If you’ve ever sailed in a cabin close to the bow of the ship, you may have been woken up in the early hours by a loud vibration as the ship is maneuvering into her berth at the pier. Well that vibration is caused by the ships bow thrusters.
A bow thruster is a transversal propulsion device installed at the bow (front) of a vessel, allowing for sideways movement without requiring forward motion. In layman’s terms, it’s a sideways propeller that’s built into the the hull and located fully underwater. Because it’s sideways, perpendicular to the ship, by pushing water to one side, bow thrusters generate force in the opposite direction, enabling sideways movement. This allows for precise control when docking, navigating through congested waters, or handling adverse weather conditions to stay stationary. Bow thrusters tend to only work when speed through water is less than 3 knots.
Ships that have a traditional shaft and rudder setup will also have stern thrusters in addition to the bow ones. Because there is already maneuverability in the stern section, typically there are fewer thrusters in the stern. If the ship has azimuthing pods instead of rudders, then you can forgo stern thrusters entirely.
Benefits of Bow Thrusters
The integration of bow thrusters provides numerous advantages, including enhanced maneuverability, which enables precise control, especially in confined spaces like marinas and ports. They also improve safety by reducing the risk of collisions through quick course corrections. Additionally, bow thrusters simplify docking and undocking procedures, often minimizing the need for tugboat assistance, thereby reducing port costs. They contribute to increased fuel efficiency by minimizing unnecessary engine use during maneuvering, leading to fuel savings over time. Furthermore, bow thrusters enhance performance in adverse conditions by counteracting wind and currents, providing stability and directional control. This is commonly used when alongside piers during gusty conditions or during tendering operations to keep the ship in one place.
History
The concept of bow thrusters dates back to the mid-20th century. In 1955, two british divers, Lionel Crabb and Sydney Knowles, were covertly sent to dive on a Soviet naval vessel, the Sverdlov (Свердлов) to better understand why she was so maneuverable. The two divers discovered a circular opening at the ship’s bow containing a large, steerable propeller. This innovation provided the vessel with enhanced maneuverability, inspiring further development of bow thruster technology by western powers. Since then, bow thrusters have evolved significantly, becoming a standard feature in modern naval engineering.
Conclusion
Bow thrusters have revolutionized modern marine navigation, providing ship operators with the ability to maneuver into and out of harbors without the need of tugs.
Hopefully this post has shed light on why your cabin can shake so much when four 7,400 hp thrusters fire up to help the ship laterally slip in alongside her berth.