OK, here''s where a bit of my utter ignorance shows through.
I honestly have no idea how much weight I''ll end up with. I''ve no desire to make is unnecessarily heavy. I''m thinking the outer hull to be made of 3 thicknesses of 1/4 inch ply laminated together at cross angles and then sealed in a couple, few (don''t know how many layers is appropriate) layers of dynel and resin. The space between hulls, likely about 4 inches and then a 2 layer (1/2 inch total thickness) inner hull made in the same manner. Add on whatever decking is appropriate, a mast, rudder, centerboard assembly and other than a few minor interior amenities, that''s about it.
I''m sure you''d have a much better idea of how much weight I''d have wrapped up in that than I would. I really have no notion.