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an equivalent size thruster. Additionally, the higher exit velocity of the discharged water increases the relative efficiency as speeds of advance, or currents, increase, as compared to standard tunnel thrusters. Some waterjet bow thrusters can be configured to provide forward and aft auxiliary propulsion, or even full 360-degree thrust.
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A waterjet thruster is a special type of bow thruster that utilizes a pumping device instead of a conventional propeller. The water is discharged through specially designed nozzles which increase the velocity of the exiting jet. Waterjets generally have the advantage of smaller hull penetrations for
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of the tunnel aperture. Ship operators should take care to prevent fouling of the tunnel and impeller, either through use of a protective grate or by cleaning. During vessel design, it is important to determine whether tunnel emergence above the water surface is commonplace in heavy seas. Tunnel
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in the tunnel can create thrust in either direction that makes the ship turn. Most tunnel thrusters are driven by electric motors, but some are hydraulically powered. These bow thrusters, also known as
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driven by a small reversible electric motor which provides thrust in either direction. The added control provided by a bow thruster helps the captain to avoid accidents while docking.
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Tunnel thrusters increase the vessel's resistance to forward motion through the water, but this can be mitigated through proper fairing
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to make it more manoeuvrable. Bow thrusters make docking easier, since they allow the captain to turn the vessel to
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How Bow
Thruster is Used for Maneuvering a Ship? by Marine Insight, September 13, 2012, By Amitava Chakrabarty
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A ship equipped with tunnel thrusters, indicated by the circled "X" markings above the water line
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emergence hurts thruster performance, and may damage the thruster and the hull around it.
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Large vessels usually have one or more tunnel thrusters built into the bow, below the
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Sail
Magazine, on Upgrade: Installing a Bow Thruster, By Roger Marshall, Dec. 3, 2012
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side, without using the main propulsion mechanism which requires some
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A retractable bow thruster lowered under the front of a sailboat
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from 30 to 80 feet (9 to 24 m) in length may have an
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A bow thruster in action. Note the transversal water jet.
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Transverse or steerable propulsion device in a watercraft
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Osmotech UK on Uses and advantages of bow thrusters
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354:. Cambridge University Press. p. 272.
351:Sea Loads on Ships and Offshore Structures
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58:adding citations to reliable sources
159:(front or back, respectively) of a
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238:Externally mounted bow thrusters
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348:Faltinsen, O. (Sep 23, 1993).
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