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Nice work, Trek. Maybe you should have just used that GT3 wing you have bolted on the front of your Lemons car!
Old 01-30-2011, 08:18 PM
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Hey!

That GT3 wing used as a splitter was good for 2 seconds at TH!


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Old 01-30-2011, 08:22 PM
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Cool home made projects guys. I'm sure there must be an easier way to test these wings apart from spending stupid money at a windtunnel. As Jack has shown elsewhere, he has done some other testing with pics. Perhaps he could show them here?
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Old 01-30-2011, 10:19 PM
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Maybe I should build a test rig that sets up in the back of my truck or trailer with streamers to show the airflow.

Video camera set-up to record the data.


KT
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Old 01-31-2011, 04:13 AM
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Upright stabilizers!

I need to weld on the mounting tabs and paint.


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Old 02-04-2011, 05:13 PM
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How are you going to fair the uprights?
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Old 02-04-2011, 05:14 PM
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Flat stock welded to the bottom at the same angle of the rear trunk.
Drill holes and bolt on.

The wing will have adjustable turnbuckles to change the angle of attack.


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Old 02-04-2011, 05:17 PM
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Oh yeah, and thin rubber sandwiched between so I don't gaff the paint.


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Old 02-04-2011, 05:21 PM
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I meant the skin on the uprights so that you are not pushing a bunch of square tube scaffolding through the air.

Long Beach Sportscar Races 2009_394
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Old 02-04-2011, 06:35 PM
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I suppose I could skin the stabilizers.

I probably won't.
It's just 1/2"x1/2" tube.


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Old 02-04-2011, 06:42 PM
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Max Sluiter
 
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But the drag coefficient is terrible!

Just bend some Aluminum sheet around it like an airfoil but with no specific camber. Just streamlined.
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Old 02-04-2011, 07:35 PM
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Jack is right in that just about any airfoil shape will be effective. The efficiency on a low power car (like most of our cars) is not a very big factor. Our top speed on the track is usually 110-120 MPH while the top speed capability of the car may be 150 or more. Since the drag goes up with velocity squared (or cubed or some such ratio) the drag from the wing is much less important than the down force it can provide. Powerful cars like in F1 can get very close to their aerodynamic top speed and so efficiency is much more important as is the idea of trimming out some of the downforce to reduce drag. I bet Trekkor will find at least 1.5 seconds per lap improvement at Infineon.

-Andy
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Old 02-04-2011, 09:00 PM
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I am of the belief that drag in the back can be just as beneficial for creating stability as real down-force can. The entire reason people put wings on their cars is to A) try and go faster and B) to make the car feel more stable in yaw and well I guess C) to make their car look faster and racier is a big factor on club level race cars as well. For the majority of the club level drivers though, creating B) causes A) to happen as they then feel more comfortable pushing harder as they were really only using 95% of the cars capability to start with. Sure in the real world of pro drivers the effectiveness of the wing and reducing drag is vitally important to getting that last couple .01s of a second off the lap time but for the majority of us, I wouldn't obsess over it. Get the car to not do anything strange or scary and just drive the wheels off of it. As Enzo Ferrari said, aerodynamics are for people who can't build engines.

If we are talking about a GT3 Cup or RSR or similar, the above is not all that true but for throwing a splitter and a wing on a non aero package optimized car like a reasonably close to stock 914 or 911 like most of us drive, no need to get too worried about any of it. I would have to say though that a plate of 1/4" aluminum and 30min with a water jet cutter does wonders for making wing uprights.
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Old 02-04-2011, 09:21 PM
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Efficiency is still important. The drag and downforce are both functions of rho*airspeed^2

If you are not going fast enough for the drag to be slowing you down, then you are not going fast enough for downforce to have much effect. You are just going to burn more fuel.

If you just want yaw stability, add tail fins like F1 cars and the new LeMans regs. They are much less draggy.

Having drag up high or a wing making downforce behind the rear wheels, you are levering up the front tires. If you are just doing it with drag, then you are going slower, burning more fuel, and have less grip at the front.

Splitters are free front downforce. You will need one to balance out a rear downforce device, particularly a cantilevered wing.
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Old 02-04-2011, 10:22 PM
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Flat Alum. Plate

I agree 1/4'' plate aluminum with a break and a backing plate,and cut to the profile of the bottom side of the wing...nice! I sure his water jet machine is in the shop! jig saw.
An race engineer said to me a rear wing of good design doesn't start to work until "about 60 mph) then the math takes placement/ surface area/shape /etc. Plus the GURNEY flap.
I might go with flat end cap and a interchangeable GURNEY flap.
NICE job!
Old 02-04-2011, 10:50 PM
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Quote:
Originally Posted by Eagledriver View Post
Jack is right in that just about any airfoil shape will be effective.
Not really. The better designs provide useful downforce at lower speeds and higher downforce levels at higher speeds with lower AoA.

But hey, you guys are welcome to throw any old shape you want out there. Though it really makes a lot of sense to use a "known good" profile like Jack did.

Scott
Old 02-05-2011, 12:59 AM
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I appreciate the comments.

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Old 02-05-2011, 08:20 AM
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Quote:
Originally Posted by Evan Fullerton View Post
I am of the belief that drag in the back can be just as beneficial for creating stability as real down-force can. The entire reason people put wings on their cars is to A) try and go faster and B) to make the car feel more stable in yaw and well I guess C) to make their car look faster and racier is a big factor on club level race cars as well. For the majority of the club level drivers though, creating B) causes A) to happen as they then feel more comfortable pushing harder as they were really only using 95% of the cars capability to start with.
I don't get this. I don't know any serious racer that puts a wing on their car to make it "look" faster. That's what "posers" do....

I don't recall hearing any tuner say that they added a rear wing to a production-based car to increase stability.

The reason you put a rear wing on a production-based car is to reduce lift or to actually impart downforce. Reducing lift or imparting downforce allows you to go around a corner faster because it increases the vertical load on the tires without increasing the lateral load.

You add aerodynamic devices to production-based cars to increase traction.

Stability? That is handled by balancing aerodynamic downforce front to rear and by adjusting the roll couple distribution to alter traction at each end of the car. By changing toe and caster settings. Because of the variability in speeds seen on a race track, you would have a real hard time adding any meaningful stability by adding aerodynamic drag at the rear of the car.

Scott

Last edited by winders; 02-05-2011 at 03:03 PM..
Old 02-05-2011, 01:59 PM
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Scott, you clearly do not represent the average club racer. I would say 80% of the racers at the club level know little about their cars and put parts on there because so and so has it, the fast guy told him that is what he needs, that is what the pros/factory use, it looks cool, or some combination of the above reasons. If that makes them not "serious", so be it but that is not how they view it. I had a hell of a time selling my very nice and quite fast 993 RSR clone because 90% of the buyers didn't like the color gray. Seriously, I had at least 10 racers tell me to paint it a flashy color and add a livery just to make it look cooler. Most of them didn't really care how fast it was or all the little details it had that made it such a good car, they were much more concerned about how cool they would look in it at the track. Nothing wrong with looking cool at the track but this is the reality of club racing. It is an escape from work and life for most people, not a 100% concerted effort to win. If you are really into winning and competition, a Grand Am ST car may be a better spot for you as besides the travel costs, they aren't any more expensive to run than a good club level effort.

Now if you have the engineering know how, time, and the money to go testing by all means build something efficient but you will find that the majority of the people club racing don't get everything that their car has to give however it is set up so if they can build anything cheaply that makes their car less likely to get away from them if it steps out at speed, they will go faster even if a pro in the car would go slower.

If you don't think drag at the rear of the car in yaw makes the car more stable, you better go tell the FIA as it is now a requirement for F1 and Prototypes cars. I have first hand experience of how great drag can be at speed when I had my 993 snap sideways at 100+ a couple times. Just keep your foot in it and let the aero bring the car strait again.
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Last edited by Evan Fullerton; 02-05-2011 at 05:04 PM..
Old 02-05-2011, 04:48 PM
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I don't want this to happen anymore...




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Old 02-05-2011, 05:56 PM
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