thanks Matt Miller for the cred
a LOT of years indeed. I sailed my first 16 about 40 years ago at age 17. Been sailing other things since the ripe young age of about 10.
I used expanded foam for years on hydroplanes that I built from about age 12 to 18 (one of which is still in service). It is a non-absorbant polyurethane that is not bio-degradeable. I have also used it in buildings, basements, for creating stage-props and to add a little more floatation to older aluminum canoes. It is probably the same thing as sold by West Marine except it doesn't say "Marine" and thus probably 1/3 of the price.
One really funny side effect is that the foam extrudes itself in the exact shape
of the cross-bar until it is done expanding. Until I figured it out I had about 3 feet of extrusion on each end of the bar. One not so funny side effect is DO NOT get it in your hair unless you're really down with "liberty spikes" that will last shower after shower
It did make it easier to get the 16 over, not because of the floatation of one bar in the water but because I was not trying to lift about 30 - 40 lbs of water 4 bars @ approx 10lbs h2o per bar. Since those days I have gained enough weight to right a small tug-boat so it doesn't matter any more ... >;D
to Will in Latrobe - can you get those little pony-cans of RR down there? I haven't seen them in years!
for more info here's the technical stuff: http://greatstuff.dow.com/literature/index.htm