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Figure 5 Toe-in principle
Keel
A
Blister
B
Toe-in angle
C
338462/B
We recommend that large diameter transducers are fitted with a
horizontal U-shaped support bar. This bar can then be secured
to the mounting ring using threaded rods.
The transducer cable penetrates the hull in a stuffing tube. Leave
an adequate loop of the cable behind the transducer for easy
mounting or removal of the transducer.
Toe-in
The primary consideration must be to allow laminar water flow.
In most cases this is achieved by designing the blister in parallel
with the keel. However, if the blister is located close to the bow,
the front of the blister may have a few degrees toe-in towards
the bow.
The angle must be chosen to allow for most efficient water flow.
It will vary with the location of the transducer; the depth below
the hull, the distance from the bow, and the distance to the keel.
Typical angles are from 0 to 3° on deplacement hulls. On planing
hulls, the angle is normally close to 0°.
Physical location
The blister is placed on one of the sides of the hull, and the
distance from the keel is a trade off between a close distance
giving a turbulent flow of water in a narrow passage, and a large
distance bringing the transducer higher up and also more affected
by vessel roll. Normally a distance of approximately 1 m is a
good compromise.
How to install the transducer
13
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