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Old 12-10-2009, 01:06 AM   #21
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[threadjack]

I don't know where to start with something like that

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Old 12-10-2009, 02:07 AM   #22
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**threadjack threadjack**

It should be fairly easy to get your car onto SpeedHunters at least - talk to Linhbergh :3
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Old 12-10-2009, 03:53 AM   #23
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my question is how important is it to have the wing not sit on the trunk but on the chassis itself so that the trunk doesn't absorb the downforce?
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Old 12-10-2009, 04:28 AM   #24
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Quote:
Originally Posted by Hi Im Simon View Post
my question is how important is it to have the wing not sit on the trunk but on the chassis itself so that the trunk doesn't absorb the downforce?
Quite important, if your wing is generating any useful downforce. The trunk isn't designed to handle 200, 300, 400, 500 lbs of force pushing down on it.
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Old 12-10-2009, 05:14 AM   #25
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but how can i tell how effective my wing is besides just feel. or the limit of the trunk.
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Old 12-10-2009, 05:30 AM   #26
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I wouldn't discount feel. Setting up a car is both what makes the fastest car and how the driver feels about the car.

Decent wings will have downforce spec sheets, such as the GTC-300 that Emillio sells (link here APR Performance - GTC-300 - CFD Data & Analysis ) and that is the best way to get information. I'd generally say, if the manufacurer of the wing doesn't put out drag/downforce numbers, don't count on it being more than a styling choice.
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Old 12-10-2009, 10:36 AM   #27
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One minor detail I seem to have forgotten. I would be using a large wing/spoiler like Chris's car and am looking to get as much as I can in downforce in the 20-55mph range and I figure catching the air right off the slope of the top (top would be up obviously), I would be able to get as much air as possible over the wing.

As for mounting the wing, I would mount it right on top of the ridege that holds the trunk seal which would keep trunk flex to a minimum and transfer of downforce to the body efficently.

Now, I do plan on eventually getting a different wing for track days...one that will sit as far back as possible and as high as possible....because there are no rules on track days.


See, on a nice sloped back car (like if I somehow got my hands on one of those new autokenexion fastbacks), a wing mounted far back works well with minimal AOA because the wing is forsing a lot of air over its top and the air going under isn't really turbulant.

*warning awesome picture*



Attached is a pic of a NC in a wind tunnel and a description of the area in question.

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Aero/wing question...with a twist...and my name is not Hyper-soft-topvortex1111.jpg  
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Old 12-10-2009, 11:43 AM   #28
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Originally Posted by Chris Swearingen View Post
When you talk to them (APR) you want the 55" GT-II wing, but you want both elements to be the 7.5" high camber wings.
Does that build more downforce at autox speeds than their GTC-300?


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Old 12-10-2009, 12:03 PM   #29
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Quote:
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Does that build more downforce at autox speeds than their GTC-300?


Yes.
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Old 12-10-2009, 12:07 PM   #30
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Originally Posted by j_man View Post
Does that build more downforce at autox speeds than their GTC-300?

The GTC wings are 3 dimensional airfoils. That means they are shaped to accomodate the airstream as it comes over the hardtop. In autocross, I don't have a top on my car.

I also think the dual element wings are capable of creating more down force than a single element wing given the same square inch surface area. I think 5 is the point of diminishing returns with regard to the number of elements. SSM limits you to two unfortunately, which I have never understood given the area limit.
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Old 12-10-2009, 12:09 PM   #31
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Old 12-10-2009, 12:10 PM   #32
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Btw, these folks are popular among the SCCA autocrossers:

Wing Shop home page

Some of their airfoil data:
Wing Shop aerofoil facts page

Looks like at 50mph their dual element one at 20 degrees angle of attack is making 84 lbs downforce for the penalty of 2.5 hp



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Old 12-10-2009, 01:24 PM   #33
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Quote:
Originally Posted by Doppelgänger View Post
thagr- I knows, about wing placement and how the rear axel acts as a fulcrum point. I am curious as to what might be the effects of putting the weight straight down on the wheels.
It would really depend on what type of air you wanted to catch with the wing. If you wanted to catch air that has already been introduced to turbulence moving the wing forward would help. However, if you wanted to catch clean air which is more linear in flow, the rearward mounting would be better. The flow that is seen in the NC can be helped with the use of vortex generators at the roof-line drop off to direct the air more linearly up and over the rear window and trunk lid but flow under the wing. This would be ideal... I will try to find the article where I saw the CFD's of before vortex generators and after...

EDIT- Found it... http://autospeed.com/cms/A_3059/article.html
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Old 12-10-2009, 01:57 PM   #34
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Quote:
Originally Posted by thagr81 us View Post
It would really depend on what type of air you wanted to catch with the wing. If you wanted to catch air that has already been introduced to turbulence moving the wing forward would help. However, if you wanted to catch clean air which is more linear in flow, the rearward mounting would be better. The flow that is seen in the NC can be helped with the use of vortex generators at the roof-line drop off to direct the air more linearly up and over the rear window and trunk lid but flow under the wing. This would be ideal... I will try to find the article where I saw the CFD's of before vortex generators and after...

EDIT- Found it... Browser Warning
Thanks for the info
But I don't think VGs will work all that well at autoX speeds :( Not to mention I would need a hard top to use them, and to use a hard top I would need to remove my roll bar for one that is HT compatable...too much work.

The question I am wondering is, for lower speeds (autoX), will it be a viable option to catch the air coming off th eroof line just before it's about to become turbulant along with catching clean air? Might there be any benifit?
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Old 12-10-2009, 02:11 PM   #35
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Ah... Was not aware we were chatting about auto-x (I may have missed it). I would still want to catch clean air hitting the wing as compared to air that has had its velocity decreased by flowing over the roofline...
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Old 12-10-2009, 02:49 PM   #36
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Is the discount vallid for NASA members as well?

Have a great day,
Jaerd
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Old 12-10-2009, 02:54 PM   #37
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Quote:
Originally Posted by Doppelgänger View Post
Not to mention I would need a hard top to use them, and to use a hard top I would need to remove my roll bar for one that is HT compatable...too much work.
And the hardtop will add 40+ lbs to your car - not good


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Old 12-10-2009, 03:00 PM   #38
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Not if you get one from Axis Power Racing...
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Old 12-10-2009, 04:48 PM   #39
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not sure, but this may help you with deciding on the wing placement.
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Old 12-10-2009, 05:40 PM   #40
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Another question... Will this be for top up or down setup? Because that will have an effect.
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