Fiberglass work, need some intel.

[Walker]

I picked up a used truck cap last summer, actually I barely had the truck in park the owner was loading it on my truck.. I wasn't sure I would like it but overall it's been good. Now, it was a free cap so it has it's share of issues, some spider cracking on the corners and the bigger issue is that the plywood that is glassed into the roof needs to be replaced. The mounting bolts for the roof rack probably weren't sealed so water got in and I'm sure it's all rotten in there. It looks like they just lay a piece of plywood in there and then hit it with chopped up glass and send it on its way. I can tell that the outer shell is somewhat separated from the plywood because there are crackling noises when I'm up there walking around. the wood inserts along the bed have rot pockets where the clamps broke through the glass. My plan is:

1. cut around the edge of the plywood and hopefully just rip it out of there.
2. cut a piece of Advantec 3/4" subfloor and bond it to the shell {with _____________?}
3.. apply fiberglass cloth over the plywood and overlap the sides 3-4"
4. cut out the bed support pieces and pretty much do the same with strips of Advantec
5. pull the windows and weather stripping and apply some vinyl wrap to hide the cracking, scratches etc.
6. fab up some steel arches to run on the inside from bed sides up to top of roof to beef up the top.
7. maybe add some carpet to the inside of the shell

I did some fiberglass boat repair a while back but wondered if anyone had any creative input...

 

[Kruez]

You are on the right track replacing the rotted wood and glassing in new. I did a fair amount of boat repair as a living in a past life. Mix Cabosil (powdered fiber used as a thickening agent) with polyester or similar with epoxy resin. To bond the new substrate to the underside of the truck cap. A notched spreader similar to that used in tile application will evenly distribute. Apply with the truck cap upside down on garage floor. Weight down substrate evenly with everything you have that's heavy. Dry fit everything first, then work fast. Cover with a layer of cloth after that bond sets up.

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[Kruez]

Use a Dremel rotary tool to carve out the spider cracks in gel coat enough to fill with west system style epoxy filler. Sand and re-paint. Will be Bullet proof when complete.

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[Kruez]

Spider cracks generaly occur where glass was over flexed. Reinforce back side at all cracked locations prior to spider Crack repair.

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[Kruez]

Sounds like a fun project.

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[Walker]

I was thinking PL Polyurethane adhesive for the plywood to cap and load the plywood with sandbags, with cap flipped. Could I mix the Cabosil with that or is it strictly for use with resins? I's sure to be a really fun project (as I shake my head "No"). I replaced floor and stringers on a late 60's ski boat and it really wasn't that bad. My 69 Correct Craft Mustang needs the same work also. What's that saying about boats?

My GMC is carbon black so I might just go with fake carbon vinyl and keep it simple.

The vinyl wrap will probably be the biggest expense but otherwise will be much cheaper than a new cap!

 

[Kruez]

I imagine your adhesive would be thick enough. The Cabosil is used to thicken resin to be used as an adhesive paste. Were you planning to lay glass cloth to seal in the plywood? It's a big project regardless. Carbon fiber vinyl wrap sounds interesting.

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[Walker]

yes, I would seal in the plywood. the roof rack bolts go right through to the inside so those should help hold things together also, maybe add some fender washers.

 

[Kruez]

And sealant / caulk, marine grade, for the fasteners.

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[Walker]

Yeah, I've got to stop the water infiltration from the roof racks. Maybe 3M double stick adhesive tape between the tracks and cap? Existing rack bolts that run through the cap are rusty, I'll be swapping in stainless steel for sure.

 

[Kruez]

3M 5200 Adhesive sealant caulk or something similar will eliminate any need for the tape. The foam tape may actually retain moisture.

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[Walker]

good call