Abstract: An improved efficiency propulsion system and method of improving the efficiency of a vessel operated in deep and shallow water depths and at constant or variable loaded and ballast waterlines contemplates the use of a variable diameter propeller means capable of varying between a maximum extended diameter D and a minimum effective diameter D mounted on a propeller shaft having an axis of rotation displaced from the bottom keel of the ship a distance less than one-half the maximum diameter D of the propeller means. In this way, because of the use of the variable diameter ship propeller, the propulsion shaft may be located closer than otherwise permissible to the bottom keel of the ship which has the result of lowering the top blade tip trajectory relative to any particular chosen waterline and also providing space for a generally larger diameter more efficient propeller installation.

Abstract: A system is disclosed for safely transferring personnel to and from a sea launch from and to a tanker, a freighter, a bulk carrier, passenger ship or any other vessel or platform relatively larger than the launch or a boat. The system comprises a carrier, which is lifted and lowered by a winch including a hoisting motor, a continuously running tensioning motor, at least one cable connected to said carrier and operatively connected to the tensioning motor and the hoisting motor, and a coupling device disposed between the hoisting motor and the tensioning motor. A weight, which is part of the carrier, or which is suspended underneath, or, alternately, a line attached to the launch and carrier, provides the necessary compensation to the changing personnel weight and allows the carrier to follow motion of the moving deck of the launch.