Teardrops n Tiny Travel Trailers

Yeah I'm asking a lot of questions....I want to learn from those that have done, what I need to do.
Got a question about the expansion of GG in channels. When I notched my foam with my Hot Wire cutter. I was able to make nice tight (precision fitting) cuts. The 2x2 was as snug a fit, as if I had used a router.
But the I got worried about the expansion of the GG. Is it possible to make your channel cuts fit so well, that the GG expansion can crack, or warp the 2" foam . My cuts are 7/8" deep

Has anyone had problems with GG expansion, when there channels /notches , fit there lumber very tightly ? Someone said that their routered channels fit very snug to the lumber. Was GG expansion a concern ?

Maybe if you are close to an edge it would be a concern, but it's just not a big problem, or at least it wasn't for me. What happens is the glue will want to expand up out of the joint, pushing the wood with it; so you have to cover with something like waxed paper/plastic wrap/packing tape... some sort of release agent... wrapped on another board and clamped (or heavily weighted) down to try and keep it all from pushing up and out.
Still, you will get some unevenness and will have to fair it. The GG sands a little harder than the base foam, so it is hard not to gouge and sand evenly. One technique that was suggested to me late in my build, but I found to work well, is to build a bridged shoe for your router that references the foam surface around a glue expansion, then float it around the area to skim everything back flush. Works pretty well on flat surfaces and more uniform than sanding.

Thanks,

If you use a lot of GG it might try to push against the foam.

When I cut my channels I put a bit of a V shape to the wire so that the inserted foam was snug at the face of the wall, but allowed about 1/8" air space as the cut tapered wider towards the center of the foam. Not sure if that make sense or not. This allowed a channel behind the wall face for the GS to flow when I sprayed it in. When I was ready to glue the shelves/bulkhead in place I slid the foam into the channel. Then I poked the GS tube into the channeled area and applied some glue. I did that about every 6-8". When I went out later I found that the GS had pushed out through the holes I applied though. The holes must have kept the pressure to a manageable level because the walls and the shelves did not deflect any.

I think with a tight fit like you describe, I would not apply glue to the bottom of the channel, just the sides. Then make sure the shelf is cut a bit short so that you have 1/8"-1/4" extra space on each side. That way when you slide the foam into the channel what extra glue that is pushed back with it will have a air pocket to expand in without pushing the wall or shelf out.