I need a quick reply to an aero question...

[TorontoWorker]

I've been in a battle on my club BBS for a year or more with a fellow member who is an Irlista.

In one of our heated battles I mentioned the fact that a lot of IRL teams are triming their cars out at anywhere near 0 degrees wing angle if not +1 or +2 degrees or more. It is my contention that this is done to break the downforce that the topside of the bodywork is generating in order to gain higher top speed.
I believe that this is a safety issue as it reduces the margin of control in the event of a change of wind direction or debris on the track causing the car to lift.

His contention is the follow:


It appears you have things to learn about aerodynamics.
In some cases you have to take out of the angle of attack in order to gain downforce. Why? Because the downforce increases exponentially by the square of the increase in speed. So, what they do is to take the wing out to speed up the car which in turn increases the efficiency of the wing to produce downforce. Up to a certain speed the driver feels comfortable with the downforce for a given wing setup but unable to gain speed and the car slides horribly in the corner. The engineer is there to suggest whether there is further speed and stability to be gained by taking wing angle out. Or, whether they have gone too far with that and a higher angle of attack benefits. There is a fine line and the driver has to trust his engineer because the whole process is counter-intuitive. The references are the lap time (average speed) and the comfort of the driver.


Many racing cars - not just Indycars or CART cars - have their wing appearing to be tilted backwards. As long as the upper surface generates higher pressure than the lower surface, the wing does it's job. By how much, is up to the type of the car and the engineer involved.

I've shown him the photo's that were posted here of the IRL cars wing angles and he still thinks that there is no problem with what they are doing.

Am I the one out to lunch?

Are there any engineeers or people with more aero knowledge then I around here? I'm looking for someone who can go through his shade tree aero ideas point for point.

[Ankf00]

as long as the top surface generates more pressure than the bottom surface is correct. that's the jist of aerofoils, it's not about where you think you're pointing it, downforce isn't generated from the loss of air-momentum imparted unto the aerofoil (although that helps *some*, the physical force of the air hitting the wing), it's the higher pressure flow on one side creating a low pressure surface in relation to the opposite side

what you want is the chord of the aerofoil in the proper orientation vs. the freestream velocity vector, the aerofoil may look funky, but as long as the chord is at the proper angle, you're good.

take a NACA 66^2-215 laminar flow cross section, simple aerofoil, even at 0 AoA it still has a coefficient of lift of .2

and ya, lift and drag are functions of the square of the velocity


keep in mind I'm friends with OGorman so naturally my explanation must be 100% off... also keep in mind I'm from Texas so naturally my explanation is 100% correct. the two balance out :gomer:

basically you want an aerofoil with the maximum lift/drag AoA producing the right amount of DF for your car and no more, otherwise you're going to lose efficiency from that peak point

[TorontoWorker]

as long as the top surface generates more pressure than the bottom surface is correct. that's the jist of aerofoils, it's not about where you point it, downforce isn't generated from the loss of air-momentum imparted unto the aerofoil, it's the higher pressure flow on one side creating a low pressure surface in relation to the opposite side

also what you want is the chord of the aerofoil in the proper orientation vs. the freestream velocity vector, the aerofoil may look funky, but as long as the chord is at the proper angle, you're good.

take a NACA 66^2-215 laminar flow cross section, simple aerofoil, even at 0 AoA it still has a coefficient of lift of .2

and ya, lift and drag are functions of the square of the velocity


keep in mind I'm friends with OGorman so naturally my explanation must be 100% off... also keep in mind I'm from Texas so naturally my explanation is 100% correct. the two balance out :gomer:


you dont want more downforce than you need, the vortices that are generated from aerofoils induce drag, and the slower you go, the more lift induced drag you have. induced drag is also proportional to the square of the coefficient of lift so the more efficient your wing, there's way more drag you're inducing

basically you want an aerofoil with the maximum lift/drag AoA producing the right amount of DF for your car and no more, otherwise you're going to lose efficiency from that peak point


I'm still trying to get my head around the idea that these cars (IRL) seem to be the only formula cars that use what appear to be angle of attacks that go against the idea that wings are for "trim" or the balance fore/aft aero weight and not to counter the body design. One would think that an ALL oval, open wheel would attempt to use as little wing area as possile?

I can't recall seeing front wings in an "up" setting before on any other formula type car.

The only cars I can recall seeing a rear wing at the IRL settings - was when F1 tried to get away with adapting a wing post that would flex backwards at a certain load - mostly near top end speeds. It would come back to normal angle of attacks at lower speeds where I guess the added downforce was needed for slow corners and the lay back to reduce drag. The FIA quickly stepped in on that little trick and ended the teams using flexi wings so to speak.

So let me understand what your saying: That you don't believe that these radical (my view) wing angles don't add to the problem of flat bottom cars going VFR?

As you notice he goes all around the issue saying that you have to work with your team and engineer. Well duh.. Thats a no brainer.

[FCYTravis]

They aren't flat-bottom cars. They have ground effects.

The real issue with the flying IRL cars is not the back... it's the front. The wings are so trimmed out that even getting the tiniest bit of air underneath them creates lift... thus the "blowover" flip. The back end sticks until the very last minute... it's the front of the car that's screwing things up.

[TorontoWorker]

They aren't flat-bottom cars. They have ground effects.



In relation to a Lola Champ Car, how deep are the tunnels?

[Ankf00]

They aren't flat-bottom cars. They have ground effects.

The real issue with the flying IRL cars is not the back... it's the front. The wings are so trimmed out that even getting the tiniest bit of air underneath them creates lift... thus the "blowover" flip. The back end sticks until the very last minute... it's the front of the car that's screwing things up.

'zackly, once they're trimmed out to the point of minimal lift so as to minimize that drag, once you upset the pitch of the car the front wings become drag chutes essentially

science isn't about what looks right, it's about emperical evidence leading to a certain end, thus you have cooky ass equations like Lift Force == Lift Coefficient* A*ro*1/2*V^2 and whatever else... instead of the AJ Foyt system of "that looks about right"


also keep in mind that aerofoils produce a downdraft, or in the case of race cars, an induced updraft off the trailing edge, this reduces the effective AoA for once, but more importantly create an induced drag that is proportional to the square of the Coefficient of Lift... so go faster with trimmed wings producing less downforce due to less skin friction and pressure drag but you also create less induced drag, and if the undertrays provide enough DF, and the wings provide that extra smidgeon more, then they're golden, again, as long as their AoA is constant, AS WELL AS the freestream velocity vector.

Interruption or sudden change in either of those as well as the flow condition (laminar, mixed, fully turbulent) totally changes the equilibrium of the system

[FRANKY]

They aren't flat-bottom cars. They have ground effects.

The real issue with the flying IRL cars is not the back... it's the front. The wings are so trimmed out that even getting the tiniest bit of air underneath them creates lift... thus the "blowover" flip. The back end sticks until the very last minute... it's the front of the car that's screwing things up.

Not sure about the "tiniest".

I'm not an engineer. Not sure anyone there is.

http://www.trackforum.com/forums/showthread.php?s=&threadid=59251

[Ankf00]

what a group of tools...

"NO. When the 737 you are flying in rotates for descent (angling its wings downward), does it produces downforce, or reduced lift?"

the ****ing flaps extend and come down and extend the functional chord length and surface area, that has nothing to do with this situation of a static aerofoil cross section :rolleyes:

to me it's about the wing angles not the chassis rake, the chassis rake shows you more you fore/aft DF ratio, but they do show that there isn't lift going on for the whole system, but who knows if the wings themselves produce lift to counter the undertray...

I am now stupider for having read that thread :mad: This is all your fault Franky :mad: :thumdown:

and what kinda unprofessional **** posts propriety information? get that **** fired and sued.


edit: now i get the 737 comment, and it's still a bunk analogy. ToolForum, when Texas A&M goes online with the University of Oklahoma...

[FRANKY]

I am now stupider for having read that thread :mad: This is all your fault Franky :mad: :thumdown:



TELL ME WHAT YOU REALLY THINK?? :laugh:

[devilmaster]

my cat's breath smells like cat food.

[Ankf00]

did you bend your wookie too? :D

[Gnam]

The IRL car is stable as long as everyone holds their breath and doesn't bump it. Disturb it a little bit and, "Vaya con Dios, muchacho."

When **** goes wrong the IRL sled makes the problem worse.

[rosawendel]

doctor says my nose would stop bleeding if i just kept my finger out of there....

[Opposite Lock]

So, do you, like... stuff?

[oddlycalm]

Interruption or sudden change in either of those as well as the flow condition (laminar, mixed, fully turbulent) totally changes the equilibrium of the system Agreed, and with the EARL cars it's a matter of the small degree of interruption or sudden change it takes to turn the front end of the car into a giant drag chute.

All aero based race cars lose their aerodynamic effectiveness if they get sufficiently sideways, which is totally understandable, but having the car get seriously airborne simply because the nose lifts an inch over minor debris seems like a dangerous problem.

oc