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jzr:

Those numbers are a fantasy far greater than APR's.

 +1  The best numbers I ever got using fluent for a dual element wing were about -3.4 doing a 2d simulation.  I want to say the 3d work I did ended up being around -2.8.  Word on the street is that the high-downforce setup for Monaco for F1 approach -4, but they're a lot smarter than me.
 

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Jim Reyenga
-Certified National Hack and Car-Whore Extra-ordinare

Jreyenga:

jzr:

Those numbers are a fantasy far greater than APR's.

 +1  The best numbers I ever got using fluent for a dual element wing were about -3.4 doing a 2d simulation.  I want to say the 3d work I did ended up being around -2.8.  Word on the street is that the high-downforce setup for Monaco for F1 approach -4, but they're a lot smarter than me.
 

Let me start by saying I have done very little research other than plugging in various numbers into the foilsim program and looking at the Excel file that APR sent me on those two wings.

Having said that, and again bear in mind that I don't know jack about this stuff, but why could you not build a wing that is exactly like what the foil sim program shows? and why would it be no where near what other simulation give? Either the program is fairly accurate or it isn't. I assume APR's number are done in ideal conditions in a wind tunnel as well. One trend I am seeing is that hardly anyone is making a high downforce low speed wing of any sort. That's why I keep going back to the dimensions/specs of the foil sim and wondering why we could not build one in that same shape to get similar results. Of course I understand that once you take it out of a simulation that you will get no where near those results.

Suggestions?

Also this one here looks surprising similar in curve/shape to what the foilsim shows you
http://www.djracecars.com/dj-racecars-image-viewer.asp?im=/wings/This%20is%20what%20you%20get%20when%20maximum%20downforce%20is%20the%20only%20design%20criteria.JPG&info=This%20is%20what%20you%20get%20when%20maximum%20downforce%20is%20the%20only%20design%20criteria

Foilsim is a fairly basic mathematical model that attempts to predict real-world happenings.  I would imagine there is a "sweet spot" around which is values are reasonably close to real-world implementations.  This sweet spot is likely centered around the speeds, shapes, and angles its creators expected the users to be most interested in. The further one diverges from this sweet spot via extreme angles of attack or camber, the further from reality the model's results.

A more powerful CFD tools like Fluent FloWizard does a much better job of analyzing and predicting real-world behavior of these sorts of things, but all the CFD time in the world can't account for good old fashioned real-world testing.

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--Jason Rhoades

Foilsim also does not predict flow seperation or 3d flow effects (ie it assumes infinite span).  At 20 deg the wing is most likely well past it's stall point at such low speeds.

Ok. With Foilsim you turn on the stall model option. -10 degrees is the max. At that setting you get 314LBs of downforce, 60mph, 8sq ft etc. At 80mph you get 558LBs everything else staying the same...

CL is -4.273 at 10 degrees. At -12.44 degree you can get a rough max of -4.543, it's stalled and 334LBs at 60mph and 594LBs at 90mph.

Still those raw numbers are way better than APR, granted the two big APR wings are not designed for low speed high downforce at all. Wish we could get some real data on their other wings...

Jamey D. Aebersold:

Ok. With Foilsim you turn on the stall model option. -10 degrees is the max. At that setting you get 314LBs of downforce, 60mph, 8sq ft etc. At 80mph you get 558LBs everything else staying the same...

CL is -4.273 at 10 degrees. At -12.44 degree you can get a rough max of -4.543, it's stalled and 334LBs at 60mph and 594LBs at 90mph.

Still those raw numbers are way better than APR, granted the two big APR wings are not designed for low speed high downforce at all. Wish we could get some real data on their other wings...

 

 

I won't even begin to talk about aero because I don't know a damn thing compared to Jim and Jason....  BUT...  I've got a feeling that the simulation isn't intended AT ALL to look at the flow regime you're trying.  Being that you just designed a wing that's 10% better than Formula One cars....

The raw numbers you get with FoilSim are garbage.
 

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Jesse
-2002-2006 E-stock 93 MR2 (sold)
-2007-2008 XP Spyder

Jamey D. Aebersold:

Ok. With Foilsim you turn on the stall model option. -10 degrees is the max. At that setting you get 314LBs of downforce, 60mph, 8sq ft etc. At 80mph you get 558LBs everything else staying the same...

CL is -4.273 at 10 degrees. At -12.44 degree you can get a rough max of -4.543, it's stalled and 334LBs at 60mph and 594LBs at 90mph.

Still those raw numbers are way better than APR, granted the two big APR wings are not designed for low speed high downforce at all. Wish we could get some real data on their other wings...

you do notice that the "stall" happens at 10.0 degrees for every speed and every camber setting.  Seems a bit fishy to me.  Also if you turn on the aspect ratio effects the CL goes up.  Not exactly accurate IMO.

129STS:

I won't even begin to talk about aero because I don't know a damn thing compared to Jim and Jason....  BUT...  I've got a feeling that the simulation isn't intended AT ALL to look at the flow regime you're trying.  Being that you just designed a wing that's 10% better than Formula One cars....

The raw numbers you get with FoilSim are garbage.
 

I'm just trying to get a base line to go from and in another thread from last year several folks had mentioned the foilsim program to use as a reference for discussion on wings in SM/SM2.

Referring to Formula One cars... well I'm sure that the claim of Maximum Downforce Wing has quite a long list of qualification to that term. In other words I doubt that they are running the absolute Maximum Downforce Wing they could. There are simply too many variable involved especially in F1.

So trying to get back on subject here.. Does anyone have any references to specific downforce numbers that they could point me towards, what exactly the wing looks like, and why it's good at making downforce without alot of drag.

On another note, last year I saw several SP cars running a big lip basically at the rear. I guess you would call it a spoiler but it's darn near vertical. I understand the purpose of them generating downforce at the extreme rear of the car body and the fulcrum principle. I would think it would have quite a bit of drag myself. So what's better? One of the spoiler jobbies or a real wing?

Jamey D. Aebersold:

129STS:

I won't even begin to talk about aero because I don't know a damn thing compared to Jim and Jason....  BUT...  I've got a feeling that the simulation isn't intended AT ALL to look at the flow regime you're trying.  Being that you just designed a wing that's 10% better than Formula One cars....

The raw numbers you get with FoilSim are garbage.
 

I'm just trying to get a base line to go from and in another thread from last year several folks had mentioned the foilsim program to use as a reference for discussion on wings in SM/SM2.

Referring to Formula One cars... well I'm sure that the claim of Maximum Downforce Wing has quite a long list of qualification to that term. In other words I doubt that they are running the absolute Maximum Downforce Wing they could. There are simply too many variable involved especially in F1.

So trying to get back on subject here.. Does anyone have any references to specific downforce numbers that they could point me towards, what exactly the wing looks like, and why it's good at making downforce without alot of drag.

The AM guys are going to be the only ones who have real wind tunnel testing, and I'm not exactly sure how open they'll be about it. 

 

On another note, last year I saw several SP cars running a big lip basically at the rear. I guess you would call it a spoiler but it's darn near vertical. I understand the purpose of them generating downforce at the extreme rear of the car body and the fulcrum principle. I would think it would have quite a bit of drag myself. So what's better? One of the spoiler jobbies or a real wing?

 

Wings are far more effective.  SP doesn't allow wings, but does allow spoilers.  DM and EM are the same... spoilers ok, wings bad.  As far as drag is concerned... seems like a non-issue to me in SM/SM2/XP, as you can just add horsepower.

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Jesse
-2002-2006 E-stock 93 MR2 (sold)
-2007-2008 XP Spyder

typical Clmax for a well designed multi-foil airfoil is 3.0,  and requires pretty big Reynold's numbers.   5.3 is in the powered or blown flaps range.  The other factor is that wings on cars are usually located in an area of messy flow,  if not completely separated flow: the average dynamic pressure will be less and the effective angle of attack will range widely over the surface;  in other words,  the wing won't produce as much lift as it would in clean, undisturbed air.

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lamoureaux
BSP 2004 STi
Wichita, Ks

After getting a bit frustrated with the lack of timely response from APR's Marketing department, I chose to go with a custom APR wing through Richard Jung at Ciro Design (rjung@cirodesign.com), who took care of the interaction with APR and provided excellent pricing.  I went with a setup pretty much identical to thaton Andy McKee's SM2 car:  dual 61" wide x 7.5" chord aluminum aerofoils and custom 12" x 12" carbon fiber endplates.  Including base supports & shipping, the entire package was <$400.  Richard even provided some setup info and instructions for adding a Gurney flap.   IMHO an excellent ratio of $ spent to downforce generated.

-Steve

p.s. Richard turned my order around in 2 weeks, which I was pretty happy with for a custom order.

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Steve Garnjobst
#75 XP
'99 Mazda Mutant