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-   -   Jeep Comanche (pickup) aero bed cover (https://ecomodder.com/forum/showthread.php/jeep-comanche-pickup-aero-bed-cover-16963.html)

XJguy 04-21-2011 06:53 PM

Jeep Comanche (pickup) aero bed cover
 
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.

https://fbcdn-sphotos-a.akamaihd.net..._3057446_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._1882954_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._2694467_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._6197663_n.jpg

bikin' Ed 04-22-2011 08:08 AM

good start
 
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.:thumbup:

bestclimb 04-22-2011 02:31 PM

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 04-22-2011 03:46 PM

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 04-22-2011 09:50 PM

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 04-23-2011 12:58 AM

Quote:

Originally Posted by comptiger5000 (Post 233360)
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.

Quote:

Originally Posted by Big Dave (Post 233407)
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 04-23-2011 01:00 AM

Quote:

Originally Posted by bestclimb (Post 233347)
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 04-23-2011 01:35 AM

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 04-23-2011 11:27 AM

Quote:

Originally Posted by XJguy (Post 233437)
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. :thumbup:

arcosine 04-23-2011 12:50 PM

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

XJguy 04-26-2011 04:25 PM

Ok, did some refining and attached the frame to the Jeep. Next step will be covering it in cholorplast.

https://fbcdn-sphotos-a.akamaihd.net..._4749024_n.jpg

https://fbcdn-sphotos-a.akamaihd.net...4_279495_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._4771899_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._1935912_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._7997656_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._5678245_n.jpg

Deezler 04-26-2011 04:38 PM

Wow that's pretty great! Perhaps the easiest way to make a properly shaped aero-bed cover! Did you by chance measure the individual pipe lengths? Could almost make it into a DIY kit or at least set of instructions.

The kick-stand prop idea is nice and simple.
Probably a brace across the top somewhere near the middle of the bed, lengthwise, would really help rigidity.

The only thing I wonder about is the excessive side taper towards the rear. Why not keep it closer to the width of the truck bed? If you visualize airflow over the top of the cab, its coming over at full truck width. Yeah, some gains could be had by letting the air along the sides of the truck taper back in... but I just wonder if it would be more effective being wider at the very rear still. Hard to say.

XJguy 04-26-2011 05:03 PM

Thanks.
I tapered the sides since they are very much a part of the aero package as anything else.

The side tapers will be compound.

XJguy 04-26-2011 06:40 PM

Wind kicking up hard to do this alone...took more pics of progress.

https://fbcdn-sphotos-a.akamaihd.net..._5037116_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._4370320_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._3257804_n.jpg

You can see how far gone the body is. Luckily we have a flawless bed to replace this one.

XJguy 04-26-2011 09:51 PM

Well I started covering the sides, my intention was to use a single sheet and bend it where needed. Alone that prove too difficult so I cut the sheet in half so that the two sections would overlap at the vertical support. The most difficult thing was matching the contour of the side of the cab, which I did not do to my satisfaction, coupled with the fact that the wind shifted things as I was drilling the holes, so I will have to redo the side. But so far I think its coming out well. Went out for a quick spin and the droplets of water on the top showed attached flow.

I probably should have made the top more narrow so that the 4x8 sheet would be perfectly sized, now I will have to come up with a nice clean solution for that corner. I also could have made the whole structure a bit taller at the cab (it was I chopped it), but I think at least I erred on the safe side, had it been too tall there would be a good chance to catch air under there possibly ripping off the whole cover or at the very least making the Jeep very unstable and light at speed.

KamperBob 04-27-2011 05:56 AM

Looking good. :thumbup: Great progress. I'm having a vicarious ball following your posts. :D

I'm curious about a few key dimensions: bed length, and heights of cab and tailgate above ground. That would inform profile comparison for flow attachment. (Remember, rain is heavy; with downslope gravity'll help drops run the preferred way.)

Have fun wrestling/twisting those sides on.

winkosmosis 04-27-2011 03:20 PM

Don't convert to 2WD. 4WD Comanches are hard to find. It will make almost no difference to gas mileage.

If you really don't want 4WD, sell it and buy a 2WD one or a Ranger.

XJguy 04-27-2011 08:08 PM

Nah, we actually saved this Jeep, its next stop was going to be a junkyard. We drove 6hrs just to pick this one up in Stowe Vt. I was actually able to speak to all the owners of this Jeep right down to the original owner....he is responsible for letting it get this way....I am guessing it sat for a long time unused, explaining the low miles and new interior. Next owner bought it to restore until he saw just how bad it was, he told me he would be surprised if it lasted one more winter (it actually didnt, holes appeared in the floors, rear brakes were obliterated, front hub nearly fell off, brake lines all fell apart, rear brake cylinder went, CAS fork cracked, and now it needs a new t-case chain, seized lug nuts cracked the wheel studs, original wheels were so rotten they were unbalanceable)...he passed it to the guy we got it from who also wanted to restore it but also felt it was too far gone. My brother and I are very good with cars, and I happen to know a lot about XJ/MJ, also have spare parts from my XJ's and know what to do to fix them. That is the only reason this thing isn't sitting in a bone yard.

We are Jeep guys so racing a Jeep is proper (I have two XJs, my brother has an SRT8, dad has a GC Limited).....NAXJA original members know/hate me well, I was one of the original members and one of the few lifetime members till I had some issues with guys there. The Street and Performance forum there exists because of me.

I would never race a Ranger....no offense to Ranger owners, its just not my bag.

Removing the 4wd system will probably lighten the Jeep by at least 100lbs offsetting the roll-cage that is going to be installed. It will also enable us to lower the Jeep as low as possible.

I have had two offers on the 4wd system by other Comanche owners, so the setup wont be wasted.

While fuel efficiency it always good, my primary goals are stability, top speed, and down force.

bestclimb 04-27-2011 08:44 PM

I dig the bumpersticker

winkosmosis 04-27-2011 08:47 PM

OK, sounds good then! I'm on NAXJA too but I don't look at their forum often these days.

arcosine 04-27-2011 10:04 PM

Ha, you can put a sheet on the side to hide the rust holes and cover the wheel opening. It's looking real aero. Tarp tape works well with coroplast. If your just racing it, why not just remove the bed and make an light weight whole tail.

comptiger5000 04-29-2011 08:25 AM

^ Because that would be butchering a rare Jeep.

XJguy 04-29-2011 01:23 PM

Actually when I picked it up, they previous owner had duct taped aluminum sheets covering all the holes....looked worse than the holes and one rainy day everything started to come lose on the highway....not good.

XJguy 04-29-2011 01:25 PM

Quote:

Originally Posted by arcosine (Post 234607)
Ha, you can put a sheet on the side to hide the rust holes and cover the wheel opening. It's looking real aero. Tarp tape works well with coroplast. If your just racing it, why not just remove the bed and make an light weight whole tail.

We will be racing it, but I want to keep it as intact and functional as possible. Still want to be able to use it as a pickup if needed.....it can carry its own spares and tools. It will remain street worthy and registered/insured.

Joenavy85 04-29-2011 01:48 PM

Quote:

Originally Posted by comptiger5000 (Post 234923)
^ Because that would be butchering a rare Jeep.

not really, you could do all that without destroying the Jeep. He already mentioned that he had a new bed that was in good condition. he could even modify the bed he has on it now, and once he's done racing it put the newer bed onto it.

XJguy 04-29-2011 08:51 PM

Here are some updates. I had to install a window since I was totally blind on the passenger side. Used some spare plexi I had lying around, it has scratches but will do the job.

https://fbcdn-sphotos-a.akamaihd.net..._5732278_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._7705356_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._2837968_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._8319568_n.jpg

Joenavy85 04-29-2011 08:54 PM

Looking good, about how much does it weigh all together?

XJguy 04-29-2011 08:57 PM

Dunno Joe, but to be honest its not a big concern. Those Jeeps are so light weight especially in the rear, that I might actually have to add ballast. I will be taking it off soon to finish up and will get the approximate weight.

KamperBob 04-30-2011 09:12 AM

Quote:

Originally Posted by XJguy (Post 235087)
Here are some updates. I had to install a window since I was totally blind on the passenger side. Used some spare plexi I had lying around, it has scratches but will do the job.

https://fbcdn-sphotos-a.akamaihd.net..._7705356_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._2837968_n.jpg

I like the visibility window. :thumbup:

XJguy 04-30-2011 09:04 PM

Spent most of the day trying to shape panels to fit the rear section ...ended up frustrated and ruining one piece. Will resume at another time. I did add another window to center panel (not pictured) and additional bracing since I now figured out I will need to section the rear portion due to the shape.

https://fbcdn-sphotos-a.akamaihd.net..._4342691_n.jpg

slowmover 05-01-2011 10:37 PM

Glad you're still using the XJGuy name . . took me back to a 173-cid question I asked you about must be a dozen years ago now.

Lot's of good reading around here as you've noticed. Please continue with pics and ideas made solid.

XJguy 05-02-2011 10:33 AM

Did some hauling yesterday.

https://fbcdn-sphotos-a.akamaihd.net..._6108842_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._6285562_n.jpg

XJguy 05-25-2011 11:03 PM

Okay its been a while but I got this thing done finally a week ago. I get the most astonished looks. One guy asked me if my Jeep mated with the Space Shuttle...LOL.

https://fbcdn-sphotos-a.akamaihd.net..._1744090_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._7906867_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._3491415_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._8063317_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._5039705_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._4855921_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._2423975_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._6214521_n.jpg

https://fbcdn-sphotos-a.akamaihd.net..._2838520_n.jpg

Bill in Houston 05-25-2011 11:08 PM

I like it.

XJguy 05-25-2011 11:22 PM

Thanks. I would say the whole thing weighs in at about 15-20lbs.

XJguy 05-25-2011 11:55 PM

Bares resemblance

http://www.dreams-cars.org/images/Ga...il_1971_03.jpg

KamperBob 05-26-2011 08:07 AM

Quote:

Originally Posted by XJguy (Post 240930)

Thanks for all the pix! Since it is so easily removable I wonder if ABA testing is in your plans. Quantifying gains with such a mod is invaluable to others. I understand if your project is done. I don't like to burn ga$ without good reason either. The least expensive road tests I can think of are coast down and Scangauge (et al) averaging over a test section of roadway. Regardless, I predict success and improvement with this mod. Even if airflow doesn't turn out fully attached you're stuffing the wake so resulting eddies can't be very big and your "bed bubble" is stable so the wake has to be less than open bed.

Rock on!

comptiger5000 05-26-2011 09:30 AM

I like it! And nice SRT8 in the background :D The one kind of Jeep that gets worse mpg than mine...

Backtobasics 05-26-2011 09:45 AM

It does kinda look like the spaceship. I think an old coffee can painted silver out the very back would be a fun way to mess with tailgaters. A sticker (STAY BACK, AFTERBURNER HOT) would be the icing.

piers.singer 05-26-2011 10:20 AM

Very tidy! Good job.


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