: One of the books said that a boat could be made with foam instead of wood has
: anybody done this?
Various closed cell foams are used in boat building. They are very expensive compared to wood. I've read that end block balsa is stonger and provides better peel characteristics than the foams. Balsa is less expensive than the foams, but by no means cheap. In most applications polyester or vinylester resins are used. Polyester represents a savings over epoxy. The trade-off is that, unlike strip building, these cores contribute little longitudinal strength to the hull/deck structure. As a result you'll have to incur the added expense and weight of a thicker glass lay up schedule.

Using foam or balsa cores requires the construction of a more complex male or female mold which is time consuming an an added expense, particularly for a one-off. Then you have to destroy the mold or store it. There's a guy who lives near me who spent too much time in the Saudi Arabian desert. When he got back he bought all the tooling from the Allied Yachts' bankruptcy. Allied built sailboats in the 30 to 42' range. So for several years these large hull and deck molds have sat in a 20 acre field next to his house. As far as I can tell he hasn't built a boat yet.

Wood/epoxy/glass composite is very hard to beat in terms of cost, weight, strength and ease of building. Unless you go with Skin on Frame or Stitch and Glue and I'm sure some of the strippers will argue with me on this point.
Hope this helps.
Geo. C.