The ‘a’ class catamaran – its place at the top table. at 18ft long with a total allowed rig area of 150ft2, but weighing in at a mere 75kg, the ‘a’ class is. Simplicity boats links of interest… = simplicity award winner! boat projects – kits & plans – information – supplies – software – sail stuff -. We have boat plans (both yacht designs, catamaran designs and power designs) for all sizes for the amateur boat builder and professional boatbuilder..