In Reply To Rolf

Concerning Kevlar. Look at Tornado Class rule 7f

"7.f Kevlar, or any similar fibre, shall not be used in the Tornado Catamaran except for running rigging.
Core materials require prior approval of the ISAF. Those containing Kevlar or other high
modulus fibres may be permitted but in addition to their structural properties the primary criteria
in deciding whether a particular core material is acceptable will be its cost and durability."

Any Kevlar I would use on a wood veneer boat would be as a core.

There is an old trick, called starved cloth core. There is an update where you use a knitted material that looks like lace with big hexagonal holes. Use just enough epoxy to mostly saturate the yarn but leave the holes free of epoxy. Use this as a core.

For various reasons this does not work well with true composite construction. However, it works quite well in veneer construction.

I hope this clears things up.