"TrailTop" modular trailer building components

[jscherb]

I've been thinking it might be fun to actually build a proof-of-concept diamondplate TrailDog shell, so I'm working on a few of the design details. What's shown here is a 9' long, 4' high cabin on a heavy-duty Harbor Freight frame. As drawn, the cabin is 4' wide so it fits between the tires on the stock HF axle, but it could be wider if either the axle were swapped for a longer one or inner fenderwells we put in the sides.

Even though it's 9' long, 4x8 sheets would be used for the side panels; there's one small joint near the upper corner of the door. The door is a unit I found on eBay. Side panels could be either plywood, plywood skinned with diamondplate fiberglass sheets like I described the other day, actual 0.042" aluminum diamondplate bonded to the plywood underlayment with contact cement, or perhaps a plywood/FRP panel sandwich using FRP panels from the home center. 4 4x8 sheets are all that's needed to do the skin.

The only modification to the HF frame is that I've moved the axle back 2'. On the stock HF frame it's centered, which gets in the way of having a decent-sized door on the side, but also limits the departure angle for trail use; with the axle moved back the departure angle is a respectable 40 degrees. This one's drawn with 32" tires, to match typical tires on an off-road Jeep or similar vehicle.



Here's an xray view, it's got space inside typical of a teardrop-style camper. The galley is a teardrop-type, with a hatch in the back. Floor space for the mattress would be about 7 1/2' long x 4' wide, so a little narrower than a standard full sized mattress, but a bit longer.

[jscherb]

The other day I wrote that I was thinking of making a mold to make fiberglass diamondplate, and I showed a 4x8 sheet of aluminum diamondplate I picked up to use for making the mold. Before doing the complete 4x8 sheet (that's a big mold to make), I made a small test mold. Here's a 1'x3' piece of fiberglass diamondplate out of that mold. I made this test piece as a thin skin to be bonded to 1/4" plywood, which I'll do next.

[KCStudly]

Interesting. There does always seem to be a market for the diamond plate look. Do you think the extra cost in labor and material is worth it for the FG version versus just using aluminum, or is it more of an issue of being able to bond the panels more effectively? Seems like the cost difference, extra material and laminating steps might push most buyers away from the FG.

Also, I wonder how you are going to finish the sharp angle cut on the corner mold at the bottom of the hatch area.

[jscherb]

Interesting. There does always seem to be a market for the diamond plate look. Do you think the extra cost in labor and material is worth it for the FG version versus just using aluminum, or is it more of an issue of being able to bond the panels more effectively? Seems like the cost difference, extra material and laminating steps might push most buyers away from the FG.

I molded this test piece quite thin (about 3/32"); you would use it the same way you would use, say, typical 0.045" thick aluminum diamond plate. So if you needed to laminate the fiberglass to plywood for a specific application, you'd probably be laminating the aluminum to plywood if it were to be used in the same application. Point being I don't think there would be an extra laminating step compared to typical thickness aluminum that you might use in constructing the sides of a compact camper.

I don't know how the cost for a finished sheet would compare. In high volumes, the fiberglass would definitely be less expensive - the cheapest I've found 0.045" aluminum sheets is at RV Surplus (http://www.factoryrvsurplus.com/product ... ct_id=2090) for $85.00 per sheet. The cheapest I've found 4x8 fiberglass sheets is at Lowes and Home Depot, they call it FRP there as I'm sure you know and it's intended for bathroom walls and such. It's got a pebble-grain finish and it's about $35 per sheet if I recall correctly. In smaller quantities I don't know what it would cost to manufacture, but I'd guess it could be in the same ballpark as aluminum.

Given a choice, I'd much prefer to work with fiberglass than aluminum, but that's just me.

Also, I wonder how you are going to finish the sharp angle cut on the corner mold at the bottom of the hatch area.

I'm not sure exactly what you're referring to, are you referring to the diamondplate TrailDog concept I posted recently? Are you asking about the angle on the bottom of the camper shell at the back?

[KCStudly]

Yes. The mitered end of the corner molding (your FG concept piece) under the tail light where it ends near the trailer frame. How is that going to be molded in or capped off?

[jscherb]

Yes. The mitered end of the corner molding (your FG concept piece) under the tail light where it ends near the trailer frame. How is that going to be molded in or capped off?

Similar to what I did with the teardrop top for the Jeep-tub trailer, the inside framing/flooring would be curved/angled to fit and then epoxied in place.

[jscherb]

Here's a sample bonded to a piece of 1/4" plywood with contact cement; it's sitting on top of an unbonded piece for comparison:



Here it is matched up to a piece of TrailTop straight rail:



Alternatively, I could have bonded the plywood to the fiberglass during the molding process, but I wanted to test bonding after molding with contact cement. The contact cement bonding works very well.

[jss06]

Would it be possible to 3d print these components? I am wondering if they would have enough strength.

[jscherb]

Would it be possible to 3d print these components? I am wondering if they would have enough strength.

I'm not an expert on 3D printing, but I'm guessing the size of the parts and the cost of 3D printing would make that impractical, even before you got to the point of figuring out if it's strong enough.

[jscherb]

I shot the test pieces of fiberglass diamondplate with one coat of rattle-can aluminum paint. In the first photo they're sitting in front of the full sheet of aluminum diamondplate.





I'll bet if I shot the samples with automotive clear coat they'd be hard to tell apart from the real thing .

One other thought - I've bonded the thin fiberglass diamondplate to 1/4" plywood for this small test, but instead of plywood, you could bond it to say, 3/4" rigid foam insulation to make a fiberglass-skinned "foamie" camper. And unlike thin aluminum diamond plate in that application, the fiberglass skin wouldn't be prone to dings and dents like aluminum-skinned foam would be. A fiberglass/foam sandwich would be quite rigid and durable.

[jscherb]

A couple of weeks ago I posted a concept drawing of a hard cover for a military trailer made with TrailTop parts. In that drawing I drew simple plywood for the flat part of the cover... here's a version with fiberglass diamondplate, although the drawing below isn't as shiny as the actual test pieces...

[IamJerryP]

really like some of the concepts in this thread

[bc toys]

Are you coming to SIMA this year and if so what both you going to be at I would like to get a chance to meet and talk with you. I work there on the power crew.

[jscherb]

Are you coming to SIMA this year and if so what both you going to be at I would like to get a chance to meet and talk with you. I work there on the power crew.

Yes I will be at the SEMA Show, but as an attendee, not an exhibitor, so I won't be hanging out at any particular booth. One of the companies exhibiting there has licensed some of my Jeep accessory product designs and will be debuting four of the products at the show, so I might be around that booth a bit more than others, but probably the best way for us to catch up at the show is for you to send me a PM before the show with your cell phone number and I can text you during the show to figure out when and where we might meet.

[jscherb]

For some of the TrailTop concepts I've drawn, different radius corner pieces are needed. For example, the TrailDog concept uses both 60-degree and 30-degree corners:



Until now, I haven't made any 30 or 60 degree molds or corners. The other day I was making a few fiberglass parts for another project, so since I was making the fiberglass mess anyway I molded two TrailTop 12" radius 90-degree corners to serve as the mold masters for a 30- and 60-degree parts. Clockwise from top left, here's the process for making a 60-degree corner:

1. The 90-degree part fresh out of the mold, just rough trimmed for now.

2. A 30-degree section to be cut out has been marked with tape.

3. The section is cut out and the halves are test-fit.

4. Once the joint has been cleaned up a bit for fit, the halves are taped together on the outside with masking tape, and joined on the inside with fiberglass. Also in this photo is a 30-degree corner which has already been bonded back together, but awaiting a little body filler to hide the joint.



And here are both the new 30- and 60-degree corner masters:



The next step for these parts would be to make a mold so more could be made, but instead of using these new parts to make a mold, for a one-off project the parts could be used as-is - after fiberglassing the two halves of a cut part back together it's plenty strong enough to be used as is, so custom angles or other one-off parts for a special TrailTop design could just be made by modifying stock parts like this.

Also, a curved outer skin would be needed to go around the radii, I've shown those parts in white in this drawing:



I've already made a mold and molded a 90-degree radius skin piece, and that would be used with these shorter angles as well. The curved skin piece would be cut to match the angle, and to replace the joining tab that was be cut off, a piece of 1/4" plywood would be epoxied or bolted in place to form a new tab. In the photo below I've clamped a 60-degree corner to the curved skin piece and marked the cut line; the piece cut off would be 30 degrees, so it would be used to skin a 30-degree corner.