Flat roof versus Curved roof??

[racer241]

Ive got a question for any aerodynamic buffs out there, with the roof on a late model being such a large amount of surface area , is it possible for a curved roof to make lift?? We had one on the car that basically had an airplane wing profile to it. This seems like the wrong way to go?? What do you guys think?

[C10]

I guess it would be possible, but the rounded roofs are designed to put more air on the spoiler. Now, if you have rules that allow a flat roof with angle in it you essentially have a huge spoiler right on top of your car.
Now for the down side of that, we went and raced years ago where they allowed "Outlaw" lates to run a sprint car type wing on the top. The cars had so much down force that my driver said it was bogging the car down so he took it off. He subsequently was so much faster then everyone else without it they couldnt touch him. So in conclusion, is the benefit worth the drag? Thats a question I cant answer because we have run both flat and curved and really didnt notice any difference.

[MasterSbilt_Racer]

Ive got a question for any aerodynamic buffs out there, with the roof on a late model being such a large amount of surface area , is it possible for a curved roof to make lift?? We had one on the car that basically had an airplane wing profile to it. This seems like the wrong way to go?? What do you guys think?

A curved roof WILL create lift. It does not "lead air to the spoiler". I have driven the same car back to back with a humped up roof and one that was close to flat. It made a very noticeable difference.

If you are racing against a guy with a flat roof, angled downward to the front, he is cheating you big time if the rules do not allow it.

[racer241]

Thanks for the replies, any other input would be much appreciated, changing around the roof/sail configuration just hoping it helps it haha. Its a home-made aluminum roof came with the car curved, I'm flattening it plus curving the left sail and A pillar to give a cleaner shot back to the spoiler

[hpmaster]

A curved roof WILL create lift. It does not "lead air to the spoiler". I have driven the same car back to back with a humped up roof and one that was close to flat. It made a very noticeable difference.

If you are racing against a guy with a flat roof, angled downward to the front, he is cheating you big time if the rules do not allow it.

Hmmm sorta like a flat roof with the right frt. corner dropped 1 1/2" huh?

[hpmaster]

Hmmm sorta like a flat roof with the right frt. corner dropped 1 1/2" huh?

Then use a 88 or 90 on the left front as a "loading" or pit tire and a 92 to race on.

[3wheelinphotos]

A RCR aero guy told me that Flat roof on a car with no windows and a curved with windows.... Look at the Team Dillon car Flat Roof.

[dirttrackrocker]

For it to create lift, it would have to have a smooth flat piece on the under side. What creates lift is the reduction of pressure caused be the air being disturbed by having to go over the curved top and the undisturbed air going under. So unless the you can smooth out the air going under the roof, it won't create lift.

[MasterSbilt_Racer]

For it to create lift, it would have to have a smooth flat piece on the under side. What creates lift is the reduction of pressure caused be the air being disturbed by having to go over the curved top and the undisturbed air going under. So unless the you can smooth out the air going under the roof, it won't create lift.

If air is going around a curved surface, it creates lift. The air on the underside would have to be displacing the same amount in the vertical direction for no lift to occur. A boxed in smooth bottom just makes the lift coefficient bigger.

[4bangerhotrod]

thats the reason you see the cars with a curved roof with a lip at the back sticking up . that lip take the lift out, it works like the elevators on a airplane wing.