Downforce on FSAE

[David Lemire]

Hello everybody

A few quick questions for FSAE team that were using wings or undertray on their car over the past years...

Does any one try the same car with and without wings on a track similar to Detroit track to compare the times, and if yes what was the time difference approximatively...

Another thing about underbody tunnels... how can you find a theoritical approximation of it since a big amount of the downforce comes from the vortex effect in tunnels... I know how to find the downforce using simple airfoil analysis software but this will not yields good results for undertray I believe..

Any help would be appreciated

David

David Lemire
Team Leader
McGill Racing Team

[David Lemire]

Hello everybody

A few quick questions for FSAE team that were using wings or undertray on their car over the past years...

Does any one try the same car with and without wings on a track similar to Detroit track to compare the times, and if yes what was the time difference approximatively...

Another thing about underbody tunnels... how can you find a theoritical approximation of it since a big amount of the downforce comes from the vortex effect in tunnels... I know how to find the downforce using simple airfoil analysis software but this will not yields good results for undertray I believe..

Any help would be appreciated

David

David Lemire
Team Leader
McGill Racing Team

[Scott Wordley]

Underbody tunnels are hard to estimate particularly if they are mounted to the chassis and see varying ground clearances, as they are very sensitive to ride height with DF dropping off very quickly with increasing 'skirt gap'. The book by Joseph Katz (Racecar aerodynamics?) has some interesting data from sportscars with diffusers.

I think full car CFD is the needed for a decent approximation because the interaction with the rest of the car/wings will have a big influence on their performance.

Other wise build them test them. There are several ways you could measure their performance on the road but not necessarily on your FSAE car if you get a little creative. http://fsae.com/groupee_common/emoticons/icon_wink.gif

Regards,

Scott Wordley

http://www-personal.monash.edu.au/~fsae

[wingman]

Hi David,

First of all, do a search key word "wings" and you will find some very interesting info....especially the "got wings" thread for which many contributed. Also check out Monash U's web site and Cal Poly Pomona's web site for test data......

If your interested in implementing aero, I recommend adding wings to an existing car and test test test..... you'll find out VERY quickly whether or not you have the recourses and the time to make them work. I will hold by my previous statements in other threads that you do not need CFD or wind tunnels to make an aero package work, but you may need them to make it work better.... http://fsae.com/groupee_common/emoticons/icon_smile.gif

So asking if aero works for FSAE cars is not a valid question, it's whether or not it works for you (i.e. your team) that matters because it greatly complicates the design, construction and testing of the car.

To answer your question, Cal Poly Pomona performed testing back in 98 on there first winged car with an FSAE enduro size course. no wing lap times were around 46 sec and erratic. Times with the wings same day/driver/course were 44 sec and much more repeatable.

Ultimately, the only way to answer your question is...it depends...and the only way you will know is to try it.....