AH HAH! Heat's ON!
This is Kurt's page, so we'll let him respond to Keith's views, most of which I agree to, viz 338, another cruiser in the making.
But not Point 4. Feel very strongly that the boat is essentially a spaceship. If something happens to it in the Indian Ocean, say, and it fills with water and it doesn't sink, there are still more life saving resources if you stay with it than on a liferaft. A liferaft supposes RESCUE. That may not be the correct assumption.
Thinking about making an Ariel unsinkable is a good exercise. I personally would not give up an inch of volume to foam fill except for a 1/2" of ensolite on the whole upper part of the hull for insulation. I think svATOM (Baldwin) has the right idea in making lockers and stowage space 'water-resistant'. I would not use or trust any foaminplace urethane. (There is an out-gassing issue and it is NOT closed cell.)
Nothing can be said about being totally smashed to smithereens, we better have some sort of alternative aboard. But total disaster may cancel out any one of those: liferaft, dinghy, pfd.
How long would you live in an emersion suit anyway? Better to think about making the boat unsinkable and repairable.
Let's explore the ways....
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Kurt, how you figure 60 cu ft? When you multiply 60 times 64 (wt cu ft water) the total is 3840# displaced.) Will that float the boat?