what adhesive for aluminum to foam?

[coal_burner]

well, the search function told me about glues that can bond aluminum to wood, or foam to cloth, but nobody has talked about gluing foam insulation onto the back side of an aluminum skin.

i have .040 skin riveted to an aluminum frame, and it oilcans ALOT.

i'm considering troweling on silicone caulk to make a foam/aluminum composite even though it's expensive, and the caulk wasn't really designed for that.

so i'll ask the best and brightest here: what adhesive works well to bond aluminum to foam?

[tony.latham]

and it oilcans ALOT.

I have to believe that even if you find the right adhesive, the foam surface will fail as the aluminum expands. But I don't know for sure.

Good luck with your quest.

Tony

[coal_burner]

thats why i'm considering silicone, since it has a little flex to it.

i know i'm not the first person on these forums who's had to figure this out.

[KCStudly]

I'd look at the spec's for PL300. It works with the foam, is pliable like silicon, I'm just not sure if it works with the aluminum. Its intended application is hanging foam board on wall structure before finish paneling is fastened thru the foam.

If it is compatible with aluminum, for your application, I wouldn't notch trowel it. I'd follow the suggested bead size and pattern. I was trying for a structural laminate on my hatch, so I troweled, and that caused trouble with curing; once the air was cut off at the edges the field remained uncured. I solved this problem by making kerf "chimneys" or air ducts in the foam to let air get through to a much larger area, but it was a lot of effort to seal all the ends of the kerfs after the laminate had cured; and that method won't lend itself to your inset 'bay' style installation.

I think the OEM recommended large bead wide zig zag pattern prevents the foam from being pressed intimately with the wall panel, and leaves plenty of air adjacent to the glue line for it to properly cure, even if some of the edges cure up solid earlier than the field. Since you have more than adequate strength in your frame structure, are only looking for the insulation value and enough stabilization to prevent oil canning, I don't think there is any advantage for you to try for a 100/ct bond full lamination. It's not worth the hassle.

I think it was while I was applying the foam core to my hatch that I figured this out, if you want to skim thru my build thread for more details on what I learned using the PL300.

[Chief-John]

I went with sprayfoam on the inside of my aluminum skinned trailer. Before that, high winds caused the skin to make noises but everything is solid now. And yes, the sprayfoam was a total mess!

[flboy]

Is the foam going between outer skin and plywood interior? If that's the case, why glue it to start? I just cut mine slightly larger (1/8 to 1/4 inch) and then compression fit between studs and then tape all seams with aluminum duct tape. Sealed well and it cannot go anywhere to start. What I also did given that foam is 3/4 inch and space between outer skin and plywood is 1 inch, I ripped 1/4 in plywood strips to stand off from the aluminum (glued strips with liquid nails. That allows the skin to breathe and any moisture to evaporate due to condensation which can occur when extreme cold and interior heated. I never seal up skin at floor to allow breathing and if there was a leak along the roof seam, it is going down on inside of wall and back out. Should never happen as I inspect yearly, but you never know. Good luck.

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