Join Date: Apr 2011
Location: Southern California
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Regarding positive flotation in a smallmkeel boat - all the Schock Harbor 20s since approx. Hull 130 have foam flotation. We install 22 cubic feet of foam in a 1,800 disp. boat. We have a 6 ft bow tank.
It required a surprising amount of calculation and testing to get the location of the foam correct.
We found that one needs to be careful when cutting and inserting the foam to make certain to try and prevent the foam from chipping. Instead of a knife, we use a heated wire to cut the foam - it seals by melting the foam.
Also, select a foam that will not under any circumstance absorb water. We did extensive long term (30 & 60 day) immersion testing of closed cell foams and discovered some closed cell foams would absorb a minscule amount of water, this might lead to nasty molds and smells.
We heat shrink the foam blocks to seal them. We considered applying resin or gel coat as a sealant ( we have plenty of those materials around ), but decided on heat shrink wrapping the foam.
I agree that one should carefully consider wherenin the boat the foam is placed, ideally if the boat swamps it floats more are less level.
One should also consider the weight of the crew and the weight of the gear in the boat.
Finally, I think you might also consider glassing in air tanks with inspection ports similar to dinghies. If a DIY has enough experience, it should be easy enough to do.