The high aspect ratio (slim sail profile) leads to high aerodynamic efficiency because less wind energy is lost over the top of the sails.
Several of the high aspect ratio sails can be ganged together to maximize total sail area and can be overlapped somewhat to realize the cascade effect. Figure 2, below, shows a concept for a personal watercraft catamaran.
Not shown in Figure 2, above, is the canvas trampoline for pilot and passengers. The craft is steered with the dual rudders at the aft end of the vessel, and the sail angle of attack is controlled by the pilot with the rope bridle ("control rope" in the figure). The masts rotate in greased sleeves (bearings) at their attachment point to the center structure, and are ganged together with control cables ("gang lines" in the figure) so they all move together. Because the sail profile is symmetrical, the force of the wind induces no torsion in the mast, so the control forces required are small.
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