308 rear spoiler (wing)

I bought a contour gauge at Lowes yesterday. I taped up the wing in the middle so I wouldn't scratch the paint and pressed the contour gauge along the top starting at the leading edge. The gauge I bought is too short to measure the surface by about an inch, so I took the measurement from one edge, traced it onto paper, then took the measurement from the other edge and traced it onto the previous trace with the approximate overlap. Picture is below.

My initial trace is very rough, but the result is good enough to know that my wing is flat on top and curved on the bottom, so it is shaped like a wing. I talked to an airplane builder friend of mine who said he would help me measure this thing and interpret the shape, so my hope is we can understand the shape of the wing well enough to know how the angle of attack plays into this to answer Crowndog's original question...
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Should be fun! My friend sent me this website link to get started once I have my measurements...

http://www.grc.nasa.gov/WWW/K-12/airplane/foil3.html

Plugging in the numbers should give us a "good enough" indication of what effect the angle of attack has.

If anyone else here is interested in participating with their own measurements go for it

 

Looking forward to the NASA simulations on our 308 spoilers, whatever the outcome.

 

I think ya'll are losing sight of it's intent.

It's not for generating killler downforce on the car body itself, IMO.

It is for relief of the vortex at the rear window, which kills cooling flow thru the engine compartment, via the relief louvers.

Not downforce for it's own sake.

 

Sounds like marketing-speak from Ferrari to justify caving to a fad. Maybe some inquisitive owner will tie yarn on his deck louvers and test the issue.

 

I think the rear spoiler gives a little down force in the back, as you can see the diff. between standing still and moving at around 75 mph.
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I made a caliper just for this! I'm finding it is 3/4"...
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That's pretty much how I see it too.

To Me, it appears that the rear window, the roof line and the rear buttresses create an area above the engine cover where there is very little (if any), air flow to draw the engine heat away.

The angle of the wing appears to pull air down across the engine cover to help draw away the engine heat a bit more efficiently.

This extra air flow is also then being pulled over the rear raised lip on the engine cover lid, not to create massive downforce, but to break away the air drag at the rear end of the car.

This is where people get confused and think that all rear spoilers on cars are there to create downforce.

Some rear spoilers are designed to produce an element of downforce (like the whale tail on the original Porsche 911 turbo and the rear spoiler on the Audi TT coupes), but the vast majority are designed simply to "spoil" the air flow at the rear of the car and cause the trailing air wake to be "snapped off" more quickly. This results in less aero drag on the car, thus making the car marginally quicker.
This is the thinking behind boot (or trunk) lip spoilers. They do not provide downforce, they reduce drag.


In the case of the spoiler fitted to the buttresses on Ferrari's 3*8 series, a more appropriate name for it would be an "air deflector", as it's not really there to "spoil" the airflow, it's actually there to redirect (or deflect), the airflow downwards.

 

BigTex - While downforce may not be the primary mission of this appendage it is still a function of the shape... Where does the info about the vortex come from? Just curious

 

What did you come up with for the angle?

 

I'm sure it would.

 

Maybe it's simply a sun visor

 

I'm as interested in the ability to spoil as I am with any downforce that might have been created. I would also really like to know where the vortex info comes from and if there are any more detail about it...

 

It's pretty effective that way, too I'm one of those odd ones who really likes the airfoil up there. To me, it's one of those QV "signatures". It would be cool to see the math though, on how it's affecting air flow over the bonnet. I look forward to seeing your results here. If I can do anything to help, let me know. It would be especially cool if we could take a couple of models back into a wind tunnel for video.

 

Robert, doesn't my pics on post #58 shows that there's a little down force?

 

You'd need to do it with spoiler on / spoiler off rather than stationary vs moving. Downforce visible when moving is largely from the aerodynamics of the whole vehicle rather than just the foil.

I measured yours with my screen ruler and it seems to be squatting by very roughly 10% (measured as a ratio of rim width to wheel centre/top of wheel arch)

 

Hey Gang,
I googled for wind tunnel software today during lunch and found the following two items. The first is free wind tunnel software that uses "STL" files, and the second is a site that actually has an STL file available for a 308!

Free "Project Falcon" Software from Autodesk Labs:
[ame]http://www.youtube.com/watch?v=UrrOA0rlaCg[/ame]
http://labs.autodesk.com/utilities/falcon/overview/

308 STL file available here for $100.00 USD (or free if you have an STL to upload):
http://www.3dcadbrowser.com/preview.aspx?modelcode=7616
http://www.3dcadbrowser.com/preview.aspx?modelcode=23789

Unfortunately I haven't been able to get back to the wing analysis since taking that center measurement, but it looks like Crowndog is running with it! I'm also probably not going to be able to play around with the wind tunnel software until the weekend, so please don't let me stand in the way of progress!

 

Did you also account for 2 occupants vs no occupants?

 

Miketuason - Regarding vaccarella's on screen measurement, were you accelerating at that time that picture was taken? It's hard to know what's causing the squat from a static picture...