Project Extended Pop-Top Aerodynamic Camper Shell ('99 Tacoma)

[ChazInMT]

I think George was talking about my lift from the sides idea.

As far as the taper goes, we gotta keep in mind that attached flow is not the end game, it is merely something that needs to be present in order for something to be aero optimized to minimize drag. It's like saying if you have Air you'll have a fire, well, no, you need wood and an ignition source too for a fire. With low drag, you need attached flow that is not creating havoc with vortex generation. I'm still pretty convinced that flow remains "Attached" at sub template shapes but in doing so often creates more drag by generating large vortices.

However, by keeping your cap high enough and very close to the template, I think you'll avoid a large low pressure area on top and will therefore not be trying to pull air up from the sides. Ideally, all the air just flows straight back. I think you'll get some air spilling up, but no enough to have a gruesome effect, and you're wanting the room inside anyway. Had you try to drop it to the tailgate top, I think you'd have needed the sides tapered. The Prius is definitely sub template with very little taper and some very square corners. You have great radiuses and are closer to ideal shape. A8ksh4 plus 2!

In short, fret no more, you're safe. Great Awesome JOB!!

[BamZipPow]

You'll need to be careful with the cab to cap gap. Too close and you take a chance of them contacting each other as the frame does flex as you drive on the roads. You could incorporate a gap cover like I did on mine...

[gone7]

Here are a few ideas that may help anyone wanting to become more aerodynamic:
1. Tapering sides is as important as tapering top and bottom.
2. On a pickup, the bed is a restraint; it is hard to taper until past it.
3. Flex material between bed and cab will create a seal without damage.
4. Side skirts for higher vehicles is a must.
5. Don't forget the dimple effect. I have known for many years that making dimples or dents all over the body will increase economy. (Think golf ball.)
6. The front (grill/headlight/bumper area) needs tapering forward to cut the wind, but I doubt that there is much improvement versus cost benefit to trying to change a windshield angle. It is already angled more than the front end.
7. If there is plenty of weight and downforce at speed, then a lifting wing may decrease rolling resistance and increase mileage.

Hope that helps some.

[JRP3]

I thought the golf ball dimple idea was debunked on a non-spinning surface?

[ChazInMT]

ACEV, your credibility was shot at golfballs. Nothing personal.

[a8ksh4]

Thanks for the posts, guys!

I picked up a test batch of resin, hardner, twill weave glass, and some matting that, per a short demonstration by the nice fellow at TAP Plastics, added 10x rigidity to the piece:



Seems that I will need ~3 gallons of resin for this, given it's size. What's the best way to do the seams where sheets of cloth meet? The cloth is about 3' wide, so I'll have several seams along the shell. Should I sand the foam a little lower where the sheets meet so there isn't a rise that I have to body-fill around? That makes sense to me...

[JRP3]

The chopped strand mat that I'm familiar with is not compatible with epoxy resin, and frankly I think using both cloth and mat, (if compatible), is overkill.
Making a trench in the foam where the cloth overlaps seems like a good idea.

[a8ksh4]

The mat stuff is "coremat", not chopped strand. It's polyester impregnated with some sort of microspheres. It's designed to NOT soak up a lot of resin, add thickness, and prevent flex.


That said, I'm leaning away from using it. I think that this will be plenty rigid, just using a layer of glass on top and bottom of the foam.

[ron]

so why don't you use the red neck fiberglass and prefect the install, cost 30ish bucks and if you have to make any changes its not going to cost you an arm our a leg. plus you can glass over it with the real stuff later

[JRP3]

OK, I'm familiar with coremat, and you definitely don't need it, you already have a thick foam core. I also don't think you need to do inside and outside with cloth. I'd just do the outside with cloth and the inside with just resin, you can always add cloth to the inside if you think you need it, but I doubt you will. I'd also sand the foam with 80 grit or so to give a better "tooth" for the resin to grab, since it's a mechanical bond not chemical.