Wingsail5561
The Slotted Sail by Dave Terry

"This design was a success in my mind, but I was blind and left behind by those who sought only to sell more than one sail. The problem was, you had to 'duck jype' the sail, as the center of effort was in the leading edge. The Main Sail was actually acting more like flaps of a plane. But you could use a huge sail in violent winds, if you could 'duck jybe'. I just kept on writing and going with the flow of the sport until it became too expensive to enjoy,then I bought a kite and started working with Laird and the boys on the kiteboarding adventures."