PorKen

Picture an aluminum sheet with trailing edge flap ('Gurney Flap'):



The aluminum sheet would be epoxied to steel bar stock laid across the rubber wing. A bolt through one of the wiper pivot holes, welded to the bar, would clamp the wing to the hatch.

Yes, I could put on a S4 or other wing. But I like the S look (for now).

Some will say that without a wind tunnel, one cannot determine a benefit, but anything ought to be better than the spongy stock wing.

Thoughts?

Good reads:
Race Tech 104: Gurney Flap
All American Racers: Gurney Flap
~thread~start~

PorKen

Mount sheet on hinge, use second wiper pivot hole to push wing (cable operated rod or reuse wiper motor with short arm) for adjustable cornering force or airbrake:



Strength issues?

heinrich

Paint it black Ken :-)

PorKen

I knew someone was gonna go all Spinal Tap on me and say: 'paint it black'.

It's cardboard, man. Vapor-ware.

I'll paint it black if I 'fab that bitch', OK?

heinrich

Ken ... is that a cucumber, orrrrrrrr ....

Nicole

Another "Kenvention"... LOL!

SharkSkin

Just when I thought I'd seen it all...

Airbrake...

PorKen

I'll call it the 'PorKlaren' S1.

ColinB

I didn't know the earlier cars had 'spongy' wings too. Thought they were rigid plastic.
I really don't know how seriously one can take a rubber airfoil. It sounds as if it should be about as effective as a chocolate teapot!
Anybody know if it genuinely produces any downforce or is it merely for show and to keep the rear window clean. Whether or not it has any aerodynamic value I'd still be happier if it was made of aluminium. Does anyone produce an aftermarket ally wing?

Colin
89GT

Nicole

Colin: First of all, it could not be made of rigid material, because in certain countries you cannot have certain hard and sharp edges like this on your car. That's why the 930 turbo wing always had a rubber edge. I believe this is to reduce the risk of injuries in accidents with pedestrians.

The S spoilers reduced the drag coefficient of the 928 from 0.42 to 0.385. That is a quite significant improvement, I would say. I don't have any information on downforce - or better: lift reduction.

Yes, these spoilers have a certain softness, but they are not as soft as a piece of foam rubber that you would use to pad your cyrstal chandelier when shipping it through the mail... They certainly did not visibly deform at Autobahn speeds of 250 km/h (155mph).

Of course, considering that with all the modifications, Ken's 928 is so light and powerful by now that it will reach warp speed, Ken needs to upgrade the aerodynamic rigidity of this baby. Otherwise, next time he flies over South Africa on his way to work, his rear spoiler might flab and he could come crashing down on your house. We sure don't want that to happen...

ColinB

Hi Nicole
Thanks for the info and data. I've been wondering what the drag figure was.

I'm running my car at the Porsche Club Cape 'top end' trials on a military runway early next month where I'm hoping to better my personal 'land speed record' (on a bike) of 255kph. I think I'm going to rig up my movie camera on a tripod in the back and see if the wing deforms.

Hopefully the military will warn us if it picks up any flying pork(en) on radar. Thanks for the warning.
Colin
89 GT

BTW What ARE you doing up at this time of the morning?

Garth S

Now, if you can mount an eccentric on the wiper motor shaft, you can assymetrically change the wing angle (left to right) to simultaneously change both lift and yaw: This should give better grip in off - camber sweepers ...

Gerry

I would hard wire the actuator into the brake light circuit so it would trigger the 'air brake' at high speeds.

PorKen

Gerry,

Thanks. Finally, some constructive posting.

I thought about reusing the cruise control microswitch, which triggers before the hydraulic brakes engage. There should be an electronically limited speed window when it would be allowed to raise. Too fast and it might be ripped off, and popping up at a stop light would look extra dorky.
...

Nicole, ColinB,

You obviously missed my recent post:

Laser (LIDAR) stealth options?

My car is nearly invisible to your sensors.
...

Q: "BTW What ARE you doing up at this time of the morning?"
A: Two words, "Jäger shots".

...

Nicole said: "They certainly did not visibly deform at Autobahn speeds"

I never noticed it until I started measuring, but the S 'wing' is quite pliable, especially the last inch or so. The safety factor makes sense, but because of the lack of rigidity, the most relevant part of the wing is not straight, and deforms with only slight pressure.

One function of the wing is to slow the faster moving air over the top of the car, to better match the speed of air traveling under the car. This reduces lift and can also reduce drag.

Recreating the S-wing assembly in fiberglass, as has been done with the S4 wings, would be ideal. This panel (painted black), should be unobtrusive, and might give some benefit.

PorKen

Is there a grade of sheet aluminum that can be bent 90 degrees?

Or should I plan on attaching an extruded 90 for the flap?