Poor Man's Aero Package, Version 2
 

My fabrication skills are, well, kind of sloppy. Fortunately, this means I limit myself to making stuff that only bolts on for short amounts of time. I've been playing around with aluminum skirts in front and the sides of my car, and fabbed up a set today that go a little bit lower than the previous ones I was using.

Iteration 1:

http://forums.pelicanparts.com/uploa...1095705283.jpg

Iteration 1B, with revised front:

http://forums.pelicanparts.com/uploa...1111376388.jpg

I figured I could go a little lower based on pictures of the car in turns, where it seems the sides don't compress down as much as I thought they might.

http://forums.pelicanparts.com/uploa...1098738472.jpg

http://forums.pelicanparts.com/uploa...1102150607.jpg

Obviously, you can't run this stuff on the street (no good reason to, either). This means the three sections each have to fold or come apart into two pieces so they can fit in the car for the drive to the track. This means a big ugly hinged joint on the side (but what are you gonna do?).

I'm planning on testing them on April 13th, with ACRA at Willow Springs. If I get my data logger issues sorted out by then, I'll try to A-B some laps to see if there's an easily-measurable effect.

Any suggestions on tweaks to the basic shape? They get painted later today.

Iteration 2:

http://forums.pelicanparts.com/uploa...1111613203.jpg

http://forums.pelicanparts.com/uploa...1111613229.jpg

Looks good, deeper/closer to the ground is always better, a projecting splitter(most rules only allow to the forward most extension plane of the bumper) wil also help

Do you need the big holes in the spoiler for cooling?

I would be tempted to have a full track only front end, along these lines, flat clean w/ only the necessary holes placed as close to the car ctr line as possible
http://forums.pelicanparts.com/uploa...1111614498.jpg

get some hard rubber, or ABS or PVC plastic, and rivet a strip to each.

On our car we used rivnut, and small button head screws to secure the strip. I made a number of different depth strips, so we can determine which depth lip offers the best performance.

The car currentlly has a much deeper lip on it, only about 1" clearancehttp://forums.pelicanparts.com/uploa...1111614688.jpg

Maybe have the forward side skirt overlap the rear side skirt so the seam doesn't get air intrusion at speed (and shear or pull the skirt)... sort of like the overlapping shingles on a roof.

Looks good Jack. I'm curious to know what the data shows. One additional thing to keep in mind is that your brake temps may increase since you are cutting the airflow to your brake cooling diverters. It may be worth it to also measure brake temps with and without the spoilers.

Looking forward to the full report. Thanks for sharing.

Fit some rubber skirts below your aero package. I'm sure after five laps they will have found their optimum shape.

Do these skirts really make much difference? Did you get any real measurable gains in lap times after installing the skirts?

Re: Poor Man's Aero Package, Version 2
 

http://forums.pelicanparts.com/uploa...1102150607.jpg

Well the bichen Camaro is in its place......

I need the front holes for my oil coolers. The downside to a track-only front piece is getting it to the track (no trailer), and keeping it from tearing off in its entirety if I go off track. The later versions of my front splitter have a 3-inch lip in front, but then a straight-down skirt below that. It's not ideal, aerodynamically, but it can take an impact with a berm and simply fold back, rather than the type I had in front that was painted red, where one impact would pull the whole thing off.

I'll try a rubber extension after the first test, since I want to proceed carefully. I'd hate to have a lot of pieces of aluminum flying around in turn 8 at Willow Springs.

I'll keep an eye on brake temps.

Thanks for the input. I'm thinking about mounting a lipstick camera on the testing day to see how close they come to the pavement, and also how much they distort at speed.

Why not leave them raw aluminum - it looks pretty cool as is.

You're discoverring what I learned many moons ago first w/otorcycles then w/ cars and later boats, street compromises track and vice versa. You may be at the point where a dedicated track car is in the cards.

Same here, I have gotten seat time in various Cup cars over the last few years and find that lesser cars are not acceptable any more.

The thought of a truck and trailer is unappealing in the extreme.:(

Jack, ya need a couple of extractor blowers powered by snowmobile engines to complete the job. :D

http://forums.pelicanparts.com/uploa...1111619493.jpg

I'll have to agree with the above, the raw aluminum looks kind of trick. The painted red looks like you're actually trying to make them look nice were the aluminum looks like pure function to me.. sweet!

This is a pretty sick front end, I love it - Who is it from?

Jack, I agree, I like the raw aluminum.

I have a simple, light answer to your hinge problem. Don't hinge the side skirts like a door, hinge them like a pair of scissors. It'll only require an overlap and a bolt.

http://forums.pelicanparts.com/uploa...1111622222.jpg

I also agree that you could use some stiff rubber or plastic like the original lip for the front to remove some of the worry, but the Al seems like it may do. It is just for the track anyway.

I painted it the same color as the aluminum. It takes such a beating that the ability to quickly repaint it is something I wanted. If I left it bare, I'd have to clean it, which would be more work.

Now all you need is a four wheel downforce measuring system to determine exactly how effective it is. ;)

Jack,
Dave @ TRE has a point. As you reduce the spacing between lip and road surface, the chances of the road biting chunks off the lip increase, and replacing the nice aluminum fencing can't be fun after a few ripoffs. It seems a sacrificial-type rubber lip all the way around will find it's lowest allowable clearance by virtue of what's left of it after a few laps.

Are floating lips allowed? That is, perhaps a series of interconnecting rubber sections that can "float" just above the road surface. I think the aforementioned Chapparel Sucker Car had this feature. This would take into consideration the roughness of the road and changing ride heights caused by racing-induced suspension travel.

Sherwood

I think you should use a thick strip of bristles instead of the rubber lip on the front air dam. The bristles would conform to the changing ride heights.

The bristles would also sweep grit and gravel etc off the track. This would give your tires a clean surface for the best possible traction, a very tricky advantage over your less creative competition.

A spanking clean track surface would also allow you to reverse the cooling fan for home-grown ground effects. The main objection to this previously was that the engine would get dirty (must be a buncha concours weenies here).

The material for the bristles will be important. I suspect German horsehair will be the best.

Hey, they probably thought Nobert Singer's ideas were crazy too . . .

Jack - I just remembered, do a search online for the 1985 Dodge daytona, I recall it having side skirts made out of some medium to hard plastic. This might give you some insight in to the durability issue.

Just my 2cents

Jack,
Your vision of the long-hood always impresses me. The combination of early grace and later muscle and technology blows most of us away.
Black Beauty, I think is entering a new stage, in reflection of race cars of the sixties and seventies. At the beginning of that period, they were lithe, almost sensual creations of aluminum. By the end, the cars had become aerodynamic devices, their design dominated by the imperative of moving the car through the molecules of the atmosphere as efficiently as possible. So much was gained in that short time. So much was lost.
As BB enters this new phase in your vision, she will no doubt be a faster, better racing tool. I fear she will lose some of the stunningly beautiful grace she possessed, rather in the way a beautiful woman's aspect changes when she developes her muscles to the extent she can be a world-class weightlifter. Is such a goal to be spurned? No. But many who once thought her beautiful will remember how she looked.
Thank you for sharing Black Beauty with us in all her aspects.
Les

Thanks. The picture of my car next to Tyson Schmidt's 1969 does show the change from the original 911 design. In a perfect world, I'd have my RSR-bodied car and also a narrow one like Tyson's, preferably with steel wheels.

My car's not going to change in any significant ways in the forseeable future. It'll continue to get sandblasted by track use until I get another coat of paint put on it. But it'll always be more of a 'work dog' than a 'show dog.' If I can get a decent data-acquisition setup on it, I'd like to continue to tune and refine it as a fast, dual-purpose, street-tired car.

And even with the blasted paint, the right photographer can still make it look good. Here's a pair of pictures by Zachary Mayne that I really like:

http://forums.pelicanparts.com/uploa...1109834133.jpg

http://forums.pelicanparts.com/uploa...1109834144.jpg

I love this pic. Love how that front tire is off the track. http://forums.pelicanparts.com/uploa...1098738472.jpg

How about that stuff the rally guys use that is kind of a rubber or plastic with a teflon coating to make it more likely to slide over an obstacle than to hook it? Let it bend down from the bottom and skid across the ground during your nose down braking. It will wear itself down to the appropriate level.

I had some left-over aluminum, so I'm doing a thrown-together diffuser for the rear. Next step is to fabricate mounts, which will tuck it up a little more on the ends. Then paint.

Any suggestions?

The bottoms of the vertical fins will be parallel with the ground. Being up on the rear ramps kind of makes it look otherwise.

http://forums.pelicanparts.com/uploa...1112137844.jpg

http://forums.pelicanparts.com/uploa...1112137856.jpg

http://forums.pelicanparts.com/uploa...1112137869.jpg

"Any suggestions?"

Yes. Don't paint yet. Instead buy some wool tufts and tape... You want to try and trace out the air flow first.

It could be that some of the areas want to be channels and others want to be bluff.

And... it's not clear that vortices from the wheels want to be kept away from the center...

Also, what does the leading edge look like? Is any air going to be scooped up above this piece?... where it can't exit?

You sure thats not going to impede the flow of air coming out from around the cylinders?

Do you have any hard data, or even WAG data that supports that all this really cool looking stuff is actually lowering your lap times at all?

I am assuming that next your going to install a full length sheet aluminum under tray. Then cut some venturi tunnels into it, channel the air up through the floor of the car, install some large blower fans to suck the air up and exit it out the rear window?

I would suggest you convert the car to a single central seat for the driver. Better weight distribution, and then you will have more room for large venturi tunnels on either side of the driver and the big fans you will need to create the vacuum effect. ;)

I can see it now.... Jack driving BBII upside down on the ceiling of various tunnels.

Jack -

Can we see a pic of the rear while on the ground?

I don't know a thing about ground effects. Thanks for sharing, looks interesting. Looking forward to your test results.

LOL, jack has been bitten by the aero and metalworking bug at the same time.

Won't that effect cooling ?

The pit crew for the Whittington Brothers (Mid 80's) simply fiberglassed a vertical layer to the lower front of the spoiler. Next they took it out to the track and ran it. The track shaved off the excess material.

To get it back into the trailer, they would remove the nose.

David Duffield

Drove at the track with a Ford GT. Was interesting to see the debris jostled up & about by the rear diffuser -

well. that diffuser is plain wicked looking- BUT as others have posted "what about the cooling?" indeed. Look at the lower shield on the 964 and 993 for guidance. i would recommend a small lip on each cylinder head rectangular opening exit so you aid the air to escape the cylinders rather than create a positive pressure pocket. You will need to do some back to back testing- coast down tests, max rpm to see if that set up is effective.

Okay, progress update: I went out for more aluminum. I bridged the new metal pieces to the plastic sheet on the underside of the car that stops at the rear swaybar. I also cut out exits for the cylinder cooling, using a 964 undertray as a guide, and making the holes slightly larger. I tried to mimic the way the exit edge of the cooling holes on the 964 tray has a ridge -- which I presume prevents the "positive pressure pocker" TRE Cup is talking about.

But I'm nervous about cylinder head temps. Is there a quick and dirty way to wire up a cylinder head temp gauge to see if using this would result in cooking my motor?

Down on the ground, it definitely looks aggressive (and un-street-worthy). I'll take some pictures tomorrow.

It looks neat but if these guys aren't worried why should you?
http://forums.pelicanparts.com/uploa...1112153532.jpg

http://forums.pelicanparts.com/uploa...1112153577.jpg

http://forums.pelicanparts.com/uploa...1112153651.jpg

The least intrusive temporary head temp monifor would be an under plug thermocouple, but I am not sure if one can be squeezed into a 911 spark plug hole along with a plug socket.

http://www.sportdevices.com/capit/sonda6_p.jpg

Isn't that transplant of your's a modern engine with a mounting area on one of the heads for the motronic head temp sensor?

Sure, but those guys have much more aerodynamic bodies on their cars, and a lot more horsepower.

Jack....

I have to tell you, you have made the list with this latest diffuser thing.

Here is a link to the NASA boards thread about "You might be a road racer if...." thread. Lots of funny stuff there.

I'll have to post this one:

You have actually constructed, installed and driven around with advanced F1 style aerodynamics on your street/track car including a full rear diffuser. Then you evaluated your improved commute times to work and planned wind tunnel time to fine tune your aero package.

True story, you saw it right here on pelican parts!

Umm.....well those cars are water cooled.....!?