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RedneckExpress · 07-04-2020, 02:59 AM

Question for those more experienced with Weldwood contact adhesive.

I'm in the process of redoing the interior of the one piece fiberglass shell that makes up the snap-n-nap on my amerigo tc-11 and need to install some wood to the interior edges so that I can anchor the RV wall board over the nnew insulation.

Normally I would just apply 3m 5200 and screw it in place, but because there's no frame, and the angle at which its going in, this isn't practical.

My thoughts instead were to apply weldwood contact adhesive to the fiberglass and wood so I can just press the piece in place, but I am wondering if this will be strong enough or will it lose the battle with gravity after awhile?

LJowdy · 07-04-2020, 07:18 AM

Contact cement will work but eventually the glue will deteriorate The preferred method of bonding wood and fiberglass is epoxy resin. Home Depot and other hardware stores sells the resin and hardener in various quantities. Wear rubber gloves and work fast. You can use a paint roller and roll on the epoxy than clamp the pieces together.

RedneckExpress · 07-04-2020, 05:17 PM

Quote:

Originally Posted by LJowdy

Contact cement will work but eventually the glue will deteriorate The preferred method of bonding wood and fiberglass is epoxy resin. Home Depot and other hardware stores sells the resin and hardener in various quantities. Wear rubber gloves and work fast. You can use a paint roller and roll on the epoxy than clamp the pieces together.

Thanks, that's what I was figuring, so it looks like I'm not going to avoid needing to build a clamping frame to hold the stuff in place while the 3m 5200 cures, drat

sam-3 · 07-05-2020, 12:55 AM

DH and I did extensive wall damage repair in our TT. Could been the time of year,but the contact cement didn't work. Sept. to January. We used heavy duty liquid nails. Cheapest at Walmart. Some have used Locktite caulk. DH used one tube in a generous s pattern. He used a flooring roller to press the layers together. Many years later and the repairs have held up. One tube of liquid nails per 4x8 sheet of paneling.

chuckbear · 07-05-2020, 08:13 AM

Why do a half-fast repair? Use the correct material for the job. Get a two-part epoxy made for fiberglass and wood. You can get it at almost any hardware or boating supply store. It's always easier to do it right the first time than to have to do it over again. Cheaper too. Chuck

rcnuts · 07-09-2020, 04:48 AM

Im a mechanical contractor and use all kinds of adhesives for all different kinds of applications. Im not so sure epoxy would be the best adhesive for your job. Im NOT saying epoxy won't work but after time epoxy tends to get brittle, and with all the flexing, vibrations, etc a better solution (in my opinion) is available. Someone mentioned this in a previous post. Loctite heavy duty, or even PL 400. Id sand your existing fiberglass slightly with 60 grit to scuff the mating surfaces. Clean with solvent!! Generous application of the adhesive will guarantee all voids will be filled. If unsure, a small test area can be sanded and a small bead of adhesive applied. Oh and Ive seen LOTS of fiberglass repairs fail, probably due to inadequate surface prep. Old glass can be tricky.

chuckbear · 07-09-2020, 07:58 AM

Quote:

Originally Posted by rcnuts

Im a mechanical contractor and use all kinds of adhesives for all different kinds of applications. Im not so sure epoxy would be the best adhesive for your job. Im NOT saying epoxy won't work but after time epoxy tends to get brittle, and with all the flexing, vibrations, etc a better solution (in my opinion) is available.

I think you need to take a look at all of the fiberglass boats out there in a much harsher environment and taking much more of a pounding than an RV ever will. They are all put together using either epoxy or fiberglass resin where wood is attached. As a marine service technician for 40 years, I have done my share of fiberglass repairs and epoxy is always the adhesive of choice. If metal, plastic, or some other surface must be mated than other adhesives or sealants are better solutions. Just my input from a lot of years of experience. No matter what you use, surface prep is very important. Chuck

RedneckExpress · 07-10-2020, 03:48 AM

Quote:

Originally Posted by chuckbear

I think you need to take a look at all of the fiberglass boats out there in a much harsher environment and taking much more of a pounding than an RV ever will. They are all put together using either epoxy or fiberglass resin where wood is attached. As a marine service technician for 40 years, I have done my share of fiberglass repairs and epoxy is always the adhesive of choice. If metal, plastic, or some other surface must be mated than other adhesives or sealants are better solutions. Just my input from a lot of years of experience. No matter what you use, surface prep is very important. Chuck

Yeah, I've got a lot of sanding to do once I finish scraping the 40 year old spraye expanding foam that was used to insulate the clamshell. Most of it, I can just stick a putty knife under the edge and tap on it with a rubber mallet and it pops off in big pieces, but there's still residue left, which will need to be sanded a little to remove it from the fiberglass, then the cleaning before I can apply the adhesive and press (And then figure out how to hold the wood for over 24 hours so that it cures in place) while also fighting gravity at the same time.

chuckbear · 07-10-2020, 08:58 AM

If possible, lay everything flat and look for heavy weight to keep everything together until the adhesive dries.

RedneckExpress · 07-13-2020, 02:54 AM

Quote:

Originally Posted by chuckbear

If possible, lay everything flat and look for heavy weight to keep everything together until the adhesive dries.

Yeah, definitely not going to happen, it's basically being installed on an existing ceiling, so its going to be fighting gravity, that's actually why I originally was pondering contact adhesive, vs what I would normally use.

So, in the end, I'm going to need to build a frame to hold in place while it dries that will sadly have no use once the wood is glued into place.

Once the underlying frame is anchored in to the fiberglass, the skin and polyisocynaurate foam board can be installed far easier, as the foam can use friction/compression inbetween the frame members to hold itself in place, and the skin only has to be held in place till the staples are shot in along the perimeter, which will anchor the sandwich together so the glue can bond it all permanently.

Bobby F · 07-13-2020, 03:57 AM

When I prepped the surfaces correctly, I never had a piece of contact-cemented formica pop off of the underlying wood countertop material. Some of those counters are still sound after thirty years of pounding, heat, and moisture. A few were in seasonal cabins here in Minnesota, which means they were subject to below-zero temps during the winter, and they held just fine. Never saw the contact cement break down.