Randy, thanks for the tip: Ted's Sailing Page does have some very helpful contributions to the discussion of floatation. (see http://sites.netscape.net/tedsailingpage/Floatation.html) Specifically, it is very helpful to know that fiberglass weighs 125 lbs per cubic foot. Using Ted's method of calculation, a fully swamped M15 would displace about 3.8 cubic feet all by itself, without any added foam. However -- the brochure states that "We also core the V-berth section of the liner with foam so that it's strong yet light." In addition, the balsa-cored decks need to be taken into account. So the swamped M-15 unquestionably will displace even more than that 3.8 cu/ft of fiberglass. But how much more? I'm willing to chalk up small unknown amounts of displacement, such as the balsa deck cores, to extra reserve boyancy and leave them out of the calculations. But what about the alleged foam-cored V-berth area? Does anyone have the slightest idea how much volume of foam we might be talking about? How thick is it? and how much of the hull liner is constructed in this way? Also, does anyone know: were all the M15s built with that foam cored hull liner? (I have already found other claims in the brochure which do not seem to apply to my #152, such as the alleged "cavernous" port cockpit locker.) Steve M15 #152