Need help with Aerocap for 05 Dodge Ram.

[Vajra]

I did this before bed, using the image Hersbird posted. Pretty close to most of what I get with the AST-2 template, just a few inches above the tail gate. Looks nice though, added a like 45 degree cut on the end, wonder if that makes a difference as I seen other aerocaps with that design feature.

[ksa8907]

That last photo looks pretty good. Any ideas what you would use for materials?

[Vajra]

I have thought about using foam with some wood, and then fiberglass. Not 100% sure on that yet. I have used foam for RC boat hulls that I glassed over, as well as having glassed balsa. I can use ribs and after it is all glassed, gut the ribs. I have considered strictly wood then sealed and painted. I think foam might be the way to do it since I can shape it easily. It would be very light, strong, insulated if I wish to use it like a camper. I am thinking some back up lights, a interior light, and windows. Any suggestions on build method? Should I go with a flat width roof and more of slanted side, or go from the cab profile, and as I go, reduce the radius from a edge to a curve in back? I have no issues backing up the truck now, but I am thinking a backup camera might be useful, especially for hooking up to a trailer. - Vajra

[aardvarcus]

I would design around construction, as the best shell is the one that gets built. I am currently building a shell for my Toyota Tacoma, using XPS foam and will be fiberglassing over it with epoxy. I am about halfway done, and have a thread going on here if you want to see it.

My suggestion is that if the template lands a few inches higher than your tailgate, just build the shell where it is a few inches higher than your tailgate. On my Tacoma, the template landed 5” higher than the tailgate, so I built my shell to match that profile. I chose to extend my shell a few inches back past the tailgate before I terminated it, but I could have ended it right there, and had a vertical drop from the end of the profile. I still might end up cutting that part off before it is all done. Personally I wouldn’t want it to come down to a razor edge right over the tailgate, you need strength right there. With most lightweight construction methods, you need some vertical height there especially if you are incorporating a window. Also I am going to mount my third brake light right there. You don’t want a curve there, you want a nice clean separation where you want the air to let go.

[Fat Charlie]

Originally Posted by freebeard

The problem here is the 2" gap should be sealed and you lose the early start to the taper.

Yeah, I misunderstood the problem until I saw the pic- I thought terminating early meant that the template came down onto the bedrails, not that the template went past the tailgate.

[freebeard]

I did this in 1/4" redwood benderboard. It was only to establish the curves and separation point so I use few and thin strips. If you stacked up the 3 1/2" boards and tapered them all together and then 'glassed the whole thing it would look like a canoe.

There would be a lot of edge gluing, but maybe you could lay it up dry and then pull the glass cloth taut before you resin it.

[Vajra]

Freebeard, that look might nice, the wood work would look nice is glassed well. Interesting project too.

Aardvarcus, thanks for the insight. I don't want a sharp drop off right above the tailgate, that is why I went a few inches out with the 45 or maybe 30 degree cut off. I figured this would do a few things. First, allow more attachment to further reduce the area. Second, allow any window or aerocap attachments some protection from sun, rain, snow both on the go or stationary. I really like the idea of a camera back there for backing up and hooking up. My trucks butt is so high, I have to use a 14" drop hitch to get the tongue of my cargo trailer "almost" level. Still could go down 2" more. So lights, camera, window, maybe a latch system. I haven't decided if I want the whole aerocap to lift up, or if I want a hatch down the length of the main bed.. I would love to see your build!

Thanks for the reply guys.. please keep the suggestions coming! - Vajra

[freebeard]

Gull-wings.

[ChazInMT]

Hey Vajra, Look over this paper and pay real close attention to the chart 4.6.1 on page 85 of the paper (not pdf page). Get 95% of your aero gain and usable space this way. I'll draw something for you later today based on this.

Truck Aero Paper

[Vajra]

Freebeard, Gull-wings? Interesting idea. Like the car and the girl, I'll take both for a test drive please!

ChazInMt - Thank you. That is some pretty interesting studies on the effects. I remember reading some suggested things and looks like 12 degrees is in fact the spot that looks sweet, That would take the curvature on the aerocap to a greater radius and not end with so little above the tailgate. The paper has some very interesting info, I'll have to read the whole thing later this week when I have time to. Thanks for your help! I seen some of your posts and your aerocap! Looks great! - Vajra