Waterproof styrofoam, again

[toller]

I am sure everyone was right about hot-tube covers absorbing water, but...

My existing swim platform is made of an old Snark styrofoam sailboat with a deck built on it. It has been on the lake for 4 years, 4 or 5 months a year. It hasn't absorbed any water, though it is physically falling apart.

Is that somehow different than the foam in hot-tube covers?

Unfortunately I now have a "new" snark to build a platform around. I was out on Monday and the sail simply disintigrated. And used snarks are cheaper than new sails... Maybe if I put the hot-tube cover on top of the snark.

[Edwin Pawlowski]

Yes, it is different.

Your boat is not Styrofoam. Styrofoam is the registered trademark of an extruded polystyrene board, usually colored blue, and used for insulation. What you have most likely is the white bead material, expanded polystyrene foam (EPS). There are some possibilities in the difference. The Snark was probably molded as one piece. When molding expandable polystyrene, you form a skin on the outer portion that aids in moisture resistance. Another factor is the density of the material. EPS is commonly molded at densities from 1 to 4 pounds per cubic foot. Chances are, your boat is closer to 1.5 or 2.0 pcf. Insulation is cut from large molded billets ranging up to about 36" thick and 16' long, then hot wire sliced. It is usually less than 1 pcf and has a larger bead structure, no skin, and thus more likely to absorb water.

We can get into high versus low molecular weight also. Not to mention fusion levels, molding techniques using cross steaming versus autoclave, fusion potential of C versus B beads. My guess is that you are bored, confused, or both right now. .