F40 rear air fence?

No. There are strange vortices's that different things produce. Windshield wipers for example. That's why on modern Le Mans cars you see them centered Vertically in the center of the windshield. Mirrors are a real issue. On P 4/5 we turned their stalk into a wing to tune out wake turbulence at the tip of the rear movable wing. There are often twisting forces and even turning around the central axis (YAW) that you try to tune out. In modern wind tunnels you "float" the car on the chassis counter balanced from below so that the wind can generate these twists and turns and you can tune them out. Two possibilities here. To counter act YAW or because of different things in the engine compartment side to side you need different Fence design to smooth the engine compartment air flow equally.
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

It all worked quite well on the track....what a car and what a drive Sanj says I stepped out of it smiling like the Joker from Batman....

 

thanks for the explanation Jim. nice pics, haven't seen those before. would be interesting to see sal take a spin in the tunnel, very aerodynamic structure he is

 

Scares me to Death.

The Gentleman in the Blue Shirt is one the most famous aerodynamic experts in the world.

 

Look how Dino Competizione's wiper parks. Pretty advanced aerodynamically for 1967.
Image Unavailable, Please Login
Image Unavailable, Please Login

 

The aerodynamic devices on your F 40 got a bit of a workout that day.

 

everything about that car is advanced for 1967

 

Fun stuff. The sensors they use in tunnels are pretty cool, the rolling road tunnels pretty trick too. PF, Leonard F, et al did pretty damn nice jobs without much tunnel-wool tufts and autostradas.

For poor bastards like me, driving in rain and looking at droplet flow and trails are a cheap wind tunnel. Even bug spatter shows airflow. I get dead bugs on side windows of 599 in 2" strip about 1/2 way back on door. Dead wasps blow completely through intake, turbulence kills them on fender exit, I suspect that's where some of my door window bugs come from. Water does a complete 180 roll going through the buttresses and dumps high flow/pressure air onto middle of trunk, a CDG ersatz wing. It leaves little boundary layer. There are fences in a few places on bottom of 599, and the tunnel in back makes a huge downforce contribution.
I'd get rear end lift at 175-180 in the Shark, but the 599 stays planted through 200+ easy.

Was that John Iley, Jim? He's a great thinker, that one. Aerodynamics worth more than bhp.

Good clip Jim.

 

It really is fun stuff and your observations are spot on. In Pete Brocks book on his Cobra Daytona Coupe he speaks of how Ken Miles figured out how to keep the air from separating from side of the Daytona Coupe and flowing into the rear brake scoops by sticking his hand out of the pickup tow truck and making a cupping foil around the rear view mirror which Pete copied in clear Plexiglas and mounted to the A pillar of the Daytona Coupe which solved the problem. Once again an aerodynamic device that worked very well at slow speeds and was discovered at slow speed.

Your observations about the 599's Buttresses are also correct. Jason and Engineeri Dot. A Cogotti, the Gentleman in the Blue shirt, specifically shaped those Buttresses for the exact reason you stated and as you've observed they work quite well on Texas's Roads.

Paul and Bobfunkle touched something that night.

http://arc.pininfarina.com/english/impianti_gess.html

 

On a drive in China a few years ago we had 3 CGT's in a row on the highway and the wingy thingys all moved up in exact unison. Pretty cool - required a few slow downs and speed ups for sheer entertainment to watch the wingy thingys at work

 

That is really cool

 

Tony Cogotti is a brilliant guy, he really advanced the science of aerodynamics using modern electronics and computer modeling. His tunnel vanes that can simulate wake turbulence of other cars/F1 cars is nothing short of brilliant. Nobody else looked at the effect other racecars had on the aero-characteristics of a car until his models. One of the guys I'd like to spend a few hours talking with. Cool.

Guess Joe found all this posing tiresome.

Glad my poor man's tunnel works. It actually works even at low speeds in town, and the only boundary layer I see is immediately above the 1/4 windows and fender top right in front of the butresses. I get a uniform dust film right there, even when dry. In bug season, I had dead bugs on side windows, and 1-2 on leading edges of the buttresses. Undertray is always clean, enough velocity coming out of there to markedly decrease the carbon from the exhausts usually deposited all over the rear bumper. The flat wheelhouse edges are pretty cool aerodynamic devices that nobody notices either.

Wish I had time to come out to a trackday with you guys. Or truck them down here to hill country for some scenic posing. You might be faster, but I lift later

 

One fine day you have to join us in the Homeland.

 

You can see from the vapor cloud behind the car just how much air moves through the under tray diffuser. The airflow sucked the water off the track, vaporised it and shot it out the back.
Image Unavailable, Please Login

 

Nice! Hopefully I will get to see the P4/5 in the flesh someday.

Any idea when the 1/18 scale version of the car will be available?

 

Hopefully soon.

 

Note movable aerodynamic device on P 4/5 in up position in this photo. It's also interesting to see what happens to tires in the
rain. Note water damming in front of the tire and how the tread deals with it but it's aerodynamically very inefficient as you can see from the droplets that form in the low pressure area behind the tires vs the nice flow of vaporised water in the high pressure area that the diffuser and under tray manage.

Watch this video of an Aston going up the hill after our pass. See how the vapor isn't flowing smoothly far behind the car but is bunched up and back filling which creates instability. Note that both the Aston and P 4/5 are both at low speed at this point of the course and for most of the hill climb for that matter.

http://www.youtube.com/watch?v=kfvYP3WEULA
Image Unavailable, Please Login

 

From side. Note how smoothed flow is not back filling.
Image Unavailable, Please Login

 

WHich then helps evacutae air from engine compartment, and demonstrates minimal lift. Ya bastage poseur. Probably doing all of 70 through there

 

All true but it was fast enough for the guy in the Aston to have a bad day...

 

LOL. Not to mention depreciation.
I love driving fast in the rain. You either got it, or not. Regenmeisters have pretty awe inspiring car control. Schummi, Senna wet laps always fun. You can see a nice hoover pattern behind the P.
http://video.google.com/videosearch?q=Formula+1+wet+lap+ferrari&www_google_domain=www.google.com&hl=en&emb=0#q=Formula+1+wet+lap+ferrari&www_google_domain=www.google.com&hl=en&emb=0&start=20
http://video.google.com/videosearch?um=1&hl=en&client=opera&rls=en&q=Formula%201%20wet%20lap&ie=UTF-8&sa=N&tab=iv#um=1&hl=en&client=opera&rls=en&q=Formula+1+wet+lap&ie=UTF-8&sa=N&tab=iv&start=20

 

Patrick's wet lap is pretty cool.

 

I thought you posted it somewhere, but I can't seem to find it right now . . . but, beside the aesthetics, wasn't the change in the exhaust because it made the air flow better?

 

Yes. Tuning the exhaust flow has several benefits. It increases HP and if used as we did it can also help aerodynamics. When we first completed P 4/5 I wasn't happy with the look of the original exhaust outlets. Pininfarina and I realized that Ferrari had addressed this issue in their 2003 F1 cars with their chimney exhausts in a very elegant way so we followed their lead. Not only did the exhausts look better they flowed much better because of the tuned outlet. The exhaust back fills the low pressure area caused by the cockpit bubble and reduces drag. It also increase the aerodynamic pressure on the wing which adds downforce.

This increase in downforce and HP is very evident and works especially well at lower cornering speeds.

When I took my MK-IV J6 to the Goodwood Festival of Speed I spoke to Dan Gurney about the aerodynamics of the MK-IV which he drove to 1 OA at Le Mans in 1967. The MK-IV was the first car that was put into a wind tunnel and even with it's longer tail, rear fence and front splitter/dam still made 952 LBS of lift at 220 MPH. P 4/5 makes over 1000 lbs of down force at 200 MPH (VMAX is 233) and you can see how the downforce at 200 pushes the car into the track in this photo. Dan told me because of the primitive aerodynamics of the MK-IV he had to let the nose "land" before he was able to begin braking from 223 to 25 for the hairpin at the end of the straight. I've driven my MK-IV at speed on a track and have noticed the same lift.
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

those are great shots thanks for sharing.