I was just looking at some thread about H4 cars and their aero, and some guy posted a link to an ebay auction with "a wing", and Johnny Mac (self described as knowing something about aero) posted saying it was too big for an H1 car let alone an H4 car. That got me curious so I looked at it and have to agree it's too much something.

So, uh, Johnny...about wings...on the back of Honda's and Acura's?

A close look at the wings on alot of current touring cars lately show pretty curvey foils run about flat...

Most of us who know anything know about lift to drag coefficients...

Are people like RTR running wings (at all) because they have to per the rules? And they run them set for minimal drag?

I remember most of the Integra's in WC running the then spec wing with alot of angle of attack, and was told by PD that it was essential to maintain high speed balance when using a full splitter and tray. Those wings were run low enough on the hatch to serve as more of spoiler than a wing???

I know you can qualify your answer into meaninglessness if you want to - but if you were going to pretend that there was a magic hammer of an answer to the vague and generic question I'm asking - I'm ready to take another lump o' wisdom. (In other words - say something even barely coherent and I'll make like I got something out of it).

Scott, who took off his wing yesterday for the duration this jackstand episode...After I ripped up a little bit of my back by standing up into one of the endplates...and it occured to me that if it weren't for the fact that Integra's look better with some kind of wing I'd be willing (Today for sure!) to take it to the extreme on the drag reduction thing.

 

Curvy airfoil run flat >>> flat/spec airfoil run at high angle of attack

Make the lift with camber rather than AOA in nearly all cases.

Of course, I probably misunderstood your question...

 

<...nodding....rubbing the latest lump protruding from my cranium>..."Mmmm-Hmmm"...

Scott, who reserves the right to respond to too much arcanery with phrases like: "You May be right"...or "You Sure about that?"...or "Your teh suck!"...hey Andy - can I use a pyrometer to check the camber on my wing?

 

much better than:

 

Oh, and even the Clark-Y is better than the "teardrop" shown in the eBay auction in the H4 aero thread.

 

...they seem to be upside down...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo &raquo;</TD></TR><TR><TD CLASS="quote">...they seem to be upside down...</TD></TR></TABLE>

Us airplane guys use them for good instead of evil.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by maxQ &raquo;</TD></TR><TR><TD CLASS="quote">

Us airplane guys use them for good instead of evil.

</TD></TR></TABLE>

Right, but how much adjustability do you have? Can you adjust for less lift? What panelties do you incur with drag? Whats the maximum angle of attack, etc.

An aggressive airfoil seems like a perfect thing, but (to me) it seems that the range of adjustment isn't really there.

 

They have "flaps" which increase camber and cord...and drag.

Scott, who's seen people lose aero parts in a race and not slow down very much...it can make you wonder...and I really like to wonder alot...sometimes while I'm wondering I miss the answer right in front of me...in politics that's called scientific scepticism...you've seen buttons and stickers that say "Question Authority"?...my new slogan is "Question Dissent!"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo &raquo;</TD></TR><TR><TD CLASS="quote">Right, but how much adjustability do you have? Can you adjust for less lift? What panelties do you incur with drag? Whats the maximum angle of attack, etc. </TD></TR></TABLE>

As much adjustability as Clark-Y as long as it's below stall (I don't have a stall region on me for that airfoil... I'll see if I can find it)

Less lift: run it at negative AOA. Although, you will pay a small penalty in drag (over a Clark-Y airfoil at 0°) for doing so, it's a short term fix... if you are always running it negative, make the wing smaller (ideally, make it a shorter chord but less span is easier).

The GAW-1 will have 10-15% LESS drag than the Clark-Y at the same lift coefficient.

I'll look up for the max AOA... but be warned, it's a function of speed.... the faster you go, the higher AOA you can get without stall.... so you have to kinda pick a speed to design to.

EDIT: The GAW-1 is NOT necessarily THE BEST airfoil for car applications... while pretty darn good and used a fair bit in such applications, it was primarily designed for cruise efficiency on an airplane at &gt;150 mph....

 

Andy - talking about specific airfoils, and L/D, and stuff like that is NOT the response I'm looking for for the question I didn't really ask...

I'm looking to Johnny Mac to provide some rough insight into "how much is useful"...

There was another thread in which he talked about the price in drag of too much splitter tray area on these cars....I noticed and took note.

Scott, for whom this is all too academic...these things only work when air is running over them with velocity...

 

"Johnny Mac is currently at TEIN right now, doing some super stuff to our suspension for the EK for the next race. Please leave a message after the tone, and he will contact you as soon as possible. Thank you for contacting Autocannon." ::BEEEEEEEEEEEP::

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by maxQ &raquo;</TD></TR><TR><TD CLASS="quote">
The GAW-1 will have 10-15% LESS drag than the Clark-Y at the same lift coefficient.

I'll look up for the max AOA... but be warned, it's a function of speed.... the faster you go, the higher AOA you can get without stall.... so you have to kinda pick a speed to design to.
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Ok, just to make sure I understand, in this application lift coefficient = amount of downforce for a given speed. Is that right? I'm trying to figure out stall speed in this application. I thought stall speed was basically the speed at which the wing no longer produced enough lift to keep the aircraft in the air. Is that right? I can't seem to wrap my tiny brain around how that works when the object is already on the ground and you're just trying to push down on it.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by maxQ &raquo;</TD></TR><TR><TD CLASS="quote">
EDIT: The GAW-1 is NOT necessarily THE BEST airfoil for car applications... while pretty darn good and used a fair bit in such applications, it was primarily designed for cruise efficiency on an airplane at &gt;150 mph.... </TD></TR></TABLE>

Sounds perfect for me. I routinely see 150mph in my H4 car.

- Scott &lt;-- uneducated in the ways of the wing and a dirty, dirty liar

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">Andy - talking about specific airfoils, and L/D, and stuff like that is NOT the response I'm looking for for the question I didn't really ask...

I'm looking to Johnny Mac to provide some rough insight into "how much is useful"...

There was another thread in which he talked about the price in drag of too much splitter tray area on these cars....I noticed and took note.</TD></TR></TABLE>

How much is useful for you? Or how much is useful for Cunningham? I think I sorta answered the question you didn't ask about the differences between the current Touring car trend and the old spec TC wing. But for an individual application specific to an amateur DC2, Johnny Mac may have knowledge of praticality than the rambling of my theoritics. Sorry to introduce a element of threadjacking.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">"Your teh suck!"</TD></TR></TABLE>
I believe the proper phrasing would be "You're teh suck!" or "j00r teh suck!"

-Chris

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FlyZlow &raquo;</TD></TR><TR><TD CLASS="quote">Ok, just to make sure I understand, in this application lift coefficient = amount of downforce for a given speed. Is that right? I'm trying to figure out stall speed in this application. I thought stall speed was basically the speed at which the wing no longer produced enough lift to keep the aircraft in the air. Is that right? I can't seem to wrap my tiny brain around how that works when the object is already on the ground and you're just trying to push down on it.</TD></TR></TABLE>

Lift coefficient is the amount of downforce for a given speed and wing area. It's a measure of efficiency regardless of whether the wing is the size of Tony Stewart's sprint car or the eBay "spoiler" on a Miata.


Stall is the moment at which the air separates from the surface of the airfoil and the spoiler begins to increase rapidly in drag and decrease somewhat less rapidly in downforce. For a car application, no catastrophe results other than a great increase in drag (straightline speed) and much less effectiveness in downforce (loose at speed). Generally, the angle of attack of the spoiler is constant (because you set it in the paddock) and will either produce lift or be stalled when you roll out of the pits and stay that way until you move it (a bit of a generalization but sufficient for this discussion).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by maxQ &raquo;</TD></TR><TR><TD CLASS="quote">... my theoritics. Sorry to introduce a element of threadjacking. </TD></TR></TABLE>

Sorry to hear it Andy...Early Onset?...I'm still hoping to be alot older before it hurts to think....

Scott, who says don't worry about the hijacking...you probably just forgot where you were going....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">
A close look at the wings on alot of current touring cars lately show pretty curvey foils run about flat...

Most of us who know anything know about lift to drag coefficients...

Are people like RTR running wings (at all) because they have to per the rules? And they run them set for minimal drag?

</TD></TR></TABLE>

Those wings are run flat because of two reasons. One, the mean airflow is angled downward toward the rear of the car due to the rear window slope. So, even a wing that is mounted horizontally "sees" air at an angle. Most wings generate maximum lift (or downforce for cars) at a angle of attack (the angle of air relative to the chord of the airfoil) of between 12 and 16 degrees.

The following discussion involves only the TC class as the GT rules are somewhat different.

RTR does not have to run a wing if they for some reason didn't want to. The World Challenge rules:

http://www.sccapro.com/05rulebook/article2.pdf

The rules allow a splitter to have certain maximum dimensions of 3" total splitter length and the leading edge of splitter can extend a maximum of 1.5" forward of the approved bodywork. The splitter is a very effective downforce producer so all of the teams take full advantage of this rule. The wing is then used to balance this front downforce such that the car does not develope the dreaded aero oversteer condition.

 

Riiggghhht....with you on the airflow over the wing - hence you even see the ocassional wing tipped back a bit....

"A guy" at HPM said that the TC spec wing made around 100 lbs at 100 mph, and we run it as far back as the rules allow to gain leverage...so in the typical 3rd or 4th gear corner we're pushing down on the back with a max of 100-120 lbs...to balance ??? however much we get out of our front end...

"A guy" (named Taz) told me that a splitter and a wing were worth 1-2 seconds on a typical track (and that he didn't particularly care for the improvement in that it cost greatly in tires and brakes)...PD may have said as much...Zellner said yep...but I see guys take a hit, lose the front bodywork, and stay in the hunt...leaving me a little perplexed since I like to believe in science at least as much as the next guy...

What am I believing in again here?

Scott, who will have his front end parts in another week or two and will start learning about this stuff in the real world...or as close as I ever get to it...Thanks for responding to the invitation Johnny Mac.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">but I see guys take a hit, lose the front bodywork, and stay in the hunt...leaving me a little perplexed since I like to believe in science at least as much as the next guy...

What am I believing in again here?
.</TD></TR></TABLE>

its in a race, and most of the time in a race they aren't running qualifying lap speeds.

And when in a pack of cars fighting for position laps can get really off of even race pace.

and what about the fact that when running nose to tail with a car, there really isn't any air coming across that front end anyways.

at least thats my take on it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">Riiggghhht....with you on the airflow over the wing - hence you even see the ocassional wing tipped back a bit....

"A guy" at HPM said that the TC spec wing made around 100 lbs at 100 mph, and we run it as far back as the rules allow to gain leverage...so in the typical 3rd or 4th gear corner we're pushing down on the back with a max of 100-120 lbs...to balance ??? however much we get out of our front end...

"A guy" (named Taz) told me that a splitter and a wing were worth 1-2 seconds on a typical track (and that he didn't particularly care for the improvement in that it cost greatly in tires and brakes)...PD may have said as much...Zellner said yep...but I see guys take a hit, lose the front bodywork, and stay in the hunt...leaving me a little perplexed since I like to believe in science at least as much as the next guy...

What am I believing in again here?

Scott, who will have his front end parts in another week or two and will start learning about this stuff in the real world...or as close as I ever get to it...Thanks for responding to the invitation Johnny Mac.</TD></TR></TABLE>

Yeah, I have one those HPM wings that's on my friend Bernardo's H1 car (yes its setup to run almost dead horizontal). I computed that it would produce about 100 lbs of DF and about 15 lbs of drag at 100 mph. It's based on an old-school NACA airfoil. The problem with every airfoil that I've looked at is they are only efficient for a couple degrees of angle of attack. I have this Selig airfoil that works great from about 4 degrees to 7 degrees AOA and then it falls flat on it's face. If my wing is not properly sized in this range of AOA, then I have a less than ideal wing. This means that you pretty much need to know about how much downforce you're looking to develop from your wing. Then you can size it accordingly. Let's say that for an H4 car that I want about 75 pounds of rear DF to match let's say my 65 pounds of front DF. I want to use the most efficient wing possible (within reason) so I set out to design the highest aspect ratio wing. High aspect ratio wing minimizes the highest drag component of downforce which is called induced drag. For high aspect ratio, I want a small chord and long span. The problem with this is a that a small chord means a smaller Reynolds number airflow, which lowers the design lift coefficient of the wing. So, you see, wing design is iterative and one should do plenty of testing to prove the wing concept that is chosen.


Modified by Johnny Mac at 11:24 PM 7/5/2005

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slammed_93_hatch &raquo;</TD></TR><TR><TD CLASS="quote">

its in a race, and most of the time in a race they aren't running qualifying lap speeds.

And when in a pack of cars fighting for position laps can get really off of even race pace.

and what about the fact that when running nose to tail with a car, there really isn't any air coming across that front end anyways.

at least thats my take on it.</TD></TR></TABLE>

You pretty much hit the nail on the head.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by maxQ &raquo;</TD></TR><TR><TD CLASS="quote">

much better than:



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The problem with both of these airfoils in that they work better in high Reynolds number flow ~ 3 to 9 million. The airfoils on a 120 mph Honda are in the 250,000 to 700,000 range. In addition the Clark Y is ancient (developed in the 1920's), which is to say, it has been supplanted by much better designs. Even the NACA 6-digit foils are not really suitable for our racing. The best designs for our racecars are actually based on the low-Reynolds number foils originally developed for sailplanes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">
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Are you telling me you gonna help me tune my wing at WS?

 

Too bad NASA banned moveable wings, my old NACA 0012 worked okay at 0 and 12 degrees AOA...