Foil arrangement for a boat and a method for installing the same

Abstract

A hydrofoil arrangement for a boat includes a fastening device, first and second rigid elements, and a main hydrofoil. The fastening device is fastened on an outside of a hull below a waterline of the resting boat. The first rigid element pivots in a first pivot plane into and out of engagement with the hull, vertical and parallel to a forward direction. The second rigid element is connected to the first rigid element and extends at an angle to the first rigid element so that a second end of the second rigid element is at a vertical distance from the hull. The main hydrofoil is fastened to the second end of the second rigid element. The first rigid element can be pivoted downwards and backwards, and thereafter upwards and further backwards, to a position where its second end is arranged stern of the hull. A method is also described.

1 . A hydrofoil arrangement for a boat comprising a hull, the hydrofoil arrangement comprising: 
 a fastening device arranged to be fastened on an outside of the hull in a position below a waterline of the hull when the hull does not move through the water;   a pivot point arranged at a stern of the hull;    a first rigid element, the first rigid element being elongated and having a first end and a second end, the first rigid element further being arranged to be pivotally connected at the first end to the pivot point so that the first rigid element can pivot in a first pivot plane to a first pivot position where the first rigid element is fastened to the hull by means of the fastening device as well as to a second pivot position where the first rigid element is not fastened to the hull by means of the fastening device, the first pivot plane being substantially vertical and substantially parallel to a forward direction of the boat;    a second rigid element, the second rigid element being elongated and comprising a first end and a second end, the first end of the second rigid element being connected to the second end of the first rigid element, the second rigid element being arranged to extend at an angle to the first rigid element when the first rigid element is fastened to the fastening device so that the second end of the second rigid element is at a vertical distance from the hull; and    a main hydrofoil, fastened to the second end of the second rigid element,    wherein the first rigid element can be pivoted from the first position so that its second end moves downwards and backwards, and thereafter upwards and further backwards, to a third position where its second end is arranged stern of the hull.   
     
     
         2 . The hydrofoil arrangement of  claim 1 , wherein a length of the first rigid element between its first and second ends is longer than a length of the second rigid element between its first and second ends. 
     
     
         3 . The hydrofoil arrangement of  claim 1 , wherein the second rigid element is connected to the first rigid element at a point aligned with, or ahead of, a mass center of the boat, when the first rigid element is fastened to the fastening device. 
     
     
         4 . The hydrofoil arrangement of  claim 1 , wherein the first rigid element is pivotally connected to the second rigid element. 
     
     
         5 . The hydrofoil arrangement of  claim 1 , further comprising: 
 a stern hydrofoil, arranged to be fastened at the stern of the hull, the stern hydrofoil preferably being smaller than the main hydrofoil.   
     
     
         6 . The hydrofoil arrangement of  claim 1 , wherein the hydrofoil arrangement has no other hydrofoils apart from the main hydrofoil and the stern hydrofoil. 
     
     
         7 . The hydrofoil arrangement of  claim 1 , wherein the hydrofoil arrangement further comprises an attack angle actuator, arranged to adjust an attack angle of the main hydrofoil, the attack angle actuator being arranged to transfer a first force along the first rigid element to a second force along the second rigid element, the second force forcing the main hydrofoil to pivot so as to set its attack angle, the attack angle actuator comprising a force transfer element at a connection between the first rigid element and the second rigid element, the force transfer element being arranged to apply the second force in reaction to the first force. 
     
     
         8 . The hydrofoil arrangement of  claim 1 , wherein the main hydrofoil comprises a port part and a starboard part that are individually pivotable to individually set an attack angle of the port part and the starboard part. 
     
     
         9 . The hydrofoil arrangement of  claim 8 , wherein the port part and the starboard part are interconnected by a flexible section, allowing the main hydrofoil to twist under torsional force. 
     
     
         10 . The hydrofoil arrangement of  claim 1 , wherein the main hydrofoil has a lateral length being the same as a lateral width of the hull within ±50%. 
     
     
         11 . The hydrofoil arrangement of  claim 1 , further comprising: 
 two first rigid elements, the two first rigid elements being arranged to pivot backwards on either lateral side of a propeller axle of the boat.   
     
     
         12 . The hydrofoil arrangement of  claim 1 , further comprising: 
 two second rigid elements, the two second rigid elements being connected to the main hydrofoil at different points along the main hydrofoil in relation to each other in a lateral direction of the hull, one such connection point being arranged at a port side of the hull and one such connection point being arranged at a starboard side of the hull.   
     
     
         13 . The hydrofoil arrangement of  claim 1 , further comprising: 
 a first locking mechanism, arranged to releasably lock the second end of the first rigid element to the fastening device; and    a second locking mechanism, arranged to releasably lock the first end of the second rigid element in a set angular orientation in relation to the fastening device and/or to the first rigid element.   
     
     
         14 . The hydrofoil arrangement of  claim 1 , wherein the first rigid element is pivotable from the third position so that the second end of the first rigid element moves upwards and forward, to a fourth position where the second end of the first rigid element is arranged above a propeller axle of the boat. 
     
     
         15 . The hydrofoil arrangement of  claim 1 , further comprising: 
 a propulsion position setting device, arranged to set a vertical height of a propeller axle of the boat, such as a sterndrive or outboard motor of the boat.   
     
     
         16 . The hydrofoil arrangement of  claim 1 , wherein the hydrofoil arrangement is fastened to the hull to a sternwise-facing surface, of the hull. 
     
     
         17 . A method for installing a hydrofoil arrangement according to  claim 1 , the method comprising: 
 providing a boat having a hull; and    fastening the pivot point of the hydrofoil arrangement to a stern of the hull and fastening the fastening device to a bottom of the hull.   
     
     
         18 . The method of  claim 17 , further comprising: 
 fastening an outboard motor to a propulsion position setting device of the hydrofoil arrangement so that the outboard motor can be raised and lowered by the propulsion position setting device.   
     
     
         19 . The method of  claim 17 , further comprising: 
 fastening a sterndrive to a propulsion position setting device of the hydrofoil arrangement so that the sterndrive can be raised and lowered by the propulsion position setting device; and   connecting the sterndrive to a drive shaft of the boat via a universal joint.   
     
     
         20 . The method of  claim 17 , wherein the boat is an existing boat and the installation of the hydrofoil arrangement is a retrofit of the hydrofoil arrangement.