Re: How much Flotation? And Where? Pour-in foam? Oh, no! Styro

Gordon (
Fri, 7 May 1999 21:01:13 -0700

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West Wight Potter Website at URL
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I'm not happy to learn that. I wonder how much water I'm carrying around in
my poured in foam. But at least it is low and forward. My V-berth deck is
also epoxy saturated plywood (exterior but not marine) with the edges
secured with fiberglass tape. I can only hope it is well sealed.

Since we don't have snow here, many of the houses in my neighborhood,
including mine, have flat roofs, and many, also including mine, now have
foam-covered roofs. I presume the spray-on foam the roofers use is the same
as the pour-in flotation foam. The foam then has to be sprayed with a white
plastic coating to protect the foam from the sun, and the coating (not the
foam) has to be renewed every 4 or 5 years. Mine does not leak and the foam
provides insulation. It can be walked on (no spike heels, of course) and,
because it is smooth, it is much easier to clean than a tar and gravel
roof. During application it is easy to fill low spots with additional foam
to reduce ponding. It is also easy to repair if it gets punched by a
falling branch.

I'm really surprised to hear the pour-in foam absorbs water although I have
heard that about the spray-can foam.

Does the polystyrene foam sold for insulation make good flotation material?

Harry Gordon
P14 #234, Manatee
Mountain View, CA

>You might be interested to know that styrofoam will float almost indefinitely
>in salt water while pour-in and "Great Stuff" will absorb water quickly. In
>about a week the pour in yellow orange foam will be half sunk.
>I used pour-in foam in my old trihull to replace ribs and stringers. Foamed
>it in completely under floor by drilling round 2" holes every 4 sq. ft. in
>floor and pouring mixed foam in until it flowed out holes . Worked great for
>about two years. Then, one day I noticed waterline was much lower while bilge
>was dry. I drilled a hole low into false pour-in foamed floor pulling some
>foam out with drill bit and found rain water in foam. It dripped out for a
>month and never dried out. By the third year it had caused blisters in
>bottom of hull.
>Rain water had leaked in thru sides of hull and marine plywood (encapsulated
>in epoxy resin) glassed joint collecting inside pour-in yellow-orange foam.
>Styrofoam blocks are better.