The present invention discloses a marine fishtail rudder, including a rudder blade, a first tail plate and a second tail plate. The rudder blade includes a first rudder surface and a second rudder surface. The first tail plate is hinged on the first rudder surface. The second tail plate is hinged on the second rudder surface. An electric motor is provided in the rudder blade. The electric motor is used to drive the first tail plate and the second tail plate to rotate, so that a trailing edge of the first tail plate and a trailing edge of the second tail plate are close to or away from a trailing edge of the rudder blade. The present invention discloses a marine fishtail rudder, wherein tail plates are respectively arranged on the two rudder surfaces of a rudder tail portion, and the tail plates are rotated by an electric motor. When steering, the tail plates are unfolded to form a rudder shape of a fishtail rudder to obtain a higher rudder effect. When sailing straight or reversing, the tail plates are closed to form a rudder shape of a streamlined rudder and reduce the resistance of the rudder.

Disclosed is a propulsion unit for propelling a vessel. The propulsion unit comprises a main body configured to be arranged at a keel of the vessel and comprising a pivot point, a fin being movably arranged in relation to the main body, and an actuator assembly for generating a heave motion of the fin in relation to the main body. The actuator assembly comprises at least one actuator. The fin is connected to the pivot point, such that the fin is arranged to pivot around the pivot point when the at least one actuator generates the heave motion of the fin, thereby generating a pitch motion of the fin.

A rudder for as ship is described, comprising a rudder blade (10) which is fastened via a rudder stock (32) to the aft end (16) of the ship, where the rudder blade (10) is a rudder blade of the suspension type, comprising a first rudder blade part (12) and a second rudder blade part (14), arranged above and below each other, respectively, the rudder stock (32) is mounted and fastened to the rudder blade (10) and extends up into the aft end (16) of the ship, where the rudder stock is coupled at the upper end to a steering gear (20) arranged at the aft end (16) of the ship. An outer tube (34) is arranged about the rudder stock (32) where the outer tube (34) is fastened in the first, upper rudder blade part (12) and the aft end (16) of the ship, respectively, and that the rudder stock (32) extends through the outer tube (34) and down into the second, lower rudder blade part (14).

A steering system on a marine vessel includes at least one propulsion device, a steering actuator that rotates the propulsion device to effectuate steering, at least one trim device moveable to adjust a running angle of the vessel, and a trim actuator configured to move the trim device so as to adjust the running angle. The system further includes a control system configured to determine a desired roll angle and at least one of a desired turn rate and a desired turn angle for the marine vessel based on a steering instructions. The control system then controls the steering actuator to the rotate the at least one propulsion device based on the desired turn rate and/or the desired turn angle, and to control the trim actuator to move the at least one trim device based on the desired roll angle so as to effectuate the steering instruction.

The present invention discloses a marine fishtail rudder, including a rudder blade, a first tail plate and a second tail plate. The rudder blade includes a first rudder surface and a second rudder surface. The first tail plate is hinged on the first rudder surface. The second tail plate is hinged on the second rudder surface. An electric motor is provided in the rudder blade. The electric motor is used to drive the first tail plate and the second tail plate to rotate, so that a trailing edge of the first tail plate and a trailing edge of the second tail plate are close to or away from a trailing edge of the rudder blade. The present invention discloses a marine fishtail rudder, wherein tail plates are respectively arranged on the two rudder surfaces of a rudder tail portion, and the tail plates are rotated by an electric motor. When steering, the tail plates are unfolded to form a rudder shape of a fishtail rudder to obtain a higher rudder effect. When sailing straight or reversing, the tail plates are closed to form a rudder shape of a streamlined rudder and reduce the resistance of the rudder.

A steering system on a marine vessel includes at least one outboard drive configured to propel the marine vessel, a steering actuator configured to rotate the at least one outboard drive, at least one trim device coupled to the marine vessel and movable with respect to a hull of the marine vessel to adjust a running angle thereof, and at least one trim actuator. A control system configured to determine a desired roll angle and at least one of a desired turn rate and desired turn angle for the marine vessel based on a steering instruction and control the steering actuator to rotate the at least one outboard drive based on the desired turn rate and/or the desired turn angle and control the at least one trim actuator to move the at least one trim device based on the desired roll angle to effectuate the steering instruction.

Disclosed are watercrafts with rotatable air propulsion steering units and retractable measurement instruments. The watercraft can include a substantially flat bottom, a top deck, a rotatable air propulsion steering unit configured to propel the watercraft and to rotate in order to steer the watercraft when the watercraft is submerged in a liquid body without requiring a submerged rudder steering system under the substantially flat bottom. The watercraft can also include a retractable measurement deck configured to alternatively raise measurement instruments above the liquid body and lower into the liquid body.

Disclosed are watercrafts with rotatable air propulsion steering units and retractable measurement instruments. The watercraft can include a substantially flat bottom, a top deck, a rotatable air propulsion steering unit configured to propel the watercraft and to rotate in order to steer the watercraft when the watercraft is submerged in a liquid body without requiring a submerged rudder steering system under the substantially flat bottom. The watercraft can also include a retractable measurement deck configured to alternatively raise measurement instruments above the liquid body and lower into the liquid body.

A trimmable rudder system for a marine vessel such as a planing power boat, the system including a pair of rudder assemblies, each of which includes a rudder blade movably coupled to the hull by way of a ball-and-socket joint. Each rudder assembly includes a rudder shaft that extends from the rudder blade through the ball-and-socket joint and can be rotated for rotating the rudder blade to steer the power boat. Each rudder shaft may be operably coupled to a pair of actuators configured to control trim and camber positions of the rudder blade so that the pair of rudder blades can collectively achieve a desired hull trim change, including listing control and planing control of the power boat. Steering position, trim position, and camber position of the rudder blades may be simultaneously changed.

A method of controlling steering of a marine vessel includes receiving a steering input from an operator-controlled steering input device, determining a desired turn rate for the marine vessel and a desired roll angle for the marine vessel based on the steering input, and controlling a steering angle of at least one trimmable propulsion device based on the desired turn rate and controlling a trim deployment of a pair of trim tabs and/or the trimmable propulsion device based on the desired roll angle so as to steer the marine vessel according to the steering input.