Join Date: Jun 2000
Location: CT/ Long Island Sound
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Aerodynamic studies have shown that the squared off top of the main not only increases sail area, but also improves the airflow vortices coming off the top of the mast so as to provide more force to move the boat forwards. Airplane wings don't end in points, the way standard sails do, because of this. It can create instability in the airflow and cause the plane to stall out. (Trailing points on wings are there for other reasons.) On a boat, a pointed top is easier and cheaper to make, but it is not the optimal shape - thus the squaring off on AC boats.