The two most successful racing sucker cars were the Chaparral 2J (1970) and the Brabham fan car (1978?). The Chaparral 2J raced four times, never won (various glitches), but set lots of fastest laps etc., then was banned (in the "free-thinking"!! Can-Am series). The Brabham raced once (Swedish GP?), won, and was banned. Obviously sucker cars work - a bit too well!

For the Chaparral see "Chevrolet - Racing?" by Van Valkenburgh, or "Can-Am Racing Cars 1966-1974" (a compilation of magazine articles) published by Brooklands Books. The Brabham was a simplified version of the Chaparral.

I see two main approaches to this problem: 1) Low suction over a large area (the whole underbody). 2) Higher suction over a smaller area.

The Chaparral used option 1 with two axial flow fans powered by a twin cylinder 45hp two stroke motor (so you will need more than a leaf blower). The skirts were Lexan (polycarbonate) connected to the suspension so that they always hung just (1/2"?) off the ground. See books for more details.

I might try option 2. A good centrifugal fan (industrial size - check catalogues) can suck harder than axial fans. Then build two "suction cups", about 1 to 2 square metres area each, and attach these directly to (under) the front and rear suspension. This way you don't compress the normal suspension springs and "skirt height" is easier to control. Make "skirts" out of 2x4" softwood (they will grind themselves to the right profile). Possibly make the suction cups diamond shaped in plan view for better sweeping away of gravel, etc. Then a separate 50hp motor and centrifugal fan with ducts to the two suction cups...

Then lots of fun!!!

Oh, maybe some heavy duty truck tyres to carry the loads...


PS. How much suction can you get? The limit is atmospheric pressure which is 1 kg/, 1 ton/square foot, or 10 tons/square metre. So with, say, 1/10 atmosphere over 4 sq.m that's 4 tons! (Make that BIG truck tyres!)