Marine propulsion and constructional details thereof

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.

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.

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.