Name: Al Paul
re: Foam and Boyancy
Derrick, I certainly wouldn't fill the spaces undr the bunks with foam. It would add no floatation and if it gets wet, would rob floatation. If you want to make the boat unsinkable you need at least enough floatation to compensate for keel, anchor(s), spars, battery motor and misc gear, assuming that the fiberglass structure is near neutral boyancy. That comes to about 800 lbs. Water weighs 60 lbs per cubic ft so that figures to 13.3 cu ft of air space or extremely light foam. To make the boat float to her gunwales, add another 200 lbs or 3.3 cu ft to bring the total to 16.6 cu ft. Call it 17.
The air spaces under bunks and installing water tight hatches over the lazarette and stowage compartments can provide about 6 cu ft so we must add 11 cu ft. You can buy 4' X 8' closed cell styrofoam sheets of various thicknesses at Home Depot. This material is easy to cut, handle and is cheap. It should be doable to stuff 6 cu ft of it aft of the quarter berths and beside the keel trunk. Then cementing a 4" sheet under the pad of the forward bunk will provide the remaining 5 cu ft. Now we have a theoretically unsinkable San Juan 21 by gasketing stowage compartments and by filling waste space with floatation and reducing headroom over the forward bunk by only 4".
Single handing a 21' boat across the Carib scares me a little. I'm a lske sailer at parsent but I've sloshed upwind in 6-8' waves in a 28 footer and am not sure I would enjoy it in anything smaller. For goodness sake, be sure you have a good, submerseable VHF. Al Paul
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