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Points of attention
while 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! |
Points of attention:
- 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. Yet make sure
that 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, clue 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.
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