External Mounting Of Streamlined Transducer - Simrad ES70 - INSTALLATION REV A Installation Manual

Simrad ES70

External mounting of streamlined transducer

Certain transducers have a streamlined housing, and these are designed for installation
outside the hull. These transducers are mainly used on smaller vessels. A location
approximately 0.5 m aside from the keel may be adequate for the passage of water
between the keel and the transducer. The figures illustrate external mounting of
transducers on steel hulls and on wood or polyester hulls respectively.
Smooth surface is important
Mounting screws or bolts must not be extruding from the transducer or the area
immediately around it. Make sure that the surface of the transducer face, the installation
hardware used to mount it, the hull plating and the putty around the transducer is as
even and smooth as possible. Obstructions on these surfaces will create problems with
turbulent flow.
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.
Figure 24 Toe-in principle
A Keel
B Blister
C Toe-in angle
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°.
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