Patent ID: 8298024
Filing Date: 2012-10-30
Classification: B63H

Abstract:
1. A propulsion system for a watercraft, including: a surface-piercing propeller including at least one propeller blade and defining an axis of rotation, the propeller blade having a tip that rotates with the propeller about a tip travel path, the tip travel path having an upper half and a lower half; a drive shaft operatively connected to the propeller in a manner such that the drive shaft is configured and adapted to rotate the propeller about an axis of rotation; a shroud unit comprising: a) an inner shroud member configured and adapted to augment propeller thrust, the inner shroud member surrounding at least the lower half of the tip travel path, the inner shroud member having a leading end disposed adjacent said tip travel path and a trailing end which is located rearwardly of the tip travel path and which extends transversely relative to the axis of rotation of the propeller; b) an outer shroud member surrounding the inner shroud member, the outer shroud member having a leading end, a trailing end, and a lower external side, the outer shroud member being radially spaced from the inner shroud member so as to define an air gap between the inner and outer shroud members to which air can be delivered, the air gap being open at the trailing ends of the shroud members and closed at the leading ends thereof, the outer shroud member having a hydrodynamic lifting formation located at the lower external side thereof that is configured and adapted to provide hydrodynamic lift when the watercraft travels through water; and a mounting assembly that is configured and adapted to mount the propeller and the shroud unit to the watercraft.