Disclosed is a system for reducing blade tip vortex cavitation by controlling mass flow. The system reduces blade tip vortex cavitation that occurs around blades of a propulsive propeller of a ship when the propulsive propeller rotates to generate force required to propel the ship across the sea by forming a plurality of flow holes in the propeller blades and controlling mass flow through the plurality of flow holes, i.e., appropriately discharging water to the outside or suctioning outside water through the plurality of flow holes, thereby reducing underwater noise and vibration of the hull. The system includes a propeller, a water feeding pipe, a water supply/suction unit, and a controller.

A pontoon for providing buoyant force to a floating craft comprises a barrel having front and rear ends and a fin extending outwardly from an outer surface of the barrel. The fin includes a first portion and a second portion positioned rearwardly of the first portion. The first portion extends at least generally parallel with or coincident with a lateral, horizontally extending centerline of the barrel. In order to enhance stability, improve handling, and/or inhibit motor cavitation, the second portion is inclined downwardly and rearwardly relative to the rear end of the first portion. Also disclosed is a pontoon boat fitted with fins on the pontoons and/or on the transom.

A pontoon for providing buoyant force to a floating craft comprises a barrel having front and rear ends and a fin extending outwardly from an outer surface of the barrel. The fin includes a first portion and a second portion positioned rearwardly of the first portion. The first portion extends at least generally parallel with or coincident with a lateral, horizontally extending centerline of the barrel. In order to enhance stability, improve handling, and/or inhibit motor cavitation, the second portion is inclined downwardly and rearwardly relative to the rear end of the first portion. Also disclosed is a pontoon boat fitted with fins on the pontoons and/or on the transom.

Disclosed is a method of decreasing pressure fluctuation induced on a surface of a hull due to propeller cavitation by adjusting a relative rotation angle of propellers of a twin-propeller ship.

A marine vessel comprising: at least one buoyant tubular foil; and at least one baffle plate positioned about the perimeter of the at least one buoyant tubular foil so as to protrude into the flow of water passing by the perimeter of the at least one buoyant tubular foil, whereby to create a high-pressure zone fore of the at least one baffle plate and a low-pressure zone immediately aft of the at least one baffle plate, whereby to create a dense stream of supercavitated water immediately aft of the at least one baffle plate.

A marine vessel comprising: at least one buoyant tubular foil; and at least one baffle plate positioned about the perimeter of the at least one buoyant tubular foil so as to protrude into the flow of water passing by the perimeter of the at least one buoyant tubular foil, whereby to create a high-pressure zone fore of the at least one baffle plate and a low-pressure zone immediately aft of the at least one baffle plate, whereby to create a dense stream of supercavitated water immediately aft of the at least one baffle plate.

This disclosure is related with propeller noise and cavitation abatement in applications like propulsion, ventilation, pumping or turbine systems on fluids by novel techniques that allows stronger propellers with improved laminar flow by means of a propeller which consists on a rotating cylindrical block or a truncated substantially conical block with one or more tunnels around it rotational axis, said block also may have flow-guiding structures at both ends that help to keep the fluid's laminar flow when it is mixing fluids with its environment, having the rotating block tunnels with either substantially circular shaped cross-section or variable shape cross-section from substantially circular to irregular oval measured in perpendicular plane to the rotational axis whereby it smoothly accelerates fluid or gas by means of either centrifugal or axial movement, also including Dynamic Balance or Imbalance or Torque Modulation Means that modulate specific vibrations which generates sound waves.

This disclosure is related with propeller noise and cavitation abatement in applications like propulsion, ventilation, pumping or turbine systems on fluids by novel techniques that allows stronger propellers with improved laminar flow by means of a propeller which consists on a rotating cylindrical block or a truncated substantially conical block with one or more tunnels around it rotational axis, said block also may have flow-guiding structures at both ends that help to keep the fluid's laminar flow when it is mixing fluids with its environment, having the rotating block tunnels with either substantially circular shaped cross-section or variable shape cross-section from substantially circular to irregular oval measured in perpendicular plane to the rotational axis whereby it smoothly accelerates fluid or gas by means of either centrifugal or axial movement, also including Dynamic Balance or Imbalance or Torque Modulation Means that modulate specific vibrations which generates sound waves.

A method is for making a marine drive for propelling a marine vessel in water. The method includes providing a gearcase; installing a propeller shaft assembly that extends forwardly from the gearcase; coupling front and rear propellers to the propeller shaft assembly, forwardly of the gearcase, such that rotation of the propeller shaft assembly causes rotation of the front and rear propellers, respectively, which thereby propels the marine vessel in the water; and reducing deleterious effects of cavitation on the gearcase by the combination of forming the gearcase with a wide trailing end portion, in particular to maintain pressure alongside the gearcase, and configuring the front and rear propellers so that the front propeller absorbs more torque/thrust load than the rear propeller during said rotation.

A method is for making a marine drive for propelling a marine vessel in water. The method includes providing a gearcase; installing a propeller shaft assembly that extends forwardly from the gearcase; coupling front and rear propellers to the propeller shaft assembly, forwardly of the gearcase, such that rotation of the propeller shaft assembly causes rotation of the front and rear propellers, respectively, which thereby propels the marine vessel in the water; and reducing deleterious effects of cavitation on the gearcase by the combination of forming the gearcase with a wide trailing end portion, in particular to maintain pressure alongside the gearcase, and configuring the front and rear propellers so that the front propeller absorbs more torque/thrust load than the rear propeller during said rotation.