Patent ID: 7568442

Claim:
A system for utilizing wind forces to provide motion comprising: a hull adapted to move across a surface in a first direction; a pivot assembly rotatably mounted to the hull and adapted to rotate about a vertical axis approximately orthogonal to the surface; a sail rotatably mounted to the pivot assembly; the pivot assembly adapted to limit the sail to two degrees of freedom; wherein a first degree of freedom of the two degrees of freedom is adapted to enable the sail to pivot around a relative-wind axis approximately orthogonal to the vertical axis, the relative-wind axis being oriented in a direction defined by the rotation of the pivot assembly about the vertical axis; wherein a second degree of freedom of the two degrees of freedom is adapted to enable rotation of the sail about a mast axis approximately orthogonal to the relative-wind axis; a ballast coupled to the sail; and wherein the ballast creates a ballast moment force when the sail pivots away from the vertical axis around the relative-wind axis.