So I am finally at the point where I am ready to start understanding wings and downforce, even though I am not yet designing the body of my open wheel project. I recently took the rear gas springs off the decklid of my extremely heavy 1994 Camaro road race car to motivate me to take some weight out of the decklid. Boy did it! The decklid weighed around 100 lbs! So I am replacing the glass with lexan (30 lbs) removed the rear factory wing and add-on spoiler (20 lbs) and stripped the lower layer out of the decklid (20 lbs). After struggling to drop even a half lb out of my race bike, I am finding it hilarious how easy it is to take weight out of this tank! So now I want to put that weight back down in the form of: a) a good spoiler to reduce the lift effect on the car, b) a wing to replace the downforce I lost from the weight I removed, or c) a wing to apply more downforce than I removed.
This inspired me to read Competition Car Downforce, By Simon McBeath. A very good read, and has really got the gears turning and got me thinking about ways to apply some of these principles to keep me out of the air with my project car, and hopefully even apply some useful downforce.
There are a couple things however, that are bothering me, and I thought that the formula community may be able to help, as you guys utilize wings heavily. McBeath shows some single element NACA airfoils in the appendix. One is NACA 4415, and there are a couple others. They both correspond to a lift coefficient of around 1.5 for a single element wing at angles around 12-14 degrees. In one example that he works out, a wing with this profile that is 3 ft by 1 ft area, gives 78 lbs of downforce at 100 mph at a lift coefficient of 1, which he uses to take into account dirty air from the car and such. Now, he also has some profiles of multiple element wings that reach a lift coefficient of 3 at the same angles, but I want to talk single element for now.
McBeath provides pictures of a wing on the Mclaren F1 race car that has an airfoil that is unlike the NACA profiles he adds in his appendix in that it is concave on top. It looks much like this wing from Tiger Racing.
http://www.tiger-racing.com/for_sale.html
This wing from Tiger Racing boasts 600+ lbs of downforce at 100 mph (calculated), yet using the formula below for downforce and the area of 12" x 68", I find it difficult to get even a couple hundred lbs with a single element lift coefficient.
L = 1/2 * p V^2 * S * Cl
Where :
L = Lift
p = Density of air ( 1.225 Kg/m^3 at sea level)
V = velocity of air
S = Wing plan surface area
Cl = coefficient of lift.
Now, obviously, this 600+ number could be hype, and no one will ever question it. But I have to wonder if it is accurate, what numbers are they using for their calculations? There seems to be very little information out there on wings supported with real downforce numbers.
I guess I'm just wondering if any of you have done any wing calculations, wing building, or have any experiences that would help. I would love to hear your thoughts!