"TrailTop" modular trailer building components

[pjo129]

Just finished the whole thread. Awesome work :-)

My vote would be a custom replacement for the old truck cap on my camper.

[jscherb]

I'm planning the strut installation to support the tilt-up feature of the cover. The cover will be hinged on the front, and will have two struts to support it when open.

I'll need struts with about a 10" difference between the open and closed length, and about 50 lbs. force each, so I searched the U-Pull junkyard for hood support struts because they should have about the right specs. I found a pair from a Kia Sorrento that look like they'll be just fine. Here's a mockup with the struts:





The height of the high end when open will be about 42", which gives about 5' from the tub floor to the bottom of the cover at the peak. Plenty of room to turn the hard cover into a camper...

[jscherb]

The ribs in place. There are two double thickness ribs made from two pieces of 1x2 glued together, those are spaced at 32", which is a typical spacing for roof-top tent mounting. They'll have tee nuts installed in them to make it easy to bolt the RTT in place from above. The center rib is a 1x2 with the wide side horizontal, that's there because there will be a joint in the plywood at that point - the tub is 5 x 7'5", which will take two sheets of plywood to cover.

[jscherb]

In addition to the ribs, there's a sill that goes all the way around the perimeter of the frame. The sill is where the cover rests on the top of the tub, and will be weatherstripped to seal out the elements. The sill is also where the hinges, latches and struts will mount. The sill is in place in this photo:



Here's a closer view of the ribs and the sill. Also you can see one of the tee nuts in the rib for bolting the roof-top tent in place.



All the wood framing parts are done now, next they'll be screwed/epoxied in place and then it will be time to put the plywood on.

One more quick test-fit on the tub before the ribs get epoxied into place. Fit is good, ready for epoxy.

[jscherb]

Getting ready to epoxy the ribs into the fiberglass frame, I've unscrewed the wood from the fiberglass and flipped the fiberglass over. I'll apply epoxy to the mating surfaces, flip the fiberglass part back over the wooden frame, and screw it back together:



I'm using West System Six 10 epoxy because it's very easy to use - fits in an ordinary caulk gun and mixes as it's dispensed. I used it to bond the curved plywood skin to the curved fiberglass hatch ribs for the teardrop and it worked very well. This photo is from that project, I didn't take another photo of the epoxy today:



Once the parts were epoxied and screwed back together I flipped it upside down so I could clean up/smooth out any epoxy that oozed out of the seams.



The epoxy needs to cure overnight.

[jscherb]

I was asked where the weatherstrip will go to seal the cover to the tub. I've drawn it on this photo that I posted earlier today - the sill gets weatherstripped, and the sill sits on the top of the tub edge. It'll seal exactly the same way a Jeep factory hardtop does.

[jscherb]

The epoxy has cured, and I'm going to do a final trim on the bottom of the fiberglass shell. I haven't done a final trim on the bottom of the fiberglass parts until now, and the reason is now that everything's epoxied together, I can mark a line a consistent distance away from the sill plate to ensure the bottom of the cover is perfectly parallel with the tub.



I'll use my D/A sander to rough sand up to the line, and I'll finish the job with my manual long board sander.



All trimmed, here it is on the tub:



Next up: plywood for the top, and hinges. Not necessarily in that order, it's easier to do the hinges without the plywood on top. Same goes for the struts and latches, I'll probably do all of them before I install the plywood.

And speaking of plywood, here's the trailer earning it's keep, just back from a plywood run to Lowes...

[jscherb]

Hinges installed:



The large black plates on the tub that the hinges are bolted to are there to make use of existing holes in the tub - I could have drilled new holes in the tub, but since holes were already there, I just made these plates to bolt to the existing holes, and the hinges bolt to the plates. Probably should paint the plates yellow to match the tub.



To get the flat hinges to bolt up nice to the curved TrailTop edge, I made up some curved spacer blocks that sit under the hinges.



The hinge bolts go all the way through the sill on the inside of the cover (need to get some slightly shorter bolts, was working with what I had on hand, also need shorter bolts for the lower half of the hinges):



For now, a 5' 2x4 props the cover open... next I'll do the gas struts so the 2x4 can be retired.

[jscherb]

Getting ready to do the gas strut installation, I'm using a bathroom scale to check the downforce at the location where I plan to mount the struts.



The scale shows 42 pounds, and I'd estimate another 25 to account for the 1/4" plywood that'll go on later. So two struts of about 35 pounds force each would the bare minimum required to support this cover. It would be good to have struts of at least 10 pounds or more higher than the minimum required for practical use.

The force of struts can also be checked with a bathroom scale by standing above the scale and compressing the strut against the scale, which is handy to do when verifying that junkyard struts are right for an application.

[jscherb]

The gas struts are installed.



One of my junkyard struts is a bit low on pressure, so it's back to the U-Pull on Tuesday for a replacement. Oh well, that's the chance you take with a used part.

Also got the latches installed.





Next I'll install the plywood.

[KCStudly]

Any concern with the struts not being at the same angle as your bathroom scale test? Seems like the change in vector could have a big effect on the load measured vs. required? How about if you add the roof top tent; will you have to change out the struts?

[jscherb]

Any concern with the struts not being at the same angle as your bathroom scale test? Seems like the change in vector could have a big effect on the load measured vs. required? How about if you add the roof top tent; will you have to change out the struts?

I'm not going for accuracy to the nearest pound, I'm doing an approximation here just to get a general range, and I will be using struts that are significantly stronger than the scale indicates.

[djb_rh]

If it went to market, will you have generic spacer blocks available, too?


--Donnie

[jscherb]

If it went to market, will you have generic spacer blocks available, too?


--Donnie

You're talking about the curved spacers for hinges and latches? It depends on what a company selling the TrailTop parts wanted to do. I made mine out of wood (well, actually TimberTech composite decking), they were very quick to cut out and spray white. But if a company wanted to offer molded urethane ones, for example, they wouldn't be too hard to make.

[djb_rh]

If it went to market, will you have generic spacer blocks available, too?

You're talking about the curved spacers for hinges and latches? It depends on what a company selling the TrailTop parts wanted to do. I made mine out of wood (well, actually TimberTech composite decking), they were very quick to cut out and spray white. But if a company wanted to offer molded urethane ones, for example, they wouldn't be too hard to make.

Yeah. Those just seem a bit trickier to make look *good*. Obviously whoever buys this stuff will likely have some woodworking skills, but "some woodworking skills" and making that outer spacer look *good* may not be the same thing. Also, I'd think it would be annoying to make something that could withstand the weather in that kind of piece of wood. Possible, but annoying. Some kind of molded piece would be better, anyway.


--Donnie