel grant so it looks likes we'll be coming over to Detroit in May (as spectators only, can't afford to bring the car). We did some CFD work (we found a PhD student who was able to do some in his spare time) but we didn't really get any useful results from it (we did get a lot of pretty pictures). Personally I'd love to get into some serious CFD but I don't have access to the software or the time to learnt it. At this stage I don't think CFD is improtant at all because there are so few teams doing aero (although this may change in the future).

In relation to the comment on questionable low speed performance, we found from our wind tunnel testing that there was no difference between high and low speed performance.

We started out desinging wings without a proven existing design to build from or any experienced drivers. Our 2001 car was a poor design which broke repeatedly at the competition (although it did finish second in the Australasian Design event behind Wollongong). The 2002 car was a completely fresh sheet design. We designed it from the start to suit the aero package and we were lucky enough to have the genius of Bob Wright to design the chassis, suspension and most other parts of the car.

I agree that single element is still a viable option (less time consuming to construct, but no simpler to design or tune), but it is a less efficient method and it limits the maximum possible downforce achievable. To put it into perspective our wings, mounts, sidepod tunnels and rear diffuser weighed around 35 pounds and gave us nearly 560 pounds downforce @ 60 mph.

To make aero really work at this competition I believe we should be aiming for the maximum possible downforce (if some is good then more is better, right?) and with limited wing area the only way to achieve this is with multi element wings.

Does anyone know where I can find any more info/websites on A-mods (all I've managed to find is racerpix.com). Those cars are awesome, kinda like an SAE car on steroids. We'd love to be able to bring our car over to compete against those guys alongside Cal Poly and UTA.

Regards,

Scott "Maverick" Wordley &
Roan "Goose" Lyddy-Meaney
MOnash FSAE Wingmen

MercerFSAE C. Burch
01-15-2003, 06:22 PM
I'm quite new to the competition, and I was wondering if anybody has done serious research into the idea of building an entirely ground-effect aero car, like the Lotus-Ford 79 Formula 1 car. With the combination of such ground effects and newer F1 technology such as rear diffusers and multi-elemnt wings, I would think that sufficient downforce could be produced at the low speeds FSAE is run at. Of course too much downforce would call for extra beefing up of the suspension due to aerodynamicly-imposed loads, which might be a negative aspect of it.

In light of the fact that ground effect cars were banned decades ago, with a mandatory flat bottom put in place, today's F1 cars employ other trick ground effects with bargeboards and other such devices that generate high-speed vortices which swirl under the bottom of the car. They accomplish essentially the same task as the sidepod tunnels, but by much more complicated means. It would be virtually impossible for anybody without a PhD in aerodynamics, an expensive wind tunnel, and sophisticated computer simulators to make it work right. So that is really not an option for teams in FSAE.

In any case, I don't see my team employing much in the name of aerodynamics for our first year car. But by 2005... who knows?

Christohper D. Burch
-an engineer with a dream

MercerFSAE C. Burch
01-15-2003, 06:25 PM
Here's a link to a Lotus 79 site:

http://www.ddavid.com/formula1/lotus79.htm

awhittle
01-15-2003, 07:34 PM
Something like this?

http://www.ncs-stl.com/Images/GEChassis.jpg

Andy

J. Cheng
01-15-2003, 07:34 PM
Wings work, just need to make them big enough. My gut feel tells me that UTA's 2002 wings can probably go twice as big and I won't be at all surprised to see a much bigger wing on their next car.

Joe

J. Cheng
01-15-2003, 07:42 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Scott & Roan:
...our wings, mounts, sidepod tunnels and rear diffuser weighed around 35 pounds and gave us nearly 560 pounds downforce @ 60 mph....
<HR></BLOCKQUOTE>
Theoretical or measured? Any photo of the car? Thanks.

Joe

awhittle
01-15-2003, 07:53 PM
Nationals 2002 Photos

http://www.showcase-photo.com/Photos/SCCA/Topeka-2002/09-12-02/Heat2%20South%20Pg1/.html

Scott Wordley
01-15-2003, 09:27 PM
Joe, that downforce figure was a combination of theoretical and measured results. Our wind tunnel doesn't have a moving floor so we didn't see any point in testing with the diffusers. The results from the rear wing were slightly less than we calculated and the front wing was about 60% of what we'd calculated, but with no ground effect it was pretty much what we were expecting.

If you want to give me your email address I can send you some photos.

Regards,

Scott "Maverick" Wordley &
Roan "Goose" Lyddy-Meaney
MOnash FSAE Wingmen

Scott Wordley
01-15-2003, 09:30 PM
Thanks for that link Andy. Some of those cars look like they could double as snow ploughs.

Regards,

Scott "Maverick" Wordley &
Roan "Goose" Lyddy-Meaney
MOnash FSAE Wingmen

Scott Wordley
01-15-2003, 10:35 PM
Hey All,

At the risk I've confusing everyone, its Scott here, Roan has been making most of the posts recently and I'd thought I'd make a few comments

Firstly Joe...

There is a picture of the Monash '02 car on the FSAE.com Photos page, click on the link at the top of your screen.

If you or anyone else would like some more detailled pics of the car you can either email me at scott.wordley@eng.monash.edu.au or download a powerpoint show with a bunch of them from our website at:

http://www-personal.monash.edu.au/~fsae/monashfsae2002.ppt

Unfortunately the site is still a bit sparse at the moment, I'll post a note on this forum when its fully finished.

Next... Chris Birch

I think if you look at the UTA '02 car in detail it is very similar if not better than the Lotus 79. Its got the wings, the underbody sidepod diffusers and whats more its all mounted unsprung like the Lotus 88 twin chassis car. Pity that one never raced but its good to know that this is about the only formula in the world where we can relive (or live for the first time?) the glories of unsprung downforce.

Ken from UTA, Ian from CalPoly and Dominic from RPI...

Its pratically Feburary, so how about some hints or teasers about the aero packages you guys will be bringing to Detroit. Its not like anyone can copy etc at this late stage.

And lastly...

Roan made a few points and quoted a few numbers from our wind tunnel testing last year. I think we'll post some of the results on the new website for you guys to check out, it might make for some interesting debate. I'll also be posting a whole lot of smoke vis tests we did in the tunnel on the website soon too. What other FSAE teams (if any) have tested aero packages in wind tunnels?

Ok one more thing...

If anyone (Ken or Dominic?) knows of any wing profiles designed specifically to work in ground effect I'd be interested to hear about them. You don't need to give away any secrets just point me in the right direction if possible.

Cheers.

Scott

Regards,

Scott "Maverick" Wordley &
Roan "Goose" Lyddy-Meaney
MOnash FSAE Wingmen

Scott Wordley
01-15-2003, 11:21 PM
Hey Roan. Check the new signature. Its only 18K.

Scott.

Regards,

http://www-personal.monash.edu.au/~fsae/forum2.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

Bam Bam
01-16-2003, 07:59 PM
I don't care what CFD or Wind Tunnel testing you did that's one UGLY f'n car. Kinda looks like it should be loopin' round a dirt oval or somethin.

awhittle
01-16-2003, 08:19 PM
And I thought it was a work of art. An Aztec is ugly.

AW

[This message was edited by awhittle on January 17, 2003 at 10:53 AM.]

Scott Wordley
01-16-2003, 08:45 PM
Sorry Bam Bam but I disagree. I think it looks damn sexy. Either way I don't think you need to worry. It looks a lot better from behind... lol.
Post a photo of your car and let us all see how a FSAE car should look. What team are you from anyway?

I found your comment that "it looks like it should be looping around a dirt oval or somehting" particularly amusing. Yes, like a sprint car it is designed for a course which is 80% low speed corners, and where your speed is only limitted by the amount of traction you can generate and not by the amount of horsepower your "custom made race engine/gearbox specifically designed for restricted performance" can produce.

What the hell are you designing for, a drag race? http://fsae.com/groupee_common/emoticons/icon_confused.gif

I've talked to Mike about Cornell's flirtations with downforce and it sounds as though aesthetics play a big part in people deciding whether or not to go with wings.

Would love to know what other people think though. Are winged FSAE car (and ours in particular) ugly or pretty? And does it make a difference to you or your team?

Regards,

http://www-personal.monash.edu.au/~fsae/forum2.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

Dominic Venieri
01-16-2003, 08:50 PM
I think wings are damn sexy.

www.formularpi.com (http://www.formularpi.com)

Richard Lewis
01-16-2003, 10:06 PM
Damn sexy... though I've seen many a wingless FSAE car that I thought was sexy too.

-------------------------
UVIC Formula SAE Team
http://members.shaw.ca/drax77/UVICFSAEcar.jpg
http://fsae.uvic.ca

Scott Wordley
01-17-2003, 12:20 AM
Bam Bam (this is Roan, the last post was from Scott), you're an idiot, but I'm sure anyone who has read any of your previous posts has figured that out for themselves already. But you're not just an idiot, you're obviously too ashamed to admit which Uni you come from.

We try and get as much power as possible from our engine, just like everyone else, but having all that power is useless if you can't put it to the ground. Rather than wasting all our time dreaming about some fantasy engine we chose to develop a system to help put that power to the ground.

The wings we developed we're designed for a specific purpose rather than to look good, although I'm sure most people who attended the Australian Formula SAE competition will agree that the Monash car was the best looking car there. I can guarantee you that our wings were much more than 'fancy lookin ballast weight' (by the way weight is redundant in that sentence).

I don't expect every other team to develop wings for their cars because I know how much work and resources are required, but if you think that you know more than Carroll Smith you're never gonna get anywhere in this competition (and you're more of an idiot than I first thought).

It takes a hell of a lot more than a powerful engine to do well in this competition and maybe if you took your hand off your dick and actually bothered learning something about vehicle dynamics you might be able to build a vaguely competitive car.

Regards,

http://www-personal.monash.edu.au/~fsae/sig.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

J. Cheng
01-17-2003, 12:43 AM
I love it.

I predict, within 5 years, most of the top cars will be running wings just as big or bigger.

Joe

Eddie Martin
01-17-2003, 05:30 AM
I think Aerodynamics are great, and they do look good.

Bam Bam putting huge resources into an engine package will never win, vehicle dynamics is where it is at. I'd rather try active suspension than a custom made engine. Also I don't really trust people who don't say where they are from.

We did start down the path of an aero kit but once we saw how much time it would take it was scrapped, but that is not to say stumpy and/or his descendants will not be sprouting wings in the next couple of years.

Scott or Roan
"although I'm sure most people who attended the Australian Formula SAE competition will agree that the Monash car was the best looking car there".

I have to disagree. I think Wollongong was definitely the best looking Formula SAE car ever. I don't think I am bias. http://fsae.com/groupee_common/emoticons/icon_smile.gif

Regards
Eddie Martin
UOW Racing
www.uow.edu.au/eng/racing (http://www.uow.edu.au/eng/racing)

wingman
01-17-2003, 09:57 AM
Hey guys, is this an educated discussion or a Jerry Springer Pissing Contest?!@#$

Who gives a flyin...F what it looks like...
DOES IT WORK??? And yes I agree form follows function, but the Cal Poly Cars 98 and 2000 were flat laughed at in Detroit, until all people were seeing was the tail end of them....

Aero/Winged FSAE cars have looks only their creators can love (All others are ignorant or scared...J/K)

OK Back to Business, I dug out some of my old data and its nothing to shout about, but it counts so here goes...max theoretical 2D performance of the 2000 Cal Poly Car @ 60 MPH was about 570 lb. downforce (total) We were able to get the whole car in a wind tunnel (no rolling plane) using our corner weight scales to measure downforce and our 3D performance was about 50% of 2D theoretical. This was expected due to the low Aspect Ratio and pesky car interference, but 40 to 50% increase in car vertical load with a 10% increase in side load due to weight of the wings ain't too shabby (do the math) and our drivers grew to feel cheated if the wings weren't on the car. But remember to estimate your average corner entry speed around the endurance course HINT HINT your not at 60MPH very long, so what does your aero package put out at 20 and 40 MPH??? Still want to do wings??

So based on my estimations, I think the specs from MOnash are a little exaggerated, and furthermore, you can BS other students, and you can BS yourself, but you CAN'T BS MR. SMITH!!
I think old Carol still feels that AERO doesn't belong in FSAE, but he wants to be "PROVED" wrong so if you show up with wings and no hard data to justify them, forget about the top of the design comp pyramid!! (historical note: Cal Poly placed 56th in Design in 98, but was top 10 in ALL the dynamic events and lead the Endurance event until the engine blew up... (BTW...AERO=DRYSUMP) http://fsae.com/groupee_common/emoticons/icon_eek.gif

My comments about design resources are based on 5 year old knowledge, so you may in fact be able to develop and tune multi element wings as an undergrad, but it may not be worth the time it takes away from testing and driver training.

Cheers,

Wingman

NJM.
01-17-2003, 12:25 PM
I think all of this discussion on wings is great. Here at NC State we have been doing some research on wings although we are not going to be using them on the 2003 car.

I wrote and presented a paper at the 2002 SAE motorsports conference, paper number 2002-01-3294. In this research I wrote a simple lap simulation code in matlab that could take in actual wing and vehicle data and calculate lap times. I found that even on our slow track speeds there can be a substantial performance benefit. (over a second on a 1 minute course) Scott and Roan's comments about wing size I have found are correct. For these speeds we don't even need to think about drag so downforce is everything. If you are looking at drag while designing, induced drag (i.e. that from trailing vortices) is the only component worth considering. Profile drag is negligible.

There have also been posts about suitable airfoils for these cars. I have also been designing some custom airfoils for both the front wing (in ground effect) and the rear. I would love to hear some Cl numbers but I understand if that is too much info. I would be happy to share some of my airfoils, when I get further along, to some teams who are serious about using wings.
Wings may not be for everyone, there are a hundred considerations, ie cost, resources, time etc, that may hinder a lot of teams. Also if your package is good enough without wings (Cornell) then why try until you are outclassed. I would love to see SAE open up the course a little and maybe incorporate some barriers to protect course workers or something. Then wings would definately be a necessity.

Anyway, best of luck to all the teams. If we all get lucky some of the Australian cars will get lost in shipping. Just kidding.

Laters,

Noah Mckay

leclercjs
01-17-2003, 03:01 PM
To much is like not enough.

Jean Sébastien Leclerc
Formule SAE Poly

J. Cheng
01-17-2003, 11:46 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by NJM.:
Scott and Roan's comments about wing size I have found are correct. For these speeds we don't even need to think about drag so downforce is everything.
<HR></BLOCKQUOTE>

A good indication is the percentage WOT (wide open throttle) time. My experience indicates that if I start running close to 60% WOT time, I need to take off the top flap from my wings to get a better lap time.

Do any of you have data on what kind of WOT time typically achieved at an event.

Joe

Scott Wordley
01-18-2003, 05:49 AM
Hi Joe,

I'd love to find out more about that Phantom Special of yours, do you have a website?

I'd also like to talk to you more about wing profiles, you can email me at roanl@hotmail.com

Regards,

http://www-personal.monash.edu.au/~fsae/sig.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

J. Cheng
01-18-2003, 09:52 AM
Scott and Roan,

Sorry, I don't have a website. However, someone took a picture of my car and it's posted on a Honda forum, http://www.honda-tech.com/zerothread?id=385911 . Back in 1997 in the wind tunnel, the flaps for the front wing got increased from 4" to 6" and downforce went up 30% (CL=3.5). For high speed events, I take off the top flap, see http://www.vcmc.ca/multimedia/knox2002/BigWinguphill.JPG . Also, the wind tunnel test showed that wing mounts (just under the bottom of the wing) should not have any kind of bolted connections. The ones you guys have really decrease the efficiency of your wing (in my opinion, the fore/aft brace is also too close to the wing, the firewall behind the driver is too high and the front wing can be moved further forward away from the front tires, these changes should all increase the oveall wing efficiency). Any bolted connections should be at least 6-7" below the bottom skin. Also, in a series of wind tunnel tests done in 1999. It shows that my side panels can be improved. I will be incorporating the new design in my new car. In fact, I have been vacumn begging the last two weeks. The rear main element should be done within the next two weeks.

Joe

Michael Jones
01-18-2003, 03:50 PM
Our wing prototype was very much of the sprint car mold, which did make the car look...uh, different. Personally I didn't find the aesthetics all that bad, others did; certainly enough to ramp up initial hostility, especially among those who'd have to change their designs to accommodate the wing.

That was overcome with a proper testing and system integration plan if initial tests proved promising. Inconclusive testing data from limited trials and a range of systems integration issues proved to kill the prototype, and so far it's been dormant since. Worthwhile R&D project though, and I'm sure interest will spike again if someone comes up with a design that convinces theoretically and on the track...

---
Cornell Racing
http://fsae.mae.cornell.edu

awhittle
01-18-2003, 04:43 PM
check out this site

http://www.aae.uiuc.edu/m-selig/ads/coord_database.html#A

Bam Bam
01-18-2003, 07:27 PM
F'n ugly lookin picture,
Not a bad lookin car.


BTW
I figure your team would appreciate it if you guys spent less time playin mr know it all on message boards and a bit more time buildin and testing your car...

Anyways I got dyno work to do later boyz.

Keep it hostile.

Scott Wordley
01-19-2003, 04:40 AM
Joe,

Yeah, the rear wing probably was a little low, but we were worried about pushing it up too high and raising the CG even further. For the next car we will be lowering the roll hoop significantly and the wing will sit above it. The rear wing mounts were not terribly elegant, but they were very simple and quick to make. I'm sure the next design will be a big improvement. We did a bit of flow viz in the wind tunnel and we were actually very surprised to see that the flow actually remained attached to the wing behind the mounts.

As far as the front wing is concerned, it can't be more than 460mm in front of the front tyres, so we're stuck with it where it is.

When you talk about side panels I assume you are talking about end plates. Any hints as to what you are changing?


Andy,

Thanks for that wing profile link (and all the others). I haven't had a chance to look at it properly yet (not really sure where to start), but I'm sure it will come in handy.

Regards,

http://www-personal.monash.edu.au/~fsae/sig.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

J. Cheng
01-19-2003, 01:47 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Scott & Roan:
Joe,
...When you talk about side panels I assume you are talking about end plates. Any hints as to what you are changing?....
<HR></BLOCKQUOTE>

Yes, I mean end plates. As to hints, take a look at an F1 car and an Indy car, then go take a look at my car and your car (it's pretty obvious if you put the 4 cars side by side). Why I didn't notice earlier is beyond me. The difference in downforce is about 3% (measured).

Joe

Bob Wright
01-19-2003, 10:55 PM
Acitve suspension is no good if your are allowd to mount you aero unsprung ( the right distance from the ground) Active was Lotus's backup plan because the T88 twin chasis was always going to be banned. Simple mechanical solutions are usually better.

Bob Wright
Monash University
Australia

Scott Wordley
01-20-2003, 04:53 AM
Joe, the problem we see with changing the end plates is the fact that the wings (including end plates) can't be any wider that the outside of the tyres. Any changes which require additions to the outside of the endplate would mean that the wing area would have to be reduced and also the aspect ratio would therefore reduce. At the front we could probably accept this, but at the rear the aspect ratio is already approaching its limit.

Regards,

http://www-personal.monash.edu.au/~fsae/sig.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

NJM.
01-20-2003, 09:52 AM
Endplates offer an effective increase in aspect ratio, as do the gurney flaps on Joe's endplates. There are a few books out there that show how to calcuate the increase in aspect ratio with these pieces. Joseph Katz has a few AIAA and SAE papers and books about these. Scott and Roan, you could probably calculate whether the increase in aspect ratio due to the endplate additions would negate the decrease in aspect ratio due to decreasing your wing area.

In Formula 1 most of the front endplate treatment is to increase the effeciency of the underbody as there are basically no trailing vortices on these wings in ground effect. (the effeciencies of these wings can be outrageously huge, 100+) The rear wing endplate treatment is aimed at reducing the effects of the trailing vortices that shed from the tips. Wing placement on the endplate, (ie longer at the front or at the rear), shape, and size are all important factors in determining the strength of the trailing vortices. These trailing vortices control the drag and are therefore very important for higher speeds of F1.

Scott and Roan, about the UIUC Airfoil Database, I would start with the SA series of airfoils. They were designed by Michael Selig and Ashok Gopalarathnam (my MS advisor). These are low reynolds number airfoils which were originally designed for remote control gliders. You can stack a few and make a multi element. The problem is there are no real high lift airfoils for low reynolds numbers. I am trying to change that by designing airfoils with an inverse design code written by M. Selig and Ashok.

What usually happens at our speeds is laminar separation. This can dominate the flow around the airfoil. I am wondering what you guys saw in the wind tunnel with your flow vis. could you see any area of separation? any transition to turbulent flow? What about trailing vortices? how big? any induced flow upstream of the wing?

If any of you autocrossers are thinking about replacing your wings anytime soon, i would'nt mind analyzing what you are thinking about using and maybe trying to design an improved airfoil.

Regards,

Noah Mckay
njmckay@eos.ncsu.edu

wingman
01-20-2003, 10:55 AM
Hey Everyone, and Joe especially, it's good to hear from you again......

OK so now that the cat is out of the bag about Dr. Selig's work, it begs the question....

Why doesn't the UIUC car have wings??

Cal Poly used Selig Airfoils on both their wing cars, and yes he has developed specific low speed high lift airfoils, but the problem is digging them out of the HUNDREDS of profiles he (and his team) have developed

And to answer the end plate question....
DO IT!! the bigger the better, just ask our drivers what happened when we lost an end plate on course at Nationals last year.....It was like the Dukes of Hazard out there...

I think Aspect Ratio is very important to consider. Low aspect ratio affects had Cal Poly running their wings about 5 deg beyond the 2D stall AOA even with the large end plates.

Also very important is minimum Reynolds # ...so I ask again, what is your car performance at 20 and 40 MPH

And what will perform better for FSAE cars, Wings or Under Body Aero??

here is another site of interest that was posted on Hybrid Z
http://www.nas.nasa.gov/About/Education/Racecar/aerodynamics.html

awhittle
01-20-2003, 12:51 PM
Have you guys seen this page. Great for diging out a profile.

http://aerolab.virtualave.net/airfoil/index.html

Most of the uiuc profiles are included.

AW

Scott Wordley
01-20-2003, 01:50 PM
Hey Wingman,

I'll post some of our wind tunnel results later today so that you (and everyone else) can get an idea of what is happeneing with our car at any speed. Like we've explained we don't have a moving ground so I'd be interested to see what everyone thinks we 'should' be getting considering ground effect for the front wing and diffusers etc. More later...

Everyone, these posted links are great, keep them coming.

Regards,

http://www-personal.monash.edu.au/~fsae/sig.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

J. Cheng
01-20-2003, 09:30 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by wingman:

Why doesn't the UIUC car have wings??

<HR></BLOCKQUOTE>
I just realized that George Bowland's new AMod car has wings designed by UIUC. See photo 6134 http://www.showcase-photo.com/Photos/SCCA/Topeka-2002/09-12-02/Heat2%20South%20Pg1/.html . They have 4 elements and they are HUGE. The photo illustrates what I believe a low-speed aero car should look like. Looking at the car head-on, you see only the driver's head and all wings, nothing else. Cal Poly's car (photo 6125) has the same approach (if there is drag in the air, it better be something that's producing downforce) while UTA's (photo 6126) approach is a lot more conservative.

On the subject of low-speed profile. I don't think the actual individual profile is important for a multi-element set up since the top portion of the individual airfoil does not see any air flow, except in the region of the slot gap. Once, I left a bunch of yarn tufts on top of the main element in the wind tunnel (26 mph wind speed), the tufts didn't move at all. Another time during field testing, I again left a bunch of tufts sitting on the main element by mistake. The car reached speed of 75 mph and the tufts was still there when the car got back. I believe the imprortant factors in designing a multi-element wing are the overall profile of the lower surface and the profile around the slot gap. Every low-speed multi-element wings I have seen on top race cars all share one common feature, and that is the aggressive overall camber from the tip to the trailing edge on the lower

surface. As Noah mentioned in his post, "...What usually happens at our speeds is laminar separation....". I noticed that in the wind tunnel. All the adjustments in angle of attack, slot gap geometry would only lead to a few percent of improvement. However, once the flow seperates, downforce drops 30-35% just like that. However, the interesting thing was that even after the flow separated, I could stick my hand into the airstream (at the trailing edge of the main element or somewhere behind the middle flap), it would disturb the air enough that the air would re-attach itself, and remain attached even after I removed my hand. This led us into looking at vortex generators and other means of encouraging the flow to remain attached. The final solution was pretty subtle and simple (sorry, can't give everything away since there are other AMod people on this list).

Joe

Scott Wordley
01-21-2003, 03:48 PM
As promised I've posted an example of our wind tunnel data results. It can be found at:

http://www-personal.monash.edu.au/~fsae/monash2002.jpg

There are quite a few important factors regarding the testing that I should repeat here to prevent the results being taken out of context.

Firstly the Monash Tunnel is designed primarily for measuring passenger vehicle drag. It has moveable pads on which the car usually sits which measure the aero loads. As we got access to the tunnel for a weekend in the middle of commercial testing we had to use a road car wheelbase and track. To do this we build the blue rhs rig pictured to mount the car and lift it off the ground slightly. This was a good thing because it allowed us to get out of the boundary layer which is about 80-100mm high at that point. But of course the rig will increase(or decrease?) the measured drag and have a smaller effect on the measured downforce. None of these factors were compensated for in the results or theoretical predictions.

Note that the car was NOT tested with either the sidepod diffusers or the rear diffuser, we didn't think we'd get anything meaningful out of them.

Also note that I calibrated the mounting rig with weights and by applying drag forces.
See this picture, the orange string is a drag line with a weight hanging below the floor. I have data files from these cal too.

http://www-personal.monash.edu.au/~fsae/monashcalibrate.JPG

You'll note that while our front wheels sit directly over the front pads the rear wheels sit in the middle of the beam. This means that the 45% of the downforce coming from the rear wheels is seen at the front pads and 55% is seen at the rear pads (as measured in calibration). Not surprisingly, this is very close to the (inverse)distance ratio. So knowing this, the downforce distribution from the measured data was shifted by the correct amounts to give actual front and rear. Obviously the total downforce did not change. The front and rear downforce graphs with WT show these results with after the shift.

If your real keen (Wingman?) you can check my math and make sure I didn't forget to carry the one. There is no BS here...

http://www-personal.monash.edu.au/~fsae/monashratios.jpg

Another graph above shows the full car lift to drag ratio (around 1.7) the left/right balance (1 of course) and the front to rear ratios both measured and theoretical. Everyone knows that without a moving floor you can't get good data for front wing in ground effect. We were expecting the numbers to be low and they were. What we still don't know is how much lower than expected they should be, or even if there is such anecdotal knowledge. If anyone has had any experience we'd like to hear about it. We were still able to tune it for best performance though, we just hope this same setting works best on track.

Anyway, so that we'd have a rough number to quote for total downforce I drew the dashed curve front downforce (theoretical). We designed our wings for aero balance which meant a front DF 0.6 the magnitude of the rear downforce. So I plotted this curve and also added it to the measured rear downforce to create the Total Downforce (Theoretical) graph for JUST the wings, no diffusers. It is an indication of the total downforce IF the front wing is working properly.

Considerable CFD...

http://www-personal.monash.edu.au/~fsae/monashcfd.jpg

...said 50% of total downforce from rear wing, 25% from the front wing and 25% from the sidepod diffusers (rear diffuser was not modelled).

So in conclusion, FROM WINGS ALONE:

Speed Measured DF Expected DF
20 mph 13kg 18kg
40 mph 54kg 70kg

Scott

Regards,

http://www-personal.monash.edu.au/~fsae/sig.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

Dominic Venieri
01-22-2003, 11:20 PM
Roan, check your email

www.formularpi.com (http://www.formularpi.com)

Superfumi
01-24-2003, 06:38 PM
Hi Scott and Roan,

I am with UQ's SAE team. I was just wondering a few things. What year are you guys going into? are you studying mech eng? and was the aero work on your car a thesis topic for either of you? By the why, you are very lucky to have such an awesome wind tunnel at monash. Good work fellas, see you at next years comp http://fsae.com/groupee_common/emoticons/icon_smile.gif

Scott Wordley
01-26-2003, 06:18 PM
Hi Superfumi, I've just completed a double degree in Mechanical Engineering and Industrial Design. I did my thesis in 2001 on turbocharging and last year I was just finishing off Industrial Design so the work I did on Aero wasn't part of any Uni subject.

Scott also did his thesis in 2001 and is now doing post-grad work (not SAE related). He wrote up our work in a paper which he presented at the Young Automotive and Transport Exectives conference and won first prize.

Regards,

http://www-personal.monash.edu.au/~fsae/sig.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

Eric Wort
01-29-2003, 03:02 AM
A wing may be included in the 2004 UIUC car. We've only recently gotten people from the Aero department interested and probably won't have time to incorporate a 'winged' design onto this year's car.

Look for the 2003 car to be sporting a wing during the summer though, even if we do just steal the aero dept's 4 element low-speed takeoff wing and bolt it right on the car http://fsae.com/groupee_common/emoticons/icon_wink.gif

Eric Wort
UIUC Formula SAE (http://dilbert.cen.uiuc.edu/soc/sae/formula/)

wingman
01-30-2003, 10:00 AM
rou...row....raggy!!! http://fsae.com/groupee_common/emoticons/icon_eek.gif

Can't wait to see the aero package on a UIUC car!!

Glad I don't have to compete against you!!

Hey Monash...thanks for posting data....

If you take your tunnel data and add your approximate percentages of down force to estimate a total, your still talking mid 300lb range at 60mph and mid 100lb range at 40 mph. is this correct??

cheers,
Wingman

Scott Wordley
01-30-2003, 09:14 PM
wingman... thats pretty close

as I wrote previously, about 150lb at 40mph and about 400lb at 60mph.

REMEMBER THIS IS WINGS ALONE! and does not include the Diffusers which should contribute around 25% of the total.

The excel fit function for km/h and Newtons is:
y = 0.1788x2 + 0.6592x + 0.9377

So what do you (and everyone else) think?
This forum is weird sometimes, we've discussed everthing concerning wings and downforce and then as soon as we post probably the first ever public FSAE wind tunnel data what happens? Silence. Dont be telling me you guys are too busy to post.

I'd almost welcome Bam Bam knocking my colour selections just to recieve some feedback.

Regards,

http://www-personal.monash.edu.au/~fsae/dudsig.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

MikeWaggoner at UW
01-30-2003, 10:48 PM
I'm still not sure of the benefit of wings overall. I don't think that the cornering benefit at low speeds (sub 25) is worth the added cost/unsprung mass/drag. However, you're obviously generating useful cornering force at 40 mph. I was given data from one school's dataloggers data by another student. I think the data is from Cal Poly (?!?! If anyone knows the source, I'd like to credit/thank them). I have a copy at http://dot.etec.wwu.edu/fsae/dlog/Enduranc%20Post.xls (you can cut the name of the endurance post to see the whole dir...).
Anyhow, I'm too busy making parts at the moment to do a good data analysis of speed vs. G's, and then compare the data to your windtunnel model, but it'd be interesting.
In my opinion, it looks like the vast majority of corners are at sub 25, and I think the wings are hurting the car in corners (higher weight up in the air, greater unsprung mass) or at least not helping. The benefit in high speed corners is (in my opinion) outweighed by the losses in acceleration caused by additional weight and drag and the scarcity of high speed corners.

Western Washington University FSAE
dot.etec.wwu.edu/fsae

Bam Bam
01-31-2003, 06:46 AM
I didn't knock your colour scheme because I thought the rainbow stripes on your graph summarized you guys and your car quite well......


Keep it hostile.

Charlie
01-31-2003, 08:12 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Scott & Roan:
This forum is weird sometimes, we've discussed everthing concerning wings and downforce and then as soon as we post probably the first ever public FSAE wind tunnel data what happens? Silence. Dont be telling me you guys are too busy to post.
<HR></BLOCKQUOTE>

Too busy to post? No. Too busy to analyze data? yes. This is 'crunch' time for the US teams. I'm sure lots of teams will be looking at your data after the US competition. However right now our cars are already designed and we have to get them built.

-Charlie Ping
Auburn University FSAE 1999-present

Dusan
01-31-2003, 03:50 PM
So I notice you quote a realized 54Kg of downforce, but later you say something about 150lbs at the same 40mph. Where does that number come from. Also, given you expect 25% from the diffuser, if 54 is 75%, then 72Kg total.

So, what's the drag and centrifugal forces involved in the additional weight? 594 lbs. let's see, w/o wings 460lbs - let's be generous and call it 50kg additional weight especially some of it way up in the air?

Do the wings make up for that and the additional drag especially considering your weight doesn't drop off as the speed does?

I think it is interesting, but I want to see what the math really works out to be.

Dushan
WWU

Scott Wordley
02-02-2003, 09:50 PM
Dusan.

Your question:
"So I notice you quote a realized 54Kg of downforce, but later you say something about 150lbs at the same 40mph. Where does that number come from. Also, given you expect 25% from the diffuser, if 54 is 75%, then 72Kg total."

In the wind tunnel from wings alone we MEASURED 54kg of DF at 40km/h. Because the front wing measures low in the tunnel we EXPECT 70kg from the WINGS on track (see the dashed line on the graph). CFD indicates that with this setup we can expect a FURTHER 20kg from the diffusers. So we expect a grand total of around 90kg at 40km/h, or about half the weight of your car.

And you don't need to be generous by saying 50kg for wings, we didn't make them out of cast iron or anything. Both wings, mounts and diffusers weighed a total of 12kg, and they were heavier than they need to be. Expect around 9kg with bigger wings this year. The RPI post confirms that they are in the same ballpark... its not hard.

I agree with Alistair on the fact that you can do this stuff without a wind tunnel, the A-Mods are a prime example of that. I don't mean to have a go at you WWU guys but of all the teams out there I thought you guys would be more open to new ideas and approaches considering the cool shit your uni has done in the past.

I don't really care for arguing about it though, people take different approaches to things and you may well be right. Even still I'm quietly confident that even if WE don't prove that wings are beneficial, that time and other teams will. I'm just happy that we took the gamble and that it paid off, and that we were the first team to sport big(not like UTA '02), multi-element(not like CalPoly), unsprung(not like UTA '01), endplated wings(not like RPI) because thats obviously the way it should be done and will be done in future.

I laugh when you talk about the prevalence of low speed corners... because we have a solution to that particular problem too. Maybe well wait to prove it on track, it may not get built if I spend as long trying to explain that one.

Regards,

http://www-personal.monash.edu.au/~fsae/dudsig.jpg
Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

Dusan
02-03-2003, 10:15 PM
But I think you'll find that while many folks will take assumptions at face value, engineers just don't go that way. We like cool stuff, and yes, we like wings. But believe it or not, even for us at WWU, it can often be a game of numbers, especially when resources are tight. Everything and every part of the competition has to be weighed carefully.

wingman
02-04-2003, 09:52 AM
Well put Dusan!!

As for you Monash Aussies....

Tis better to be thought of as immature know-it-all blowhards than post and remove all doubt.

You asked why people weren't posting replies to your information...well how about proving you are potential engineers by posting responsibly with quality information rather than emotional dribble! How about winning a competition BEFORE you associate yourself with the likes of UTA and Cal Poly Pomona. Don't you have anything better to do than live on this forum, say like build a car???

Yes everyone likes the way your car looks...
Just remember, wings don't make a car, they make a good car better.....IF they are done right!!

If you have the skills and the background to implement unsprung, underbody tunneled, multi element winged aerodynamics... congratulations....but even with all that, your measured partial/estimated total downforce is not much more than UTA and Cal Poly were measuring, so I guess we're all a little confused as to your statements.

How about students posting information and/or data on testing methods and design methods for aero development??? How about more posts on reference sources to allow teams to explore aero??

Quick thanks to Mark Twain and BASF for catch phrase references

Cheers,
Wingman

James Waltman
02-04-2003, 10:18 AM
Scott & Roan,

We are big supporters of doing things differently. I think that we all appreciate your wings. I also think that you did them right. There is a chance that we will have wings in the future. We are pressing you to prove yourself because of our curiosity not our disbelief. If you learned anything during the process then you are better off than teams that never tried. I think it's the same for our V8. It's strange to me how much resistance it gets. Some people think that it was a waste. Did the V8 make a faster car? Though question. I know that the people involved are much better off for having participated with it even it didn't fully compete and even if it didn't make a faster car.

With that said I am not sure if your wings make your car faster. Your times in FSAE-A are respectable but if you transfer them to Detroit they are mid pack. Your skid pad times would put you in about 74th place in Detroit. Your Acceleration times would put you in about 65th place in Detroit. This makes me wonder where you would be in the Endurance and Autocross (not as easy to correlate a time because of different tracks). Maybe your car really shines on the Autocross and Endurance. Now, it may not really be the wings that slow you down but more the wings detracting from other things. If you didn't have the wings could you have made your car lighter than 600lbs? Could you get it under 500lbs? Would the lighter car do better in the acceleration event?

Is a faster car better? Not necessarily. I think that gets into the Winning vs. Learning debate in the Off Topics forum.

While I am posting from the other wings thread:
ps loaded qeustion. How many of the FAST autocross cars have aero downforce... the answer Every One

My question is how many of the fast autocross cars have at least twice the HP as a Formula car and average speeds greater than 30mph ..... the answer: Every One


James Waltman
VRI @ WWU

Charlie
02-04-2003, 10:29 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by wingman:
As for you Monash Aussies....

Tis better to be thought of as immature know-it-all blowhards than post and remove all doubt.

You asked why people weren't posting replies to your information...well how about proving you are potential engineers by posting responsibly with quality information rather than emotional dribble! How about winning a competition BEFORE you associate yourself with the likes of UTA and Cal Poly Pomona. <HR></BLOCKQUOTE>

Amen.

-Charlie Ping
Auburn University FSAE 1999-present

Scott Wordley
02-04-2003, 07:24 PM
Wow... I'm blown away by your hostility Wingman and frankly what your saying doesn't really make much sense, at least to me (Scott).

Where do I start....

You say:
"How about students posting information and/or data on testing methods and design methods for aero development??? How about more posts on reference sources to allow teams to explore aero??"

Have you even read this thread? What do you think I was trying to do with all that wind tunnel data? Not only that, I took the time and effort to explain all our assumptions, our test procedure and even the way we analysed the results. I even posted pictures. We've held up our work for your criticism and put our credibility on the line which is more than anyone else has done. What more do you want?

Lets see your(and UTA's) wind tunnel test procedure and data? I seem to recall you quoting 285lb measured downforce using corner weight scales(!). Comparing apples with apples we MEASURED 325lb from our wings at the same speed, again no diffusers. Please correct if I'm wrong. On your rig did you check that the drag component wasn't increasing or decreasing the downforce reading? Maybe we should toss our Kistler Triaxes and upgrade, at least for the sake of parity. As for UTA I think I remember Dr Bob mentioning a 'wind room' for testing, what is that exactly? I do know you guys have both done lots of datalogging on track though(and we will too this year), I'm just asking that you be fair and more specific in your critisim so that maybe we can learn from you guys because you have the experience.

As for the emotional dribble, I know Roan has blasted BamBam with a few over the top comments but any serious comment regarding aero has been at least been backed up by a reason. I joked around with a reply to Jack from WWU on the other thread but it was just that: a joke (as designated by the "hahahaha" and the stupid picture). If you can't have a little fun on the forums every now and again why bother. Did you even notice the 16 or so rules of thumb that I followed with? We don't care in the slightest what the car looks like, form will always follow function, we just think its amusing that other people do.

You then accuse me of trying to associate ourselves with the giants of the competition such as UTA and yourselves. What I was doing was comparing our respective aero packages and stating my opinion on where aero in FSAE is headed, not saying we are as good or better than anyone else. But if your still worried I have a suggestion for the forum, perhaps everyone's font size should be inversely proportional to their team's most recent placing, that way you know whose posts to read. And so you can see us Aussies coming maybe our text should be printed upside down. Furthermore Monash posts should be printed backwards just so you don't confuse us "immature know-it-all blowhards" with quality teams like Wollongong and WA. If that qualifies as emotional dribble I apologise in advance.

James, thanks for your considered and well informed response. The only thing you are missing is the fact that Monash (and some of the others teams who got through scruitineering on time) ran skidpan and acceleration in standing puddles of water(I think I've explained it elsewhere on the forum before). Due to the fact that scruitineering was delayed on Saturday morning several teams (Wollongong included) were allowed to COMMENCE all of their skidpan and acceleration runs up to an hour and a half AFTER the scheduled close of both events and after we had completed all our runs. We attempted to stall for time but were pushed through in front of teams who had yet to run, all the time being assured by the marshals that the event was closing at 12PM. Extremely poor marshalling which probably cost Uni of WA the overall event and could have done the same for us had we finished enduro. Anyhow by this stage the track was completely dry and we went from a clear win in the skid pan and 2nd in Acceleration to placings of 11th and 5th respectively. If you don't believe me please check the race timing I'm pretty sure it has the actual times of day for the recordings. If any Aussie teams or RIT are listening please second or dispute this interpretation of events as you see fit.

Ian, you wonder how I find time to build our car... but how do you ever find time to build your car?

Anyway... I don't want to fight with you guys because I respect you all a lot. If anything I'm dissappointed that the respect is not mutual.

Scott

Regards,

Scott Wordley & Roan Lyddy Meaney
Monash FSAE Wingmen
http://www-personal.monash.edu.au/~fsae

[This message was edited by Scott & Roan on February 05, 2003 at 12:50 AM.]

Pat D'Rat
02-05-2003, 01:58 AM
Hi Wingman, If your team want a real wake up call, then ship your car to Adelaide next December. You will find that the water running the wrong way down the drain is not the only thing that is different in Oz.
Down here we are friendly and helpful, but on the course, we compete as hard as anyone. The Aussie cars, on average, are the best in the world, and Scott and Roans big blue device is one of the best, so I would put my brain in gear before running off with criticism.
It is no accident that Aussie engineers are No. One on the shopping list of race teams all over the world, despite that the population of the whole country is less than that of LA. Come down here and see why ! Not only that, but the sun will shine and the Aussie sheilas will dazzle !
Rodent

'Near enough' means you missed !

wingman
02-05-2003, 10:39 AM
OK guys Practice what you preach here, I obviously need to......

First, I appologize for having a little too much fun with my last post, but the comment about associating Monash with UTA and Cal Poly was taken out of context. I don't doubt your technical skills or the potential of your car Scott, my point is that several schools have dabbled with Aero and tried the options you tried, but all this was before the time of forums like this and in most cases the teams in question were bit by the same demons you guys were (bad luck/timing/preparation at the competition), thus they were not top ten and are now forgotten. So your statement about you guys being the first car to do this or that was a bit out of line and disrespectful to those who have come before you. (hence the reason for my Mark Twain reference) Remember we are all acutely aware of our respective cars and the details that go into them, but not so aware of the details of other teams cars. We "ASS U ME" as a result......enough said.

Second, several have posted with confusion about the data you posted. I commend you for posting the info, but don't bash us for not understanding some of it, it was not very clear.... We have already discerned that drag is not of great issue here, so talking in lift terms only, your graph has a picture of the car with front and rear wings but no diffusers, and your post stated that the percentages were 50%rear 25%front 25% diffusers so based on that the total downforce estimates seamed high. Also please include the velocity units in the graph (i.e. m/s or mph) your forces were in Newton's so I ass-u-me-d m/s but please clarify..... And you are still getting considerable help from ground effect if you are within half span distance from the floor. Anyway, trying to compare performance and tunnel data is ridiculous given the variables involved, so there is an inherent generalization of data to deal with here. Bottom line is Cal Poly's old cars had enough downforce to justify the aero, so if you are getting more downforce in the Monash car, that's greater justification. My previous comments were a bit loaded in that I will never forget that it is REALLY difficult to justify aero to judges that are familiar with it given the time you have to present, it is almost impossible to justify it to a judge that's used to designing bumper brackets (not that there is anything wrong with designing bumper brackets)So if we had trouble understanding the data you posted you can bet they will.....

Finally I'm an Aerospace alum NOT a student, so I have the luxury of time to post and the benefit of information (all be it dated) that I am willing to pass along to you in return for the great discussions that we have on this forum. I am not even directly affiliated with the Cal Poly team anymore (haven't been fore years now) so I will be interested to see what they come up with for a car this year.

Peace Gentlemen...

Wingman

James Waltman
02-05-2003, 12:33 PM
I thought that there might have been rain. Everyone's times were way off of Detroit times and now it seems like I remember it being mentioned. So I guess my time comparisons are bad please disregard them. I wasn't trying to make you look bad, only to show that some areas may have been sacrificed in the name of wings. Maybe nothing was.

I really don't care who is faster. I have said it before here: I think that the point of the competition is to learn the goal is to win. There is a difference. If you were learning then you were on the right track with the wings.

James Waltman
waltmaj@cc.wwu.edu
http://dot.etec.wwu.edu/fsae/
Formula SAE
Vehicle Research Institute at
Western Washington University

King Missile
02-05-2003, 02:29 PM
Hello,

My name is Brett and I have driven cars for Cal Poly (Pomona, not SLO) from 1996 through the 2000 car.

I am not going to pretend to discuss why the wings worked as that is not my field of expertise. I can however shed some light on wings from a drivers point-of-view, as well as a team member.

Yes I did feel cheated whenever we did benchmark testing and the wings were not on the car. Before the 98 car I had never driven/raced a car with aerodynamic aids of any sort. In initial testing the wings actually did slow the car down. This fueled the anti-wing faction of the team (which included me at the time). I was relying heavily on my experience with the previous cars. Unfortunately with the wings you really have to relearn how to race the car.

I simply wasn't going fast enough through the corners to utilize the benfits given me. With the 98 car you could up your entry speed little by little and you'd start losing grip, until you got to a point where the grip began coming back. This was less of a factor on the 2000 car because the aero (at least from my point of view, wingman may argue this) came in earlier.

Drive time is a resource that is in scarce supply anyways. I recommend a minimum of 4 weeks of testing prior to the event, not only to dial in the car, but the get your driving team ready. With wings youre looking at lots more testing and tuning and A LOT steeper learning curve for your drivers, requiring a lot more seat time (if only to avoid hitting stuff with the endplates).

Cal Poly has moved to a 2 year design cycle to compensate for the extra design/tuning/driving issues that come with wings. If you team has the resouces then it may be possible to cram it into one year. Also remember that wings are something that is constantly in development as evidenced by UTA's progress (not that they were all that bad to begin with). Dont be so quick to discount a car with wings the first year. They have laid the groundwork for big divedends to come.

Sorry for the rambling, Ive been up all night on durability teasting.

Time to go home...

Brett Miller
Cal Poly FSAE 96-00

Where are we going? And why are we in this handbasket?!

awhittle
02-05-2003, 04:21 PM
The most dificult thing to learn is if the car will not stick at 40 then try 60 mph Brett is correct, the learning curve is huge. Joe, care to chine in http://fsae.com/groupee_common/emoticons/icon_smile.gif

Andy

J. Cheng
02-06-2003, 09:13 AM
It's true that a driver needs to learn how to drive an aero car. Most drivers have conditioned themselves to judge how fast the vehicle has to be just prior to the turn-in phase. Up to that point in time, there is no g loading on the driver and his decision is mainly based on visual inputs to the brain. I don't believe the human brain (at least not mine) is sensitive enough to determine a speed difference say between 30 and 33 mph purely based on visual only. When a driver visually sees a corner coming up at some un-godly speed, the first instinct is to slow down to a pre-conditioned comfort level before turning the steering wheel. Once that corner entry speed is established, it governs the downforce the car has for that corner. If the entry speed is too slow, it's really hard to gain it back in mid corner. The driver needs to have enough seat time in the car to re-program his brain so that he doesn't freak at corner entry, especially when the corners are faster ones and the speed differential between mechanical grip and aero grip becomes farther aparat. The goal is to tune the car with a consistant mild under-steer at corner entry should he becomes too brave in using the aero. This would induce confidence and therefore he is more willing to use it.

There was a saying, "...you give a driver 10% extra power and he still complains the car is not fast enough. You give him 10% extra downforce and he drives like a hero...."

Joe

Joy Pathak
06-03-2009, 07:53 AM
What does everyone think of Wings NOW?

Wesley
06-03-2009, 08:35 AM
About the same, really. The debate hasn't changed that much.

Joy Pathak
06-03-2009, 10:05 AM
But... a winged car won FSAE? http://fsae.com/groupee_common/emoticons/icon_eek.gif

BrettHutchens
06-03-2009, 11:07 AM
its not the size of your wang that counts, its how you use it

oh and UTA won the inaugural Japan Competition

Superfast Matt McCoy
06-03-2009, 11:27 AM
Originally posted by Joy Pathak:
But... a winged car won FSAE? http://fsae.com/groupee_common/emoticons/icon_eek.gif

I bet if you went back and averaged the finishing times of the winged cars vs. the nekked cars, you'd find a pretty consistent trend.

Joy Pathak
06-03-2009, 11:51 AM
Originally posted by BrettHutchens:
its not the size of your wang that counts, its how you use it

oh and UTA won the inaugural Japan Competition

Technically...with wings...It would be bigger the better given the speed limitations. But maybe Missouri or UTA have found some exceptions? Multi-element obviously though.

Joy Pathak
06-03-2009, 11:53 AM
Originally posted by Superfast Matt McCoy:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Joy Pathak:
But... a winged car won FSAE? http://fsae.com/groupee_common/emoticons/icon_eek.gif

I bet if you went back and averaged the finishing times of the winged cars vs. the nekked cars, you'd find a pretty consistent trend. </div></BLOCKQUOTE>


Lol...but...but..but...a Winged car WON.

I have had so many debates on winged cars with my previous team-mates and all I ever was told in reply, "A winged car has never won, nor will they ever, it." Nuf said now.

Yellow Ranger
06-03-2009, 12:09 PM
and in a couple weeks, hopefully another wanged car will win http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

Mike Cook
06-03-2009, 12:18 PM
I'm ok with that...

On all the tracks we have run on our winged cars have been consistently faster. I could show easily with calculations the benefit of wings in terms of downforce. I can't easily calculate how much the extra weight and inertia hurt our vehicles performance.

Of course FSAE is about more than just raw performance, especially with the fuel rules now. Wings add a lot of complexity to the project and may lose you points in this way.

mike
"our wang is bigger than yours"

Joy Pathak
06-03-2009, 12:27 PM
Proving wings work is super easy, especially the downforce calculations.
It's all about breaking the mentality.
At my school I was refused to build an aero package because nobody wanted to build their car around the body. They wanted to build around suspension the way it has been done for years at my school. Body is just for aesthetics apparently.

Neil S
06-03-2009, 12:54 PM
If anyone doubts that they make the car faster, look at the number of teams that have put forth a proper effort on developing/testing with them and see how many of them are still using the wings. I think you would find that the majority of teams are still running them or would like to be able to run them.

OU, KU, SDSM&T, Maryland are all running them. As far as I recall Cornell is the only team to have tested wings and not actually continued to run them, maybe they know/think they know something that the rest of us don't.

VFR750R
06-03-2009, 02:06 PM
i hope I don't speak out of turn, but NC state had some nice wings (and i believe there is an SAE paper on them) but they don't run them at competition.

Marshall Grice
06-03-2009, 04:07 PM
Washington tested with wings and didn't run them at comp. Calpoly Pomona ran wings for years and they no longer do. We'll have to see what Calpoly SLO does this year.

J. Vinella
06-03-2009, 04:11 PM
Originally posted by Marshall Grice:
Washington tested with wings and didn't run them at comp.

That was not because they did not make the car faster.

I think Washington was running wings at MIS. http://fsae.com/groupee_common/emoticons/icon_eek.gif

Marshall Grice
06-03-2009, 04:21 PM
I'm still waiting for some 'out of the box' thinking on aero. like 45"+ cord wings mounted along side the cockpit a couple inches off the ground, or tunnels with the upsweep starting right behind the front a-arms.

everything i've seen to date has been just copies of the highly regulated 'big boy' racing cars.

Scott Wordley
06-03-2009, 05:00 PM
This thread just doesnt die does it? haha

Having been around 10 years, and competed in 11 competitions to date, I cant believe that im still messing round with these stupid little cars. They are fun though.

Its also interesting to note how the more things change the more they stay the same.

At the end of the day every team needs to walk their own path. If you believe wings will make your car faster, you need to make the effort to build some and find out for yourself. If your car will score more points with them, use them, if not, don't.

There is a lot of information, advice and opinion on this forum but no hard and fast answers. Just get in there and do it.

You need wings to do this though...

http://www.youtube.com/watch?v=h-uYfH726Q8

Take it easy...

Scott Wordley

'00-'09 Monash FSAE
4th Place Overall 2008 FSAE-A
3rd Place Overall 2007 FSAE-A
6th Place Overall 2006 FSAE-A

Check out my 3 papers on FSAE Aero:
http://www.sae.org/technical/papers/2006-01-0806
http://www.sae.org/technical/papers/2006-01-0808
http://www.sae.org/technical/papers/2007-01-0897

Joy Pathak
06-03-2009, 07:54 PM
Ah the Great Scott Wordley.

One of the reasons I got into FSAE was after seeing the 02 Monash car I think. Talked to Roan for like hours and hours at a time about Wings on msn.

I think I still have the old emails you sent me Scott back in 05 on the excel sheets of using wings and so on. Multi-element vs single and so on.

Wings work. No one can deny it anymore. If you search through the forums there were HUGE wing debates back in the day with basically Wordley,Roan(roan on scotts account), and "wingman" being the only ones defending wings.

Goodtimes.

Wesley
06-04-2009, 06:44 AM
Originally posted by Joy Pathak:
Body is just for aesthetics apparently.

Don't worry, we still seem to think that for some reason, even with the wing package.

Kirk Feldkamp
06-04-2009, 11:09 AM
Originally posted by Marshall Grice:
I'm still waiting for some 'out of the box' thinking on aero. like 45"+ cord wings mounted along side the cockpit a couple inches off the ground, or tunnels with the upsweep starting right behind the front a-arms.

Is this the path the A-mod car is headed down?

-Kirk

Superfast Matt McCoy
06-04-2009, 11:10 AM
Originally posted by Wesley:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Joy Pathak:
Body is just for aesthetics apparently.

Don't worry, we still seem to think that for some reason, even with the wing package. </div></BLOCKQUOTE>

They do make the cars look better. Most of the time.

http://jalopnik.com/5278644/fr...oks-dumb-sets-record (http://jalopnik.com/5278644/front-wing+equipped-scion-tc-looks-dumb-sets-record)

R33E8
06-05-2009, 08:13 PM
Ha! I wouldn't mind that on my fsae car! As long as it works good I'll do it!! No need to worry about hitting cones with the front wing... http://fsae.com/groupee_common/emoticons/icon_smile.gif

Erich Ohlde
06-05-2009, 09:23 PM
Matt, where do you find these things?

Jersey Tom
06-06-2009, 05:37 PM
For a long, long, LONG time.. I was a big skeptic.

I say right now, without a shadow of a doubt.. if you got a quick driver and a well-designed aero package it is massive. 2+ seconds a lap on a FSAE course. Wet or dry. Ridiculous.

If you design isn't good... probably just slows you down. If your driver can't take advantage of extra grip... probably just slows you down. If your project and time management doesn't have the extra room for the R&D time... waste.

If you pull it off though... big speed.

VFR750R
06-06-2009, 07:51 PM
I'm waiting for the first team to go the 'Super Modified' route for wings. I mean, if 2 is good 3 must be better right?

http://www.flickr.com/photos/16837963@N00/264687477/

Superfast Matt McCoy
06-07-2009, 10:05 AM
Originally posted by Erich Ohlde:
Matt, where do you find these things?

Jalopnik.com, mostly

There's also this winged solution for teams with more money than time: http://wheels.blogs.nytimes.co...-sells-parts-online/ (http://wheels.blogs.nytimes.com/2009/06/05/toyota-f1-team-sells-parts-online/)

Zac
06-07-2009, 02:42 PM
"But if youre looking to cobble together your own racecar from the Toyota F1 parts, youre out of luck. The parts are sold with the condition that they cannot be used for any road or race applications."

aww

Yellow Ranger
06-07-2009, 03:48 PM
hey matt, remember our 05 car?

http://img174.imageshack.us/img174/420/sprintwingni8.jpg

Mike Cook
06-07-2009, 05:52 PM
me gusta...

how did that sprint car wing work out?

Yellow Ranger
06-07-2009, 09:49 PM
well it did look absolutely ridiculous but it made that pile of a car from almost guaranteed bottom 5 to middle of pack at SCCA Nationals in 2006.

Aero testing on a trailer was performed days prior, proving the shear awesomeness of the sprint car wing

jm1495
06-07-2009, 11:42 PM
If all else fails put the wings on and tell the judges that it adds "static downforce" and see if they get it!

PatClarke
06-08-2009, 01:47 AM
If all else fails put the wings on and tell the judges that it adds "static downforce" and see if they get it!

Uh? ? ?

The judges actually made up that joke

Pat

Zac
06-08-2009, 05:26 AM
Makes sense, that joke is old enough...

Superfast Matt McCoy
06-08-2009, 09:05 AM
Originally posted by Mike Cook:
me gusta...

how did that sprint car wing work out?

Works great, except the "5 second egress" becomes a "25 second, falling out of the side of the car."

It's hard to do gracefully, and from the outside it always looks like a sperm whale giving birth to The Stig.

Wesley
06-08-2009, 09:32 AM
We pondered explosive bolts, but didn't feel it would be complete without an ejection seat.

Joy Pathak
06-10-2009, 06:42 AM
Rotating cylinder instead of wings would by fun. http://fsae.com/groupee_common/emoticons/icon_smile.gif

Adambomb
06-10-2009, 03:34 PM
Another thing to consider is the competition itself. S&T won at VIR with wings, but from the pics that looked like a very fast course. The autocross and endurance courses at Michigan this year didn't look aero friendly at all (in fact there were a couple times I was concerned we would have to do a 3 point turn http://fsae.com/groupee_common/emoticons/icon_biggrin.gif ).

We have considered wings in the past, but we've also always gone to Michigan, which typically hasn't been a fast enough course IMO to justify aero...however next year we're thinking about going to West. I've heard mention before that Michigan had the tightest (slowest) courses, anyone else care to comment on that? How do the other venues stack up?

D Collins Jr
06-10-2009, 07:20 PM
Michigan is terribly slow. In fact, I'd say Michigan is terrible-y about a lot of things. And although it wasn't run on the backstretch of the worst track on the NASCAR schedule, in 2007 the Michigan event saw two winged cars (UTA and OU) run away with auto-x. If I remember correctly, there was over a second gap between 2nd and 3rd, and less than a tenth between 1st and 2nd in autocross. VIR this year was completely wide open, but the year before was (I am told) very choked down and much slower. West is usually slightly faster than Michigan, and if nothing else, is a better facility.

Also, you're only considering some of the overall event. Wings will help on some autocrosses and hurt on others. Notably, they will help on wide open, SCCA courses. So if you're going to nats, take wings. They should also help in skidpad, and if you do it right, they don't hurt you at all in acceleration. And neat thing about accel and skidpad, they're normally the same no matter what the venue, track conditions not withstanding.

Pete Marsh
06-10-2009, 08:30 PM
That '07 auto-x track at Romeo was REALLY fast. You couldn't have asked for a better aero car track with the cars sounding like they where wide open through most of the corners. UWA did not get in a good lap either, so the speed difference would have been a little less if we did, but still a big difference.

BUT, the avaerage speed was WAY over the target in the rules, and that what your suposed to design for. On the enduro track, which was still faster than the rules require for the leading cars, the winged beasts adavntage was gone with no aero cars in the top three speed wise.

What is the speed range of SCCA events? In hilclimbs and sprints in Aus the speeds are much higher than FSAE and wings are obviously a big advantage.

Pete

Wesley
06-11-2009, 06:30 AM
If you mean final top three, yes, because we couldn't restart and UTA threw a chain. (both unrelated to wings) but we were still seconds ahead of everyone with our driver driving one handed (bypasssing a shorted wire with the relay "arm" button)

Superfast Matt McCoy
06-11-2009, 09:04 AM
'scuse me while I step on this soap box.

Racecar Engineering, more than almost anything, should be dictated by the data and not at all by the way people "feel" about something.

If several teams swear by it, then it's probably worth the time to do a quick analysis. If the analysis shows promise, then do a CFD. If that looks good, then do a full car test, and if that looks promising then you join the winged crowd.

I realize it's a time issue, but you have to focus on the things that benefit the most and you're only going to know what those are if you sit down and really do the math.

If you'll allow me the liberty of pulling a number straight out of my ass, I'd bet wings are worth at least 15 horsepower. So if you shifted the resources that are spending thousands of hours squeezing out that last 5 or 10 horsepower to wings, you might get a net benefit.

You won't know unless you do the analysis.

And if the leadership on your team refuses to look at the data because they just know better, then you've got a much bigger overall problem and that issue needs to be dealt with before anything else.

Also your team leadership has a promising future in North Carolina.

Jersey Tom
06-11-2009, 10:01 AM
Can't speak for equivalent horsepower, but on a 40mph course I'd put a good aero package at 3-4%

(That's a lot)

overdrive535
06-11-2009, 10:01 AM
Possibly in the Charlotte area?

vreihen
06-11-2009, 10:13 AM
Originally posted by Pete Marsh:
What is the speed range of SCCA events? In hilclimbs and sprints in Aus the speeds are much higher than FSAE and wings are obviously a big advantage.

Per the SCCA Solo (autocross) rulebook, the course must be designed so that drivers are only exposed to the same speeds as they would normally experience driving at legal speeds on the public highways. There are no published hard numbers due to fear of litigation and each event site being different, but there are two hints given:

(1) The maximum speed of any stock or street-prepared car shall not exceed the mid-60's (MPH) at any point on the course.

(2) (From a protest ruling about course legality at a National Tour event) The maximum speed through any corner shall not exceed 45 MPH.

From what I've heard, the trick to a successful aero car is putting a loose nut behind the wheel with enough, um, testicular fortitude to hold the throttle down even in the corners..... http://fsae.com/groupee_common/emoticons/icon_smile.gif

J. Vinella
06-11-2009, 01:39 PM
Originally posted by vreihen:
From what I've heard, the trick to a successful aero car is putting a loose nut behind the wheel with enough, um, testicular fortitude to hold the throttle down even in the corners..... http://fsae.com/groupee_common/emoticons/icon_smile.gif

So true. In a typical Formula SAE car you enter a corner a bit too hot and hopefully the car pushes (under-yaws) and the next time you take the corner at a slightly lower speed or a compromised line. You have reached the limit of the car at that speed or lateral force and steering angle.

In an aero car a higher speed might work. Think of it as local maximums. There is fast speed or just a few MPH higher you are off course, a few more MPH and you need new underwear but still on the course and cooking. It takes guts to try it but once you see that it works it makes wings very appealing. Not to mention the high speed braking stability which is very hard to quantify.

I will note that the car with an engineer driving has the potential to go faster but with the added confidence that the wings will "help"... http://fsae.com/groupee_common/emoticons/icon_smile.gif

Oh and is this the same Jersey Tom that started this thread:
http://fsae.com/eve/forums/a/t...48/m/49810447041/p/1 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/49810447041/p/1)

I have let the data change my mind too.

Jersey Tom
06-11-2009, 02:09 PM
Yep. At the time I had seen no data from any team. Just handwavy claims.

And it is still a waste of time if it isn't developed worth a damn. Much better effort spent elsewhere.

But when it IS done right... man... some serious grip.

Adambomb
06-11-2009, 04:59 PM
Yeah, I remember the '07 autocross, it was fast. Romeo was a lot more wide-open. I also remember watching UWA in endurance they were constantly on someone's a$$ waiting to pass http://fsae.com/groupee_common/emoticons/icon_smile.gif

I wish we had wings every time we go to an SCCA autocross...60 mph is not uncommon. I'm thinking when we take our '07 car to nationals we might have to try out one of those OSU style sprint car wings http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

Would really like to take that step, just haven't been able to find the "right person" that can pull the project to completion. We had a couple people in '07, but they didn't have the support of the leadership (of course that leadership is gone now). It is actually a fairly big step in terms of integrating it into suspension and chassis design. We had a diffuser designed this year at least, but again, it was lower on the list (behind things like brakes that held fluid, muffler that passed noise, etc), so it didn't get done. But hey, it was a YOUNG team (only like 3 people who had been around more than 2 years...again thanks to '07 leadership). Maybe in '10.

t21jj
06-11-2009, 10:05 PM
Originally posted by Adambomb:
Yeah, I remember the '07 autocross, it was fast. Romeo was a lot more wide-open. I also remember watching UWA in endurance they were constantly on someone's a$$ waiting to pass http://fsae.com/groupee_common/emoticons/icon_smile.gif

I wish we had wings every time we go to an SCCA autocross...60 mph is not uncommon. I'm thinking when we take our '07 car to nationals we might have to try out one of those OSU style sprint car wings http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

Would really like to take that step, just haven't been able to find the "right person" that can pull the project to completion. We had a couple people in '07, but they didn't have the support of the leadership (of course that leadership is gone now). It is actually a fairly big step in terms of integrating it into suspension and chassis design. We had a diffuser designed this year at least, but again, it was lower on the list (behind things like brakes that held fluid, muffler that passed noise, etc), so it didn't get done. But hey, it was a YOUNG team (only like 3 people who had been around more than 2 years...again thanks to '07 leadership). Maybe in '10.

Definitely wish we had wings at scca autocross events.

With our 2007 car at our last autocross event we saw mid 60's most of the course and I was cursing not having wings.

Big Bird
06-12-2009, 02:29 AM
A few thoughts from one who is a bit of a wing cynic..

I wont argue about wind tunnel figures as there are people out there who know a lot more about aero specifics than me. But from a vehicle dynamics perspective I reckon they do some funny things to vehicles of our size and speed.

Ive heard figures of around 60kg downforce and 40kg of drag for a rear wing, at 50kmh (typical cornering speed for FSAE), and around 40kg downforce at front (so maybe around 27kg of drag?). Anyone is welcome to argue these up or down.

So at first glance we have 40kg/60kg front to rear downforce split. Already this is a bit of a problem, given most of us are fighting understeer in our vehicles.

Drag Effects:
Now think about the drag on the rear wing. Usually these wings are right up in the air to get free air flow, so the drag force is acting on the vehicle at maybe 1.0 metre above ground. This creates a moment about the rear axle, tending to load the rear and unload the front. Given a 1.5 metre wheelbase, and summing moments about the rear wheel, that means we are lifting around 27kg off the front wheels.

So our effective aero split, as seen at the tire contact patches, now becomes around 13kg front : 87kg rear. So if we had understeer before, now weve got huge problems.

Caster Effect and Steering:
Now, in regard to steering geometry, caster tends to push the inside wheel into the ground and lift the outside wheel. On a go-kart we use this to our advantage the kart now tends to rock around the diagonal from inside front to outside rear so when we are braking into a corner we rock onto the outside front and lift the inside rear off the ground, thus negating any understeer from the solid rear axle.

In the aero case above, we are now pushing down hard on the back of the vehicle, so when we are entering a corner at speed we are more tending to rock onto the back inside and lift the outside front off the ground, which I would say is pretty well exactly what we dont need. It is going to take a pretty major jab on the brakes to get that outside front down to give us a decent turn in.

I know an aero team that just couldnt get their car to steer, and in their desperation they tried zero caster. Apparently it worked, so I guess the above might have some truth to it. I dont like what zero caster would do to your camber gain, given that you are still going to have some KPI, and that will give you positive camber gain on turn-in.

Fuel Economy: Given the drag figures above, say for instance your average aero drag over the whole track was around 60kg, or 600N. Energy equals force times distance, so the actual energy to drive these wings around an endurance event for 22km is around 600 x 22,000 = 13,200,000 Joules, or 13.2MJ. Say the thermodynamic efficiency of your engine is 20% (which is a decent first approximation for an Otto cycle) you will use around 66MJ of petrol energy to overcome this drag. Petrol is 44MJ per kg, so youve used around 1.5kg of petrol, or around 2 litres. What is 2 litres worth in the new rules maybe around 30 points?

The above figures will depend on your own wing setup and my simplified hand calcs will be a bit out. But FSAE is more than just autocross - and it is easy to see what you want to see and ignore the consequences.

Weather Sensitivity:
To get decent downforce at low speeds the wings need to be really speed sensitive (high angles of attack etc). What happens when you get some variation in the weather?

Downforce and drag vary with velocity squared, with the effective velocity being the air speed against the wing. For the above case, where we have known figures at 50kmh, what happens if we have a wind blowing at 25kmh? When we are driving into the wind at 50kmh vehicle speed, our incident air speed is 75kmh, or 50% greater therefore we have 1.5 squared = 2.25 times as much downforce and drag (effectively 29.25 kg downforce on the front, 195kg on the rear). When we are driving away from the wind at 50kmh, our incident air speed is now 25kmh, and our aero figures are 0.5 squared = 0.25 times the original downforce and drag (effectively 3.25kg downforce at front and 21.75kg downforce at rear). Now think of a 180 degree corner, taken at 50kmh, and the varying angles of attack during the process would mean downforce is varying somewhere between those two figures. It would make for interesting driving.

The point I am making is that with high sensitivity aero packages we are making ourselves very susceptible to conditions outside of our control. Ive seen aero cars work very well in FSAE, but mainly on perfectly still days. On blustery days, the poor driver is effectively dealing with a highly sensitive random force generator mounted directly behind his head, pushing the car in all directions according to an input (the wind) that he cannot see.

In F1, Indy, etc, you are dealing with much longer cars (less pitch effect) and the higher speeds mean a few wind gusts are going to have a much lesser percentage effect on the incident air speed than at our low speeds. And with our sport we are dealing with much less skilled drivers, so it makes for a much more significant mental load for the driver.

Anyway, enough for now. Youre all welcome to pick the above to pieces, Im sure Ive made some hand calc errors somewhere.

Cheers,

VinceL
06-12-2009, 04:45 AM
Very nice analysis Geoff. I have to say, you are one of the best first-principals-analysis people I have ever come across.

There is one thing from your post that I am not very clear on, maybe you can explain it a bit more. In terms of castor I don't see how castor becomes a problem with aero. You are saying that the castor will unload the inside rear-outside front diagonal, which I agree with. Then you say that the rearward biased aero split will then further unload the outside front, even more than it would have had there not been aero. This is the part that I don't see. In my view the two can be separated. The castor load transfer can be separated from the aero load transfer. So increasing your castor should decrease your understeer, aero or no aero. Transferring the load off of the outside front-inside rear diagonal to the outside rear-inside front diagonal should change you dynamic wheel loads in to the direction of less understeer.

Also, can anyone confirm the 13:87 downforce split? I don't have the Saunders and Wordley paper on me now. (And I don't remember if they quoted a downforce split in it) I think that a 40-45% front downforce split would be about where you want to be with these cars. In my view you can use this to set your mechanical balance towards fixing understeer in slow corners, and then use the aero to keep the car stable in the higher speed stuff. But that's just my opinion, I've never tried it.

Jersey Tom
06-12-2009, 05:51 AM
Geoff-

I had been every bit as skeptical. I have however seen back-to-back track testing, wings on/off/on with a FSAE car. This particular team generally has a driver/vehicle combination fast enough to win autocross or endurance (on pure time), and consistent within a few tenths per lap.

On a competition style course, 1 kilometer long... wings are worth seconds. Sunny days, rainy days, windy days, you name it. 2+ seconds come off the time with the aero on.

Having watched them run now a couple times, I'm 100% convinced.

MH
06-12-2009, 06:24 AM
Just a question: what was the last time a winged car won a major competition? I'm talking about FSAE, FSUK, FSG or FSAE-Australasia. (Don't want to take away anything from Missouri S&T, winning this year's FSAE-VIR)

I have to say that I very much agree with Geoff. I also would like to add that comparing wing-nowing is difficult to say the least. How about setup? I reckon you need a totally different setup of the car for wings than without. If your car was setup for wings and your drivers trained for it, of course it will mean 2+ seconds when you take them off. But is it a right conclusion to say that wings work??

I would even go further. I think a totally different design of your car, think of suspension geometry, tyres, weight ratio etc. has to be taken into account.

I would say it's very difficult to draw such a conclusion. I've heard that on some occasions the winged cars were seconds clear of the rest. However, for example in FSG 2008 the top 3 teams were within 8/100 of a second. Number 4 was 1 second behind and the rest more than 2 seconds. What does that tell you? Setup and drivers (and a bit of luck http://fsae.com/groupee_common/emoticons/icon_wink.gif) Not wings.

cheers.
Miki Hegedus
Delft University of Technology

Jersey Tom
06-12-2009, 08:08 AM
Originally posted by MH:
Just a question: what was the last time a winged car won a major competition? I'm talking about FSAE, FSUK, FSG or FSAE-Australasia. (Don't want to take away anything from Missouri S&T, winning this year's FSAE-VIR)

I have to say that I very much agree with Geoff. I also would like to add that comparing wing-nowing is difficult to say the least. How about setup? I reckon you need a totally different setup of the car for wings than without. If your car was setup for wings and your drivers trained for it, of course it will mean 2+ seconds when you take them off. But is it a right conclusion to say that wings work??

I would even go further. I think a totally different design of your car, think of suspension geometry, tyres, weight ratio etc. has to be taken into account.

I would say it's very difficult to draw such a conclusion. I've heard that on some occasions the winged cars were seconds clear of the rest. However, for example in FSG 2008 the top 3 teams were within 8/100 of a second. Number 4 was 1 second behind and the rest more than 2 seconds. What does that tell you? Setup and drivers (and a bit of luck http://fsae.com/groupee_common/emoticons/icon_wink.gif) Not wings.

cheers.
Miki Hegedus
Delft University of Technology

I feel pretty confident it was a fair comparison, aero on and off.

What do you feel really necessitates a dramatically different setup? If we act like the mass change isn't THAT significant, I'd keep the same relative level of spring and bar front to rear to keep the balance the same (from load transfer). If the aero is set properly, it should just add proportional amounts of load through some usable speed range so there isn't a big difference in low and high speed handling. Furthermore since load variation is relatively low I doubt going softly sprung gives any appreciable amount more mechanical grip. Other than a slight air pressure change, I wouldn't imagine you need much if any setup adjustment to have a car that handles well with a lot of wing cranked on, or none at all.

For that matter I wouldn't do the kinematics or suspension design any differently. Within the cornering load range, the strong performing (bias) tires in this series are very insensitive to camber with regard to peak grip. In my opinion on these cars the thing that's more important than steady state camber is a suspension design that promotes predictable behavior.. ie really minimizing roll- and bump-steer, compliance, etc. This will be the same no matter what. Don't think it would necessitate a tire change either.

Looking at overall competition results may not be telling either. You're trying to evaluate two variables at once. One - wing vs no wing, two - generally how well the rest of the package operates. I definitely agree the second element is much more dominant. Having a sharp team and a generally good package, along with luck, gets you to the top of the pack. Once you're there though, you need something that will kick you in 1st place.

You could have Team A, no aero, that generally runs say a 45 sec autocross run, and Team B that generally runs a 55. Even with an incredible aero package, if Team B only runs a 53 it doesn't appear to be any good. But that still doesn't change that Team A could probably drop down to a 44!

VinceL
06-12-2009, 08:20 AM
Let's say we accept the assertion that wings will give you 2s in autocross. Then let's also say that Geoff is right and it will lose you 30 points in fuel economy. The two cancel out, and at the end of the day you spent a lot of time on something that got you to the place you started from.

Wesley
06-12-2009, 09:18 AM
We run accel runs into and out of the wind, and we're in Oklahoma, mind you, where the wind comes sweeping down the plains regularly at 30-40mph.

So, into the 30mph wind, you'd see a significant impact on time, yes?

Well, the correct answer is about 3 hundredths of a second. Depends on your definition of significant, I suppose.

It also seems, in your comparison, that an aero package adds drag, but you're neglecting body drag, which is a significant fraction of total drag. In fact, I would venture to say that wings only increase frontal area by 2 square feet or so, and only the rear wing at that. In fact, a proper aero package can reduce parasitic drag around the tires.

So you're not gaining that drag, your increasing it, if you have a well designed body/ducts by less.

Sorry, I've made a ton of edits to this post as I've re-read the previous posts.

ben
06-12-2009, 09:47 AM
Originally posted by VinceL:
Let's say we accept the assertion that wings will give you 2s in autocross. Then let's also say that Geoff is right and it will lose you 30 points in fuel economy. The two cancel out, and at the end of the day you spent a lot of time on something that got you to the place you started from.

I think that's probably true. In the heat of competition with inexperienced drivers and other cars on the track on an unfamiliar track layout, have we ever really seen a clear advantage with wings?

The reality is if someone wants to take on the engineering exercise of developing a wing package good on them, but for most teams (and the points tables for most comps don't lie) you can easily win one of these events without wings. That being the case why spend scarce resource (human and financial) on a non-essential system?

Ben

Wesley
06-12-2009, 10:46 AM
Most of the cars with good aero packages have had other reliability issues, been black flagged, or other. You may point out that those wouldn't have happened if they hadn't wasted team resources on aero, but I beg to differ. Spending less time on aero doesn't correct design flaws in other systems, despite having more time available.

This competition is a tradeoff between winning the competition, and trying something new. Often the two don't go hand in hand, but rather the teams that stick to the tried and true excel. However, even the tried and true was new technology at some point.

BrnoMugello
06-29-2009, 01:05 AM
If there is teams that do use wings around here,
what is the average area of your wing?
and what will the average C_L be of a FSAE wing?

Big Bird
07-07-2009, 12:51 AM
Originally posted by VinceL:

There is one thing from your post that I am not very clear on, maybe you can explain it a bit more. In terms of castor I don't see how castor becomes a problem with aero. You are saying that the castor will unload the inside rear-outside front diagonal, which I agree with. Then you say that the rearward biased aero split will then further unload the outside front, even more than it would have had there not been aero. This is the part that I don't see. In my view the two can be separated. The castor load transfer can be separated from the aero load transfer. So increasing your castor should decrease your understeer, aero or no aero. Transferring the load off of the outside front-inside rear diagonal to the outside rear-inside front diagonal should change you dynamic wheel loads in to the direction of less understeer.



Hi Vince,

Sorry to take a while to respond, I don't get much spare time to hang around here much these days.

The caster & FSAE wings issue is something that I have spent a bit of time thinking about, and I haven't come to an absolute conclusion on that one.

My base argument is that we have more load on the back axle than we might realize, due to the drag issue as mentioned. This pushes the back of the car into the ground.

The caster weight transfer you mention is due to the fact that caster forces the inside front wheel into the ground, and lifts the outside front. I can certainly understand your argument, and I've spent a few years thinking about it myself - the caster effect loads the inside front wheel, keeping the front axle more evenly loaded when undergoing lateral weight transfer, and therefore using the tyre load sensitivity effect to our advantage on the front axle. Also, it causes rear axle to be less evenly loaded under weight transfer, therefore overloading and losing grip. More front grip, less rear grip = less understeer.

My question (not my argument, I dunno which way to swing on this point), is how significant is this understeer-correction-due-to-tyre-load-sensitivity effect? Since seeing the TTC data, I'm not as convinced that tyre load sensitivity is a big thing with our tyres. If it is not great, is there an opposing (maybe dynamic) effect from lifting our outside front that is overwhelming any caster advantage? I know it sounds odd, but I have seen wing cars struggling with understeer that are entering slalom corners with the outside front visibly off the ground. I just can't believe that is a good thing. I've also known of situations where wing cars have increased their initial turn-in bite by reducing caster (to zero in the case I had mentioned above). So it is sort of doing my head in a bit.

Maybe the two effects (caster and downforce distribution) should be isolated from each other, and treated seperately as you mention. I can see that argument too.

Jersey Tom and Wesley, thanks for the responses. I've seen results that indicate that a well set up wing car can be faster than a non-wing car. I'm certainly never going to argue that it is definitely not the case. I just wonder (often aloud) whether for example points gained through track speed are more than those lost through cost and fuel used. And whether resources used to chase aero points (non-critical vehicle improvement), in some cases could have been spent better elsewhere (base vehicle wasn't 100% in the first place). Ben hit upon the same point, and we've shared a few conversations along these lines over the years.

I might have seemed an outright cynic, and I know I said so in my post. I'm not, and in fact when I saw the UTA car at FSAE California 06 I thought it looked like a pretty balanced package. But I rarely see arguments for wings that seem much more than sales pitches (highlight advantages, ignore or gloss over disadvantages). And many of the examples I have seen have tended towards excess and seemed to lack a little balance in my opinion.

Anyway, jury is out in my mind, and my full respect to those that have fought through the process to make those things work.

Cheers,

Red Mist Racing
07-07-2009, 03:16 AM
Upright mounted pushrods allow the caster effect on WT to be tuned quite easily; reducing or increasing the resulting non-dynamic steer induced weight transfer. I wrote a program to model all of these effects. Playing about with the longlitudinal attachment position relative to the steer axis yields interesting results.

A lateral offset, of the pushrod attachment to the upright, from the steer axis also will result in a ride height change, allowing front ride height to be reduced with large steer angles, moving the front wing into ground effect and moving the centre of pressure forward.

bob.paasch
07-07-2009, 04:05 PM
Originally posted by Big Bird:
I've seen results that indicate that a well set up wing car can be faster than a non-wing car. I'm certainly never going to argue that it is definitely not the case. I just wonder (often aloud) whether for example points gained through track speed are more than those lost through cost and fuel used. And whether resources used to chase aero points (non-critical vehicle improvement), in some cases could have been spent better elsewhere (base vehicle wasn't 100% in the first place). Ben hit upon the same point, and we've shared a few conversations along these lines over the years.
Cheers,


Nice post as usual, Geoff. I think your point about points gained through track speed verses those lost through cost and fuel is the critical point. The recent competition in California had some of the very best aero cars around. Here are the top 10 FSAE California autocross cars:

1) RIT (aerodynamic undertray) 150 points
2) Kansas (wings) 147
3) Missouri S&T (wings) 144
4) Maryland (wings) 143
5) Washington (wings) 133
6) Oregon State (non-aero) 130
7) UT Arlington (wings) 130
8) Western Washington (non-aero) 126
9) Oklahoma (wings) 123
10)Cal Poly Pomona (non-aero) 115

So the top 5 autocross teams, and 7 out of the top 10 ran some sort of aero. Looks like a big advantage for aero. Endurance was similar, with the three fastest times coming from aero cars: Maryland, Kansas and RIT, with OSU the best non-aero car at 4th, 10 points down from Maryland. But OSU won combined endurance/economy by 28 points, and OSU (running a CRF450) was 1st overall in the dynamic events. This year's reality is that fuel economy is worth 100 points, and the fuel economy gap from OSU to the aero cars was huge: 34 points over Kansas, 41 over Oklahoma (both running Apes), 76 over RIT, 77 over UT Arlington, and 89 over Maryland. To be fair, much (most?) of the gap is engine selection, OSU also had a 53 point advantage in fuel over non-aero, 600/4 WWU. But pulling from the "What are we designing/building" thread, the gap in fuel from 1st to 5th was 41 points. That 1-5 gap is the biggest of any event at FSAE Cali.

What will be interesting is to see if any of the lightweight single teams try aero, and what impact it has on their fuel score.

Scott Wordley
07-07-2009, 05:05 PM
A very interesting analysis.

It is also interesting to see Cal Poly Pomona on that list and in the non-aero categorgy, being one of the first teams to run a serious wing package and the first team to win with them at Formula Student in 2000.

Also, I dont think I'm letting any cats out of the bag but thought I would mention that Monash is going to a single in 2010 and that we will be designing, building and testing a wing package for this car. I dont think it will take long for most teams to move in this direction. As you have illustrated the change in fuel scoring is virtually a death knell for 4-cylinder cars, which i personally think is a shame. It was nice seeing the 4s, singles, turbos and winged cars all going head to head with a similar chance of winning. Was any justification given for the rule change? Was it a green washing exercise?

Scott

bob.paasch
07-09-2009, 09:50 AM
Originally posted by Scott Wordley:
As you have illustrated the change in fuel scoring is virtually a death knell for 4-cylinder cars, which i personally think is a shame. It was nice seeing the 4s, singles, turbos and winged cars all going head to head with a similar chance of winning.
Scott

I respectfully disagree. I don't believe the fuel scoring change is a death knell for the 600/4s, nor is it for wings. In either case, teams are going to have to optimize their systems for an endurance/fuel economy event that is weighted differently than in the past. In my experience, many engine teams in the past (including mine) would tune for maximum usable power, then back off their maps just enough that they didn't go over 26 liters/100 km. Now teams might have to trade off some performance for economy. TU Graz showed what was possible last year at FSG, posting a very competitive endurance time while using only 3.15 liters of fuel. At Detroit they used 3.17 liters. All three US events this year were won by 4 cylinder cars.

Another interesting tidbit is the fuel economy scoring at FSG09 incorporates a time factor. The best fuel economy score might not go to the team that uses the least fuel, but will go to the team that optimizes performance and economy. In the overall scoring, they essentially count the endurance time twice.

Winged teams are going to have to maximize downforce while minimizing drag. I already see teams readjusting their wings for minimum drag for the acceleration event. I imagine we will now see more readjustments between skidpad/autocross and endurance.

In the end, FSAE/FS is an engineering competition, not a race. The scoring change just changes the target a bit, now teams will have to consider economy during design, and will have to do a bit more analysis and testing on settings that are both fast and efficient. 4 cylinder teams will face some challenges that they did not face in the past, but good engineering is still going to win.

Nice Vans
07-09-2009, 10:46 AM
Originally posted by Big Bird:
I rarely see arguments for wings that seem much more than sales pitches (highlight advantages, ignore or gloss over disadvantages). And many of the examples I have seen have tended towards excess and seemed to lack a little balance in my opinion.
Cheers,

Unfortunately, that seems to be all the design judges want to hear - "How much downforce do ya get???" is the first question. There's so much more than that to aero. I also agree that you must really examine the disadvantages to the system.

Scott Wordley
07-09-2009, 08:20 PM
Bob,

I think teams have been trading off performance for economy in endurance event for a long time. I remember Chalmers using 3.0 L in the Aussie endurance way back in 2003 with quite a fast car. They won fuel economy from memory, even beating out the singles!

Like wise I think wing teams have been working to increase their lift to drag ratios for a long time. We have always had low drag acceleration event settings for our wings, which involve turning out all the flaps to zero degrees. Max downforce, with a front bias setting is used for skid pan (get it to point and drive off the throttle), while endurance and autocross is slightly less downforce and drag and a more neutral balance.

Back on the topic of singles versus 4s. Its an interesting exercise to recalculate the scores from past events based on the new scoring for fuel. I would particularly suggest looking at comps where pointy-end single teams like RMIT and Delft have competed to their full potential. Even the using a "best case" scenario of 3.0 L for a fast four cylinder, you are giving up a lot of points on fuel. Take those points and figure out how much FASTER than RMIT/Delft etc you have to go in order to make up that deficit. Its scary, trust me.

We made the call that we wouldn't be able to beat them on that basis, but maybe someone else can? It should be interesting regardless, at least until a new equilibrium has been found. I just sincerely hope that that mix does include 4s, it would be so much more boring without them, and eliminate a whole raft of interesting "macro" design choices and solution trails. Like I said, I thought the comp was well balanced with the previous scoring (which has weathered the last 20 years without serious change, until now).

But at the end of the day, If you can't (or don't think that you can) beat 'em, then join 'em!

Erich Ohlde
07-09-2009, 10:09 PM
sticking my nose in here. single vs 4 cylinder vs bitch motor (ape...yes it is a bitch) and fuel economy vs power output.

This all comes down to Engine tuning. I actually rather like the new rule as it pushes teams to really develop good engine calibrations rather than the (run that sucker lean!) method.

I would be very interested to know what Oregon State U did as far as time spent tuning the fuel/ignition map and what facilities/equipment were used (anyone from Oregon-SU care to pipe in).

Fuel economy is almost always put on the back burner and it should not be (2005 24 hrs of le mans anyone?) Especially now the new endurance/economy method will force teams to re-evaluate engine calibration strategy and no this does not mean at all that the car will be slower because the engine makes less power. I do think however that the new economy rules should take into account raw time when calculating the economy scores.

Aero throws a wrench into the equation. With more downforce comes more cornering speed, less braking and more time at or near WOT....theoretically. No team, I repeat, NO TEAM is close enough to the edge of engine tuning for the aero to have a major impact on fuel economy...

Two questions in closing:
What strategy do you use for your rev-limiters (ignition cut/retard or fuel cut/retard)?
Do you cut fuel at off-throttle points above a certain engine rpm?

I hope you enjoyed my rant.

Scott Wordley
07-09-2009, 10:52 PM
Erich,

I do agree that the rule change will focus increased attention on fuel economy.

But, a properly tuned 450cc single should be more efficient than a properly tuned 600cc 4.

Likewise a properly tuned 600cc 4 should be more powerful than a properly tuned 450cc single.

If you accept that (and focus on the top teams, who drive the trends for the whole comp), then it is not just down to tuning, it comes down to how your engine choice affects your ability to score the maximum points. If there is a clear benefit by going in a certain direction, then designs will converge in that direction.

Also, I don't have any data to support this, but running an aero package will have some impact on fuel economy, how much I'm not sure. Its hard to test experimentally particularly given driver/tire/condition variation.

I agree that most teams put fuel economy on the back burner. The teams that win events don't leave anything on the back burner. I think the top teams (Monash not included) are pretty close to the edge in terms of engine tuning currently. I dont think they sacrifice much, if any power to be more efficient, they just do it a lot smarter. There is plenty of times on-track when u dont need fuel but the lazy option is to keep pumping it in there any way "just in case" and because its easier than taking it out.

That said, it can be an expensive process finding out how lean you can go, and when.

Erich Ohlde
07-09-2009, 11:05 PM
Originally posted by Scott Wordley:
Erich,
...


If you accept that (and focus on the top teams, who drive the trends for the whole comp), then it is not just down to tuning, it comes down to how your engine choice affects your ability to score the maximum points. If there is a clear benefit by going in a certain direction, then designs will converge in that direction.


Only when engine tuning is perfect for the different engine choices. For every team out there the engine tuning is good for driving the car but no where what it could be for driving the car and saving fuel.

bob.paasch
07-15-2009, 12:06 PM
Originally posted by Scott Wordley:

Back on the topic of singles versus 4s. Its an interesting exercise to recalculate the scores from past events based on the new scoring for fuel. I would particularly suggest looking at comps where pointy-end single teams like RMIT and Delft have competed to their full potential. Even the using a "best case" scenario of 3.0 L for a fast four cylinder, you are giving up a lot of points on fuel. Take those points and figure out how much FASTER than RMIT/Delft etc you have to go in order to make up that deficit. Its scary, trust me.

We made the call that we wouldn't be able to beat them on that basis, but maybe someone else can? It should be interesting regardless, at least until a new equilibrium has been found. I just sincerely hope that that mix does include 4s, it would be so much more boring without them, and eliminate a whole raft of interesting "macro" design choices and solution trails. Like I said, I thought the comp was well balanced with the previous scoring (which has weathered the last 20 years without serious change, until now).

But at the end of the day, If you can't (or don't think that you can) beat 'em, then join 'em!

I think we will all have a lot more clarity on this issue by the 10th of August. In three weeks, the 2009 Formula Student Germany is going to feature some of the best singles against some of the best fours.

450/singles:
RMIT (1st, FS 07)
TU Delft (1st FSG 08)
ETS (3rd, FSAE Michigan 09)
OSU (2nd, FSAE California 09)

600/fours:
Stuttgart (1st, FSAE Australasia 08, 1st, FS 08)
UWA (1st, FSAE Michigan 08)
TU Graz (1st, FSAE Michigan 09)
RIT (1st, FSAE California 09, 2nd, FSAE Michigan 09)
TU Braunschweig (2nd, FSG 08)

BTW, Oregon State made the decision to go to a 450 single before the 2009 rule changes were announced. Our decision was based primarily on project management considerations; we felt a 450 motocross engine simplified powertrain development. Our conservative analysis of the competition point scoring showed a possible slight disadvantage to the single under the 50 point fuel scenario, but we felt the engine system simplification worth it. Needless to say, we are very pleased with our decision so far.

bob.paasch
07-15-2009, 01:29 PM
Originally posted by Erich Ohlde:

I would be very interested to know what Oregon State U did as far as time spent tuning the fuel/ignition map and what facilities/equipment were used (anyone from Oregon-SU care to pipe in).



Four months on the engine dyno, but most that was on intake/exhaust development and cold/hot starting. We also have a pretty good GT Power model. But the best tool we had for fuel economy tuning was the Motec M400 ECU and ACL data logger, and a good Lambda sensor. One thing about the single, you only need one Lambda sensor, so you can get a good one. http://fsae.com/groupee_common/emoticons/icon_smile.gif http://fsae.com/groupee_common/emoticons/icon_smile.gif

Last year I was a design judge at Formula Student Germany. In my design queue there were 8 teams. Only 2 had done development work on their fuel consumption. I expect that will change this year.

Wesley
07-15-2009, 07:28 PM
We got asked about BSFC comparisons between the F4i and the Aprilia (after switching this year) and were caught flat footed without the data - we actually have done very little actual fuel consumption analysis. We've found, in most of our maps, that the majority of the fuel economy is picked up at partial throttle. We have developed good partial throttle maps based off of logged O2 data, but that data is incomplete.

I really wish we had access to an exhaust gas analyzer/dyno. There is so much economy we've left on the table with ignition strategy alone, and a lack of dyno time has made that difficult to even approach. Considering our engine only ran on a dyno 3 times, two of those on a 1500HP superflow, we did ok.

Combustion pressure sensors, exhaust gas analysis, all these things are going to start coming into play.

Erich: Our rev limiters are ignition cut, simply because it's a little softer on the cylinders, as well as our shift cuts. I advocated doing some testing with both, but time cut that out.

We also do employ fuel cut at off throttle, I don't have the map in front of me, but I think it's around 6,000

Additionally, we haven't noticed an economy difference with wings vs. without, but we haven't done any testing specifically oriented towards it.

Also, I agree with Erich in that most teams, even those with a good engine tune, don't have an engine tune that really has economy in mind. I know that with a big enough radiator/fan, f4i's will run in the 16's through a couple endurances (and use about .75 gallons, we accidentally did it in 2007 Akron)

I hope my team delves into the fuel economy issue this year, because we completely forgot to mention it to the judges, and it was one of the reasons we switched to the Ape in the first place.

Scott Wordley
07-09-2012, 06:37 AM
Some of our team were reading through this old thread today in preparation for FS UK and considering the current discussions around aero I thought it might be timely to bump it back to the top.

Its an on-going discussion about the potential usefulness of wings in FSAE, which goes back 10 years now.

Interesting to see how perceptions have changed and our approach to this particular issue and the competition as a whole has evolved over that period.

ZAMR
07-09-2012, 12:24 PM
I think its pretty funny that the first posts were about making a winged car under 500lbs.

And I'm not sure about the rules back then, but I think the wings have gotten bigger? The downforce to weight ratio for the cars+driver ought to have increased by a factor of at least 1.5.

-Zach

JulianH
07-09-2012, 03:18 PM
Yes, the envelope of the allowed aerodynamics package was increased for the 2011 season.

Now you are allowed to place aero parts about 30cm behind the rear wheel which makes it a lot easier for undertrays and rear wings.


We will see how the 2012 season will play out. So far the winged cars are two out of two http://fsae.com/groupee_common/emoticons/icon_smile.gif

Additionally, the weight is of course reduced. I think GFR is in the range of 320-330lbs. Our winged e-car will be around 365lbs.

Dunk Mckay
07-10-2012, 06:17 AM
If you really want to revise the discussion I will put in my humble and honest opinion that a proper full body tunnel will outwigh wings any day and should be the first priority with aerodynamics. Then depending on the location of your "centre of downforce" (don't ask) contemplate a small wing for aero balancing. If you've really done your job well I would hope for a relatively forward CoD, so a small rear wing that will not only create a small amount of additional rear downforce and allow you to balance you aero, but can also enhance you're underbody performance. A personal preference would be to have two seperate small rear wings above the exit of the rear of you tunnel(s), one on either side, so that they are running in relatively clean air, and not in the turbulence behind the central chassis, driver and engine. Of course if you can't devise a way to mount these that isn't heavier than having as ingle wing then go single, lateral adjustment is not needed, if it is you're either being very very clever (active aero steering?) or have something fundamentally wrong with the dynamics of your car.

ZAMR
07-10-2012, 09:01 AM
Originally posted by Dunk Mckay:
If you really want to revise the discussion I will put in my humble and honest opinion that a proper full body tunnel will outwigh wings any day and should be the first priority with aerodynamics. Then depending on the location of your "centre of downforce" (don't ask) contemplate a small wing for aero balancing. If you've really done your job well I would hope for a relatively forward CoD, so a small rear wing that will not only create a small amount of additional rear downforce and allow you to balance you aero, but can also enhance you're underbody performance. A personal preference would be to have two seperate small rear wings above the exit of the rear of you tunnel(s), one on either side, so that they are running in relatively clean air, and not in the turbulence behind the central chassis, driver and engine. Of course if you can't devise a way to mount these that isn't heavier than having as ingle wing then go single, lateral adjustment is not needed, if it is you're either being very very clever (active aero steering?) or have something fundamentally wrong with the dynamics of your car.

What is your reasoning behind using a tunnel only? You can achieve much more downforce with some decent wings with a very high Cl. Also, designing a proper undertray/tunnel/diffuser is WAY harder than everyone thinks. Creating and funneling vortexes under the car in a consistent manner is difficult.

Wings are becoming lighter every year, down to about 15lbs for an entire wing package. When you look at downforce to weight ratio, wings win. Also if you do a careful yaw analysis you can see at what speed your wings will increase your yaw rate (This is a very fun exercise).

-Zach

Dunk Mckay
07-10-2012, 04:28 PM
Originally posted by ZAMR:
What is your reasoning behind using a tunnel only?

Fuel efficiency = 100 points. And, while I'm a little dubious about underbody aero being dozens (or hundreds) of times more efficient than wings as Claude claims in the quote below (at least not in formula student) it is still a very significant factor difference.


Originally posted by Claude Rouelle:
Many students seems to focus and the front and rear wings while in fact the underwing efficiency (if the underwing is well designed, rigid and well attached to the car) is several dozens (if not hundreds) times bigger than the front and rear wings efficiency. Basically for a given car the drag penalty of the underwing is very small for a huge amount of downforce.

Link: http://fsae.com/eve/forums/a/t...48/m/91020556151/p/1 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/91020556151/p/1)

Z
07-11-2012, 04:52 AM
Originally posted on page 2:
Bam Bam (this is Roan, the last post was from Scott), you're an idiot...
...
But you're not just an idiot, you're obviously....
...
and you're more of an idiot than I first thought....
...
and maybe if you took your hand off your dick and actually bothered learning something...

Roan Lyddy Meaney
Monash FSAE Wingmen
Geez, seems I've missed this eloquent and erudite thread on all things aerodynamic.... http://fsae.com/groupee_common/emoticons/icon_biggrin.gif
~~~o0o~~~

Anyway, there have been several posts suggesting that the "Wings or not?" question should be answered soley by checking the numbers.

Unfortunately, the majority of the "anti-aero" posts (ie. the majority of posts on this thread) seem to be based on the argument that "not enough other teams are doing it yet". This then backed up by "it looks like a heck of a lot of work", and "it will cost a lot in Fuel Economy", and, etc, etc. Not many numbers in those arguments.

Admittedly, much of this thread dates back to 2003. But then again, blind Freddy knew that aero wins races back in the 1960s.

I will save the numbers for later (if anyone is interested), but briefly for now. Any team that wants to use minimum Fuel in FSAE should look first to aero. Two reasons.

1. Low fuel consumption comes from a streamlined (ie. low aero drag) car. This was known back in the 1920s. Furthermore, high downforce does NOT imply high drag. Think underbody or "ground effects" aero (as noted in above posts). And... err..... wheel-pods! Or, both together = DeltaWing!

2. A high enough downforce car corners fast enough that it wins AutoX/Enduro without ever accelerating hard, and without ever touching the brakes (except at beginning and end of event). WOT acceleration burns lots of fuel, and braking then throws it away. Instead, think roller-coaster with 3G minimum lateral for this year, 4G next year, and so on until the rules are changed.

Z

STRETCH
07-12-2012, 03:42 AM
Originally posted by Z:

2. A high enough downforce car corners fast enough that it wins AutoX/Enduro without ever accelerating hard, and without ever touching the brakes (except at beginning and end of event). WOT acceleration burns lots of fuel, and braking then throws it away. Instead, think roller-coaster with 3G minimum lateral for this year, 4G next year, and so on until the rules are changed.

Z

Z,
Are you suggesting that a car with more downforce (i.e. faster in corners) burns less fuel? Because I'm afraid reality is quite the opposite. Imagine being power limited everywhere, you'd use a hell of a lot more fuel than coming off throttle for corners...

As for tunnels vs. wings, a good floor can develop just as much downforce as a pair of wings, and at >10x the efficiency, personally I think its a no-brainer! But I can understand why teams resort to wings (sometimes instead) as they are probably easier to comprehend and optimise their geometry in CFD. Plus they aren't ride height sensitive which isn't a bad thing on a bumpy FS track. Just don't mount them between bill-board sized endplates!

Z
07-12-2012, 04:50 AM
Originally posted by STRETCH:
Z,
Are you suggesting that a car with more downforce (i.e. faster in corners) burns less fuel? Because I'm afraid reality is quite the opposite. Imagine being power limited everywhere, you'd use a hell of a lot more fuel than coming off throttle for corners...
Lee,

Think it through.....

You only have to go fast enough to win. That is, go faster than all the other cars, which are either non-aero, or air-braked. I figure only steady half-throttle of a half-max-power engine is needed (ie. 1/2 x 1/2 x 120hp = ~30hp).
~~~o0o~~~


As for tunnels vs. wings...
An efficient aero-underbody does NOT need "tunnels".

Think it through, boys and girls... http://fsae.com/groupee_common/emoticons/icon_smile.gif

Z

ZAMR
07-12-2012, 08:08 AM
Originally posted by STRETCH:


As for tunnels vs. wings, a good floor can develop just as much downforce as a pair of wings, and at >10x the efficiency, personally I think its a no-brainer! But I can understand why teams resort to wings (sometimes instead) as they are probably easier to comprehend and optimise their geometry in CFD.



Show me an FSAE underbody that makes 180lbs of downforce at 30mph and I'll believe you.

-Zach

Dunk Mckay
07-12-2012, 08:24 AM
Originally posted by Z:
An efficient aero-underbody does NOT need "tunnels".


Loving the quotation marks on "tunnels". I'm guessing that means you are differentiating between huge big ground effect wing(s) and a flat tray with long and narrow (relatively speaking) tunnels. Either way you need a surface that approaches the ground and some sort of method (there are many ways) of isolating it from any air that could be sucked in from the sides and allow the pressure underneath to increase.

Rex Chan
07-19-2012, 11:31 AM
Hey there Z!

Any news on those numbers?

And what do you think about the (Monash) wings I'm retrofitting to the 2011 Melbourne car? Worth it? <needing motivation to work on it>. The 2011 car was a heavy (250kg) 4 cylinder spool car. With big Monash wings, it will (hopefully) be like a fatter version of the Monash 2010 car.

The wings made 45kg in the wind tunnel, and hopefully more on track.

Z
07-21-2012, 05:18 AM
Originally posted by Rex Chan:
... what do you think about the (Monash) wings I'm retrofitting to the 2011 Melbourne car?
Rex,

I guess the above is just for testing? If so, then good, the more testing the better (and usually fun!). ~50kg on a 250kg car (+driver) won't make much difference, but always good to put numbers to these things.

I'm not sure about the spool, especially if you start to develop serious downforce (could be hard work unloading the inner rear tyre). For a serious aero car I'd suggest an open diff and more rear weight (say ~40F:60R).

If the above is for an aero-test-car, then you might also want to experiment with undertrays. Try fitting the rear wing down low, just behind the undertray, and measure changes in pressure at various underfloor positions, with and without the wing. IMO this is where the biggest gains can be found. If this is all experimental, then don't worry about making it pretty. Just use plywood, Maxbond, duct tape, whatever. http://fsae.com/groupee_common/emoticons/icon_smile.gif

Z

Rex Chan
07-21-2012, 05:28 AM
Yep, just for testing. UNdertray you reckon? Not sure I'll have time, but I suppose if we get good data from just the wings, it might help motivate more work.

Oh, so is *that* why all those Euro cars have such low rear wings. STupid me didn;t make the connection with the undertray.

JulianH
07-22-2012, 09:08 AM
2012 seems to be a good year for the wing-cars.

They took Michigan, Lincoln, Silverstone and Austria, so far. Let's see what Germany brings.

I think, what we saw is "a lot helps a lot". In Formula Student, the downforce seems to help more than drawbacks like highered drag or raised CG.


Z, I totally agree with the "fast corners, low acceleration" to win the fuel event. But looking at the drag numbers, I don't think, that achieving a low drag vehicle will give you the edge. There are much "richer fields" to save energy. With cD*A of 0.4-0.5 for a non-winged car, the amount of energy that will be destroyed due to drag is pretty low. GFR used aweful less fuel in Austria with the high-drag setting while destroying everything on track, I think they showed the way.

Concerning the undertray vs. wings stuff. Of course you can create even more effective undertrays compared to the "tunnels" that are run right now, but I am quiet sure that no undertray in FS will ever create the downforce rates of some bad-ass wings. In addition to the undertray, we tested some of this "lowered rear wings" to improve the undertray in the wind tunnel, it didn't work in basically every location. The air is just too turbulent behind the front wheels if you are not "up in the air".

For fun I also tried some of your "brown go kart" features in CFD to see if it is really possible to get a car which is able to run on the ceiling below 80kph. Most of this stuff didn't work at all and therefore we didn't build anything of the "wheel wings" or so.



Cheers

Dunk Mckay
07-22-2012, 11:45 AM
Originally posted by JD944:
Concerning the undertray vs. wings stuff. Of course you can create even more effective undertrays compared to the "tunnels" that are run right now, but I am quiet sure that no undertray in FS will ever create the downforce rates of some bad-ass wings. In addition to the undertray, we tested some of this "lowered rear wings" to improve the undertray in the wind tunnel, it didn't work in basically every location. The air is just too turbulent behind the front wheels if you are not "up in the air"

Then you need to find a way of reducing that turbulence, the easiest way is at present under much dispute, regs wise. But if you go for the small low "dual" rear wing concept I have suggested in the past, then there is an easy way to get lots of nice smooth air going over low rear wings to enhance an undertray to great effect.

I do hope someone tries it. I've heard talks of design restrictions (the academic staff want us to polish a turd) for my team next year. I'm finally at the point where I think I have enough knowledge and know how to design the aero car they've been wanting for a while, and they decide that we can do better by rebuilding the same car as the last 4 years but just a bit better. Oh and with less money. Fools!

JulianH
07-22-2012, 12:04 PM
We had little wind tunnel time, sure but even without rotating wheels it is very difficult to get rid of these turbulences.. Maybe a lot of CFD work can do it but we tried your "low dual" rear wing and got no significant effect that would legitimate the manufacturing effort and the additional weight.


Concerning your academic problems: Don't care about them. It doesn't matter what the academics say. Do what you want. Do what you think works best. That's the spirit of FSAE...

Dunk Mckay
07-22-2012, 01:44 PM
Originally posted by JD944:
Concerning your academic problems: Don't care about them. It doesn't matter what the academics say. Do what you want. Do what you think works best. That's the spirit of FSAE...

We got our best results ever a few years ago that way I think (before my time). Although I'd be risking my nuts if I told you how and why, so I'll keep schtup. Suffice to say that their controls are much tighter now so it won't be possible again.

I still maintain that the small low rear wings can be done, there's a trick to it, but I'm gonna keep that one to myself for now. If I manage to get it done next year you'll all see and go "Oooh, nice!" If not then I'll tell you my idea and you'll either go "Ooh, nice idea!" and try it yourselves. Or you'll say "yeah, we tried that too and it didn't work at all." There are some mistakes you just have to make for yourself, because no matter how much your told otherwise, unless you see it failing first hand, in your mind it's always going to work.

EDIT: I should add that Formula is also our main thesis for our final year (bachelors) or even final two years (masters), counting for a very large part of our degree. If we don't do what the "man upstairs" wants, then we get bad degrees.

Z
07-24-2012, 06:38 AM
Originally posted by JD944:
Concerning the undertray vs. wings stuff...
I am quiet sure that no undertray in FS will ever create the downforce rates of some bad-ass wings.
JD944,

IMO undertrays and wings are both just surfaces that interact with the air flow. Except that an undertray is the first step in making a REALLY BIG "bad-ass wing" (ie. with plan area of the whole car). Note that high-lift wings benefit from slotted flaps. So do high-downforce undertrays.

Your testing/modelling of undertrays may not have been successful, but that is not "proof" that they don't work. My testing/modelling suggest that they do work, and very well indeed! As you noted, it is a good idea to control the turbulence from wheels, etc. (although this is not difficult). I think Dunk is on the right track.

Z

Dunk Mckay
07-24-2012, 07:01 AM
I'm currently tussling with the interference in airflow that arises from turning wheels (not spinning, turning, to be clear). Integrating a turning plane with the upright works fine for trapping the pressure underneath so to speak(see Z's beam wing sketch for clarity). But it doesn't change the fact that the front of one of the fron wheels swings inwards and the rear of the opposite wheel does the same, this significantly narrows the gap air can enter under the car.

Some clever wheel pod design can reduce this effect somewhat by redirecting air past one of the wheels, but the other side is still going to struggle a little. Any body have any clever (or dumb to be honest) suggestions/workarounds?

Z
07-24-2012, 07:28 AM
Originally posted by Dunk Mckay:
I'm currently tussling with the interference in airflow that arises from turning wheels...
Dunk,

"Turning" = steered?

Briefly (it is after midnight), I think the bigger issue here is that the wind approaches the front of the car at a large angle, maybe, ~45 degrees from straight ahead (ie. from the direction the front wheels are pointed). That is, the airflow is effectively curved. More correctly, the air is stationary, but the car is travelling on a curved path.

I reckon most CFD models ignore this effect. Wind tunnels are incapable of modelling it (they only do straight flow).

But not really a problem, IMO, for the right design of undertray...

Z

PS. Consider Monash's huge front end-plates, as the car goes around a hairpin!

Dunk Mckay
07-24-2012, 08:26 AM
Err, yeah sorry, steered. I knew there was a proper word for it. I think the heatwave here is frying my brain.

I guess I can be a bit too CFD minded sometimes.

So let me think... (insert grinding gear noises here).

If the under tray was divided down the length of the car into separate ducts by various fins/internal skirts, whatever you want to call them, with the outermost ducts further out than the internal distance of your front wheels.
They remain relatively untouched when in a straight line as they are behind the front wheels, except for any air you can pull through with a good diffuser section that is (diffuser section that narrows between the rear wheels of course, but as it is expanding upwards this can all be compensated for.
But when cornering, the outside one recieves air "scooped up" by the upright mounted body work (big turning end plate), and the inside one recieves air directly from the outside of the car, maybe also some flow redirected slightly by the wheel as well. I'm thinking cleverly designed brake ducts and carbon hub caps that could direct air from above the underwing out around to the lesser used side in cornering.

Ok, so that last part might be a bit excessive. That hard part will be getting any useful test data. The only real way is to build it, stick it on a car and run some pressure sensors and tassles.

Has no one made a CFD program that can simulate stationary air and moving objects? I wonder if you could make a really simple "wind cylinder" that spins car models on the end of big arms and looks at the air flow around the model? Easily variable corner radius, just slide up and down the stick. Surely if it were practical someone would have done this before. Perhaps the airflow is too disturbed after the first pass, also any significant sideways disturbances are going to have some effect when you get to the other side, unles you have a big piller, but then you're too close to a wall...

Hmmm... interesting.

Z
07-25-2012, 05:33 AM
Originally posted by Dunk Mckay:
I wonder if you could make a really simple "wind cylinder" that spins car models on the end of big arms and looks at the air flow around the model?
...
Surely if it were practical someone would have done this before.
Dunk,

And indeed they did! Right at the beginning of this great big aero adventure the Lillienthal brothers, Otto and Gustav, used the above sort of mechanism to discover that thin curved plates made much better wings than flat plates. These "arcuate", or "sail-like", aerofoils are very efficient.

Otto wrote a book in 1889(?), "Birdflight as the Basis of Aviation", that is a fascinating story about two farm-boys who decide that they are going to fly. Any students wanting to push the envelope on FSAE aero could learn a lot from this book. It is basically about taking a "big picture" view, doing the fundamental calculations, learning from nature, perserverance, etc., etc.

Unfortunately, in 1896(?) after ~2,000 glider flights Otto crashed and died. Nevertheless, his and Gustav's work inspired many similarly minded young men, including the Wright brothers, and the rest is history.
~~~o0o~~~

... any air you can pull through with a good diffuser section ...
VERY IMPORTANT! You do NOT have to have a high mass flow of air under the car for good downforce.

Joe Katz, on page 50 of his book "Race Car Aerodynamics", says,
"There are those stylists who make every effort to block the flow under the vehicle
and those brave few who try to push as much air as possible under the car.
... if high downforce is sought then the latter approach is inevitable."

NOT TRUE! And, surprisingly, on page 184, Figure 6.7 D, Di, & Dii, Katz actually explains how to get high downforce with minimal airflow under the car.

All this is easier to explain with a few pictures. When I've finished draining the swamp (literally!, and in the middle of this cold, wet, and miserable winter!), I'll see what I can do.

Z

Kent Slaughter
08-29-2012, 11:58 PM
Hi all, long time silent, I designed a (spool) diff for UQR in 2007, had a car accident, now I'm designing a wing kit for Melbourne. No one I can find in the real world knows anything (and it's more than a little late in the year!) so can you guys help? I've been reading lots but I can't find anything about this.

https://www.dropbox.com/s/l9rshmsceb12dv9/wing.png

That is a 3 element wing with 2 elements at 50 to the ground. It isn't my actual proposition, but I wanted to try a high angle of incidence to confirm my intuition that (*) wings with high incidence can only provide "downforce" normal to the wing surface - ie drag, and not much downforce.

Yes, I was right. But, the best I can design (with a good angle of incidence) gives 8 kg of downforce, nowhere near the required 100kg to ensure the inside wheel is loaded through a corner. Or, I suppose it doesn't need to be. But still, we need ~150kg to generate 0.5G of downforce. Are my targets too high, or how can I reach them?

Thanks, and sorry if I'm missing a post that I should have found.

Ben A
08-30-2012, 01:28 AM
What wing profiles do you use?

First i would chose a wingprofile for low speed and then go with that and add. Some more wings.

Lorenzo Pessa
08-31-2012, 03:28 AM
Originally posted by Kent Slaughter:
That is a 3 element wing with 2 elements at 50 to the ground.


At a brief look, I think the main (first) profile has a too big AoA.

I think you can find useful looking for aeronautical flaps (I found useful to have a look at Abbott).
Don't forget that aeronautical airfoils you can find easily are designed for low drag.

Scott Wordley
08-31-2012, 07:32 AM
Kent, I would be careful when making big assumptions based on little data and intuitions.

There are many reason why that design might not have made much downforce, and the one you mention is just one of them.

How big was the wing that you tested anyway?

Diving straight into a complex multi-element design is a bit dangerous. Better to run some CFD on simpler and well documented single element profiles first and build from there. Compare with the published data as you go, and refine your model and techniques, and check your sensitivities to turbulence models, domain size and mesh refinement etc.

Regarding the high angle of attack of the flaps, you are correct that the flaps themselves will not generate much downforce in and of themselves. But what they do do is drive the circulation, and pump heaps more air under the main plane, and that is where the downforce is actually generated.

So think of it as a system with each part affecting the other parts. This philosophy (perhaps sadly!) extends beyond just the wings. They interact with the rest of the car quite strongly.

So once you get your wing "perfectly optimised" be sure to add it to the car and see how much performance is lost, and then start the process all over again http://fsae.com/groupee_common/emoticons/icon_wink.gif

Racer-X
09-10-2012, 05:07 PM
I think if you do it right as in keep it light and not ruin the CG they can be effective. I can't imagine under trays do a lot for us at the speeds we see though. Our last one made 20lbs of down force at 40mph and weighed 12 pounds... But what do I know I'm the engine guy.

ANMF1
10-25-2012, 11:12 PM
i have a question about 2D Airfoil design. There are a few methods - Airfoil optimisation/Inverse Design ETC. Does every FSAE team out there write their own code for airfoil design or are there publicly available codes? (even PROFOIL is not available). Writing a code for inverse airfoil design will take at least a month or two. I presently have 3 airfoils which I want to use for a optimised airfoil and am stuck with only one option- write my own code? Considering the fact that I have to design the complete package by January, is there any way out?

Francis Gagn
10-26-2012, 07:00 AM
In the Human Powered Submarine we used JavaFoil (available online) to make preliminary design. It worked quite well for that purpose. There is also X-foil that is available for download under a GNU license.

DannytheRadomski
11-01-2012, 04:58 PM
I haven't read this whole thread, but from what I have read, some teams have used adjustable wings. I was wondering if anyone has tried using an airbrake like on the McLaren MP4-12C, or if it is against the rules.

Kirk Feldkamp
11-01-2012, 05:14 PM
Nope, never.

Not sure if this is "Active DRS" or an "Air Brake". http://www.youtube.com/watch?v=7wozSqFXitY

Rex Chan
11-02-2012, 12:41 AM
Read the aero rules - they're very short. Seems like air brakes are 100% allowed.

You're basically only limited in plan area of where you can have wings/aero devices, and no fans sucking air from under the car. ANything else goes.

DannytheRadomski
11-03-2012, 10:00 PM
That's basically what I was thinking of, thanks.

trip
11-07-2012, 02:15 PM
Hi,
This year we are going to introduce front and rear wings and I would like to know some method ( appart from CFD's) to uplift this part in the design part.
We have thinks tubes pitots but we can't afford this solution and the result of using gauges in the carbon fibre wishbone suspension will be insignificant.

Thank you,

Dunk Mckay
11-09-2012, 05:40 PM
If you have (a) consistent driver(s) simple lap times would be a good place to start. Check you fuel consumption as well though.

Tuft tests are also very useful, some flo-viz paint maybe. But you don't me to tell you this, you'll have read this in all the relevant literature already wont you?

Luke Phersson
11-22-2012, 05:43 PM
Interesting discussion so far - although a little heavy on the 'gut feelings'.

Z is correct when he states that if you're looking to win economy/efficiency you should look to underbody aero heavily.

However, if you're interested in winning competitions you need to look at the point sensitivity (not just lap time) of these vehicles to changes in parameters such as CL.A, CD.A, Power, Weight, CG height, Track width, etc. You're looking for the best COMPROMISE between them all. You also must consider the resources available to your team and what resources you can acquire within your area/country through sponsorship. Basically you want to focus your resources in the area where you will get the highest points return on investment. Bang for buck.

Back to aero... Yes underbodies alone are very efficient at making a decent amount of downforce, if they are designed well. That is the problem. It is enormously computationally expensive to capture all the important flow structures, mainly from the large velocity gradients between the undertray surface (no slip) and the ground (moving no slip - symmetry/free streamline assumption is wrong if you think about it) - you need a lot of elements to capture the boundary layer, depending on your turbulence model try to get a y+ (wall/surface distance made dimensionless with friction velocity and kin. viscosity) between 30-100 and use a wall function. The other major resource sink is capturing the details about your longitudinal vortices and accurately predicting their stability and how they interact with your boundary layer growth which in turn controls where parts of the diffusing section will separate. Typically for a given circulation, the higher the vorticity the tighter and more stable the vortex. Don't even bother with 2D CFD or trying to design the undertray without rotating wheels and the rest of the car in there (level of model complexity will be driven by your computing resources, mainly meshing so time and ram), you'll get an educational benefit but it won't represent reality at all. Also, beware a lot of things claimed about the early ground effect cars and what is 'good' for an undertray. Due to the short wheelbase of FSAE cars seals are not particularly helpful, full ones anyway, as a lot of the undertray flow needs to come from the sides.
^^ all of this said, it's still a good idea to take your results with a large grain of salt. Nothing will beat physical testing in the real world - either via simply driving different radius circles and logging G's or through pressure tapping surfaces.
The main advantage I see in CFD is using it as a visualization tool which helps you better understand what's happening (or maybe not happening!)..
http://imageshack.us/a/img696/9199/utpt.jpg
^^On-track pressure contour vs. CFD pressure contour for our 2011 undertray.

One thing Z has mentioned previously, is how it is advantageous to use slotted flaps (like the flaps on most of our current wings) as part of the diffusing section of the undertray. What this actually does (this is very simplified..) is restart the boundary layer growth by injecting high velocity air into the underside of the diffuser tangent to the surface, (hence why slot gaps are converging to accelerate the air) this also pumps the diffuser and draws more air through the throat further increasing downforce. One major problem with conventional FSAE cars is getting usable air to these slots, typically behind the driver the flow is quite stagnant.

Start rant..
Youd be surprised at how few engineers actually understand how wings work the actual mechanism for lift.. and if you start saying anything to do with Bernoulli you get an F how can a flat plate make lift? Go study Helmholtzs laws of vorticity (if youre really interested check out Hans J. Lugt).
End rant..

As for not using/using tunnels... Tunnels in my opinion are a consequence of packaging and vortex management theyre useful for building and controlling vortices which you can use to entrain more flow/cleaner flow into the undertray as well as keeping your boundary layers under control. One concept Id love to explore is taking the full frontal packaging area (762mm in front of front tyres) for the undertray inlet, youd likely end up with the throat occurring around/before the front tyres (not an adverse pressure gradient so you can converge quite quickly), and then diffusing for the length of the vehicle (305mm after rear tyre)... A major problem here is packaging and CG height (which dictates how narrow track you may go which for FSAE legal tracks is more important than aero and any load sensitivity) you dont want to go sticking a 30-70kg engine 500mm above the ground to clear the diffuser. Youd have to come up with a pretty funky vehicle layout to make all this work... Im thinking engine/batteries between the left side front and rear wheels, which is less aerodynamically usable than the centre of the car, and the driver between the right pair of wheels. This would give you ~1.85+ sq. m of effective undertray, at 60 km/h with an average Cp. of 3-4, you could get 1000+N of downforce for very little drag. As the throat is so far forward, the centre of pressure would be around the front wheels so youd need a rear wing to get a decent aero balance, which will also drive the diffuser harder (you generally want your centre of pressure at ground level to be on or just rearward of your CG).. so you could end up with 1500-2000N downforce at 60km/h for relatively modest drag.

So, this brings me to another important point risk management. The above (batshit crazy) idea would be a large risk youre basically stepping into unchartered territory with any number of likely problems. Teams already have enough issues designing the same car they did the previous year with a few minor modifications. Im not trying to say this approach is wrong, but its something you as a team need to decide on what is important to you guys? An example of this is probably Marylands 2012 car, the car had an awesome aero design but they seem to have compromised too much in terms of serviceability and reliability (hope you guys get this concept going!).
You can design and build the above supercar but chances are you wont have it running well before competition if you turn up to competition with only one week of testing and driver training you will still be slower than the traditional 200 kg non aero 600 cc that has been testing for 3 months. An important part of engineering is acknowledging your capabilities and limits. You need to balance your risk vs. reward.

As for CFD of the car actually cornering with curved flow, weve just developed a model that does just that. So we can set any chassis slip angle, front wheel slip angles, and corner radius to see the effects (especially aero yaw moments). Essentially its just a curved domain with a rotating reference frame and an added inertial component to the fluid body forces. This is a lot more computationally expensive, so its only really used to double check designs and help make the compromise on front and rear endplate sizing. (As just yawing in a conventional wind tunnel is incorrect)
http://img835.imageshack.us/img835/9894/tkew.jpg
^ Shows the asymmetry of the turbulent kinetic energy of the wake while cornering in the 2011 car.

The first wind tunnel was actually a whirling arm (as Z said) made in the 1700s by Benjamin Robins, and slightly later used by Cayley who built the first glider from what he learned. This approach was later abandoned due to the model running in its own wake (from the previous revolution).
http://wrightflyer.umwblogs.org/files/2011/03/robins-whirling-arm-300x174.jpg
^ Whirling Arm

To put a number on how much downforce I think a well developed undertray on a traditional FSAE car could make.. I'd say between 350-450N at 60 km/h, with negligible increase in bare vehicle drag. All the underbodies of the top Euro/US/Australian teams I've seen (most of them) sans wings, I'd say they're between 100-250N at 60 km/h.
For a team looking to try out aero for the first time, I'd recommend front and rear multi-element wings. Basically because it's easy and low risk. This all clearly depends on your team, resources, and what you actually want to get out of the competition.

Wow, that was some good procrastination! Sorry about the mass of text!

Cheers,
Luke.

Jay Lawrence
11-22-2012, 06:24 PM
Luke,

thanks so much, that was epic!

MCoach
11-22-2012, 08:14 PM
His name is Luke Pherrson.

*slow clap*

Good post. Glad to see this contribution surface from one of the top aero research groups.


Luke, are you familiar with the front mounted diffusers from formula 1?

This one being the Willianms W15:

http://upload.wikimedia.org/wikipedia/commons/thumb/8/81/Williams_FW15C_-_Donington_Park.JPG/640px-Williams_FW15C_-_Donington_Park.JPG

Moop
11-23-2012, 01:39 PM
What makes you say that the ground being a streamline is wrong? In 2D, neglecting the fact that it's rough, the air cannot penetrate the ground, so the velocity perpendicular to the ground is zero. Assuming no wind, the ground has the same speed as the on coming air. This means that the velocity vector of the air at the ground is tangent to the ground, so the ground is a streamline.

My fluids prof has tried to beat it into us that wings make lift because they curve streamlines which creates a pressure gradient due to centripetal acceleration. Although I know there's another reasoning based on circulation and what not.

Thanks for your advice on underbodies, especially regarding analysis. My team is looking at adding aero next year and given that we don't have much in the way of computational resources(or people very knowledgeable about what CFD is actually doing), I think we'll stick to wings. I was thinking of looking at something in 2D to get a rough guess of how much downforce we'd be making to see if it was worth our time, but given what you've said I don't think I'll bother.

Luke Phersson
11-25-2012, 02:57 AM
Thanks for the kind words guys.

MCoach,
There really isn't anything different between a 'diffuser' and a wing - all the principles remain the same. Airfoils also have a 'diffusing' section which is designed to recover pressure as quickly as possible without stalling. An undertray (which has a diffusing section) on a car just differs in that it doesn't have an aerodynamic top section, and it also has to deal with a lot more turbulent/messy air than a typical wing.

Moop,
The ground and the speed of the on coming air isn't really the whole story. Picture it like this, the car is traveling at 100km/h with no ambient wind, so using the car as the reference frame the road is moving under the car at 100 km/h, same as the on coming air. What happens underneath the front wing? The air is accelerated above 100 km/h. We now have a velocity gradient between the road and the air, this develops a kind of boundary layer.
Generally this symmetry/streamline assumption is used in wind tunnels without a rolling road to simulate ground effect. We tried this a few years ago..
http://imageshack.us/a/img19/849/syma.jpg
Essentially you just build a mirror image of the front wing/undertray, then connect one of them to a force balance (or pressure tap it like we did^). The middle streamline between the two bodies is supposed to represent the ground - it does this far better than a non moving floor, but is still not completely accurate, due to the reasons above.

Haha yeah, aerodynamics is full of 'chicken or the egg' type problems. Did the curved streamlines create the pressure gradient, or did the pressure gradient curve the streamlines... One of the more ridiculous explanations of lift involves packets of air traveling along the top and bottom of the wing mysteriously having to meet up at the same time at the trailing edge...

There is nothing wrong with just sticking a big sheet of aluminum under your car and manually bending up an inlet or diffuser.. Then just drive different radius circles and record times. Alternatively you can fit soft springs and shock pots to measure displacement vs. velocity (beware varying ride heights though). Maybe play around with different diffuser angles? Agricultural but it will tell you if it works or not. If you can show that this was the best use of your time/resources design judges should not mark you down for that.

We actually do the different radius circles to figure out our 'effective' CL.A and CD.A, which takes into account load sensitivity and extra tyre drag due to aero.

Luke.

Z
11-25-2012, 04:29 PM
Luke

"Start rant..
Youd be surprised at how few engineers actually understand how wings work the actual mechanism for lift..."

I'm more surprised at how few Fluid Dynamicists get it! In fact, I have so much to say on this subject that I'll have to leave it for another time. http://fsae.com/groupee_common/emoticons/icon_smile.gif

Meanwhile, thanks for the above objective information (err,... any chance of some kPa numbers for those pretty colours? http://fsae.com/groupee_common/emoticons/icon_smile.gif).

When I have more time I will post some numbers that I think are possible, and some simple underbodies that might do it.
~~~o0o~~~

Moop,

Don't give up on underbodies yet!

Also, as Luke said (and IMO), driving in circles is the best way to test these things. Do CFD to get a rough idea of what might work. Then plywood, ally sheet, Maxbond, duct tape, wool-tufts, circles... Then more cutting, bending, PU spray-foam, "gotta get these wool-tufts pointing in the right direction", and more circles...

Z

Hi-oct
05-21-2013, 07:23 AM
Now i currently working on mulielement wings. I observe that the downforce is max and drag min when the overlap is 0, which counters the theory I learnt. Also, as gap increases downforce increases continuously. Is this the right observation or am I doing anything wrong in my CFD?

JulianH
05-21-2013, 10:53 AM
I'm quiet sure that your CFD is wrong.

Increasing gap over a certain point wil definitely decrease your downforce.

Overlap = 0 is also not the optimal point when it comes to downforce in our observations. Additionally "max DF and min drag" at one single point sound quiet counter intuitive.

Could you upload a picture of your setting? That might help.

Z
08-16-2013, 10:04 PM
Most of the Northern hemisphere comps are now over, so teams will be celebrating, or commiserating, and hopefully thinking hard about how to do better next year. With the exception of those very few teams who won their comps, the best way to do better is to score a lot more points.

So, how do you score a shedload more points?

Well, AERO, of course!!! (Which is why I dug up this old thread... :))

So in the next post I give some "big-picture" numbers showing how DOMINANT aero can be in FSAE. In later posts (next week?) I will give some hints of how to achieve these numbers.

Z

(PS. It seems this new Forum doesn't like long posts, hence I have to break this one up...)

Z
08-16-2013, 10:08 PM
WHY AERO?
===========
Consider the following two cars.

Car-1.5G.
This car corners at ~1.5G = ~15m/s^2 (lateral Gs, flat track, as many good FSAE cars can do these days).
So this might be a non-aero car with the good racing tyres currently available, which have average Mu = ~1.5 (ie. including TLS, etc.).

Car-3.0G .
This car corners at ~3.0G = 30m/s^2.
So this might also be a non-aero car that happens to have magical tyres with Mu = ~3, but good luck finding those!

So, instead, assume this is an aero car with similar (though slightly larger) tyres to the 1.5G car above, but with "drive on the ceiling" downforce at the given corner speed (ie. DownForce = Weight of car).

Note that 3G cornering is quite tame these days, with many aero racecars getting up into the 4 and 5Gs. These 4+G forces are hard work for the drivers, but are by no means impossible.

Now consider the points difference between these two cars in the Dynamic events (as calculated by the formulas in one of the 2013 Rules floating around the web...).

(Note that current good aero FSAE cars are somewhere between the above two cars, although closer to 1.5G than 3.0G. The following is intended to show how dramatic a difference high cornering speeds (or Gs) can make.)
~o0o~

ACCELERATION.
No significant difference here, because this event is won mostly at "launch" where the speed is too low for any big aero effect.
~o0o~

SKID-PAD.
This is the easiest event to put numbers to, with,
Car-1.5G having laptime = 4.8 seconds, with speed = ~11 m/s (40 kph, 25 mph), and
Car-3.0G having laptime = 3.4 seconds, with speed = ~16m/s (57 kph, 35 mph).

With the 3.0G car as "Tmin", and thus scoring the maximum 47.5 "performance" points, the "maximum" time Tmax = 1.25 x Tmin = 4.25 seconds. Thus any car slower than this, such as the 1.5G car (which would be considered very fast these days), scores NO performance points at all! In fact, to score any points a car would have to corner at greater than 1.9G.
~o0o~

AUTOCROSS.
Here the scoring formula has Tmax = 1.45 x Tmin. This means that any car taking 45% more time to complete the event than the fastest car (Tmin) scores no "performance" points out of the 142.5 points available.

The 3G car corners 41% faster (ie. x sqrt(2)) than the 1.5G car. So, ASSUMING (see below!) that these speeds are similarly translated to overall average speed, any cars cornering at 1.5G or less score maybe 10 points at most.
~o0o~

ENDURANCE.
Again the scoring formula has a scaling factor of Tmax = 1.45 x Tmin, but this time with 250 "performance" points available. So, using same assumption as above, this time any cars cornering at 1.5G or less score maybe 20 points at most.

The assumption above, namely that cornering speed advantage is also translated to the rest of the track, is a big one. But the essence of FSAE-style "autocross" racing is that it is mostly about corners and the transitions between them. Many of the recent FSAE events (from video I have seen) seem to be an almost endless series of corners with very few, and rather short, straights between them. Also, coming out of a corner faster than the other cars, and being able to enter the next corner faster, makes it much easier to develop a higher average speed along any of the straights between the corners.

So, if the 41% speed advantage is even close to true, then, so far, the 3G car has a massive advantage of over 400 points (!) over the 1.5G cars. Cars capable of 1.5G cornering are quite fast by today's standards, although current aero cars are gradually passing this mark.

But what about the oft-mentioned "big disadvantage" of aero? .....
~o0o~

FUEL ECONOMY/EFFICIENCY.
Firstly, note that in olden days racing (pre WWII), "aero" was about "streamlining" the car to reduce drag, so as to increase top speed in a straight line (the top speeds were the same in the 1930s as now (high 300s kph)). This streamlining is still useful in FSAE today, but would be used mainly to minimise fuel usage (wastage!), rather than increasing top speeds.

However, in FSAE, as in most modern racing, "aero" is mostly about adding downforce to increase corner speeds. Fortunately, this can also lower Fuel usage for the simple reason that the car can win comfortably without braking hard before corners (throwing away valuable kinetic energy), nor accelerating hard out of the corners (burning valuable fuel to regain the kinetic energy just thrown away).

[Nerd Note]
Force-vector(Dot-product)Velocity-vector = Power.
If F and V are parallel (= acceleration), then Power is high and positive (= burn fuel to make kinetic energy).
If F and V are anti-parallel (= braking), then Power is high and negative (= heat brakes to dump kinetic energy).
If F and V are almost perpendicular (= cornering at low slip-angle), then Power is almost zero (= good!).)[/End Nerd Note]

So, energetically speaking, not only are high cornering Gs almost free, but they can, in fact, save fuel!

And, very importantly, A HIGH DOWNFORCE CAR CAN ALSO BE A LOW DRAG CAR! (It is true! See next week... )
~~~~~o0o~~~~~

CONCLUSION.
So, IMO, the goal of "aero" in FSAE is to build an almost "constant speed car". This car should be capable of very high lateral Gs, but require negligible longitudinal Gs. Imagine a car like the "Wild Mouse" (http://en.wikipedia.org/wiki/Wild_Mouse_roller_coaster) fairground rides. These rides have ~constant downward slope, so constant forward speed, but also a seemingly never-ending series of corners at 3+Gs lateral. For your "Initial Design Concept Meetings", I suggest you take your data-loggers to the fairgound. :)

The potential points advantage of this sort of car against the current "state-of-the-art" non-aero cars is far in excess of any other means of improving performance. I leave it to you students to do more detailed point and laptime simulations. But no amount of increase in power (limited by restrictor), reduction in weight (not a huge factor TLS-wise), magical new tyre compounds (good luck with that...), Nth degree refinement of suspension (again, ultimately limited by tyre Mu), nanosecond paddle-shift gear-change (:D), or even the best driver in the world (once again, limited to the ~1.5G that the tyres can bring...) will ever come close to the huge gains possible from aero.

Also worth noting here, a team that does the absolutely best that is possible in the Static events of Cost, Presentation, and Design, might only get a handful more points than the next best teams. That is, the Static events are scored essentially independently. But in the Dynamic events (as currently scored) an exceptionally fast team pushes all the other teams backwards. The ~400 point gain in the above examples comes from taking points AWAY from the other teams.

Before getting to the aero details, it is worth noting that these 3G numbers will require a LIGHTWEIGHT and STRONG car. The car SHOULD be lightweight because the increase in competition points won is directly proportional to the ratio of aero-downforce to car weight. Less weight means more points from a given amount of downforce. The car MUST be strong because the forces acting on the car increase in this same ratio (ie. the structural loads become much greater than those of a non-aero car!).

Hence, my many suggestions over the years to keep the rest of the car as simple as possible. So, think of a HEAVY-DUTY "brown go-kart, with aero-undertray".
~~~~~o0o~~~~~

AERO DETAILS.
Finally, what is needed from the aero to achieve the above?

Assuming a 150 kg car (not too hard, with KISS), with 50 kg jockey and the currently available Mu = 1.5+ tyres, the DF = W equation suggests the car needs ~200 kg of downforce (ie. ~2 kN), at the given corner speed. As shown above this corner speed is ~16 m/s on the Skid-Pad, and this is also close to the current average AutoX/Enduro speed. This speed drops to about 10 m/s around any hairpins, as they are specified in the Rules. But most circuits these days seem to have very few real hairpins, despite discussion on other threads asking for more of them.

So, if your car can develop at least 2 kN of downforce at 16m/s, then you should have a massive jump on the non-aero opposition. Well, at least until they catch up! And some teams are (slowly) getting there ...

In conventional aero terminology (Force = Half-Rho-V-Squared.CL.A) the above numbers imply a CL.A = ~13 m^2.
(3G cornering around a hairpin (V = ~ 10 m/s) implies CL.A = ~33 m^2.)

A fairly compact undertray can have Area = ~2 m^2.
Utilising most of the plan area allowed in the Rules (say, about 1.4 m wide, by 3 m long, less cut-outs for wheels) gives Area = ~3 m^2.

So, for 3G cornering at average Enduro speeds the total car lift-coefficient, based on plan area, needs to be ~CL = 4 to 7.

Are these CL numbers at all achievable?

Looking through aeronautical textbooks would suggest NOT LIKELY!!!!!
(Err, ... except that Handley-Page got CL = 4+ back in 1910, and that wasn't even in ground-effect... ;))

So, should I go and talk to the fairies at the bottom of the garden??? :)

As always, comments and criticisms welcome.

More next week...

Z

(PS. As a teaser, putting the above figures in a more sensible way, and depending on plan area, the average pressure drop under the car for 2 kN downforce needs to be about -700 Pa to -1,000 Pa (since most aero forces come from "suction", not pressure above ambient, and 1 Pascal = 1 N/sq.m). This is less than 1% of atmospheric pressure, which is 10 tons/sq.m (= 100 kPa).)

JulianH
08-17-2013, 02:59 AM
I think you are correct in one area: An Aero-Car achieving this magical numbers would destroy everything out on track.

But, after that, it gets difficult:




Note that 3G cornering is quite tame these days, with many aero racecars getting up into the 4 and 5Gs. These 4+G forces are hard work for the drivers, but are by no means impossible.


(Note that current good aero FSAE cars are somewhere between the above two cars, although closer to 1.5G than 3.0G. The following is intended to show how dramatic a difference high cornering speeds (or Gs) can make.)



I think it is not possible to achieve 4G's in FSAE. The speeds are just too low so that Aero isn't even more important. F1 cars (with lower cL*A compared to massive FSAE-Aero) achieve these figures at 200kph+ when Aero is like 2-3-4 times their weight

Good FSAE Aero cars reach over 2.5G's on a FSAE track (I heard in Lincoln it can be even more. But in Germany we logged about that). So we are not too far away. "Problematic" for your calculations is, that good Non-Aero cars pull close or even over 2G's... So the "Delta" is not that large.



SKID-PAD.
This is the easiest event to put numbers to, with,
Car-1.5G having laptime = 4.8 seconds, with speed = ~11 m/s (40 kph, 25 mph), and
Car-3.0G having laptime = 3.4 seconds, with speed = ~16m/s (57 kph, 35 mph).

With the 3.0G car as "Tmin", and thus scoring the maximum 47.5 "performance" points, the "maximum" time Tmax = 1.25 x Tmin = 4.25 seconds. Thus any car slower than this, such as the 1.5G car (which would be considered very fast these days), scores NO performance points at all! In fact, to score any points a car would have to corner at greater than 1.9G.
~o0o~

The problem here is simple. It is not possible to achieve 3.0G in Skidpad. It just won't work. It probably even comes down to the driver. As said before our car, that is able to destroy all Non-Aero cars we ever built on track is only 2 tenths faster than our last Non-Aero Car from 2011 in Skidpad. Maybe the kinematics were better back then but still...
Even further. The current FSAE "World Record" in Skidpad is somewhere at 4.6-4.7 seconds (Monash at FSAE-A 2012 or Rennteam Stuttgart at Silverstone 2013). Even the car with probably the best Aero out there cannot pull more than 1.5G in Skidpad. Because the speeds are just too low.


AUTOCROSS.
Here the scoring formula has Tmax = 1.45 x Tmin. This means that any car taking 45% more time to complete the event than the fastest car (Tmin) scores no "performance" points out of the 142.5 points available.

The 3G car corners 41% faster (ie. x sqrt(2)) than the 1.5G car. So, ASSUMING (see below!) that these speeds are similarly translated to overall average speed, any cars cornering at 1.5G or less score maybe 10 points at most.
~o0o~

You can't drive 41% faster than a Non-Aero car that is good. It simply doesn't work! In Germany 2012, the fastest non-Aero car in AutoCross was Delft with a 76.370s. 41% faster would come to a 45.05s. The fastest Aero car did a 75.933s. That means not 57kph average speed but 97.6kph. Sure the Delft car was exceptional but that is always an issue ;).
And the German track is "Aero friendly". It is just ridiculous to come up with such numbers and then say "ah you are so fast the other don't get any points then...".



So, if the 41% speed advantage is even close to true, then, so far, the 3G car has a massive advantage of over 400 points (!) over the 1.5G cars. Cars capable of 1.5G cornering are quite fast by today's standards, although current aero cars are gradually passing this mark.

Yes, and a 400hp car with 120kg is also nice...


But what about the oft-mentioned "big disadvantage" of aero? .....
~o0o~

FUEL ECONOMY/EFFICIENCY.
Firstly, note that in olden days racing (pre WWII), "aero" was about "streamlining" the car to reduce drag, so as to increase top speed in a straight line (the top speeds were the same in the 1930s as now (high 300s kph)). This streamlining is still useful in FSAE today, but would be used mainly to minimise fuel usage (wastage!), rather than increasing top speeds.

However, in FSAE, as in most modern racing, "aero" is mostly about adding downforce to increase corner speeds. Fortunately, this can also lower Fuel usage for the simple reason that the car can win comfortably without braking hard before corners (throwing away valuable kinetic energy), nor accelerating hard out of the corners (burning valuable fuel to regain the kinetic energy just thrown away).

So, energetically speaking, not only are high cornering Gs almost free, but they can, in fact, save fuel!

That's correct. With the new formulas, you just drive the hell out of your car. GFR 2013 in Germany won Endurance and Efficiency. That works.



And, very importantly, A HIGH DOWNFORCE CAR CAN ALSO BE A LOW DRAG CAR! (It is true! See next week... )

That's were I don't think you are correct. You presented some "ideas" in the past. And I tried them all and they all don't work. If you want high Downforce you have to pay the "Drag price". But as mentioned, it's not a big issue. Even with a possible "3G car everywhere" you just use a DRS (you need it anyway because you would break the whole thing at speeds close to 100kph).




CONCLUSION.
So, IMO, the goal of "aero" in FSAE is to build an almost "constant speed car". This car should be capable of very high lateral Gs, but require negligible longitudinal Gs.

That is true. GFRc 2013 is the best example.



So, if your car can develop at least 2 kN of downforce at 16m/s, then you should have a massive jump on the non-aero opposition. Well, at least until they catch up! And some teams are (slowly) getting there ...
In conventional aero terminology (Force = Half-Rho-V-Squared.CL.A) the above numbers imply a CL.A = ~13 m^2.

You can't pull 2kN at 16m/s. It won't work. Period.
cL*A of 13 is just not possible.





So, for 3G cornering at average Enduro speeds the total car lift-coefficient, based on plan area, needs to be ~CL = 4 to 7.

CL = 4 is possible. 5 maybe, 6 nah.



Summing Up:
Yes, Aero works. Yes, Aero gives you an advantage.
No, you can't get 400 dynamic points compared to a good Non-Aero car.
No, you can't pull 3G in a slow corner.
No, you can't achieve your magical downforce numbers.

I'm quite sure that we all are doing "bad" Aero designs. I mean the most teams are doing it for 2 years. Look at all the "first 2 years chassis". Of course in next years the cars get better. But even then, you will not achieve such numbers.
Talking about "ah everybody does it wrong" does not help. As said, we are far from "optimum" but more when it comes to efficient designs not max. downforce.

Other thing:
I heard they want to penalize Aero again because you "need it" to be fast. So probably with the 2015 Rule Change it even gets more difficult.


Cheers,
Julian

DannytheRadomski
08-17-2013, 03:16 PM
In terms of building a high lateral downforce car with low longitudinal downforce, would active aero be best? Something like the MP4-12C or the Veyron? It would have to calculate angles for the wings based on speed, braking, throttle position, steering position, etc., so it might be a little much in terms of programming. Then again, the payoff could outweigh the drawbacks if it were done well.

mech5496
08-17-2013, 05:27 PM
Danny, check out what Sooner racing team (and a few others) have done...

http://www.youtube.com/watch?v=7wozSqFXitY

JulianH
08-17-2013, 06:25 PM
In terms of building a high lateral downforce car with low longitudinal downforce, would active aero be best? Something like the MP4-12C or the Veyron? It would have to calculate angles for the wings based on speed, braking, throttle position, steering position, etc., so it might be a little much in terms of programming. Then again, the payoff could outweigh the drawbacks if it were done well.

Active Aero is a possibility. Karlsruhe just does it with driver input.
I think the most "important cases" to activate DRS can even be programmed quite simple. Speed/Throttle > X and Steering < Y or something like that. Monash showed that the "closing" of the DRS can be done very quickly so just the braking pedal or the linear acceleratometer could be used.

Don't know how complicated that would be in a combustion car, but if you programm Torque Vectoring in an electric car, it's a bit more difficult, at least they tell me that all the time :)

Dunk Mckay
08-18-2013, 08:32 PM
I'm not sure I think DRS is valuable for these cars. I mean sure, in theory it's gonna reduce your fuel consumption a little bit due to reduced drag. But how much is the dragged reduced compared to the weight you have to get up to speed, so it's even less of an offset. It's certainly not going to be reducing drag because of lack of power when accelerating, just spend the time making more power instead of design a fancy DRS system.

The other issue I have with it is why go to great lengths for low fuel anyway? Perhaps with the old fuel economy system, but not anymore, not with fuel efficiency. With speed counting as much as fuel consumed now, why waste time with anything other than leaning out your map a little?

DRS for me is just a heck of a lot of phaff for so little gain.

Mbirt
08-18-2013, 09:09 PM
The other issue I have with it is why go to great lengths for low fuel anyway? Perhaps with the old fuel economy system, but not anymore, not with fuel efficiency. With speed counting as much as fuel consumed now, why waste time with anything other than leaning out your map a little?I wouldn't say we went to great lengths for low fuel consumption this year, but it was certainly easier to win fuel efficiency at all three competitions we entered by setting Vmin instead of Tmin. We were 85-90% as fast as the endurance winner with a 400 lb spaceframe single with aluminum bodywork on 13's. For us, using 33% less fuel with engine design, controls, and calibration was far more obtainable than finding the last 10% of pace.

Z
08-18-2013, 10:19 PM
Julian,

Ahh, so young, and already so cynical and set in your ways ... :)

I thought it was only dried up, stale, old people who thought that "there is nothing new under the sun, because we've already figured it all out...". For example, all the experts who proclaimed that "heavier than air flight is IMPOSSIBLE", even as the Lilienthal and Wright brothers were building their flying machines!
~o0o~


"Problematic" for your calculations is, that good Non-Aero cars pull close or even over 2G's... So the "Delta" is not that large.

If a Non-Aero car can pull 2Gs lateral, then adding DownForce = Weight (and maybe using same compound but wider tyres, to cope with TLS) will let it pull 4Gs. The Delta stays the same (ie. ~+41% faster speed through corners).

Also, as a general note regarding logged "lateral Gs", momentary spikes don't count. They are just noise (eg. vibration, bumps...). And a small amount of banking to a corner can make a big difference to the sustained lateral Gs (eg. a bit more than 6 degrees (~1:10) banking can make Mu = 1.5 tyres look like they are pulling steady 2 Gs lateral).
~o0o~


The problem here is simple. It is not possible to achieve 3.0G in Skidpad. It just won't work.
... [no, no, no Z,... it is just tooooooo haaard...]
Even the car with probably the best Aero out there cannot pull more than 1.5G in Skidpad. Because the speeds are just too low.

Think positive Julian! You can do it!!! Stay tuned ... (I'll wait til end of week for other responses).....
~o0o~


You can't drive 41% faster than a Non-Aero car that is good. It simply doesn't work! In Germany 2012, the fastest non-Aero car in AutoCross was Delft with a 76.370s. 41% faster would come to a 45.05s. The fastest Aero car did a 75.933s. That means not 57kph average speed but 97.6kph.

Because I am picky...

41% faster than 76 seconds is (1/sqrt(2))*76 = 0.707*76 = ~54 seconds.
Average speed goes from 57 kph to 1.41*57 = 80 kph. That is not too fast.
~o0o~


With the new formulas, you just drive the hell out of your car. GFR 2013 in Germany won Endurance and Efficiency. That works.

Agreed. At FSG-2013

http://www.formulastudent.de/uploads/media/FSC13_Scoring_eff_all_01.pdf

there was a good correlation between Fuel Used and Enduro Laptimes, across the whole field. The fastest cars used the least fuel, and the slowest cars used the most fuel! And many of the fastest cars were aero-cars, with the big air-brakes (ie. rear wings, which are very INEFFICIENT)!
~o0o~


You presented some "ideas" in the past. And I tried them all and they all don't work. If you want high Downforce you have to pay the "Drag price".
...
You can't pull 2kN at 16m/s. It won't work. Period.
cL*A of 13 is just not possible.
...
CL = 4 is possible. 5 maybe, 6 nah.
...
No, you can't get 400 dynamic points compared to a good Non-Aero car.
No, you can't pull 3G in a slow corner.
No, you can't achieve your magical downforce numbers.

And all those tricks that young skateboarders do are PHYSICALLY IMPOSSIBLE. Err..., except that they keep doing them... But only because they dropped out of school before they got educated enough to know that, ..., ummm, ..., that stuff is IMPOSSIBLE... :)
~~~~~o0o~~~~~

Regarding the "active aero" mentioned in other posts, as Julian said;


Even with a possible "3G car everywhere" you just use a DRS (you need it anyway because you would break the whole thing at speeds close to 100kph).

I interpret DRS as "DownForce Reduction System". With 200 kg of DF at average speeds (say, 16 m/s), the car is getting close to a TON of DF at the top speeds (ie. ~800 kg at 2 x average speed). So, for a start, I suggest tossing those girly 68xx wheel-bearings, and fitting some proper tapered-rollers!

The DFRS mechanism itself would be quite easy, IMO. Just manual/electric/pneumatic/whatever actuator on the flaps. But I would leave all that until after the car is consistently getting the ~1 ton DF.

Z

JulianH
08-19-2013, 02:50 AM
Dunk,
DRS is not too bad. The thing is, the rear wings are just Drag-Monsters if you set them to max. Downforce. We tested DRS in the wind tunnel and we could reduce drag by about 40% (overall!). If you have a 800g system and reduce cD massively, maybe you are in the "trade-off-area".

I haven't done calculations for combustion cars, but for electric cars, the new Efficiency scoring forces you to drive faster in Endurance and therefore Drag is more important. We basically all calculate "How fast can we go while using the whole battery". Our simulation said, it does not work, the effect is too small. But Karlsruhe, Washington, Monash... they seem to disagree.
If your aero gets "insane" (aka Wonderland-cL assumed by Z) you surely need it.

Z,
maybe I am not "bright enough" for "the future". I am not really constrained by my education. I started Aero with no idea of how air works (therefore I believed some crazy-ass Lift coefficients of bad CFD setups and got quite big eyes at the first wind tunnel test...).

I never said, that "everything is figured out". I just think, that your magical numbers are not achievable. The evolution also failed to make penguins fly. The probably also dream of your cL values but it simply does not work.

It is nice that you throw out ideas and try to push the students to think outside of their given ways. I really look forward to see some of your designs on how these numbers can be achieved. I will fire up the CFD and prove you wrong (or maybe right ;)) as soon as possible.

Sadly I'm done with FSAE Aerodynamics, so I can't be a part of "this future", but if a car is able to achieve a sub-3.4s in SkidPad, I will sponsor you a whole evening of Foster's (I heard that can be expensive for Australian guys, but at least the flight costs are probably cheaper then..).

Cheers,
Julian

Marshall Grice
08-19-2013, 03:10 AM
I'm dying to see what this revolutionary aero design is.

I've got pretty good data on something like this:
http://images61.fotki.com/v665/photos/3/43793/11609276/IMG_0155-vi.jpg

obviously doesn't meet the FSAE rules but its no slouch. if i change my spreadsheet to the weight, mu, and speed numbers you use and keep my aero performance, i calculate it would only generate 1.8g steady state at 16 m/s. Clearly well short of the needed 2kn of downforce.

With FSAE power levels (sans DRS) it would be drag limited to ~25 m/s at which point it would still be only able to pull ~2.4g. i.e. 3g not possible in this case.

If I increase the plan area to 3 m^2 and unrealistically assume it could maintain the same performance (the wing would be basically as wide as the skid pad course width :)), that still puts it at only 2.2g @ 16m/s and drag limited to ~20 m/s but could pull 3.0g at that speed.

so like I said, i'm dying to see this revolution in aerodynamics.

TurboTom
08-19-2013, 03:26 AM
A fairly compact undertray can have Area = ~2 m^2.
Utilising most of the plan area allowed in the Rules (say, about 1.4 m wide, by 3 m long, less cut-outs for wheels) gives Area = ~3 m^2.

So, for 3G cornering at average Enduro speeds the total car lift-coefficient, based on plan area, needs to be ~CL = 4 to 7.

Are these CL numbers at all achievable?

Looking through aeronautical textbooks would suggest NOT LIKELY!!!!!
(Err, ... except that Handley-Page got CL = 4+ back in 1910, and that wasn't even in ground-effect... ;))


Co-efficients of lift 3-4+ are definitely possible with the 2 or 3 element wings with leading edge slots that you alluded to, likewise a plan area of 3m2 easily acheivable with a large floor, however I think the combination of the two is what is likely to cause some problems.

The image I have in my head a UWA style car, but instead of a 'traditional' undertray, just a long wing. Picture going down to your local aircraft graveyard and cutting one of the larger planes wings into a 3*1.1m section (3m being the chord length) and attaching some wheels to it. A couple mounting points for your driver cell/fuselage chassis and the mandatory spring/damper or two and voila.

However getting this CL back up to 3-4 would be difficult, especially because of the drivers cell chops out a big chunk of your effective area, and the wheels essentially render the outer edges of this 'wing' useless past the front axle, again eliminating more useful area.

So whilst your total area is approx 3m2, you only get an area that is of any use approximately half of that. A lot of smart design in designing the chassis/fuselage bodywork (especially aft of the driver) and mitigating the effect of the wheels would have to be done in order to get CL's anywhere back to 3-4.

My thoughts in summary
- It is possible to get wings with CL 3-4+
- It is possible to have an undertray area of 3m2 with min wheelbase
- The combination of the two (even in ground effect), given the other factors (wheels, chassis, engine etc...) will take SERIOUS (3-4 years of development) work to get near the necessary 2000N required to pull 3g in skid pad.

Unless there is something that I'm missing....
Z?

--
Tom

Z
08-19-2013, 07:58 AM
http://images61.fotki.com/v665/photos/3/43793/11609276/IMG_0155-vi.jpg

With FSAE power levels (sans DRS) it would be drag limited to ~25 m/s ...
Marshall,

The above is a very good example of how inefficient (ie. high drag) those rear wings are (ie. basically low aspect ratio + high CL = very high vortex drag).

The only good reason I can see for such rear wings is to shift aero DF backwards. That is, the higher the rear wing, the higher is the drag vector's LoA, and thus the more DF taken off the front wheels and put onto the rear wheels. This can be beneficial in FSAE since the Rules allow a lot of aero out front (~ 0.7m in front of front wheels, IIRC?), but not much behind the rear wheels (~0.3 m behind rears?).

Oh, and NOT a "revolution" at all. Has been "rediscovered" lots of times in motorports, and banned almost as many times...
~~~~~o0o~~~~~


Originally posted by Turbo Tom:
...
Picture going down to your local aircraft graveyard and cutting one of the larger planes wings into a 3*1.1m section (3m being the chord length) and attaching some wheels to it. A couple mounting points for your driver cell/fuselage chassis and the mandatory spring/damper or two and voila.
...

My thoughts in summary
- It is possible to get wings with CL 3-4+
- It is possible to have an undertray area of 3m2 with min wheelbase
- The combination of the two (even in ground effect), given the other factors (wheels, chassis, engine etc...) will take SERIOUS (3-4 years of development) work to get near the necessary 2000N required to pull 3g in skid pad.

Unless there is something that I'm missing..
Tom,

I will cover this classic "inverted wing in ground effect" (= first Lotus GE cars) soon.

And no, you didn't actually miss the important point, but I did highlight it above so it stands out.

The very important point is that while a conventional curved aerofoil shape works great up there in the air, it is not what you want when flying upside-down very close to the ground. The ground effect greatly changes the question, which likewise changes the answer.

Z

(PS. Julian, I brew my own. About 20c per bottle (if you are ever down-under, then you are welcome to as much as you can manage :)). But thanks for the offer!)

Claude Rouelle
08-19-2013, 08:36 AM
A few years ago, Max Mosley, the director of the FIA was told that with the new rules limiting the engine capacity (from 3.0 to to 2.4 liter) would put the maximum power of the engine at 700 HP BECAUSE OF THE LAW OF PHYSICS. That is what F1 team engineers told him. A few years later F1 engine were above 800 HP. The same lesson could go for downforce. 6 or 7 years ago a light car was just under 200 kg. Now alight car is under 150 kg, even with wings. We do not know what the power, the grip, the downforce, the weight of a 2016 or 2017 FSAE / FS car will be. Imagination is the limit more than anything else. Never say never.

Marshall Grice
08-19-2013, 09:26 PM
Marshall,

The above is a very good example of how inefficient (ie. high drag) those rear wings are (ie. basically low aspect ratio + high CL = very high vortex drag).

The only good reason I can see for such rear wings is to shift aero DF backwards. That is, the higher the rear wing, the higher is the drag vector's LoA, and thus the more DF taken off the front wheels and put onto the rear wheels. This can be beneficial in FSAE since the Rules allow a lot of aero out front (~ 0.7m in front of front wheels, IIRC?), but not much behind the rear wheels (~0.3 m behind rears?).

Oh, and NOT a "revolution" at all. Has been "rediscovered" lots of times in motorports, and banned almost as many times...
~~~~~o0o~~~~~

the rear wing is so high chasing max df. we're trying to get as much of the wing in ground effect as possible which leads to a very front biased CP without the rear wing so high. we'd have to push the wing backwards much further than we push it up to find clean air and balance. We are plan area limited (with no limits on HP) so we'll make use of any force we can generate in large quantities; turns out it's pretty easy to make a crap load of drag. :)

In my (admittedly limited) experience, with a narrow front track width the ability to generate large Cl from the available area behind the wheels is limited without ground sealing. the tires REALLY screw up the air flow.

Claude Rouelle
08-20-2013, 12:46 AM
" the tires REALLY screw up the air flow"

If you speak to a professional single seater aerodynamic engineer (F1 for example) he will tell you that
40 % of the aerodynamic problems are front and rear wings
40 % the wheels
and 20 % everything else.

For example the tire deflection especially the lateral one, have an immense influence of the aerodynamic properties of the car.

That is why professional 60 % wind tunnel tests are organized with tire which do deflect as real tire... but as nearly no grip so there is minimum mechanical grip influencing the aerodynamics force and moments measurements. And these 60 % tire do have nitrogen temperature and pressure sensors. What a world! Give 50 millions dollars to a F1 engineer he will find a way to spend it (besides his salary)....

bob.paasch
08-21-2013, 08:35 PM
" the tires REALLY screw up the air flow"

If you speak to a professional single seater aerodynamic engineer (F1 for example) he will tell you that
40 % of the aerodynamic problems are front and rear wings
40 % the wheels
and 20 % everything else.


We've been working on aero since 2008. That includes an MS thesis (with another starting next year), and some of our best undergraduates. I don't doubt that a team will eventually break 3gs, but it's going to take a lot of effort. The tires really screw up the airflow. Plus, FSAE/FS is unique: cornering speeds are low, steering angles are high, and yaw rates are high. Mid-corner, the air is coming in at a substantial angle off axis, very likely higher than in any other form of motorsport. CFD has to model this, requiring a complicated full body model with rolling wheels and a lot of elements. Rolling road wind tunnels are necessary to get ground effects, but even then they can't test at high steering angles.

And big front wings make cooling a challenge. :)

Claude Rouelle
08-21-2013, 09:42 PM
Additional info going the same way as Boob Paasch,

1. There is a single seater car racing series we work in, where the mechanical part of the simulation created from tire car analysis clearly show that we need a pro-Ackermann geometry. Despite of that we do use big anti-Ackermann ....for aerodynamics reasons. Wind tunnel, CFD, data analysis clearly prove that aero pushes that car to have toe in in steering.

2. Many years ago I tested a F 3 car in a wind tunnel. The work was decently organized and the day went well so we had a bit of free time at the end of the day so we tested a car with no rolling floor with 0 and 5 degress of toe in on each front wheel. We knew it was not realistic (huge rolling resistance, maximum width outside the rules etc...) We also knew that without the rolling floor the numbers would not be realistic but at least it was a apple to apple comparison, just to see. The downforce increase, the drag reduction, the cooling improvement, the shift in aerobalance were so big that with such a difference (if it was mechanically feasible) we would have won the championship easily, even with a bad driver.

3. One of the reason Renault F1 struggle in 2007 after winning the 2006 championship was the (mandatory) switch from Michelin to Bridgestone. The difference in the tire tread (at that time grooves were mandatory), shape (for the same outside diameter and width the shape was slightly different) and tire deformation completely discombobulated the aero engineers for several months.

Ahh if we could race a car with no wheels: the dream or every aerodynamic engineers....

And don't get me wrong their effect on "covered" wheels cars (Le Mans or DTM for example is still huge)

Claude Rouelle
08-22-2013, 08:47 AM
One more:

One on the main reason of the very long wheelbase of an F1 is aerodynamic. In a simplistic way.....Rear wheels disturb rear wing and diffuser. But front wheels disturb front wing, side pod, underwing and..rear wing. The further away you can put the front wing from the rear wing the better. There are other reason for long wheelbase which are related to inertia, control stability etc... but the main reason of long wheelbase is aero.
With everything parts so tiny in F1, if they wanted to make a very compact car believe me they could.

Z
08-23-2013, 09:18 PM
Well, I have spent some time at the bottom of the garden, and the fairies there have very kindly lent me a magical box of "Crayons For Drawing"! With these I have managed to sketch some, ... err, ... "Colourful Flow Diagrams" that may help explain my thinking on aero-underbodies.

I will spread these sketches over several posts because this new Forum doesn't like too much thrown at it at once...

Please note that fairies are notoriously mischievous, and love playing all sorts of tricks on gullible schmucks. Consider the following sketches as only big-picture, rough guidelines of directions you might want to investigate. Note also that even wind-tunnels are prone to deception. Especially so if they have a fixed floor, since the following important flows are mostly very close to the ground. And wind-tunnels don't do curved flows, which are just the flows you want to model, given that FSAE aero is about going fast around tight radius corners (see discussion several pages ago - page 17+ on this new Forum...).

So, for best results in the real world it is best to do most of the modelling and development there too. Fit aero to last year's car, drive in circles, and measure lap times. Attach wool-tufts, use other flow visualisation methods, take pressure readings, and try to figure out what is happening. Modify aero, and re-test...
~~~~~o0o~~~~~

In the following "Crayon..." sketches the car (well, the sketched "underbody") is about 2 metres long, and moving leftward at 10 m/s (or the road and wind are moving to the right at 10 m/s (36 kph)). Importantly, these sketched flows are planar (ie. "2-D", because they are just hints!).

For the purpose of force calculations the flow is assumed to be between two walls 1 metre apart. So imagine these underbodies as having "skirts" either side, just inside the wheels of a typical FSAE car. So plan-view area is about 2 square metres.

Some important 3-D effects will be covered later.

The forces quoted below (at 10 m/s) become ~2.5 times greater at 16 m/s, which is the target speed to "drive on the ceiling". At the maximum FSAE speeds of, say, 32 m/s (~115 kph, 72 mph), the forces will be ten times greater (because forces increase with square of velocity). The pressures shown scale up similarly (by square of velocity), but the flow speeds just scale linearly (eg. a "red" streamline showing, say, 20 m/s (= x 2), will be 64 m/s when the car is at 32 m/s).

Z

Z
08-23-2013, 09:19 PM
DIFFUSER + GURNEY.
======================
These first two sketches show the classic inverted-wing type underbody used on the first Lotus 78/79 ground-effect cars. Note that these only work well if used with very effective (ie. well sealing) side-skirts that make the flow close to 2-D-ish, and which were legal back then. In fact, they worked so well that the side-skirts were quickly banned!

https://lh6.googleusercontent.com/-7q2vcdkf4E4/Uhb39U3KQYI/AAAAAAAAAOE/zU7z45jtOgE/s800/D%2526GStrm.jpg

This particular "inverted-wing-in-ground-effect" is of very crude shape. Just a couple of constant radius arcs, straight lines, and a small "Gurney" at the back. The highest point of the Gurney is ~0.25 m above ground (= ~axle height) and the narrowest part of the "throat" is ~4 cm.

Despite the crude shape, the flow speed at the throat is ~27 m/s, with a pressure drop there of about -360 Pa. Overall downforce (at 10 m/s) is about 35 kg (340N) and drag is about 1 kg (11N). At the target Skid-Pad speed of 16 m/s the downforce climbs to 88 kg. Even if this undertray is stretched to 3 metres long (for 3 sq.m area, and assuming the aero forces scale accordingly) the downforce only gets to 130 kg at 16m/s.

In standard aero terminology the 2 metre long undertray has CL.A = 5.5 sq.m, and the stretched 3 metre long undertray might get to CL.A = 8.3 sq.m.

So, not enough!!! (And see bad news below.)

The drag is so low that it is barely worth considering. In fact, for almost all underbodies you can expect drag to be far less than that from the wheels, main-roll-hoop, driver's head (!), and a lot of the other, unfortunately necessary, non-aero rubbish you have to fit to the car to make the wheels go round...

https://lh6.googleusercontent.com/-yVZnN6u1ATg/Uhb34VNGdaI/AAAAAAAAAN8/qMk9XwCMoSg/s800/D%2526GPres.jpg

There are quite a few disadvantages to this design, some covered by Luke Phersson a few pages back (page 18). A big one is that a lot of the underbody has to be high above the ground, so heavy parts like engine and driver might have be raised, giving a high CG.

Another big problem is that the flow in the diffuser section (= rear half) is against a so-called "adverse pressure gradient". This means that air that is dragged along by the car in its "viscous boundary layer" is actually getting pushed even faster forward, wrt the car, by the pressures in the outer flows.

Bottom line here, is that a big "Blue-Bubble" blob of air gets tripped up by the unsteady boundary layer movements. This "BB" then attaches itself to the rear of the car, and becomes, quite literally, a PITA! This air is "blue" because its speed wrt the car is very low (ie. it moves with the car), so its streamlines are conventionally coloured blue.

These BBs are invisible in the real world, but you can rest assured that they are always there, following you around the track, behaving like big floppy extensions of the car, and potentially making a real mess of your carefully designed aero.

The "Streamlines" sketch above shows a smallish BB just behind the car/underbody. Without the Gurney this BB might be much bigger, filling the diffuser section, reducing the flow through the throat, and thus reducing downforce. The Gurney lifts the BB upwards somewhat, making it behave like a floppy though conventionally tapered tail to the wing.

There are lots of ways of controlling these BBs that have been, and still are, used in conventional "tunnel" cars (see Luke's post^, and below...). One way is to make the diffuser section longer, so the "adverse pressure gradient" is less steep. But even short tunnels take up a lot of valuable space that could be used for other important stuff. Making them longer wastes even more space.

And, importantly, the largest parts of the tunnels DO NOT suck the car down. There is only a small section of very low pressure (= the "throat") that provides most of the useful downforce.

So, let's try something else...

Z

Z
08-23-2013, 09:20 PM
OPEN-SHOEBOX.
==================
This approach to racecar aero has been rediscovered countless times, often by amateurs who have given up trying to make their wings work, and have instead decided to take a KISS approach to the whole problem of going fast (ie. build simple car + lots of driver training/testing...).

The essence of this system is to provide bodywork that stops the air getting through the front, sides, or top of the car. Nothing more! So like an inverted "shoebox" that is open at the rear, and maybe with the front bevelled, or rounded off a bit.

The system works by letting the low pressure air that is behind the car (sometimes called the "base drag", or "wake") to also "communicate" its low pressure all the way under the car, thus giving downforce.

Since the same low pressure acts on the plan-view area of the car as acts on the rear-view area, the Lift-to-Drag ratio is simply the ratio of the two areas. For constant width, enclosed-wheel, sportscar style bodywork, L/D = Length/Height, which is considerably better than many "bewinged" cars. See Joe Katz's "Race Car Aerodynamics", Figures 6-7D, 6-12, ++, for some examples...

https://lh3.googleusercontent.com/-2t5Cct6hmEw/Uhb4FyZZ0XI/AAAAAAAAAOU/dpjL5WUFYjQ/s800/SBxStrm.jpg

This particular "open-shoebox" has a front "splitter" about ~2 cm off the ground, and the top of the rear Gurney is about 0.28 m above ground. Importantly, details of the shape are NOT important. Any old rubbish can fill the centre section, including low mounted engine and driver, suspension parts, etc. The main requirement is just to seal the underbody area from any flows from front, sides, or top.

Here, overall downforce (at 10 m/s) is only about 12 kg (<120N) and drag is about 1.8 kg (18N). The Gurney has increased both these numbers by throwing up a "rooster tail" of air behind the car, which has lowered pressure in the wake more than would be the case without it. The L/D stays at about 7:1, which is similar to Length/Height.

At the target Skid-Pad speed of 16 m/s the downforce would climb to 30 kg, and stretching the underbody to 3 metres long might get downforce to 45 kg. The 2 metre long undertray has CL.A = 1.9 sq.m, and at 3 metres long CL.A = 2.8 sq.m.

So, nowhere near enough, but good news below!

https://lh3.googleusercontent.com/-ZBbFRXzN_2g/Uhb4B7R1KbI/AAAAAAAAAOM/TjqjRW5K3MU/s800/SBxPres.jpg

A key feature of this type of aero is that it is all but FOOLPROOF!

The normally PITA-BB that follows the car around is now, in fact, providing the downforce. All that the aero-guy need do is let the low pressure BB behind the car to also get under the car. Not hard! Lowish front and side "splitters" help keep the BB under the car, and can also do a lot more (see later).

As noted above, amateur racers often stumble onto this type of aero and find that it works far better than their expensive, but finicky, real "wings". The only cost to a low-resource FSAE team trying this concept is the small amount of time spent building a crude undertray, plus a few extra kilos. Note that at higher FSAE speeds of ~30 m/s (108 kph) the shorter 2 metre long undertray would give over 100 kg (~1 kN) of downforce. This gives a good "safety net" of grip, and would boost driver confidence in high speed corners...

[Nerd Note]
As mentioned earlier, the BBs are "low speed" air (wrt the car). Importantly, they can be at "low pressure" wrt ambient, as in the wake of the car above, OR they can be at "high pressure". For example, as pointed out by Mr Prandtl in early 1900s, a BB could form at the inner corner of the Gurney (where pressure is "orange" and above ambient). So Mr Bernoulli's oft-quoted principle that "high speed flow means low pressure, and vice versa" DOES NOT APPLY to the BBs! This is obvious if you read the assumptions of Mr Bernoulli's Principle, but few people do...

Also, Mr Helmholtz explained the BB's role in creating drag on non-streamlined bodies way back in the middle-1800's. Thankfully, this resolved poor old Mr d'Alembert's Paradox (middle 1700s), where, after doing numerous experimental tests and knowing that drag is ever present, he spent a lifetime trying to calculate the "resistance" theoretically, only to keep finding that it was always "absolutely zero"!

The interesting point here is that nowadays many Fluid Dynamicists, and much of their teaching, insists that this sort of drag is intimately related to the fluid having "viscosity" (ie. internal friction). This, IMO, completely misses the point, which is that this mechanism of "form drag" (= the major part of drag) is fundamentally one of INVISCID, UNSTEADY flow. Look up Kelvin-Helmholtz Instability (KHI) for background, or at least to see some very pretty pictures. [/End Nerd Note]

Anyway, the "Shoebox" gives a few clues as to how to increase downforce.
1. The underbody surface does NOT have to be carefully shaped, and could possibly be flattish (for easy packaging of other stuff, and low CG).
2. Having lowest possible pressure under largest possible area of the underbody seems to be a good idea.
3. The low pressure zone under the front splitter looks interesting...

Z

Z
08-23-2013, 09:23 PM
FLAT-BOTTOM + DOUBLE-FLAP.
==============================
In this 2-D example the majority of the underbody is flat and parallel with the ground. At the rear a double-flap creates a low pressure at the exit to the main underbody, and this low pressure extends under the majority of the floor area. This arrangement might be called a "double-slotted triple-diffuser".

Conceptually, this is like taking the Shoebox and creating a greater amount of base suction over a lower height base area, for more downforce with similar drag.

https://lh5.googleusercontent.com/-jjU6nXbmJWs/Uhb3zktUAfI/AAAAAAAAAN0/_gOXNZIg_dU/s800/W%2526DFStrm.jpg

The majority of the underbody here is ~5 cm above ground. The trailing-edge of the rearmost flap is 0.28 m above ground. The two flaps and main underbody are very simple shapes, just a few constant radius arcs. The flaps are just 4 such arcs (top, btm, f, r), with the trailing edges (of all 3 surfaces) being R = 2 mm. Exotic "aerofoil" profiles are NOT needed.

Overall downforce (at 10 m/s) is now ~70+ kg (700N). YAHOO!!!

Drag remains very similar to the Shoebox at a negligible ~1.8 kg (18N). Drag could be reduced, but why bother?

At the target Skid-Pad speed of 16 m/s the downforce would now be ~180+ kg, and stretching the underbody to 3 metres might get downforce to 270+ kg (albeit only in this "skirted" 2-D form, but see below...).

In CL.A terms the 2 metre long undertray has CL.A = ~11 sq.m, and at 3 metres long CL.A = ~17 sq.m.

So, mission accomplished, and off to the pub!!! :)

Err, ... except for all that 3-D stuff, and wheel-wakes, and driver and engine getting in the way...

https://lh3.googleusercontent.com/-NSaxF1m1UW8/Uhb3sAykwfI/AAAAAAAAANs/M3e96JuaWsQ/s800/W%2526DFPres.jpg

The two main real world problems to be addressed before celebratory drinks can be drunk are:

1. 3-D UNDERBODY FLOWS.
The low underbody pressure will suck air in from the sides of the car, so the flow will NOT be entirely longitudinal as sketched.

This is not really a big problem as long as the underbody surface is appropriately profiled to accept these side flows. Hint: have front and side edges of the underbody closer to the ground (say, ~2 cm), with the central and rear sections similar to the sketches (section under driver and engine can be lower). Also, have the side edges at full width of the car just in front of the rear wheels (so ~1.4 m wide), then tapering towards front of car.

Another approach (that can be used together with above) is to look at pictures of the DeltaWing racecar when it was first displayed for publicity pics, and then later when it actually raced. Look at the bottom-leading edges of the "delta" sides of the raced cars. Or google "BLAT". Or just read this article (http://www.motorsportmagazine.com/race/sports-cars/the-secrets-behing-the-delta-wing/).

(BTW, I reckon "Boundary Layer Adhesion Technology" is a misnomer. IMO, the vortices are there to provide a stable exit route for any Blue-Bubbles that start to build up under the car. In this case you do NOT want the BBs "adhereing". You want to get rid of them! Also, the longitudinal vortices can act a bit like side-skirts, if properly managed, thus making the flow more 2-D-ish.)

2. GOOD FLOW TO THE FLAPS.
The rear flaps will only suck hard on the underbody exit if they have a good, clean flow to their two "slots".

So the driver and engine should be packaged in a reasonably "streamlined" fuselage. NO SILLY SIDE-PODS! The narrower this fuselage tapers (in plan-view) at the rear, the better (hint: air-cooled single-cylinder engine looks good!). This tapered rear gives more working width to the rear flaps.

Turbulence from the rear wheels (= floppy BBs!) can be controlled by rounded "noses" in front of the wheels, these joined to vertical-longitudinal "fences" just inboard of the wheels, and then tapered tails behind the wheels. The rear flaps should span between these "end-plates" to improve their effectiveness.

Turbulence from the front wheels is mostly above the underbody, so should not affect the under-flows too badly (especially if side vortices are used, as suggested above). But this turbulence could adversely effect the rear flaps, so should be steered outwards (the vertical type "fence" required here should be obvious).
~~~~~o0o~~~~~

Finally, the above Non-Aero requirements might not suit your current thinking. For example, you might want to build a mini-F1 car, so you want at least a 4-cylinder engine, fashionable F1-style side-pods, and so on. If so, then good luck with your choice...

But the big-picture points simulation several pages ago suggests that the sort of good aero in the above two sketches, together with a simple, strong, "brown go-kart" designed to suit this aero, will blow away almost every other FSAE car currently out there. Seems like a simple choice to me!

Comments and criticisms always welcome... :)

Z

mech5496
08-24-2013, 01:04 AM
Z, thanks for the insight. Speaking of BLAT and DeltaWing, take a look here (http://www.auto123.com/ArtImages/158050/deltawing-inline4.jpg) and here (http://dlstatic.speedtv.com/imageserve/051KduYddEbW7/575x459.jpg?fit=scale&background=000000)

MCoach
08-24-2013, 11:06 AM
Z,

I welcome these new posts of yours. They are informed, informative, and provide a more depth analysis than is typically seen. I don't have much to add, but very much appreciate the read. Thank you.
I'm anxious to see the this thread continue to develop.

Z
08-31-2013, 12:30 AM
Speaking of BLAT and DeltaWing, take a look here (http://www.auto123.com/ArtImages/158050/deltawing-inline4.jpg) and here (http://dlstatic.speedtv.com/imageserve/051KduYddEbW7/575x459.jpg?fit=scale&background=000000)
http://www.auto123.com/ArtImages/158050/deltawing-inline4.jpg
Harry,

Thanks for links.

The above top-view of the DeltaWing undertray shows how simple it is. The air enters the front of the tunnel at an angle, which gets the air in the tunnel swirling. This swirling then messes up any "Blue-Bubbles" that try to lodge themselves in the rear diffuser section, and effectively blows them away. Result is high and stable downforce. Also, this approach allows for side-pod mounted radiators. But the rear diffuser sections still take up a fair amount of space.

The "slots" in my last post do a similar job of blowing the BBs away. Looking at the "Streamlines" image shows that there is still some "dead air" following the car, which is lowering its downforce (look between the two streamlines coming off the TE of main underbody). Little "vortex generators" could be used to blow this dead air backwards for even more downforce than quoted above.

These vortex generators would only have to be postage-stamp sized plates fixed somewhere near the lower slot, with the plates set at about 20-30 degrees to the oncoming wind. Look at the tops of jumbo-jet wings for similar devices (though these are usually about credit-card sized). (Edit: see Katz "Race Car Aerodynamics" Fig. 4-37 for these vortex generators.)

Z

mech5496
09-02-2013, 05:35 AM
Z,

There is a paper on aero drag reduction by vortex generators (http://www.4g63.de/facts/vortexgenerator-evo-mitsu.pdf) which could give an idea on how they work. IMO the side swirls on the DeltaWing do a fair amount on sealing the underbody preventing vacuum loss without skirts touching the ground. Regarding your last design, it has an inlet converging "throat" which forces air under the car. I was wondering if this is needed or a "shoebox" style splitter could work the same. I.e. do you think it is better to increase airflow under the car or block it?!

Z
09-03-2013, 09:00 PM
Harry,

"... paper on aero drag reduction by vortex generators..."

Those vortex generators (VGs) are very useful for controlling all sorts of flows. The two Hoerner books referenced in the paper cover experimental aero work done 50++ years ago, and show that VGs were widely used back then (ie. old tech!). FSAE teams could probably get significantly more downforce from their conventional wings by using appropriately placed VGs.
~o0o~

"Regarding your last design, it has an inlet converging "throat" which forces air under the car. I was wondering if this is needed or a "shoebox" style splitter could work the same. I.e. do you think it is better to increase airflow under the car or block it?!"

Interesting subject!

I will state here categorically that, IMO, JUST AS MUCH DOWNFORCE can be got with a "Shoebox" style underbody, as with the smoother underbody shown in the last two images.

So take the "Shoebox" shape, remove the rear Gurney, bend the back of the shoebox down to ~5 cm above ground, and then add two flaps as in the last images, to get similar overall downforce. A "blue-bubble" will fill the underside of the Shoebox and make it behave as if it has a smooth, low friction, bottom (eg. see BB under nose of Shoebox).

The reason I didn't post this solution is that the magical box of "Crayons For Drawing" that I borrowed from the fairies is NOT VERY GOOD at depicting real flows! Some of the problems are that these magical Crayons are very slow if you sharpen their points (ie. use small cell size), are even slower when trying to draw 3-D flows, and in their standard form are utterly incapable of modelling unsteady flows. Oh, and they have an extremely UNFRIENDLY "user-interface". (Aaaarghh!!! Engineers should NOT be allowed to write computer interfaces!!!).

Bottom line here is that the Crayons kept drawing "blue-bubbles" closely following a Shoebox-and-Double-Flap style underbody, with these BBs lowering overall downforce (ie. they block flow behind the flaps, lessening the peak "suction" under the first flap). Providing a smoother underbody to the main element convinced the Crayons to let the BBs slip away.

In practice (= in the real world), the best method of shaking-off the BBs would be a few appropriately placed VGs. But to draw that would have required me "sharpening" the Crayons (to ~1 mm cell size?), and doing a "3-D sketch" (= squillions of cells), for which I had no patience.

I note that even if I had tried to model VGs with the magical Crayons, I doubt that it would have given realistic results. This is partly because of issues such as "numerical diffusion", but more so because the Crayons implicitly expect the flow to be "steady", even though most real flows are thoroughly unsteady!

The disappointing bottom line here is that even though VGs are old tech and have been proven to work very effectively (eg. golf balls), the modern approach to designing aero with magical CFD, rather than with "real" experiments, might suggest to the designer that VGs do not work, and messy underbody flows cannot generate significant downforce. So Crayon wielding students (such as Julian?) might tell you that FSAE cars can never get to 3G-lateral on the Skid-Pad, because "It is impossible! The magical Crayons tell us so!!!"

Such is progress! :(

Z

(BTW, if anyone has detailed numbers or links to papers++ on the DeltaWing aero, BLAT, etc., then please post them! :) )

mech5496
09-04-2013, 02:57 AM
Nothing detailed in those numbers, but the claimed figures for DW are 12000N of downforce for 2500N of drag at 90m/sec, with the downforce distribution being 25/75 front to rear.

Not quite sure if you are familiar with the '81 AAR Eagle that pioneered BLAT. It sure reminds me of your proposed double flap undertray that narrows up front.

http://www.indycals.net/images/decal_images/med/81pepsieagle.jpg

http://m9.i.pbase.com/o2/21/783021/1/127806629.9teGXMcV.DSC_3651640.JPG

http://www.motorstown.com/images/eagle-indy-05.jpg

http://1.bp.blogspot.com/_DsmBRYLt31E/S-IY5xAxcZI/AAAAAAAAAcY/-RmHFFLtV9U/s1600/140_140.JPG

(Note the interesting front upright/hub/a-arm attachment)

Z
09-04-2013, 09:48 PM
Harry,

Yes, and the 75% rear aero distribution is because the DW has ~72% rear weight (IIRC).

Anyone worrying that since the DW can only get CL.A = ~2.4 (from above numbers), "... then how can we poor students get any more?", should keep in mind that the DW races on circuits where it has to do ~90 m/s on the straights. That is 324kph or ~200mph. The quoted downforce is already about twice the static weight of the car, and since no "active aero" is allowed, any higher CL.A and the car would probably bust its axles, or pop tyres...
~~~o0o~~~

Some comments about the 1980/81 AAR Eagles.

* The top pic seems to show the car pre-BLAT. The bottom two pics have the "extra little bit" that creates the side-vortices.

* F&R "winglets" are probably mainly for trim control (ie. adjusting F:R aero balance).

* Overall the cars look quite low drag. Nicely streamlined engine cover, wheelpods to control flow around the rear...

* The ~triangular plan-view underbody shape conveniently gives F:R aero% = ~mass% = ~tyre%.

* Front suspension is double-wishbone, but the upper-wishbone-outer-BJ is fitted directly IN the axle-centre, for good load paths and lower CG.

* The total package was obviously TOO GOOD (blew the opposition away), because it was banned within a few years. Ahhh... motorsport!

Bottom line, I reckon a good car for FSAEers to draw some inspiration... :)

Z

mech5496
09-05-2013, 06:36 AM
Z, the first pic is actually from a model car, so they must have missed that detail. I just included it because it shows very well the triangular plan view shape of the car. On the success of the design, keep in mind that the 81 Eagles were powered by a small block NA Chevy engine while all others used turbocharged Cosworth engines (660 vs 750+ hp).

"On the aerodynamic side, rather than the sidepod tunnels being fitted to most Indycars at that time, the Eagle carried its low-pressure-creation apparatus in what was essentially a box built around the engine and rear suspension. With downforce from bodywork shaped specifically to generate powerful vortices beneath it, the ’81 Eagle became one of those racecars that turns out greater than the sum of its parts. "

"The ’81 Eagle turned out to be exceptionally good in practice as well as theory. In Mike Mosley’s capable hands the dart-shaped yellow and white machine qualified second fastest at Indianapolis, while earning the prestigious Louis Schwitzer Award for engineering excellence from the Indiana chapter of the Society of Automotive Engineers.
On race day, however, the hope generated by that front-row starting position went unrealized when the engine broke a connecting rod early in the race. The following week at Milwaukee, however, Mosley started from 28th and last grid slot as a promoter’s option after missing qualifications, then fought his way through the entire field to score a brilliant victory with the last car ever to win a National Championship race using a true stock-block engine.
After Mosley’s heroics at Indy and Milwaukee, Geoff Brabham qualified the road-race car on the pole at Riverside, more than a second ahead of the field, then led the race handily until a wheel nut was cross-threaded during a planned pit stop and the euphoria of the moment evaporated. Rocky Moran gave a similar performance at Watkins Glen, only to be derailed by a fuel hose problem." And after that a rule change came...

(Text in quotation marks from www.vintageracecars.com)

Cunningham
04-22-2014, 03:53 AM
All, I've done some searching--without success--for clarification on rule T9.3:

T9.3 Minimum Radii of Edges of Aerodynamic Devices
T9.3.1 All wing edges including wings, end plates, Gurney flaps, wicker bills and undertrays that could
contact a pedestrian must have a minimum radius of 1.5 mm (0.060 inch).

Would one of you please enlighten me on what is considered an edge that could contact pedestrians? Do this include trailing edges of wings and endplates? Gurney flaps on upper elements of front wings?

My team is new to aero this year and as such, we do not have the benefit of discussing these questions with the technical inspectors.

Thanks.

mech5496
04-22-2014, 04:45 AM
Cunningham,

I suppose you could ask via e-mail; however, just to be sure, I would keep all radii above 1.5mm

JulianH
04-22-2014, 06:49 AM
I'll second what Harry said.
We got different answers to that question at all competitions.

In the beginning (UK 2012) we said "All the trailing edges cannot contact a pedestrian so we have them smaller". In scrutineering we had to adjust all of them.
Afterwards we started to ask for rules clarification and at least in the UK and Germany the "just all radii above 1.5mm" seems to be the best solution.

404namenotfound
04-22-2014, 09:28 PM
Has anyone else seen the GFR wings this year? I saw a photo from their unveiling today and was surprised with their design. I'll admit my knowledge of aero is limited but it seems the double front wing wouldn't be effective given how close the elements are to each other. Thoughts?

Some Guy
04-22-2014, 10:57 PM
I think we have started to get to the point where aero>everything else in terms of vehicle design. Certainly when it comes to "top" teams that have most of the other vehicle aspects well sorted. I'm not complaining (much), if the aero rules get clamped down you would probably just see those resources got to other areas like composites or kinematics.

Even if it's only a 10% down force increase (likely more), there are lots of other gains to be had in terms of countering pitching moment due to the rear wing and overall vehicle balance. In other words you gain a lot from a little.

I thought Ann-Arbor's aero was more interesting personally. Definitely a liberal interpretation of "open wheel" in the rear.

Cunningham
04-23-2014, 04:33 PM
Thanks Harry and Julian.

Z
04-23-2014, 09:42 PM
Has anyone else seen the GFR wings this year? I saw a photo from their unveiling today and was surprised with their design.


Posted by Some Guy:
I thought Ann-Arbor's aero was more interesting personally. Definitely a liberal interpretation of "open wheel" in the rear.

Does anyone have pics of these cars that they could post, please? :)

Z

Trevor
04-23-2014, 10:13 PM
GFR: https://www.facebook.com/media/set/?set=a.724955744223420.1073741840.130002227052111&type=1

Ann Arbor https://www.facebook.com/media/set/?set=ms.792484457447158.792484460780491.7924846207 80475.792485050780432.792484630780474.bps.a.698608 193501452&type=1

Z
04-23-2014, 11:12 PM
Trevor,

Thanks!

Both cars seem to be following a "more is better" aero philosophy. In both cases I agree that they will work better than previous less-area wings. Ann Arbor's huge rear-end-plates should be also be beneficial.

However, IMO even more is possible from a well designed UNDERTRAY ONLY. Same plan-area, but (much) more downforce is potentially available, and with a lot less drag and mass.

Big rear-end-plates are always an aero advantage, though cost/benefit is worth evaluating (easiest via real testing, given the ease of building/fitting big end-plates). Note that these are advantageous even for a non-aero, "oversteery" car.

A suggestion for any other teams wanting to follow this path, is perhaps try using transparent polycarbonate (= "Lexan") for the upper-flap of the front wing. Or at least ask your drivers how they feel about the lost visibility of cones at the apexes.

Anyway, the "wings will never work" argument from ~10 years ago, does seem to be losing its support. :)

Z

404namenotfound
04-25-2014, 10:59 AM
Anyway, the "wings will never work" argument from ~10 years ago, does seem to be losing its support. :)

Z

I always found it funny that the main argument against wings was drag and that we're going to slow for them to work. That argument is pretty weak when you figure we're traction limited anyway and if we're going fast enough to make drag the wings are also making down force. Only real arguments I can see against them are based on the mass and sheer size of what teams are coming up with now.

Markus
04-26-2014, 01:48 AM
Z,

Don't forget the aero rules were opened up quite a bit a couple of years ago.
Before that the actual benefits from wings were a lot more subject to debate.

MCoach
04-27-2014, 04:47 PM
Keep in mind "huge wings" used to look like the car on the left before the rules change several years ago.

https://www.facebook.com/photo.php?fbid=333720379982554&set=pb.185745901446670.-2207520000.1398635166.&type=3&theater