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Jack Olsen's Avatar
 
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Quote:
Originally posted by randywebb
- eventually you may want to move the ducktail to a different location
If the wing puts enough stress on the fiberglass decklid, then the ducktail might end up moving to a different location on its own.
Old 09-05-2006, 12:42 PM
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And here's today's mystery photo for a related project. This is a new wing I'm building, no skin on it yet. It's 37 inches wide, with the same airfoil and cord length, but it has a single 'foot' type mount, right in the forward center of the wing, and two tube entrances on the rear sides for additional mounting points. Anyone want to guess where I'm thinking of putting it?

Old 09-05-2006, 01:00 PM
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My WAG. On the rear engine mount (behind the license plate panel). That location behind the vehicle receives fairly clean air flow. Close?

Sherwood
I'm observing your project via Google Earth map.
Old 09-05-2006, 01:16 PM
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Jack, always a pleasure to see a man obsessed
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Old 09-05-2006, 01:45 PM
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It is intuitively obvious that the new wing is meant as a canard for the front hood. there are several reasons for this:
1. it is the only part of the car that has not been modifed with aero devices yet!
2. the center mount is a dead giveaway - you will be able to use it as a sighting device for lining up on the cones.
3. what what would be more obsessive?
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Old 09-05-2006, 02:12 PM
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Quote:
Originally posted by randywebb
It is intuitively obvious that the new wing is meant as a canard for the front hood.
Was my thought.

Would be going from this:


To this:


Only Porsche style.

Have to see it, could get scary.
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Old 09-05-2006, 02:32 PM
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It's impractical to put a wing in front of the bumper or on the corners for a car like mine -- especially if you go off track as often as I do.

But why has no one ever put a wing on the front of a 911?

Well, one reason could be that it's a terrible idea, and that it will destroy the airflow behind it, rendering the front half of the car and the rear wing less useful as aero devices for a very small gain.

But I don't know that, yet.

And I'll try anything once. So I'm considering a wing 'right between the eyes,' mounted to a set of spare headlight covers and then a support going down to the center of the front bumper.



The way the air speeds up as it moves up the hood might even allow me to have a very aggressive angle of attack without separation and stall.

Crazy? Maybe. Probably. Let me know what you think.
Old 09-05-2006, 04:07 PM
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Jack - Here is a quote for you -- was on the Google quote of the day service today:

Most advances in science come when a person for one reason or another is forced to change fields.
- Peter Borden
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Old 09-05-2006, 04:15 PM
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G'day Jack,
You might like to take a look at Princetons 993TT.
The front Spoiler would probably do the same job as your new front wing concept.(See post I'm humbled)
The only problem would come from offroading too much but that front spoiler combined with under car diffusers would have the car stick like wet s**t to a blanket.
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Old 09-05-2006, 04:44 PM
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I have seen this approach tried before on a 911. No data on the effectiveness, but it was quite ugly (sorry Jack!). However, the idea seems sound to me, I will be curious about the yarn/string tests on air coming over the top of the car with this wing in place. I don't need tell you to make the mounts strong!

Go Jack, Go...
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Old 09-05-2006, 08:40 PM
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I thought the movitivation for this project was to reduce the visual impact of the big wing?

a couple random thoughts;

Positioned as you have it above the hood, you need a fair amount of seperation between hood and wing underside. Otherwise the low pressure of the wing underside is seen by the hood, and is canceled out. I would imagine you'd want 1.5 X the chord or more.

911s normally lose traction at the rear first. A front wing might be counterproductive unless you run an even bigger wing on the rear to balance. Remember any downforce in front of the axle actually lightens the rear end, seesaw effect.
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Old 09-05-2006, 09:25 PM
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I agree with Chuck on the aero advice. A wing up front is a bad trade-off. It would create more down force than you need in relation to the rear, at a great drag penalty.

Kind of a lose/lose situation unless you have serious rear downforce and 1000hp.
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Old 09-05-2006, 10:39 PM
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Quote:
Originally posted by Chuck Moreland
I thought the movitivation for this project was to reduce the visual impact of the big wing?
Ugly doesn't matter so much on the track -- although if this were to work, I have to admit I'll be leery about using it because of the ugly factor.
Quote:
Positioned as you have it above the hood, you need a fair amount of seperation between hood and wing underside. Otherwise the low pressure of the wing underside is seen by the hood, and is canceled out. I would imagine you'd want 1.5 X the chord or more.
I wish I understood this better. Front wings perform better closer to the road surface. But of course, the road is moving (relative to the wing) and my hood isn't.
Quote:
911s normally lose traction at the rear first. A front wing might be counterproductive unless you run an even bigger wing on the rear to balance. Remember any downforce in front of the axle actually lightens the rear end, seesaw effect.
True. But I've more than doubled the rear downforce going from the 42-inch to the 70-inch wing. And if I'm remembering Frere's tests, improving aero on one end spills over to the other, in that the two halves of the car aren't independent. A ducktail and no front spoiler still improves downforce over the front axle.

But drag might be an issue. And the wake of the wing might actually hurt the car's overall aero performance.

I'd say there's a 90% chance it will make things worse, not better.

But heck, a 10% shot is worth gluing some skin on the wing and running the test.
Old 09-05-2006, 11:11 PM
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Go ahead and try it. It won't kill you (well probably not) and then you'll know for sure.
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Old 09-05-2006, 11:32 PM
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If the idiots won't try the crazy stuff, then who will?

I've also thought about a couple of other conceivable wing locations.



'A' probably wouldn't pass anyone's tech. I'd be a hazard to every ankle in the paddock.

'B' might work, but it also might raise my hood and ruin my rear wing's aero with its wake.

'C' doesn't seem to make sense, until you consider the pressure changes in the picture of the SC down below. The speed with which the air is coming up the windshield could be put to work on the underside of a wing. Of course, I have no idea how you could do a non-destructive mounting there. And it might also ruin the rear wing's effectiveness with its wake.



'D' would be a double wing to compensate for any improvement up front. But I've since learned that actually getting a pair of wings to work in concert is a nightmare -- not nearly as easy as the thousands of ready-made double wings you see on Nissans would suggest.
Old 09-05-2006, 11:39 PM
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Here's a crazy hail mary: what about a pair of molded verticle wings from the fenders ala F15?
The outsides would be flat to maintain the side airstream, but the insides moulded to direct the flow towards the engine cover.
-It looks like there's a lot of cavitation/drag in that area, so most of it won't be in the direct airstream on a straightaway where downforce is not necessary.
-In understeer situations however, they will keep the tail from getting sideways fast, which would allow more agressive throttle.

The top of the rear window area also looks like a drag area as well. Maybe a thin, curved foil would take a small bite of the top airflow for the engine lid and push it right at the fan

Downforce is a roundabout way of overcoming air forces- it has to push and compress the suspension, which creates higher tire friction(!), which creates steering force and control.
At 60mph+ your at the liftoff speed of the smaller planes. The german F156 storch of WW2 had a takeoff speed of something like 35mph.
Old 09-06-2006, 04:57 AM
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Quote:
Originally posted by Jack Olsen


It's impractical to put a wing in front of the bumper or on the corners for a car like mine -- especially if you go off track as often as I do.

But why has no one ever put a wing on the front of a 911?

Well, one reason could be that it's a terrible idea, and that it will destroy the airflow behind it, rendering the front half of the car and the rear wing less useful as aero devices for a very small gain.

But I don't know that, yet.

And I'll try anything once. So I'm considering a wing 'right between the eyes,' mounted to a set of spare headlight covers and then a support going down to the center of the front bumper.



The way the air speeds up as it moves up the hood might even allow me to have a very aggressive angle of attack without separation and stall.

Crazy? Maybe. Probably. Let me know what you think.
I think you will find that there is a problem with that the location for a front wing. We tend to think of wings as creating force because of the air stream pressing on the bottom of a wing. (OK, it is the top in this case but I will continue to refer to this as top being down and bottom being up...) Sticking your hand out the window in a car is an easy way to reinforce this idea.

The truth of the matter is that the low air pressure on the top of a wing is what really creates the lift. Its failure to counteract the pressure on the bottom gives you the lift.

The problem that relates to your wing location is that your low pressure area on the "top" of the wing is now also a low pressure area on the top of the hood. These cancel each other out. You are going to create drag and disturb the airflow without gaining any downforce. (or lift!? )

I can't remember how far the low pressure area extends above the wing. The rule of thumb was some sort of multiplier of the wings chord.

This would probably work...

You would probably have to get past a number of other problems... Visibility down the track on banked corners and people laughing at you in the paddock comes to mind. On the plus side it could help with sun glare late in the afternoon!
(Of course if it works really well people will quickly stop laughing and start copying...)
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Old 09-06-2006, 07:43 AM
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I think we are heading down the Can-Am road now. High wings!
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Old 09-06-2006, 07:49 AM
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Jack,

You asked for opinions: and Tyson has it in a nutshell!

Even if you get the spacing above the hood correct (as several others have mentioned), and even if you were to achieve F/R aero balance, you will have created SO MUCH DRAG that you will not be able to hang enough turbo chargers off the motor to generate any downforce.

Ed
Old 09-06-2006, 08:26 AM
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This cracks me up.... it is fun to read about. 911s have gone through all manners of aero transformations... people have tried everything-- my guess is there is really nothing new. But people have to have fun.

This type of front wing deal was recently run on one of our PRC cars. I am sure that jack has seen the car.

The driver/builder (an ex-IMSA pro) ran a 3.8 wing element up front, just rearward of the headlights. The driver/buiilder knows all of the tricks from the old days, but he was looking for a "little more" than he could get with additions to his splitter. He ran it for a season-- did not make a huge diference. The car was a mid-70's with Getty 993 bodywork, and a ~650-700 bhp 3.8 twin turbo. Weighs about 1900. Anyway, he tried it, and stopped using it after last year.
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Old 09-06-2006, 08:41 AM
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