Structure: 12 mm thick ring. Rigidity 40 x 40 x 4 mm Hull skin: Side wall 4 and 5 mm Gaskets 6 and 8 mm Waterproof Bulkhead: Watertight bulkhead in the annular frame 1, 4 and 14 2 crashes boxes in the bow. Insulation: The hulls, the deck of the bridge and the roof are completely insulated from heat and sound with: - polyethylene foam of closed cells of 20 mm thickness - A TRISOMUR concept composed of 8 elements of 10 mm thickness.