Hydrofoil

Abstract

A hydrofoil for a watercraft comprises a mast as well as a front wing and a rear wing, which are arranged, based on the forward travel direction, one behind the other at a free end portion of the mast. The rear wing is designed as an annular wing and, in addition, includes at least one tubular portion, which is oriented to the forward travel direction in such a way that water is able to flow through said tubular portion counter to the forward direction of travel.

What is claimed is: 
     
         1 . A hydrofoil comprising:
 a mast having a first end portion and a second end portion,   a front wing and a rear wing intended for generating lift and arranged at the second end portion of the mast,   the front wing being designed as a mono-plane wing panel, and   the rear wing being arranged behind the front wing in the flow direction based on a forward travel direction,   wherein the rear wing is designed as an annular wing and additionally has at least one tubular portion which is oriented toward the forward travel direction in such a way that water can flow through said portion counter to the forward travel direction.   
     
     
         2 . The hydrofoil of  claim 1 , wherein the annular wing has exactly one tubular portion, the longitudinal axis of which is oriented in the forward travel direction. 
     
     
         3 . The hydrofoil of  claim 1 , wherein the annular wing has two tubular portions arranged in parallel with each other. 
     
     
         4 . The hydrofoil of  claim 3 , wherein the tubular portions are mutually spaced apart transversely with respect to the forward travel direction and interconnected by means of a bridge. 
     
     
         5 . The hydrofoil of  claim 1 , wherein the at least one tubular portion has a constant through-flow cross section throughout its axial length or has at least a portion that has a constant through-flow cross section. 
     
     
         6 . The hydrofoil of  claim 1 , wherein the at least one tubular portion has throughout its axial length a through-flow cross section that narrows or widens in the through-flow direction or has at least a portion that has a through-flow cross section that narrows or widens in the through-flow direction. 
     
     
         7 . The hydrofoil of  claim 1 , wherein the at least one tubular portion, in the through-flow cross section thereof and/or upstream of said cross section, has one or more struts that extend transversely with respect to the through-flow direction. 
     
     
         8 . The hydrofoil of  claim 1 , wherein the annular wing and the front wing are interconnected by means of a connecting rod which is in turn connected to the mast, the annular wing and the front wing being spaced apart from the mast. 
     
     
         9 . The hydrofoil of  claim 8 , wherein the connecting rod, based on the vertical direction of the hydrofoil, is level with the through-flow cross section of the at least one tubular portion. 
     
     
         10 . The hydrofoil of  claim 8 , wherein the connecting rod, based on the vertical direction of the hydrofoil, is arranged below or above the through-flow cross section of the at least one tubular portion. 
     
     
         11 . The hydrofoil of  claim 1 , wherein the at least one tubular portion forms an inlet edge which extends in a plane, perpendicular to the inflow. 
     
     
         12 . The hydrofoil of  claim 1 , wherein the at least one tubular portion forms an inlet edge which extends in a plane that is inclined with respect to the inflow at an angle of more than 0° up to a maximum of 20°. 
     
     
         13 . The hydrofoil of  claim 1 , wherein the at least one tubular portion has a continuous longitudinal slot in the through-flow direction. 
     
     
         14 . The hydrofoil of  claim 1 , wherein one or more outwardly projecting outer wings are arranged on the outer circumference of the at least one tubular portion. 
     
     
         15 . A hydrofoil comprising:
 a mast having a first end portion and a second end portion,   a front wing and a rear wing intended for generating lift and arranged at the second end portion of the mast,   the front wing being designed as a mono-plane wing panel, and   the rear wing being arranged behind the front wing in the flow direction based on a forward travel direction,   wherein the rear wing is designed as an annular wing and additionally has at least one tubular portion which is oriented toward the forward travel direction in such a way that water can flow through said portion counter to the forward travel direction,   wherein the annular wing and the front wing are interconnected by means of a connecting rod which is in turn connected to the mast, the annular wing and the front wing being spaced apart from the mast, and   wherein the at least one tubular portion, in the through-flow cross section thereof, has one or more struts that extend transversely with respect to the through-flow direction.   
     
     
         16 . The hydrofoil of  claim 15 , wherein the rear wing is detachably connected to the connecting rod. 
     
     
         17 . The hydrofoil of  claim 15 , wherein the rear wing is connected to an axial end of the connecting rod. 
     
     
         18 . The hydrofoil of  claim 15 , wherein connecting rod has a diameter within a range of 10 to 25 mm. 
     
     
         19 . The hydrofoil of  claim 15 , wherein the struts extend across the center of the cross-section of the tubular portion. 
     
     
         20 . A board equipped with a hydrofoil, said hydrofoil comprising:
 a mast having a first end portion and a second end portion,   a front wing and a rear wing intended for generating lift and arranged at the second end portion of the mast,   
       the front wing being designed as a mono-plane wing panel, and
 the rear wing being arranged behind the front wing in the flow direction based on a forward travel direction, 
 wherein the rear wing is designed as an annular wing and additionally has at least one tubular portion which is oriented toward the forward travel direction in such a way that water can flow through said portion counter to the forward travel direction.