Forum: HoseHeads Sprint Car General Forum (go)
Moderators: dirtonly  /  dmantx  /  hosehead

Anyone know what was illegal about his wing??

I've got an idea. At La Monte this past Saturday and at the race last night I noticed he has some "air scoop" (that's the best term I can come up with) devices on the back of the top wing. I don't know what sort of advantage they are supposed to have. One of my racing buddies used to have a similar looking device on the side of his pickup truck and the idea with them was to get better gas mileage, but I'm not sure if they worked for him. Here's two pictures of the wing I took at La Monte last Saturday. I wondered about the legality of it last Saturday.

Ask Frank

Those are commonly used on Semis, Toters and Trailers to increase fuel mileage. Honestly, I do no see an advantage of them being placed at the rear of the wing, it may create more dirty air for the car behind him possibly, I think it was done more for people talking about it than it was for an advantage.

I think the rules state it clearly:

WINGS: Maximum top wing size of 25 square feet with 30” side panels. Maximum
center foil width is 60 inches. The deepest point allowed in the top surface of the
wing will be 2½” measured from top front of wing to the rear edge. Flat wings only
are allowed a 1” wicker bill. Dish wings can not use a wicker bill. No additions to
center foil.

Vortex generators.  Aircraft uses them to smooth out air flow over surfaces.

Yes it does, that it why he was DQ'd!

Good work with the camera Coltan.  I may still have some photos of the elliptical tubing Karl Kinser used for the cage on the car Mark drove.  This tubing was later ruled illegal and all tubing must be round.

+1

Those are not true vortex generators.....Pictured above is something used on semi trucks. True vortex generators as used on aircraft look like this http://www.greghughes.net/rant/content/binary/Windows-Live-Writer/cf44af1760e8_928C/DSC00492.jpg

Their purpose on aircraft are indeed used to direct airflow, but more importantly they breakup the "boundry layer" of air, which would work great to create a lower pressure on the underside of a sprint car wing, thus creating more downforce.

Member of this message board since 1997

would it work better if they were in the front of the wing instead of the back? if it breaks up the "boundry layer" wouldnt it create more lower pressure throughout the whole under side of the wing as aposed to just the minimal amount towards the back? I have no idea what im talking about but from what you stated, this is my thought.

You are exactly correct.....I actually proposed this to a local 360 racer about 8 years ago.

Member of this message board since 1997

The pressure drop that causes the vaacum happens at the rear of the wing. The rear of the wing is where the air has to speed up to keep up with the air on the top of the wing...The "Downforce" is actually a vaccum from the underside of the wing. Under the rear of the wing the air starts swirling, kind of like an empty hotdog wrapper blows around in a vertical circle in the bed of a pickup. Those "vortex generators" will basically speed up and clean up the swirl.

For max efficiency, you don't want anything hanging off the belly of the wing on the front half-2/3 of the wing. The more unobstructed the air is there the better the wing works. Thats why internal runners were invented, why everyone uses recessed rivets, and why round or eliptical tubing is used on the sideboard struts that attach to the bottom of the wing

Loose is when you hit the wall with the rear of the
car, tight is when you hit the wall with the front of
the car. Horsepower is how fast you hit the wall and
torque is how far you move the wall.

I can't remeber which wing builder it was, I think it was "vortex" wings, but they used to put several dimples on the rear belly of the wing, in the same place Cornells triangles are, that basically accomplished the same thing. They looked like perfect dents made from something between the size of a golfball and a baseball.

Loose is when you hit the wall with the rear of the
car, tight is when you hit the wall with the front of
the car. Horsepower is how fast you hit the wall and
torque is how far you move the wall.

so if you put the "vortex generators" 2/3 the way back wouldnt that keep the air from swirling and speed the air up earlier creating a bigger vaccuum?

The swirling air also acts as a parachute of sorts, so cleaning up the swirling air will get it off the wing.  A couple of years ago Pittman came to the track with dimples like a golf ball in the back foot or so of the wing, to break up that swirling air.  I think these in question will disturb the swirling air and increase downforce and decrease drag.  However, if your not at Knoxville, Eldora, The Grove somewhere with big speed... They are like the spoilers on the "rice burners", not really doing anything.

DA

I hate to nit pick.....But there is no such thing as a vacuum (unless you're in space). Also, you have two types of lift (in this case downforce) for an airfoil, whether it be a wing...aileron...elevator...rudder...propeller or even a rotor blade on a helicopter. You have the lift (downforce) created by the pressure differential that is created by the air moving at two different speeds (Bernoulli's principle) as Darnell explained, which is around 80% of the lift (downforce), then you have "impact lift" which was argued by the brainiacs for decades, but in the end was proven. This happens when the relative air hits the surface of the airfoil (think of sticking your hand out the car window when you were a kid)....hence, the use of wickerbills.

Flush rivets and ellipictal tubing don't have much to do with lift (downforce) at all....That is all about parasitic drag (from having more surface area), which the devices on Cornell's wing would create a TON of drag...Flush rivets will stop a little bit of the turbulence on the wing surface, but it is pretty negligible. I don't know a whole lot about the effects of a vortex generator on the front or rear of a sprint car top wing, but speaking for my years from working in aviation experimental flight test with, the maximum efficiency of a vortex generator is achieved when it is mounted opposite of highest area of pressure...Which is the front....Also....One last thing to remember....When you see vortex generators on an aircraft wing, it's because in testing, they realized the wing wasn't designed to it's maximum efficiency, because vortex generators in the end, create drag, and more drag means more fuel consumption which means a degraded overall performance.

Member of this message board since 1997