effects of a roof wing?
 

im always interested in aerodynamics but im skeptical of a roof wing having a positive effect on downforce. i already have a Stillen roof wing and a duckbill on the trunk, but would the roof wing counter any positive effects of the trunk lip?

No idea, but a good question. What does your car currently look like?
:needpics:

I had this in mind when I read the title of the post:

http://chivethethrottle.files.wordpr...int-car-20.jpg

http://www.frsport.com/Stillen-KB210...-_p_69725.html

thats what it its. not much angle to it

i doubt either wing does anything other than cosmetic purposes

I was wondering the same thing actually. I feel like it would almost create an air pocket above the rear window, like the way a pocket is formed on a truck when the truck has the tailgate up and the air pocket forms basically in the bed. Correct me if i'm wrong though, it's only a thought and I have no proof or anything to back it up haha.

Are you also part of the flat earth society?

Spoilers on car do exactly what they say, they spoil the lift generated from the car traveling at speed. It's not so much that you have to worry about it crushing the trunk like a real sports car wing however it does negate the lift. Is the critical point at which the car becomes unstable without one anywhere near the speed limit? No, but a blanket statement that they're cosmetic only is pretty closed minded.

OP, it's hard to tell honestly without doing a bunch of research such as photographing the car at various speeds with strings taped all over it and a couple smoke bombs to watch the air flow. They probably don't interfere with each other although the roof wing will create a larger area of low pressure air behind the car.

lol flat earth. ya the wing doesn't have much of a lip to it, but everything has an effect small or large. im guessing vortex generators would give the effect to assist the trunk lip.

Yep, a vortex generator will create the necessary turbulence to allow the air to re-converge closer to the car and clean up the air going in to the trunk spoiler and reducing the size of the negative pressure "bubble" behind the car.

There is a speed at which the roof spoiler would "throw" the air so far off of the car that it wouldn't be able to converge in time for the trunk to have an effect. Do I have any idea what speed this is at? No, but it's probably honestly pretty darn fast.

I'm kinda curious now to have someone drive next to me with a camera and a smoke bomb on a stick so I can get some aero photos of the car.

ya im interested to see it. id assist but i dont know if u live in nj

Nah, I'm down in Dallas, TX. I'll probably have to wait for the fireworks stands to open up before I can even get any smoke bombs big enough to be able to tell and I'll just have to coordinate with some friends to be able to take the pics. I'll let you know if/when I do this.

my opinion is thay you will be much better of with diffusers to help streamline the air over the rear glass and trunk.

this to me just seems inefficienct.

Take a look at a golfball. See the dimples? Those are on there to get the air in the boundary layer directly around the golf ball to be turbulent and to get the air to converge quickly following behind it. If these didn't have the dimples they would fly very slow in comparison and tumble all over the place.

Not just any turbulence is good either, I'm talking about breaking up the air in the closest inch or two to the car and leaving the rest untouched to do it's thing.

not sure what you are commenting on

diffusers on the end of the roof would do to the car what you are describing

the OP's winglet would not, it would only further icnrease the turbulance over the rear window which is present even with nothing on there.

Flow stays attached to rear glass pretty well without anything. No vortex generators needed. I could make some assumptions about a roof spoiler, but it would just be an assumption.

The picture below shows how the fluid stays attached

http://i1291.photobucket.com/albums/...pscff3c53c.jpg