Marine propulsion and constructional details thereof

Abstract

A propeller ( 1 ) comprising a hub, and a plurality of fins ( 3 ) extending radially outwards from the hub, wherein each fin is moveably connected to the hub such that, during rotation of the propeller, the dihedral of each fin can be altered and controlled over a working range by movement of that fin about one or more axes of rotation (BB).

1 . A propeller comprising:
 a hub; and   a plurality of fins extending radially outwards from the hub, wherein each fin is moveably connected to the hub such that, during rotation of the propeller, the dihedral of each fin can be altered and controlled over a working range by movement of that fin about one or more axes of rotation.   
   
   
       2 . A propeller according to  claim 1 , further comprising a closed loop control system to vary the dihedral angle of the fins during use. 
   
   
       3 . A propeller according to  claim 1 , wherein each fin is pivotable about a radial axis so as to control the pitch of that fin. 
   
   
       4 . A propeller according to  claim 1 , wherein each fin is pivotable about an axis generally parallel to the root chord of the fin, so as to vary the dihedral of that fin. 
   
   
       5 . A propeller according to  claim 1 , wherein the fins are discretely moveable about at least one axis between at least two positions. 
   
   
       6 . A propeller according to  claim 1 , wherein the fins are continuously moveable about at least one axis between two positions. 
   
   
       7 . A propeller according to  claim 1 , further comprising dihedral angle control means for moving the fins between first and second positions. 
   
   
       8 . A propeller according to  claim 1 , wherein the dihedral angle control means is arranged to vary the dihedral angle of the fins during use. 
   
   
       9 . A propeller according to  claim 2 , further comprising pitch control means for controlling the pitch of the fins. 
   
   
       10 . A propeller according to  claim 9 , wherein the pitch of the fins is continuously variable. 
   
   
       11 . A propeller according to  claim 8 , wherein the pitch control means is arranged to vary the pitch of the fins during operation. 
   
   
       12 . A propeller according to  claim 1 , further comprising means for varying the dihedral angle of one or more fins during one revolution of the propeller. 
   
   
       13 . A propeller according  claim 1 , further comprising means to vary the pitch of one or more fins during one revolution of the propeller. 
   
   
       14 . A propeller according to  claim 11 , further comprising a closed loop control system to vary the pitch of the fins during use. 
   
   
       15 . A propeller according to  claim 1  in which the propeller is a surface-piercing propeller. 
   
   
       16 . A propeller according to  claim 1 , wherein the range of dihedral angle is independent of the pitch angle. 
   
   
       17 . A propeller according to  claim 1 , wherein each fin has a master spline within a dihedral section of that fin for, in use, aligning the fin in the desired orientation with respect to a hub. 
   
   
       18 . A propeller according to  claim 1 , wherein the centre of pressure of each fin is located at a distance of between 50% and 60% of the working surface span from the root section. 
   
   
       19 . A propeller according to  claim 1 , wherein the centre of pressure of each fin is located at a distance of between 60% and 70% of the mean chord from the trailing edge. 
   
   
       20 . A boat having a hull and at least one propeller, the propeller comprising
 a hub; and   a plurality of fins extending radially outwards from the hub, wherein each fin is moveably connected to the hub such that, during rotation of the propeller, the dihedral of each fin can be altered and controlled over a working range by movement of that fin about one or more axes of rotation;   wherein the hull is provided with a fairing in front of the or each propeller and wherein the fins are moveable such that they may be wholly positioned within the hull or the fairing profile when viewed from the front.   
   
   
       21 . A boat according to  claim 20 , wherein the hub of the propeller is contained wholly within the hull profile when viewed from the front. 
   
   
       22 . A vehicle such as a water craft, ship, aircraft or helicopter having at least two propellers, each of the propellers comprising:
 a hub; and   a plurality of fins extending radially outwards from the hub, wherein each fin is moveably connected to the hub such that, during rotation of the propeller, the dihedral of each fin can be altered and controlled over a working range by movement of that fin about one or more axes of rotation;   wherein at least one propeller is arranged to the starboard side of the longitudinal axis of said vehicle and at least one propeller is arranged to the port side of the longitudinal axis of said vehicle.   
   
   
       23 . A vehicle according to  claim 22 , in which any propeller arranged to the starboard side of the longitudinal axis of said vehicle rotates in the opposite sense to any propeller arranged to the port side of the longitudinal axis of said vehicle. 
   
   
       24 . A vehicle according to  claim 22 , in which any propeller arranged to the starboard side of the longitudinal axis of said vehicle rotates in a clockwise sense when viewed from the rear and any propeller arranged to the port side of the longitudinal axis of said vehicle rotates in a counter-clockwise sense when viewed from the rear. 
   
   
       25 . A craft comprising a hull and at least one propeller comprising
 a hub; and   a plurality of fins extending radially outwards from the hub, wherein each fin is moveably connected to the hub such that, during rotation of the propeller, the dihedral of each fin can be altered and controlled over a working range by movement of that fin about one or more axes of rotation; and   a closed loop control system to vary the dihedral angle of the fins during use;   wherein the control system is arranged to optimise at least one of the following: the trim angle and motion of the craft by varying the dihedral angle of the fins of the propeller(s); the roll motion of the craft by varying the dihedral angle of the fins of the propellers relative to each other; the roll motion of the craft by varying the dihedral angle of the fins of the propellers and their rotational speed relative to each other; the roll motion of the craft by varying the dihedral angle of the fins of the propellers and their pitch angle relative to each other; and the yaw motion of the craft by varying the pitch of the fins of the propellers relative to each other.