Foam to fiberglass glue

Silicone. Used in the signage industry for years to adhere eps or extruded foam to anything.

When I repaid my Lance i used a 3M spray adhesive designed for foam. My of the adhesives will disintegrate foam. I also used spray foam in some of the areas.

I just used some 3M high strength 90 in a spray can for a project and it worked amazing. That stuff holds anything, only problem was that I wanted to glue everything around the house with it :-)

Advantage with silicone is that it will bridge across gaps or dished areas to flat foam better.




Self appointed engineer and carpenter.

Bigfoot uses a spray contact adhesive. You want something that is somewhat resistant to softening with heat, and with solvents that do not melt the foam. Given that there is probably residual contact adhesive on the fiberglass, using the same type of product might be advisable as other things may not stick well to it. Silicone would be near the bottom of my list, it is not a very strong adhesive and yet will be hard to clean out it if comes loose, nothing at all stick to it. When boatbuilders use foam core, they will mix polyester of epoxy with fillers to thicken it, then use a notch trowel to apply.

Blue foam (extruded polystyrene) is a better choice for a core material than bead board (expanded polystyrene). I don't know why Bigfoot changed - XPS is less expensive I guess.

Beadboard (usually white, with little beads bound together) is EPS. Extruded polystyrene (blue, pink, etc) is XPS.

You need to do some serious research into using either EPS or XPS as a SIP (in this case, the structure is the wall/camper shell). There are very specific adhesives you can apply (with a paint roller, mop, or, via spray gun) to bond the EPS or XPS...some of the adhesives go on quite thick, and can bridge "bowing" in camper structure shells, but, if you press (roll the SIP assembly with the glue sandwich) or vacuum-bond the structural panel, the adhesive will ooze out along the wall's edge. Some of the adhesive used in making Our Outfitter Mfg XPS-to-FRP structural walls oozed out during the vacuum bonding stage, and dried a 1/4 inch thick (probably much thicker than a silicon bead!).

Good luck.

On the edit: i changed the word "bowling" to "bowing".

Exterior construction glue in caulk will work as well, but that thing needs days to dry.
If you are replacing insulation, think about upgrading to polyurethane.
Not only R value is about 15% higher, but much stronger mechanically.

Polyurethanes are interesting, however, also have a look at XPS grades in the 600 type VII to 1000 psi type V strength grade (no kidding; these panels are nearly like plywood). I think the Formular brand (Owens Corning?) are readily available. Do your due diligence with all the products out there.

*disclosure: I do not work for, nor own any position in any foam manufacturing industry

I agree a good polyeurethane adhesive caulk would be great if applied with beads 1/2 inch apart. That would be a no nonsense way of doing it.

Fortunately I have not needed to glue the fiberglass on my TC. I would use the blue foam.

This link, Two Northern Lites with Cab over failing and Basement sides, might offer some help.

I would do a test section using Gorilla glue. It is available at most hardware stores. I would not use silicon.

For locating the leak, my first guess would be the weep holes in the window frames. They get plugged and can let water in the TC. Another place is the seal between the window frame and fiberglass.

Every TC I have owned has had window leaks at some time. I have had to rebuild the wood inside the walls in three TCs due to the window leaks. On my 1988 Bigfoot (see photo), I use butyl tape only (sticky on both sides-see photo), and absolutely no silicone. That is what was used by the manufacture, and did just fine for twenty years. The butyl tape is common at RV Supply stores, and I have heard it is available at Home Depot in the caulk area of the store.

I am having issues posting with photos. I will try separating the photos from the post.