BTW Nico, what is wrong with
plywood?
It is in almost all boats, under the winches, the
autopilot motor, the
anchor winch etc.
Plywood is great IF and this is a big IF the end grain is well sealed.
In this tri I think the plywood would form the shear web for the crossbeams. This is a really good use of plywood. Plywood is used in your house for beams that do just this.
If you want to know if the ply will be a problem, stick your head into the beam and look at it. It should still be golden coloured, still covered with epoxy and looking lovely for another 25 years. It can't go wrong unless it gets wet. It is not rocket science - ply can't
rot unless it gets wet and if the epoxy has done its job, this one is epoxy saturated, then you are fine to go.
Every material has its limitations. Glass has
osmosis, foam delaminates, balsa mushes, ply rots. Well built boats are built to get around the limitations of the material.
PS Holmek - have a sail on a well designed and sailed multi. Be careful you may get hooked.