Patent ID: 8863681
Filing Date: 2014-10-21
Classification: B63B

Abstract:
1. A hydrofoil comprising: a first face and a second face, at least one of the first and second face including discontinuities to induce separation of a flow from a surface of each of the first and second faces and the formation, above a ventilation speed, of a downstream cavity defined by a first cavity surface extending from the first face and a second cavity surface extending from the second face, the cavity surfaces being downstream of the discontinuities of the first and second face, downstream of the discontinuities, the first and second faces are configured to deflect the flow to provide a changed lift and or drag and or pitching moment when operating at speeds below the ventilation speed; wherein the discontinuities are on the second face, the discontinuities comprising a first discontinuity, and a second discontinuity downstream of the first discontinuity, the second face being progressively angled at each of the first and second discontinuities to further deflect the unventilated flow, producing an increased lift coefficient, the progressive angling of the second face being configured to provide a reduction in pressure coefficient with each downstream discontinuity such that, in operation, ventilation develops in steps with increasing speed starting at a hydrofoil trailing edge and successively extending to each discontinuity until a foremost second face discontinuity is reached; an attaching strut attaching the hydrofoil to a hydrofoil vessel; wherein the attaching strut provides communication between air above the water surface to the hydrofoil under the water surface when the hydrofoil is in a ventilated mode of operation; wherein the attaching strut further comprises a plurality of surface discontinuities; and wherein at least one of the plurality of surface discontinuities of the attaching strut extends from the hydrofoil part way along the attaching strut towards a water surface, the at least one of the plurality of surface discontinuities of the attaching strut providing communication of air above the water surface to the hydrofoil under the water surface when the hydrofoil is in the ventilated mode of operation.