Yup, Jersey Tom is bringin the hate on two of the most prominent things in high-end Formula racing recently. Or at least their application for FSAE teams.
Allright fine well I'm not really bringing all sorts of hate necessarily but I would not personally put them on a FSAE car. I've always been a skeptic of everything (which IMO is required of all engineering, especially at this level), and being an alum now, I am even more so.
Anyway. Not knocking the teams that use them, but I'm curious to see other team's analytical justifications of monocoques or enormous wings.
Monocoque
Did a quick model of a chassis goin into a turn as two rotational spring mass damper systems (F&R end of car with susp) linked by a torsion spring (frame). Idea was since the rear load transfer and slip angles are initiated by the front, the speed at which they do so (and turn in) is in a big part affected by chassis stiffness. Put a step roll moment on the front end and watched as it and the rear end moved around. Not the best model of what's going on, but not a bad ballpark. At 1000 ft-lb/deg the response was very quick, on the order of .01s, which I deemed good enough. Beyond that it was a point of diminishing returns getting response to thousandths of a second. Very attainable with a steel frame chassis.
Steel frame materials - $350, fairly quick and painless other than the stupid large gaps I had to weld at times, and seemed a lot more bulletproof and easier to analyze than a carbon tub. It amazes me sometimes that after this, and after not even being able to vacuum resin infuse a flat carbon plate this year, some people are still considering trying a vacuum infused monocoque at CU.
In testing we could make damper adjustments and either end of the car would be plenty sensitive to them, and the car was very neutral and predictable through turns and slaloms so I feel pretty happy we have a stiff enough chassis. There's definately large potential weight savings with a tub, but that assumes you can do good accurate analysis of one, which as I understand is a nightmare.
Wings
Now I don't doubt the importance of aero, and I've been looking at it for a project car I intend on building in Ohio. Running some idealized numbers, on wings with fairly high aoa's (near stall, tho admittedly single element), I find it hard to believe the claims I hear walking around of multiple hundreds of pounds of aero download at 60mph. Perhaps this is with some massively efficient venturi diffuser, though I'd want to see pressure sensors on the top and bottom of the car to be convinced of it.
Beyond that, even if you had an appreciable amount of download at low speed, the thing that I think kills it for FSAE cars is the wild high load sensitivity of FSAE tires (6x higher rate than I'd expect to see on a GP car from even the early or mid 90s). Even if you can get some appreciable increase in available down force, the roll off rate of the tires lateral grip capability makes the increase in available lateral force small.
Beyond the usual headache of problem solving and fixing issues on a new FSAE chassis every year, and figuring out mechanical balance, I would think that having to figure out aero balance and how to get enough performance out of the package to make an appreciable amount of difference would take a lot of valuable time.
But that's just what I think. Other thoughts?