Installation manual

Simrad 50-7
outside the direct line of sight from the propeller are favourable.
On small vessels with short distances it is advised to mount the
transducer on that side of the keel where the propeller blades
move upwards, because the propeller cavitation i s strongest on
the other side. The cavitation starts most easily when the water
flows in the same direction as the propeller blade, and that is to
some degree the c ase at that side of the keel where the propeller
blades move downwards.
Bow thruster propellers are extremely noisy. When in operation,
the noise and cavitation bubbles make the echo sounder useless,
almost no matter where the transducer is installed. And when not
in operation, the tunnel creates turbulence, and if the vessel is
pitching, the tunnel may be filled with air or aerated water in the
upper position and release this in the lower position. Therefore,
an echo sounder transducer should be placed well away from
the bow thruster.
Inclination of the transducer face
Ideally, the transducer face should be mounted in parallel with the
sea surface when the vessel is in normal trim, as this will provide
the most accurate echo information. However, it is also very
important that the w
ater flow over the transducer face is laminar.
In order to ensure l aminar flow, the transducer face may be tilted
slightly upwards in relation to the water fl ow. This allows the
flowing water to meet the face directly, and assures laminar flow.
The inclination angle must however be determined carefully. The
angle must be small on transducers with narrow beam angles. A s
a rule of thumb, mount transducers with beam angles smaller
than seven degrees with minimum inclination angle. The smaller
beam angle your transducer has, the smaller the i nclination angle
can be.
Ensure that you do not mount the transducer with a negative
inclination a ngle. This may cause turbulence under the transducer
face, and reduced echo sounder performance.
Summary and general recommendation
Some of the above guide lines are conflicting, and each case has
to be treated individually in order to find the best compromise.
Generally the propeller noise is the dominant factor, and a
recommended transducer location is in the fore part of the hull,
with maximum distance from the bow equal to one third of the
total length o f the hull a t the water line.
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