wood or plastic

Originally posted by JimC However quite a few class rules make it very difficult to use the materials to best advantage, and for those classes wood will probably still be better.

In Merlin Rockets plastic and wood are equally quick, which is precisely what the rules are intended to achieve. Wood for new designs (it is a development class after all), plastic to allow low-maintenance copies for those who want it.

I know less about Solos, but from what I've heard plastic and wood perform much the same there too.  

It depends...

Solid fibreglass with sprayed on chopped strand mat is a far inferior construction material than plywood. However if the boat is heavy enough it probably doesn't matter that much. Few dinghies are that heavy though.

Foam sandwich with reasonably quality glass or better is superior to plywood if the materials are used correctly. However quite a few class rules make it very difficult to use the materials to best advantage, and for those classes wood will probably still be better.