Two Element, Airfoil Grubbing

[Scuderia_Russ]

How much is this mother going to weight do you think?
How will you mount it?

[EAKMotorsports]

very interesting.

[GIGAPUNK]

How much is this mother going to weight do you think?
How will you mount it?

I spoke with my Uncle the composites expert. He suggested a single layer of 36-10 tri-axial fiberglass. With the mat side to the foam. No need to pay for carbon. He said the glass would hold. He said to drape the glass over the leading edge with a longitudinal strand parallel to the span. My wing is almost 8 sq ft per side. And fiberglass generally requires 2 oz. of resin per oz. of fiberglass. With the suggested fiberglass weighing 46 oz/sq yd...

Should be 15.1 lbs of fiberglass and resin

plus the 1-2 lbs of foam

plus end plates and mounting hardware.

[Jersey Tom]

IMO.. if you're going to go through with the effort to do this you might as well be serious about it. Ie, not half-assery and just bolting some random big wing on.

Why does it even have to be two element? Why so highly cambered on the primary airfoil?

Where is this even going to mount? The front? The rear? If you throw it on the rear of the car, it will have absolutely diabolical understeer. If you throw it on the front somehow, the car will be wildly skatey and loose at high speed to the point of being undriveable.

You've got to have a provision for a front and rear aero device. No point in doing this otherwise. On the front it makes the most sense to have a simple splitter (think: NASCAR). On the rear, a wing sure.. but maybe something less aggressively cambered so you're not stuck in "mega downforce mode" with no way to trim it out.

Of course there's the other issue that this is a convertible.. and even if the soft top is up (or even if it was a hard top!), what kind of airflow is the rear going to get?

[marcush.]

In my view you are putting on the saddle from the wrong side...

To justify all the effort (also from third parties you may find useful later on in your life) I would resist to go forward before you exactly know what you need .

So first of all ,will downforce help your car in the wayys you are using or are going to use it ?Is this sort of wing even allowed where you are going to use it?
a two element wing can be a very involved project in itself in determining just how big airgaps need to be or AoA of both wing sections.. how will you mount the two sections to the endplates...and what is your plan for adjusting the flap precisely..
I feel the decision of profile is less than 1 % of the work to be carried out before you even think about cutting cores....
before laminating you must be sure of your mounting concept(endplate only,or mid of the wing single or twin beam etc how would you spread the loads into the wing itself ..there is no ways just to put a skrew into this to attach the wing to the wingstay ...obviously there are people out there taking no prisoners and wondering why they do not produce results..

and of course a BIG splitter is needed to counter the downforce at the rear.

Ever seen the underside of the splitter of a corvette C6r ? that thing is 2m wide
and has two BIG difussers to produce downforce....but of course they also have a big duct for the radiator outlet in the hood,as the engine waste heat has to go somewhere and usually these cars are bottom breathers...Seal the floor and the engine collapses..

Welcome in the game..Start turning one stone and the hole mountain comes down..

[GIGAPUNK]

A front splitter will be the first thing to get done after the wing. I think that this may be the best off the shelf option for the miata

http://www.iscracing.net/miata_fiberglass.html

SCCA solo rules allow the wing to have 200 in^2 endplates, and allow the wing to be mounted 6" higher than the highest point of the car and flush with the rear of the rear bumper. They also allow a maximum of two elements. I plan to push all of these rules to the limit. I have a hard top and can run with it on if it makes a noticeable difference.



I didn't realize how much interaction would be likely until I just made this picture! Short wheelbase... Ugh. I wonder if I could move the wing back another 3.5" by arguing that the flap is not part of the wing!?

Regarding mounting.

I want to stretch the rules regarding endplates while maximizing efficiency by mounting the wing by the bottom of the endplates. I think that if I use something simlar to these chassis mounts turned 180 degrees, I can use solid mounts (they'd have to be tilted out at a slight angle) to effectively increase the size of the endplates. But I'm hoping it still fits into the rules since my "endplate extensions" are really my mounts.


Imagine the stantions without the cutouts and angled out slightly attaching to the endplates instead of the underside of the wing.

Regarding the two elements and hi camber profiles:

My last autocross i never got over 60 mph. At these low speeds I don't think crazy understeer from rear aero will be a problem. My car already has so much power on oversteer that I just pulled the rear sway bar completely. If I get tons of downforce from this thing then I can put the rear sway back on, then I can work on the front splitter.

[Mystery Steve]

Just be careful you don't mount the wing too high. The rear wing unloads the front tires due to both downforce and drag. The higher you mount the wing, the effect due to drag becomes greater. Just because they allow you to put the wing out there doesn't mean it is necessarily the optimum location.

[GIGAPUNK]

Steve,

It seems like I'm always hearing about "clean air", and my knee jerk response was to go as high and far back as possible.

I'm presuming that you'd reccomend lowering the height of the wing before moving it forward if I end up with the handling too tight?

[Mystery Steve]

Generally, the best place to locate the wing would be directly above the rear axle and as low as possible while maintaining effective lift. The further you get from that location, the more the front wheels will unload due to lift and drag on the wing. If you check out just about any vehicle dynamics or vehicle aerodynamics book, this subject should be covered. Race Car Aerodynamics by Joseph Katz is a good place to start.

Yes, clean air is important for the effectiveness of the wing, but you don't want to go to extremes. You only want to mount it high enough to get it out of the boundary layer caused by the car body. I'd recommend starting with Katz's book and just do some simple calculations to determine the wheel loading sensitivity to the wing loading at different velocities. You may find that you are fixing your oversteer by causing it to understeer due to unloading the front wheels. This is why Tom has recommended a front splitter.

[mep]

Just be careful you don't mount the wing too high. The rear wing unloads the front tires due to both downforce and drag. The higher you mount the wing, the effect due to drag becomes greater. Just because they allow you to put the wing out there doesn't mean it is necessarily the optimum location.

Very good point.
Having your wing mounted to high brings only negative effects (unloading front, higher bending loads on your mounting strut), while having it mounted a bit behind your rear axle at least increases the load on rear wheels.
When you have so much power oversteer than I think it is ok to put a big wing behind rear axle without changing anything on the front in first instance.
Its all about the right compromise, when you notice you unload your front to much you can reduce your wings angle of attack or add something to your front.
Nevertheless I would do some calculations before building anything.

[marcush.]

examples of how I would not do it...S2000 in Germany (Nurburgring VLN )
http://farm4.static.flickr.com/3052/260 ... 6c.jpg?v=0
http://farm4.static.flickr.com/3225/297 ... f4dbef.jpg
http://farm4.static.flickr.com/3291/266 ... ca.jpg?v=0

as always ,not only the good things get copied... sometimes it
makes sense to use your brains as well....