roerpropellers

Rudder propellers, or roerpropellers, are propulsion devices in which a propeller is used to generate not only forward thrust but also steering moment by directing flow through or near the vessel’s rudder. The concept combines propulsion and steering, typically located at the stern, to augment yaw control, especially at low speeds where rudder effectiveness is limited.

Designs vary. Some configurations place the propeller so that its thrust passes through the rudder blade or stock, enhancing turning by increasing rudder effectiveness. Others embed a propeller in or just behind the rudder assembly, sometimes with a retractable or swiveling feature to extend or reduce its influence as required. The propulsion power may come from a dedicated motor, or be drawn from the main propulsion system via gearing.

Operation and control are coordinated with the vessel’s steering system. The rudder propeller can provide an increased turning moment without large rudder angles, improve maneuverability in tight quarters, and aid station-keeping in docking operations. However, the additional mechanical complexity, potential for flow interference with the hull and rudder, and higher maintenance costs are important considerations.

Applications and historical context vary. Rudder propellers have been implemented on certain ships and submarines where enhanced low-speed maneuverability was desirable or where bow thrusters were unavailable or insufficient. In modern merchant and naval practice, bow thrusters and azimuth thrusters are more common, reducing the reliance on rudder propellers in many applications.

See also: bow thruster, stern thruster, azimuth thruster, rudder.