2" or 1.5" Foam

[Dirke]

Hello again,

I was wondering if anyone has experience working with both 2" and 1.5" foam. I was toying with the idea of using 1.5" to save a few pennies plus there is a vinyl molding strip that is exactly 1.5" and very flexible. I thought it might work great for doors and windows as it would give a good place to put a latch, etc. Anyway, I am leaning toward the 2" for the extra strength but the money savings and convenient size with the molding is tempting. Is the strength difference that much?

[GPW]

You could use the thinner material and double it up in high stress areas if you’re worried about strength ... 1/2” not gonna’ make That much difference ...

[atahoekid]

I don't think the weight would be that significant but I don't think there are 1 1/2" sheets. My big orange store only had 2" then 1" then 3/4", 1/2". Two smaller sheets cost more than 1 sheet. If you glued up a couple of 3/4" sheets to make a 1 1/2" sheet, it might cost more than the 2". I'm not positive but check it out

[Dirke]

Our BBS had 2" and 1.5" both the pink stuff made by Dow.

[KCStudly]

I'm using 1.5 for walls and floor, with 3/4 thick for the bulkhead, and under the galley counter dividers. For the roof I plan 2 layers of 3/4 thk for ease of bending, hopefully w/o having to kerf. I had to order the 3/4 in special (they actually delivered a bunch of dirty 1/2 inch that had obviously sat out on some job site, but I rejected it and made them bring me the 3/4 that I had specified). 2 inch is also readily available in my area, but the 1.5 matches 2x nominal thickness lumber, so I decided that that made more sense for framing compatibility. That way my door surrounds, wall sill plates and roof spars match up reasonably close (the foam not having the same tolerances as the wood).

[Dirke]

I keep changing my mind but I am toying with the idea of using FRP and gluing that to the foam. If so, I should be able to use 1 1/2 " no problem. I think it would be easier to glue the FRP on before doing the cutting.

I may also try and glue vinyl to the foam instead. My uncle-in-law works for a billboard company so that would be free and weigh less than the FPR. I am guessing Gorilla Glue would be the best for that.

I sat down and made a list tonight of all the possible ways I can build the roof and walls. Looks like I could make a never ending array of TDs.

[bonnie]

I sat down and made a list tonight of all the possible ways I can build the roof and walls. Looks like I could make a never ending array of TDs.

That does seem to be part of the allure. KISS would apply here, too, I think. Of course simple for some is not so simple for others.

[KCStudly]

You may want to do a sample of the foam and FRP, both to confirm your glue and cutting method.

The FRP can chip out and I am sure it will cut harder than the foam. Not sure it is an issue, depending on your method, but I have had problems touching up places where hard stuff (in your proposed case FRP) is next to the soft stuff (foam).

In my case it is dealing with the expanded GG. Just trying to sand that down smooth to the foam is a PITA. The foam wants chunk and disappear while the GG goes nowhere. Just saying that you may want to test to qualify your method, before committing to full scale.