Jeep Comanche (pickup) aero bed cover

[XJguy]

This little rusty Jeep is going to be converted into a race car...no joke. I will be making many enhancements to it, many of which will be aerodynamic. Its gonna be raced in 24hr Le Mons, so the budget is very restricted. As such PVC and chloroplast to the rescue. This is what I have so far.

[bikin' Ed]

I'd not thought of PVC for a frame--I like it. My thought is that the back seems to slope too quickly for attachment (although that may just be an illusion).

I'll be following with great interest in both the build and the race.

[bestclimb]

What are you planning on covering it with? The Stewart aircraft process is a good one latex rather than oil based. Smells way better.

[comptiger5000]

How can you do that to a Comanche? They're pretty rare. Certainly a cool project, but I'd hate to see it die that way

[Big Dave]

Good start. Like the general shape.

Minor quibble: You are too steep. Mine was. I went from the top of the cab to 1 inch above the tail gate. That was about 17 degrees. I had separation, so I ditched that cover and am moving to something different.

The best aerolids keep the angle to 12 degrees or less. That's about a 1-in-5 pitch. Raise your "tailgate" pipes up til you get a 1-in-5.

[XJguy]

Originally Posted by comptiger5000

How can you do that to a Comanche? They're pretty rare. Certainly a cool project, but I'd hate to see it die that way

They are rare, and I love it, but in spite of having only 80k original miles and 5 speed, it lived in northern Vt, Stowe to be exact, and is very extensively rusted. I will be doing repairs, but it would be cost prohibitive to restore it to like new. Besides it will be treated very well, provided no one crashes into us, we will race it hard but be like proud parents when getting work done. I am removing the 4wd system and converting it into 2wd.

Originally Posted by Big Dave

Good start. Like the general shape.

Minor quibble: You are too steep. Mine was. I went from the top of the cab to 1 inch above the tail gate. That was about 17 degrees. I had separation, so I ditched that cover and am moving to something different.

The best aerolids keep the angle to 12 degrees or less. That's about a 1-in-5 pitch. Raise your "tailgate" pipes up til you get a 1-in-5.

I was concerned with that but according to the book I read New Directions in Race Car Aerodynamics Designing For Speed, I am within spec as per my measurements.

But I might change that very end like you suggest, because I accidentally deviated from my original design, after realizing my mistake I decided to keep it to provide a pressure relief via that square portion at the end of the taper for any air that might sneak up in there as well as if I have the bedside window open.

[XJguy]

Originally Posted by bestclimb

What are you planning on covering it with? The Stewart aircraft process is a good one latex rather than oil based. Smells way better.

If I were building this to go into just a regular racing class I would build a buck and mold it in carbon fiber, but since its Le Mons, I need to keep costs way, way down, as such it will be covered in red Cholorplast.


With much trepidation I am thinking of drilling into the cab and screwing in hinges that way I can lift the whole assembly up and not lose total function of the bed should I need it. I'll be installing a latch at the rear and possible some guide pins on the bed side tops. Eventually this thing will also be getting some gurney flaps at the trailing edge as well as a proper wing to keep the extremely light weight rear end planted.

[War_Wagon]

Man you need my Comanche, original paint 1991 Sportruck, 4.0L H.O., 5 speed, 2wd. Ironically I will be converting it to 4x4, where as you want to convert yours to 2wd.

[KamperBob]

Originally Posted by XJguy

I was concerned with that but according to the book I read New Directions in Race Car Aerodynamics Designing For Speed, I am within spec as per my measurements.

But I might change that very end like you suggest, because I accidentally deviated from my original design, after realizing my mistake I decided to keep it to provide a pressure relief via that square portion at the end of the taper for any air that might sneak up in there as well as if I have the bedside window open.

Interesting project. Thanks for mentioning the book. I'd love to hear more about what it says about form specs.

If you have not already done so you can overlay Phil's streamline template. In side view it indicates if the top taper might be too soon using ground reflection symmetry based on max height. In top view it can indicate how quickly (if at all) you can round and taper the sides using the vertical symmetry plane of the truck for reflection based on max width. You just need good pix of your truck (long view and centered to minimize camera distortion) and some image overlay software (like GIMP - possibly).

Best of luck on the build and race. I look forward to following both.

[arcosine]

It's going to need a little more bracing to withstand the wind. I think you can arch some pieces in the middle.