Design help needed: Custom aero camper top

[oldtamiyaphile]

Most Euro vans now have CD's in the 0.31-0.33 range, not exactly bricks anymore

[turbothrush]

lGot a couple ways to make it that I'm pondering.

One would be to make the side templates out of 3/4 inch ply and add 2x3 cross beams then lay and curve 1/4 ply to shape fiberglassing over the out side and coating the inside with epoxy.

Or make the whole top out of 1/4 using a boat construction known as stitch and glue which would be less sturdy but much lighter. Coule be attached with sheet metal screws and the strongest body adhesive I can find. Then for extra security I can add some drip rail clamps that pull everything tight.

I will also need to have racks on top for paddleboards and gear but these could be removed

Another idea to think about is to make the side templates from 1" or 2" extruded polystryene foam board and the top from 2" foam. Put kerfs in the top so that it will easily conform to the side templates. No ribs or cross braces required.

Then cover the whole thing with fiberglass cloth and epoxy. Do the inside last while it is upside down. Let hardwood blocks into the foam before glassing to be used for your rack attachment points.

The foam would allow you to do a nice radius where the sides meet the top plus it is about R5 per inch.
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[grins2go_brett]

Originally Posted by Frank Lee

Brett: while I'm sure the aerodynamicists worked on a clean aft cut-off, that huge arse end also has a huge trailing wake. The "micro boat tail" also gives micro results. It ain't slippery and the reason Sprinters have relatively good eco is the well-matched diesel drivetrain.

No argument here Frank. I know the diesel drive train is responsible for most of the efficiency. I've had an idea in my head for a while for creating a Trailer Tail type boat tail for my van, to preserve access to the rear doors, which is a requirement for me. It will probably never get done though due to time available, and business looks.

[freebeard]

Originally Posted by turbothrush

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Wut?

[Xist]

I see a "Strong ba" in there, but it's getting eaten... by some... Linux

[aerohead]

Originally Posted by huntersirg

Thanks Aerohead for the ideas, I actually have a boat that would almost work but would still require someone over 5"6 (I'm 5"8) to hunch over a bit. Also the thing is quite heavy and way to thick for to highest point on the van.

How about the corners on the sides would a sharp edge cut better or a smooth wide rounded side like most tops I see be more efficient?


Got a couple ways to make it that I'm pondering.

One would be to make the side templates out of 3/4 inch ply and add 2x3 cross beams then lay and curve 1/4 ply to shape fiberglassing over the out side and coating the inside with epoxy.

Or make the whole top out of 1/4 using a boat construction known as stitch and glue which would be less sturdy but much lighter. Coule be attached with sheet metal screws and the strongest body adhesive I can find. Then for extra security I can add some drip rail clamps that pull everything tight.

I will also need to have racks on top for paddleboards and gear but these could be removed for long distance trips.

Thanks again!

*For the leading edges at the sides I would just mimic the radius Ford has on the A-pillars of the Econoline.
*On the top/side edges I'd think about an 80mm minimum radius to keep flow attached in crosswind and side gusts.There are some You-Tube videos of RV trailers blowing over in crosswinds.I've seen a bunch of 18-wheelers on their sides from running empty,with sharp edges,and crosswind.
*At the back,FIAT wind tunnel studies actually recommend a radius for squareback type vehicles,with the roof radius continuing down the rear edges for a 4.5 % drag reduction.
Others have shown a drag reduction with a radius there also

[huntersirg]

Wow really impressed with all this info!

I've been doing a lot of reading on the foamie teardrop trailers with this cheap fiberglass alternative.

Seems they are making a lightweight trailer bodys just by using blue or pink bigbox store insulation foam, then covering it in this order titebond II/drop cloth canvas/gripper primer/exterior porch paint and claiming a very strong super lightweight waterproof shell.

Might be a good alternative to chloroplast for boattails and such as you can gorilla glue the foam to your desired shape then just wrap it with the canvas.

I'd like to do the radius on the edges but not sure how to go about the foam shaping. Thinking I would need to build frame on the inside and then that would need to be screwed and glued to the roof of the van and the top.

How about an adhesive to glue the whole thing on like 3m 5200 or ? and how to make sure the leading edge it held down securely.

Thank you for sharing the knowledge!

[skyking]

If you bumped up the 16" in the center and smoothly curved it to 6" at the side, and then a 6" radius to the straight section of the existing side you'd be doing as good as it gets, IMO.
The side radius is money.

[freebeard]

But then you get lift in crosswinds. A trolley-top would have less frontal area.

It's complicated?

[skyking]

the lift is less important to me than the other negative effects of the crosswinds.
The airstreams pull extremely well in windy conditions because the flow does not get to grab the leeward side and pull as much. That pull produces a steering force.