Aerodynamic Aids - What a drag, What’s your drag? Options

[URY914]

I'm getting in on this thread a little late, but for you non-believers that think wings don't work at low a/x low speed, you are full of horse-hockey. Have a look at some of these cars....

[Twystd1]

Yea...

Those wings "MUST" be just for the bling factor..... (IMG:style_emoticons/default/chair.gif) (IMG:style_emoticons/default/slap.gif) (IMG:style_emoticons/default/stirthepot.gif) (IMG:style_emoticons/default/poke.gif)

Those guys just spent all that money and engineering for looks....


Claytonious

[URY914]

There is a ratio for a wing's height to its depth that is used for low speed down force. I used it when I designed and built my wing. Joe is right (for once) that wings absolutely make a difference, that is why they are closely regulated.

Here is a quote from a A-Mod designer/builder:

"In regards to wing design for autox, the problem is finding a profile that is efficient for low-speed applications. Most of the profiles out there for airplanes and race cars are all designed for higher speed. For low speed applications, you need a "thick" body relative to the wing's cord (measurement from leading edge to trailing edge). The goal is to find a profile that approaches 20% in that ratio."

[alpha434]

Ken. That statement was half-joke. But only half. It was used as a transitional statement into the subject of formula car tech, and their expenditures in developing better aerodynamics in different angles.

And "slab area" doesn't matter as long as everything you calculate uses the same variables. What does it matter to you or anyone else to know the exact resistance. It doesn't. But as long as you apply the same equation to every car you consider, you'll have accurate data for improving the design.

Besides. I've been blown over 2 lanes by crosswinds before in my 914. 914s are lighter and have MUCH less traction than most cars. That's never happened to you? WTF with your statement?!?

[Twystd1]

Chris...................

Be nice dammit.

Da old man.

[d914]

ok, jumping in, no areo background and for the neophytes out here like me..would a package like the below work??? do any of the pieces work???

operating arena 80-140mph

front spoiler for flared car ( member vendor)
air tabs at back of targa ( work??)
sheridan 4 or 6 in blade spoiler

what are the cheap$$ jap wings that work and that will hold up to speed
(ricards ??) Does it have to be above the targa ala gt class pca cars??

[Joe Ricard]

My wing was not cheap and it is NOT a "RICER" wing. Got to APR Racing. Find the GT wings.
They may look the same but there is significant differences in the shape of the air foil that make mine provide down force and recude drag

Yes if you have a 914 the wing MUST be even with or better yet above the roof line to provide any benefit.

Not sure why I am trying to convince ou guys. Maybe if I was racing against you I would just tell you "yea it's just for show" Don't spend you money here.

Never mind that nearly every class champion in STS, SM SM2 XP and most of the Mod classes had wings. and thier cars go significantly faster than 50 MPH on course.

[d914]

didnt mean it as a shot, just alittle toward styling, I have your wing booked marked, but compared to gt racing at a $1000.00 just for the wing and about $1500.00 mounted yours be cheap!!!

Again, I like yours just checking on use, autocross vs track, and effectiveness..

Sorry for the shorthand, I don't like typing much..


http://www.aprperformance.com/index.php?op...4&Itemid=44

$340-570.00

Huge differnce in pricing, hence my questions.....By the way I do believe you even used the ricer like wing back when you first posted about the wing way back when . Again did in no way mean it as a shot... performance parts are perfomace parts, I'll look any where to save a buck on something that works..

ohh and one last edit, look at the engine in my avitar,,,,,subie with the tranny, I can't but go ricer!!! (IMG:style_emoticons/default/smile.gif)

[sean_v8_914]

my wing a ling your wing a ling, won't you play with my wing a ling. those HUGE wings do work at lower speeds but look at how ridiculously large they need to be.

wind resistance is non-linear

someone flip that turtle. the underside of the 914 has some area of improvement under the engine to where the air exits at the rear bumper valance/ air brake. we could benefit from a belly plate diffuser ala Exige or Enzo...not just a flat cover but a channeled diffuser where the channels increase in size as the air exits. sorta like a funnel flowing in reverse. this would reduce relative pressure

the primary confuddlement is in wing vs spoiler. a wing is more effective at lower speeds than a spoiler, however, since wind resistance is non linear, the wing must be HUGE to work well at low speeds. a huge wing becomes a huge drag at big track speeds. the wing MUST be in clean air above the path of air flow that has been modified in direction by the car passing thru it. notice how high the wing is on the slower cars. notice that it is much lower on faster F1 cars. notice the severe angle of attack on those wing monsters as compared to the less extreme angle on the faster F1. notice also the the wing airfoil is inverted so it wants to fly towards the ground.

in summary: no answers are absolute here. the answers are strickly dependent on the use of the car

somebody make us a belly pan

[Mikey914]

I agree, the wing must be suited for the application. In aircraft design, low speed 45-70mph the chord of the mean camber or thickness of the wing is on a curve that the slower it is effective, the thicker it will need to be. The real problem is that when lift is created (negative lift for this application) you also create Parasitic drag, now decreasing your top end speed.

If you were to use a wing it would have to be tuned specifically for the application for optimum benefit. Hence the $$$$$.

The real solution would be to have a variable camber wing that was controlled by air pressure. This would be the easiest way to regulate the mean camber. The Helio courier is an excellent example of simple application of this concept, it is low tech, yet does some really incredible things. This aircraft has slats that drop down below 55 and when the air pressure is greater than 55 they roll back, buy airpressure. This allows the aircraft a minimum speed of about 30 mph, and it can cruse at 165 mph. With the exception of the top end these are the speeds that you would be operating at, and I bet the benefit of the changing geometry at about 55mph would also benefit.


http://www.stolaircraft.com/
http://www.bush-planes.com/helio-courier.html

For what it's worth.

[Mugs914]

Just a few somewhat random thoughts to add to the discussion:

Sean is right, "wind resistance" is not linear. Aerodynamic forces (drag, lift, downforce, all of the above) function as a square of the speed. In other words, double the speed and aero forces quadruple.

When you are looking at a various race cars for examples of things to try, keep in mind that the wings on those things are very tightly restricted by the rule book. Even those humongous billboards on the A mod cars are restricted (If I remember correctly) in the overall area and number of elements. Most of time what you see on race cars are not the ultimate solutions to an aero problem, but the best solution they can come up with and still be within the rules.

I did a study once looking at low speed wings in an autocross application. I found that a 6'span, 1' chord wing with the proper airfoil and camber (Very similar to the wing Paul has built, by the way) could produce as much as 45 pounds of downforce at 30mph. Doesn't sound like much, but last time I looked they time autocross down to the thousandth of a second... A small advantage is still an advantage!

Very, very generally, downforce helps in the turns, drag reduction helps in the straights. Look at where you spend most of your time on the track and in most cases an increase in drag in exchange for more downforce is a good swap. The only place I know of where minimum drag wins races is at Bonneville... (IMG:style_emoticons/default/biggrin.gif)

Suit on; flame away...

[chris914]

The real solution would be to have a variable camber wing that was controlled by air pressure. This would be the easiest way to regulate the mean camber. The Helio courier is an excellent example of simple application of this concept, it is low tech, yet does some really incredible things. This aircraft has slats that drop down below 55 and when the air pressure is greater than 55 they roll back, buy airpressure. This allows the aircraft a minimum speed of about 30 mph, and it can cruse at 165 mph. With the exception of the top end these are the speeds that you would be operating at, and I bet the benefit of the changing geometry at about 55mph would also benefit.

Hmm, now that might make a good fluids and controls project for the students.

[Mugs914]

Another couplea thoughts:

Airplane wings operate at almost constantly changing angles of attack (Chord angle relative to direction of travel), and have to be designed to operate over that wide range. Race car wings operate at fixed angles of attack and can have airfoils designed more specifically for those angles.

Most places we race won't allow any movable aero devices like the slats on a Helio, but some don't say anything about it. As I recall autocross rules (PCA, anyway) only mention "spoiler/wing" and say nothing about movable bits.

Hmmmm... (IMG:style_emoticons/default/idea.gif)

[alpha434]

The real solution would be to have a variable camber wing that was controlled by air pressure. This would be the easiest way to regulate the mean camber. The Helio courier is an excellent example of simple application of this concept, it is low tech, yet does some really incredible things. This aircraft has slats that drop down below 55 and when the air pressure is greater than 55 they roll back, buy airpressure. This allows the aircraft a minimum speed of about 30 mph, and it can cruse at 165 mph. With the exception of the top end these are the speeds that you would be operating at, and I bet the benefit of the changing geometry at about 55mph would also benefit.

Hmm, now that might make a good fluids and controls project for the students.

Early race car wings were actuated by the brakes. Hit the brakes, and the wing flopped down. Let off, and the wing went straight. Easy.

Also, I have pictures of 356s in the 60s with wings mounted on the front trailing arms and tied to the body. When the suspension moved up (the wheel starts to leave the ground,) the wing exposes more surface area and holds the wheel to the ground. Easy.

[Air_Cooled_Nut]

... those HUGE wings do work at lower speeds but look at how ridiculously large they need to be...the wing must be HUGE to work well at low speeds. a huge wing becomes a huge drag at big track speeds. the wing MUST be in clean air above the path of air flow that has been modified in direction by the car passing thru it. notice how high the wing is on the slower cars. notice that it is much lower on faster F1 cars. notice the severe angle of attack on those wing monsters as compared to the less extreme angle on the faster F1. notice also the the wing airfoil is inverted so it wants to fly towards the ground.

...

somebody make us a belly pan

Thank you! I'm glad someone else understands this.

I agree w/the belly pan idea. (IMG:style_emoticons/default/beer.gif)

[Air_Cooled_Nut]

...http://www.amazon.com/Aerodynamics-Hp1267-...720&sr=1-23

http://www.amazon.com/Race-Car-Aerodynamic...7760&sr=1-2

http://www.amazon.com/Competition-Car-Aero...7760&sr=1-1

I know that there are books out there that I could use, however, I didn't ask for book recommendations. I was hoping someone knew of a web site that had this info instead of me having to waste time searching for it.

[Mugs914]

Early race car wings were actuated by the brakes. Hit the brakes, and the wing flopped down. Let off, and the wing went straight. Easy.

Not quite so easy... I don't know of any that worked off of the brake. One reason is that the wing going "straight" when you let off the brake minimizes the downforce just when you need it most; right when you're trying to accelerate through the corner.

Mercedes had an air brake mounted behind the cockpit of their LeMans cars in 1955 but it was hinged at the rear and operated only as a brake and not in any kind of (intentional) downforce producing capacity. A couple of cars in the original Can-Am experimented with aero braking, but all of the ones I'm aware of used a separate panel rather than the wing itself.

The wings on the various Chaparrals were connected to a pedal on the left side of the floor where the clutch would normally be (They used an "automatic" transmission with no clutch). The driver controlled the wing using high angle for braking and cornering and flattening it out for the straights.

Most of the movable wings were connected directly to the suspension and were designed to increase angle of attack as the suspension extended, just like you described on the 356.

Sorry to go on so. One of my favorite subjects!

Also, I have pictures of 356s in the 60s with wings mounted on the front trailing arms and tied to the body. When the suspension moved up (the wheel starts to leave the ground,) the wing exposes more surface area and holds the wheel to the ground. Easy.

I'd like to see those. Post 'em!

[Allan]

You know what they say:

The bigger the wing, the bigger the $&^%.... (IMG:style_emoticons/default/biggrin.gif)

[Mugs914]

You know what they say:

The bigger the wing, the bigger the $&^%.... (IMG:style_emoticons/default/biggrin.gif)

(IMG:style_emoticons/default/av-943.gif)


This guy must have REAL issues...

[alpha434]

Well... You're right about the "no downforce when accelerating through corners" problem. But the tech was banned by numerous race organizations. Including the modern FIA.

But now we have the ability to rig a moving wing to a linear actuator and wire up a time delay circuit. Something like 1,5 seconds of braking switches the wing into downforce position and it will stay there for the next 2 seconds after letting off the brake. BAM! Downforce throughout the whole corner.