Tony et al -

I have found thru experimentation that Gorilla Glue (and likely its similarly-chemical cousins) can be made into a sort of an 'expanding glue'. You just have to mix it with a lot of water (and fast, and apply it fast - pot life is like maybe 10 minutes).

I will be bonding sheet foam (EPS - pink or blue) to the hull using this. Besides a very strong bond, I think the 'foaming' property will cut down on the "holidays" Ebb mentions. Condensation forms from atmospheric water (humidity), so if you can seal off a small area, you shouldn't have that as a problem. I'll be adding a layer of luan/doorskin ply to the outside (the cabin-side) of the foam, and a layer of 10oz glass over that to protect it and make a durable, easily-cleaned surface. Because the EPS foam will be behind wood, I will be able to use cheaper polyester resin instead of epoxy when glassing over it (People may poo-poo polyester it seems, but the stuff has held the boat together fine for the last 40 years, so I have no problems using it where I can!).

I'd like to sneak in a radiant barrier right up against the hull if I can. A layer of mylar 'space blanket' material would work great, or maybe aluminum foil. Have to play with that a bit yet, make up some test pieces, see if the GG can bond to either of those materials, or if I'll need to perforate it...

I'll be putting insulation (AKA 'flotation' ) against every bit of hull I can, above and below waterline. Condensation forms all over, everywhere - I have seen it often in the past 4 years of living aboard. It is a bit more prevalent below the waterline, when conditions are right - but that is not always. I also want to treat the overhead in the v-berth, somehow...

I like the GG because I think once it is cured, it will not 'outgas' much, if at all, and seems to be a really stable substance. The other material I considered was something like 4200/5200, but the GG can do the same job for much less money and mess. I want whatever it is to be pretty much permanent - it would suck to have your hull insulation/liner delaminate after a few years, and my experiments with other glues like contact cement, Goops, acrylics, and such showed me that you need to make sure it is a really good bond, when going up against the hull. Most of these failed to some degree. GG becomes an inert solid after it has set up, whereas the rubbery adhesives are always slowly degrading (outgassing) to some degree - losing some of the very stuff that makes them what they are. How long until that has an adverse effect on the job they are doing? Your guess is as good as mine. So I am opting for a glue which does not have that propensity.

I like the idea of solidly encapsulating a solid foam (as opposed to gluing in a pliable foam) because it seems that would hold the materials in stasis better, for longer. If balsa can stay as dry as it does in the deck for 40 years (assuming no water penetration), so that it looks like it was installed yesterday when brought into the light, it just seems to me that encapsulation is the way to go.