Quote:
Originally Posted by j.fro
I'm not really looking for the whole car. I'm just interested in info about the spoilers/wings. I know that to get the exact answers, the math is complex, but approximations can be made, particularly if you are using airfoils with similar shapes but different surface areas. A method for determining coefficient of lift for different shapes is the element I'm really after.

well when you're talking about lift, you have to consider the entire car. a spoiler 'spoils' airflow to reduce the lift generated by the shape of the car's body. to figure out how much a spoiler reduces lift, you have to consider the shape of the car both with and without the spoiler, calculating lift in each configuration.
calculating downforce generated by a wing is much easier, but depending on the shape of the wing, it can still be rather complicated. the easiest equations treat the wing element as a simple inclined plane. downforce is calculated by finding the resultant z vector of the incident airflow. for example, if air flowing at 100mph is incident on a wing with a force of 200lb and the wing is a 45deg angle, then 1/2 of that force is down and the other half is drag. downforce would be 100lb.
most wings use a combination of inclined plane and bernoulli. for non racing wings, the bernoulli effect is probably a small component of the total downforce, so using kinematics and trig will probably work well enough to compare relative downforce between two elements.
there is another component to consider: drag. well designed wing elements can produce tremendous downforce with very little drag component.