Apparatus and method for powering a vessel with wind

A method for move an apparatus at the interphase of a first fluid body comprising a liquid and a second fluid body comprising a gas, said apparatus comprising:

• a. a hull form having buoyancy in said first body to float at said interphase of said first fluid body and said second fluid body, said hull form having an upper hull surface, bottom hull surface, first hull end, second hull end, first hull side and a second hull side, said first hull end, second hull end define a hull mid-line and a mid-plane, said mid-plane running between said first hull side and second hull side, said hull form substantially symmetrical about said mid plane, said upper hull surface for positioning towards said second fluid and said bottom hull surface for immersion in said first fluid;
• b. a keel element affixed to and descending from said hull bottom surface and having a first keel end toward said first hull end, a second keel end towards said second hull end, a first keel side surface facing towards said first hull side and a second keel side surface towards said second hull side, said keel element and hull form having a line of attachment which line of attachment is parallel to or on a line from the first end to said second end, and said keel element having at least a one segment in which the first keel side surface and second keel side surface have an offset angle toward said first hull side;
• c. a sail element projecting from said hull upper surface about said mid-line, said sail element for receiving and responding aerodynamically to relative movement of said first fluid body and said second fluid body;
• d. said hull form having an at rest position in which the sail element is not receiving and responding to relative movement of the first fluid body and said second fluid body and a power position in which said sail element is receiving and responding to the relative movement of said first fluid body and said second fluid body;
• in said at rest position said sail element and said interphase of said first fluid body and said second fluid body define a first rest angle towards said first side and a second rest angle towards said second side, said first rest angle is smaller than said second rest angle, and in said power position said sail element and said interphase of said first fluid body and said second fluid body define a first power angle towards said first side and a second power angle towards said second side, said first power angle is larger than first rest angle and approaches or exceeds said second power angle;
• e. said apparatus tacking by rotating the hull form and keel element to place the first hull side toward the apparent direction of the second fluid body;
• said method comprising the step of rotating the hull form and keel element to place the first hull side toward the apparent direction of the second fluid body and reversing the direction of the hull form in the first fluid body.