NASA racer

no point in thinking about doing regionals in DSR in the Radical now...not fond of being lapped in 20 lap races heh.

ryoung

In many cases I'm sure that wicker's do provide essentially free downforce with minimal additional drag, but in high HP cars running very high downforce wings near stall.

Imagine two wings, one with a 6 ft span at a 6 deg angle of attack, and the other a 3 ft span (limited by class rules) at an 18 deg angle of attack. Assume these two wings generate identical downforce, but the wing at an 18 deg angle of attack is close to stall, has flow seperating under the wing which reduces downforce, wastes energy in turbulence, and produces high drag. In this case, the wicker is one possible solution. It adds the equivalent of a degree or two to the angle of attack, but more importantly, the low pressure area directly behind the wicker helps reatttach air flow under the wing. The result -- much more downforce, and even with the small amount of turbulence generated by the wicker itself, the wing generates much less total drag. [You wouldn't see the main element of a wing at 18 deg, but you often see wickers on the nearly vertical flaps used in IRL, CART, and F1.]

Then there's are low powered racecars ... We haven't got the horsepower to push high downforce two or three element wings (except in the rain when the benefit outweighs the cost). About the most we can manage is a medium downforce setting with the flap of a two element wing at a modest angle. At these angles, flow seperation under the wings is rare, and even the modest turbulence generated by a wicker is additional drag without any benefit.

On a related subject, note that you never see wickerbills on airplane wings, but you often see vortex generators on the wings of even the newest commercial jets. This is why we use them under our front wing and in the center third of the lower support element of our rear wing. In the latter case, the bodywork generated enough dirty air that the lower wing flunks the streaking oil test without the vortex generators.

Note the VG's on this Cessna
<img src="http://www.microaero.com/ImageGallery/Images/CP210.jpg">

Mark Dalen

Thanks. Nice explanation.

ryoung

I'm definitely curious about how much downforce your Radical generates. Please post some results after you get them :-)

And you said CSR/DSR is probably only a year or two away from full tunnels!! Wow, talk about free downforce. I can't imagine how much this is going to knock off of lap times, but it'll be a bunch.

Jeff Vader - boscoj

thanks for the ideas . . .

Mark Dalen

I will be happy to share the info as I generate it. It will be the new Stohr that gets this data, not the Radical. From others, I understand the car will make ~600-700 lbs of total downforce at 100 mph. Weight should be ~950 lbs with driver, gear, etc.

John/TSR

Bob is one of our local mad scientists. Much GT-4 and GT-5 lunacy in his past, but he's making the dive back into aero cars. Haven't seen his aero book...but I talked to him about it a few months ago while screwing around in a paddock somewhere. Every time I see him at Mosport on a race weekend, he tells me how much I suck at Mosport. Gee thanks, Bob.

I did beat him twice this year, even if he was in a different class in the race group. Just not at Mosport.<ul><li><a href="http://megadawn.com/">Cosmic Bob's Aero Book</a></li></ul>

Mark Dalen

I have it and it is very simplified. I think the McBeath book is much better.