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Selecting the correct bow thruster   |   Considerations   |   One or two propellers?   |   Installation





Points to consider in selecting the correct Bow Thruster

  It is the thrust of a bow propeller, not the capacity of its electric motor (in kW or hp), which determines its effectiveness. This thrust is the result of the following combined factors: capacity of the electric motor, the propeller (shape, dimensions and number of revolutions) and the efficiency losses in the tunnel. VETUS bow thrusters ensure a thrust of 33 to 40 lbf per kW of the electric motor. Contrary to this, other bow thrusters have been introduced on the market with an effective thrust of no more than 9 lbf per kW!
  • The Propeller
      VETUS applies plastic propellers, which cannot corrode. Due to their low weight, the maximum thrust force is obtained very quickly and with minimum use of energy. The propeller blades are shaped in such a way, that the thrust is equal to both sides. They are also designed with a special view to being used inside a tunnel, thus avoiding cavitation(=unwanted noise!).
     
  • The Tunnel
      The smaller the diameter of the tunnel, the less resistance it will cause to the boat when under way. Moreover, a smaller diameter also allows for a more forward installation into the bow, which enhances the turning moment of the boat. VETUS has obtained the optimum compromise between high efficiency of the bow thruster and little resistance when the boat is under way. For vessels made of steel, aluminum and fiberglass VETUS offers steel, aluminum or fiberglass tunnels.
     
  • The Tailpiece
      Application of a streamlined tailpiece by VETUS not only ensures a better efficiency through lesser resistance but also a lower noise level. Disturbance of the free flow of water through the tunnel, caused by a non- streamlined tailpiece, results in cavitation or, again, unwanted noise! In order to protect the bronze tailpiece against corrosion by electrolysis, a zinc anode is standard supply with each VETUS bow thruster. The transmission gear inside the tailpiece consists of cogwheels, which produce far less noise than chain transmission.
     
  • The Electric Motor
      In order to ensure the highest possible efficiency, in conjunction with an optimum lifespan, VETUS have solely specified electric motors, which are built to Suit the special purpose of being used as bow thruster motors. Contrary to modified starter motors, the VETUS motors allow for continuous running 'at full throttle' during several minutes.
     
  • Installation Possibilities
      The motor of the VETUS bow thruster may be installed in any position i.e. horizontally as well as vertically. The motor is positioned above the propeller at
    all times.

What factors will affect the thrust efficiency?
  The nominal thrust force can only be obtained under optimum conditions and the following factors will influence the efficiency in a negative sense:

  • Low voltage of the power supply to the motor, due to a too low battery 
    voltage or a too large a voltage drop through the battery (main supply) cables.
  • When the actual tunnel/hull connection is not executed in the best possible way; in other words: the shape of the tunnel openings is a discerning factor.
  • When the tunnel openings are provided with grids; also the shape of the grids may cause another reduction of efficiency.


Selecting the correct bow thruster   |   Considerations   |   One or two propellers?   |   Installation


Copyright 2004 Joe Molinaro's East Coast Bow Thrusters; technical information
and graphics copyright 2004