If the wing puts enough stress on the fiberglass decklid, then the ducktail might end up moving to a different location on its own. ;)

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?

http://forums.pelicanparts.com/uploa...1157486414.jpg

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. :)

Jack, always a pleasure to see a man obsessed :)

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?

Was my thought.

Would be going from this:
http://www.autozine.org/countach/pic/lp400_1.jpg

To this:
http://www.lamborghiniregistry.com/c...S/1121112b.jpg

Only Porsche style.

Have to see it, could get scary.

http://forums.pelicanparts.com/uploa...1157497456.jpg

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.

http://forums.pelicanparts.com/uploa...1157497325.jpg

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.

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

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.

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...

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.

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.

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.
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.
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.

Go ahead and try it. It won't kill you (well probably not) and then you'll know for sure.

If the idiots won't try the crazy stuff, then who will?

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

http://forums.pelicanparts.com/uploa...1157524531.jpg

'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.

http://forums.pelicanparts.com/uploa...1157524985.jpg

'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.

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.

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!? :p)

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...
http://forums.pelicanparts.com/uploa...1157553461.jpg
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! :D
(Of course if it works really well people will quickly stop laughing and start copying...)

I think we are heading down the Can-Am road now. High wings!

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

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.

It's some darn nice work for (let alone) a car nut - but you're into the territory of aircraft assembly here - which is impressive for a guy who tends to keep his hands clean.

However, I'm curious whether you really need or really want to keep expanding upon ground effects (downforce) since all of that technology doesn't seem to be of the period when RS or RSR models ran in early years. Meaning, that the more expert one becomes at the track - the more you will avoid mishap from a car getting loose in the turns. ???

Anyway, I'm wondering the desirablity of a pseudo 'Martini rsr' type of setup. ...you know, how the basic idea was to extend the ducktail laterally upon the back fenders in what looked like a very integral design. And a few shots I've seen where guys tried to imitate it by what appeared to be removable items that rigged left and right of the ducktail.

This may not be as feasible as I'm making it sound. And most likely would not generate quite as much downforce. But it would add more than a ducktail and the appearance would be outstanding for photo shots etc.

______________
(....not quite the rsr shot I had in mind)

http://mishami.image.pbase.com/o4/53/615153/1/52667194.MartiniRacing1973Porsche911RSR2.8literPho to2.jpg

How about skirts and a big fan to suck the car to the road. The car has a big fan already :)

http://www.f1rejects.com/hall/beta/fancar.jpg

Only thing is, people complained about getting sprayed with gravel when they were behind it and it got banned.

This looks like an interesting read..

http://www.bentleypublishers.com/gallery.htm?code=GAER&galleryId=768

If the 911 engine sucked air like an Osprey (or was that Harrier jet) from the bottom, and spit it out of the fan like Jim Hall's Chapparal or the Brabham BT46, maybe we could harness that. :)

Sherwood

That's exactly what they said the fan was for on the Brabham - engine cooling. Didn't fool anyone though.

Maybe the only additional down force needed would be winglets on the bumpers. They can be adjusted to size and angle of attack at the track according to environment that day.

http://forums.pelicanparts.com/uploa...1157638463.jpg

Here's the package for this weekend's testing. The 70-inch rear wing has better reinforcements where the uprights mount to the car, as well as a piece of cold-rolled steel stock inside the insert tube that connects the two halves of the wing. There should be no flex, now, even if the wing were able to generate 300+ pounds of downforce.

In front, I've made a new splitter that extends 5 inches out in front of the base of the bumper. If that makes the car tail happy, I can switch back to my old 3-inch splitter.

I don't think I'll be testing the front wing idea, since some of the posts here have got me reconsidering the best place to mount it, and honestly I don't think I have the time to get it all put together and tested before Satruday morning.

http://forums.pelicanparts.com/uploa...1157661888.jpg

I'll post here with my subjective driving impressions (and/or reports of the wing's spectacular and catastrophic disintegration ;) ).

try using Yakima roof rack clamps to clamp the F wing onto the fenders

good luck!

Nice work Jack!

One thing that might be interesting is that a rear diffusor actually adds downforce in the front of the car. This sounds a little counter intuitive, but measurements show that that is the fact. The effect can be increased if the diffusor is used together with a flat floor pan with "guard rails" stopping the air from going out sideways.

/Peter

Going to Bunnings tomorrow for materials...with the car in the suspension shop and paint, I'm climbing the walls. Not having something to wrench with is driving me crazy.

Jack, are you OK if I borrow some ideas?

Question I have for anyone who often runs at the track:

Do 911 owners always benefit from 'goundeffect' packages that add hundreds of Lbs. of downforce to their cars ? If the car becomes effectively 'glued' to the surface in the turns - something seems funny about that...

Doesn't a lot of the skill needed to drive the car go to the wayside if you've got an elaborate setup of groundeffects ?

Seems to take away control from what the driver should be involved in. Need more info please.

http://www.pelicanparts.com/support/smileys/wat2.gif

Aero doesn't change the way you drive the car at all, really. It just raises the threshold point where you're making your corrections. So instead of throttle-steering through turn 2 at Willow at 85 mph, I'll be doing it at 95-100 mph.

Viewed another way, any car is 'glued to the surface' right up until the point where its tires begin to lose adhesion. Aero mods simply raise the point at which that happens. You're still dancing on the edge, but you're doing it at a higher speed.

ABS, traction control, computer-controlled launch assistance and automatic transmissions are all driver aid devices that would be -- in my opinion -- in the kind of category you're talking about. They fundamentally change the driving experience. Aero would be more like wider or stickier tires (only cheaper) in that they don't do any work for you. They just change the point on the speedometer where the work gets done.

In fact, since they change the car's behavior in less predictable ways than an unmodified car, you could easily say they make the car more of a challenge to drive. You have the normal dynamics and characteristics of the car, and then also the dynamics and characteristics of your aero package.

As a side note, none of the mods discussed in this thread are ground effects. But trust me, that's a thread I hope to start in the coming months. ;)

No problem there, so long as you watch this space for the weak points I find in what I built.

The key ingredient if you're working in aluminum is the adhesive you use. I tested 2500 lb per square inch two-part epoxies that were terrible. I could peel two pieces of aluminum apart without any trouble at all. The Scotch-Weld DP460 is the one I finally settled on (after a number of others were tested). It's expensive (US$12 for 1.25 oz, and it took me four tubes to make the wing), but it's very strong.

Of course, we'll see how strong this weekend.

I just drove into Lancaster. It's windy - if it keeps up should make the aero testing interesting...

Thanks Jack. I just got back from the supply shops with about 200 aussie in materials.

I bought from "pro" shops and asked lots of questions so I hope to have the right start. You should have seen the looks on the guys faces explaining to them I am building a`wing for the car. Of course that always led to a sad discussion on Brocky...I haven't seen it commented on yet on this board, but Peter Brock died in the WA Rally yesterday in his Daytona Coupe. A real gentleman, Peter was, and a hell of a driver.

One idea I had was to inject some lightweight expanding foam core into the structure...i'll try it without first. It sounds like the strength issues might primarily be in the mounting and brackets. If there is any flex at all in the wing I might drill out a few holes and squirt something like that "Great Stuff" you get in the US. That might add a few ounces, but its super-sticky, quite stiff while still retaining some relsiliance (sp?) and would seem to add rigidity and damping to the wing.

Ok...plywood, clamps, extrusions, sheeting, epoxy, rivet gun, 6-pack of Coopers Extra Stout, I'm ready to go!

BTW, how did you choose that exact wing cross-section? And how thick is your "skin" and internal braces?

One simplification I am making is to keep it one piece. This is a track-only car so I don't care about breaking it down, though that is a very cooll piece if additional engineering!

john

I am about to try "Aradilite Maximum Bond" with rivet reinforcements in the internal joins. I wish I had a TIG rig and knew how to use it...

Is that a "flap" on the training edge of the wing stencil, or just an extraneous line?

http://forums.pelicanparts.com/uploa...1157770512.jpg

Construction:

A - Ribs are Alloy 3003 .02 inch, folded over to 3/4 inch tabs

B - Anchor rib: Alloy 6061 .9mm
Rear leg doubled up with same material
Front leg doubled up with 1.1 mm by 3/4 inch bar, L-shaped to meet up with 1/2 tube, secured with clamp and glue

C - Spars are 35" each Alloy 6061 T-Section 5/8" X 1/2" X 1/20" Thk
Spars are bridged with 4" rectangles of Alloy 3003 .02 inch

D - Main tube is Alloy 38.5" 6063 .625" Od, .527" Id,
with inserted 36" Alloy 6063 .500" Od, .370" Id

E - Rear tube is 14" 6063 .625" Od, .527" Id,
with inserted 7.5" Alloy 6063 .500" Od, .370" Id

F - Skin is '0.86 gauge' Aluminum flashing material

Also:

Gurney lip is made with 35" each 1/2-inch L-shaped Alloy 6063 1/16" thick

Where tubes meet ribs, the junction is reinforced with a snap-on piece of PVC pipe, about 1/3-1/2 inch, secured all around with adhesive.


What I would (will) do different next time? The core of my wing's strength is two-fold. The I-beam that runs the length of it provides its rigidity, and next time I might use thicker aluminum between the top and lower T-shaped pieces, maybe reinforcing those with rivets. The 'anchor' of the whole thing is a path that goes from one upright, to the cross tube, and back to the other upright. This is the part that shouldn't fail even if the wing kinks and bends. Next time, I may do two complete tubes to double this strength.

Also, the aluminum I'm using for the skin is probably too thin. I love that it's light (and was cheap, since it's roofing flashing (US$40 for 50 feet of 24-inch wide aluminum). It's not a structural problem, since it's strong. But it dents too easily -- almost like fabric on the old biplanse, but more prone to dents.

And here's a shot of some of the extra last-minute reinforcements I did.

http://forums.pelicanparts.com/uploa...1157770944.jpg

Oh, and the line off of the tail end is a half-inch L-shaped piece -- it helps structurally and functions as a Gurney flap.

The Gurney flap is named for driver Dan Gurney, who tried to convince his competitors that it was only a structural reinforcement for his wings. In fact, it adds a vertical component to the air velocity at the trailing edge of the wing, deflecting the airflow up (like a spoiler, sort of) and increasing a wing's downforce with a surprisingly small drag penalty. It also slows the airflow over the top of the wing, which slightly increases the static pressure in that region, adding a little more downforce. The vortices it creates at the trailing edge of the wing also help adhesion on the underside the wing. You can run a slightly higher angle of attack on your wing with a Gurney flap before inducing stall.

On my wing, it also helps structurally. But then, that's what Dan Gurney used to say.

...Some interesting viewpoints. Got some rethinking to do.


The Scotch-weld may be terrific. However, I always have had very strong bonds with JB Weld - provided one is willing to 'prep-sand' the aluminum first. If you use a 60 grit and cross hatch the sanding (X X X )- followed by a 40 grit - it's a surprise on how tough JB Weld can be. But with your thin sheet type of aluminum -you may have trouble scratching it up.

SmileWavy

________________

'80 928
'82 Targa sold

I have JB Weld, but I didn't test it.

For prep, I etched the surface with a brass wire wheel and then cleaned it with denatured alcohol.

Very impressive Jack!

Did you happen to do a writeup on the underbody aero/diffuser? I've been thinking about that for my car for a while and would love to get some more detail on that.

Did you do any quasi-science on outlets for cooling the engine?