A method and device is provided for increasing the efficiency of jet drives by recuperating effective power from the propulsion flow. A ducted propeller in the propeller housing, driven by a driving engine via a drive shaft, conveys the fluid for the jet drive out of the interior V.sub.i of a radial turbine. The fluid is accelerated axially and ejected backwards against the direction of travel. This creates thrust. Because the pressure in the interior of the turbine decreases, new fluid from the environment flows directly via the blades of the rotating radial turbine from the outside to the inside, thereby driving them. A guide apparatus is missing. The power of the radial turbine is transmitted via a transmission to the drive shaft of the propeller, which relieves the driving engine and increases the efficiency of the jet drive. The invention is particularly suitable for electric drives.

A water sports device is provided, and includes at least one propulsion device which has at least one motor. The motor can be controlled by a control unit and is provided for propelling the water sports device. The parts of the propulsion device are arranged on sides of the foil and/or retaining device or—if separate connection elements are arranged between these two devices—between these two devices, and can be moved with the foil device from a starting and/or resting position into the operating position and back. In order to propel or pull the water sports device, the device has its own propulsion device. This is part of the retaining and/or foil device, which can move relative to the floating body, in that at least one propulsion element in the form of a propeller or impeller accelerating water against the principal direction of movement is moved with the respective device (retaining and/or foil device).

A water sports device is provided which is configured for self-stabilization. The water sports device includes an active stabilization means, in the case of which the control unit provides control signals for actuators of the water sports device, actuators being active adjusting means. These can be a motor of the propulsion apparatus, adjustable flaps or nozzles, or adjustable fins, rudders, hydrofoils or individual adjustable sections thereof. Input data such as data about the position of the water sports device, power output of the propulsion apparatus, speed, acceleration and/or user inputs are evaluated in the control unit, and control commands for an actuator or a plurality of actuators are generated.

A water sports device is provided in which a propulsion device has at least one sensor arrangement which is usable for position determination. A control unit of the water sports device is designed for generating control signals on the basis of signals from the sensor arrangement for the purpose of geofencing and/or homing. One or more controllable elements of the water sports device are activated by means of the control signals. Such elements may include a motor of the propulsion device, movable means for generating an alignment of a water jet (e.g. a wing, motor, rudder blade, a fin and/or nozzle), and/or retractable and extendable elements (a centerboard, a holding and/or hydrofoil device) which influence the floating properties of the water sports device.

A novel watercraft propulsion device is disclosed that includes multiple propulsive elements improving power and efficiency over prior designs. A self-adjusting variable pitch propeller is combined with a water jet and an exhaust driven turbine to provide optimal thrust and efficiency across the range of engine power, load and watercraft speed. In the preferred embodiment, propulsive elements are axially disposed around a central drive shaft and exhaust port with the combined water jet/exhaust turbine disposed closest to drive shaft and the variable pitch propeller attached to the exterior of the water jet housing. A rotating duct is fixed to the propeller blades and rotates with the blades to reduce cavitation. Combined apparatus provides increased performance and efficiency over all watercraft speeds/load as well as additional safety due to the ducted propeller.

A method for controlling a marine vessel having first and second steering nozzles and first and second trim deflectors comprises generating at least a first set of actuator control signals and a second set of actuator control signals. The first set of actuator control signals is coupled to and controls the first and second steering nozzles, and the second set of actuator control signals is coupled to and controls the first and second trim deflectors. The acts of generating and coupling the first set of actuator control signals and the second set of actuator control signals result in inducing any of a net yawing force, a net rolling force, and a net trimming force to the marine vessel without inducing any other substantial forces to the marine vessel by controlling the first and second steering nozzles and the first and second trim deflectors. Also disclosed is a system for controlling a marine vessel.

A method for controlling a marine vessel having first and second steering nozzles and first and second trim deflectors comprises generating at least a first set of actuator control signals and a second set of actuator control signals. The first set of actuator control signals is coupled to and controls the first and second steering nozzles, and the second set of actuator control signals is coupled to and controls the first and second trim deflectors. The acts of generating and coupling the first set of actuator control signals and the second set of actuator control signals result in inducing any of a net yawing force, a net rolling force, and a net trimming force to the marine vessel without inducing any other substantial forces to the marine vessel by controlling the first and second steering nozzles and the first and second trim deflectors. Also disclosed is a system for controlling a marine vessel.

An underwater motor module for a water sports device is provided, which forms at least one flow channel each having at least one inlet opening and an outlet opening. The underwater motor module has a motor which is in the form of an internal rotor motor and comprises a hollow rotor, which concomitantly forms the flow channel by way of its inner side. On the outer side of the motor directed away from the flow channel is mounted outside the flow channel, and which bears blades. The motor also comprises an external stator arranged in a housing.

An underwater motor module for a water sports device is provided, which forms at least one flow channel each having at least one inlet opening and an outlet opening. The underwater motor module has a motor which is in the form of an internal rotor motor and comprises a hollow rotor, which concomitantly forms the flow channel by way of its inner side. On the outer side of the motor directed away from the flow channel is mounted outside the flow channel, and which bears blades. The motor also comprises an external stator arranged in a housing.

A small watercraft system includes: a watercraft body; a watercraft body manipulation member through which a watercraft body manipulation command is input by an operator; a drive source that allows the watercraft body to plane; a steering device that allows the watercraft body to be steered; and a control device that controls the drive source and the steering device to operate the watercraft body. The control device determines whether a mode switching condition is satisfied, the mode switching condition including an operator's absence condition that the operator is absent from the watercraft body. Upon determining that the mode switching condition is satisfied, the control device executes an operator-absent manipulation mode in which the control device moves the watercraft body by controlling the drive source and the steering device based on an operator-absent manipulation command independent of the watercraft body manipulation command.