The Nacra 18-square is 18 feet long. It has the same hulls as the Nacra 5.5 -- just wider beam.
It is impossible to imagine that it has 324 square feet of sail in main alone -- almost 90 sq. ft. more than the original Tornado that had main and jib. So I'm not buying the idea that 18-square refers to the sail area.
1 square meter is 10.76 square feet, so 18 square meters is only about 194 square feet.
