Wait let's clarify first downforce and drag are two different forces in fluid dynamics.

 

I was thinking more of the AoA going negative due to deflection and putting unintended forces on the wing causing it to fail. This sort of failure might look like a wing failure from the outside when it’s actually an install problem. I’m really just speculating though...

 

Anything will fail if you install it poorly enough. Trunk mounting is not unsafe if done properly.

 

I mean my wing is 6 bolts through the lid. Hard to mess it up. But I know I've read of others bracing the lid or sheetmetal around the the lid. Was just curious what others have done.

I'm sure the AoA is going to change slightly as the lid and wing will deflect at speed. I can tell just pressing gently on the wing. Granted I've only got 4 of 6 bolts installed but still. The trunk sheetmetal is pretty flimsy.

 

The stock trunk deflects a fair amount, like 1-2 inches with only 30-50lbs. As you pull down and back (like wind does) the front part of the trunk lifts and bends a good amount, opening up a gap for air to come in instead of deflect off. With the bulkhead sealed off I was wondering in the beginning why I always had a small pile of sand and rock in the trunk area - turns out this was why. I haven't gotten around to finding a good fab guy in my area to drop it off to but when I do I'll be hard mounting the wing to the area above the rails and putting a dry carbon "slide on" design with 3 or 4 latches. The whole uber mounts that go way back and weld to the chassis are a bit much for us club racers.

 

Don't know what wing you're running but my trunk doesn't do that. I've solid mounted it at the sides so it can't move. When the latch is engaged the steel trunk stops I have slightly dig into the chassis. I can push in on the middle of the trunk if I push hard enough but it doesn't affect the wing angle at all.

 

I'm wondering if the people experiencing wing AoA deflection are mounting in the stock location (outer edges) or more inboard. This was discussed a few months ago on another thread about wing options. Beerad said he had a go pro on his wing and saw the wing deflect and lose AoA at high speeds when trunk mounted and the trunk would be warped. But not sure where he mounted to on the trunk skin.

 

Sounds like active aero to me. Have you all replaced the rubber mount between the trunk and the frame with something hard? My trunk cant go down in the rear without bending the frame.

 

TLDR just skimmed through this. The biggest issue ive found with wings mounted to the trunk is the middle front of the trunk actually deflects upwards and that is the weakest point. As mentioned earlier by somebody if your mount points are where the factory wing is you should be getting good deflection down. If your still stock trunk lid with all the internals and everything then youll be fine. its when you cut all that out or go for a carbon lid it gets complicated.

Obviously you can brace straight down to the chassis rails to transfer the load more directly but the gains will be un noticeable to the amateur.

Weve got some big towers inside our boot area that mount straight onto the chassis rails at the bottom and the hood sits on the top of these towers when closed (carbon lid with the inner skins removed) and you bolt through the hood into these towers which is where the base of the wing is attached.

But definately the biggest weakness area we have found is the front middle of the hood trying to twist off the car as the load comes on the wing. weve had to put an extra pin here to try hold it. (it tore the guts out of a quik latch)

 

So pics of the boot setup because I was thinking along these lines. But you keep saying hood twisting, do you mean the top front part of the boot lid? That's what I mentioned earlier and how it pulls it high enough to lift off the rubber seals and sucks all sorts of crap in.

 

i have some somewhere i will dig them up.

Yes the top front part of the lid in the middle was lifting for us. But im talking carbon skin lid not stock so i dont know what a stock one would do.

Basically just hang off the back edge of your wing in a downwards motion and see what flex's.

A cheap fix if ur worried about dust is to just put some tape over the leading edge

 

This is a friends setup, I cant find the photos of mine. i will take some later on.

But anyway this is how he did it. the bootlid is just cut away on the edge and he has a fill in panel which goes onto the brackets to fill up the void that stays there permanently

 

if you run a proper stiff wing element it wont defect. i had my kognition north of 140 at watkins glen, never an issue.

 

incorrect. the wing wont deflect sure but the boot and everything else does lol.

 

the cfd on the kognition wing element says that at 140mph i was making 39 poounds of drag and 465 pounds of DF, which is then lowered by quality of airflow over the wing when actually on the car and other factors...but it at least gives you an idea.

if the element is adequately stiff and transferring the majority of its force directly to the uprights, the deflection chances are low. were not talking thousands of pounds of df here...

the few major cases of wing failure/deflection that i have seen were in HIGH drag wings which of course changes the direction of the force on the trunk. the upright/mounting angle of the element also matters.