Regarding cored boats, there are more and more of them seen on the market place for both sail and power. Kady Krogen, which is considered to be one of the premier trawlers out there has gone from solid fiberglass hulls to cored hulls and so that lightening up of displacement enables them to plane now, where before they were displacement hulls that plowed through the water. Fuel consumption and time to reach destinations drastically change because of this. Early sailboat construction, including J/Boats, didn't know about vacuum-bagging and so there were a lot of failures with cored hull construction. But, after vacuum bagging and resin infused processes like Bill Seiman's SCRIMP development they were able to build very strong hulls, with exact ratio's of resin and cloth, eliminating all air pockets (large and small), maintaining quality control and adhering to weight restrictions (which is particularly important with race boats) so that there was a very well built product that lasts a long time. They would even include motor barriers and hull structural grids that were incorporated all at once instead of making these things separate components to be affixed in the hull after the hull had cured. That created chemical bonds rather than mechanical bonds (even if fiberglassed in place). Many mega yachts are built from Aluminum, but there is one company (at least to my knowledge) who builds fiberglass cored hulls and they have been doing it for many years (ChristensenYachts). I might add that Everette Pearson who was a pioneer in fiberglass construction for many products beyond boats, died over the holidays at 84, and he was one of the people who started using vacuum bagging and resin infusion construction at the git go. Many of the luminaries who started this sport out in one way or another are departing our world unfortunately. Like Gary Mull, Tom Blackaller, Ted Hood, Carl Schumacher, Paul Elvstrom, Lowell North, Peter Barrett.......I digress.