Technical information

EQ-55 Operators Manual 950-70017001/Iss 1.
2
Installation Instructions for the EQ-55 Page 4.1
3
Kongsberg Simrad Mesotech Ltd.
Port Coquitlam, BC - Canada
Bow thrusters are awful machines. When they are 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.
4.3.5 Vessel Heave
Heave is the up and down movement of the vessel. It disturbs the echo traces in
the echogram, so that a flat bottom is displayed as a wave. A transducer
location in the middle of the vessel minimizes the influence of vessel roll and
pitch.
4.3.6 Noise From Protruding Objects on the Hull
Objects protruding from the hull, such as zinc anodes, sonar transducers or even
the vessel’s keel, generate turbulence and flow noise. Also holes and pipe outlets
are noise sources. They may act as resonant cavities amplifying the flow noise
at certain frequencies. Do not place an echo sounder transducer in the vicinity
of such objects, and especially not close behind them.
4.3.7 Summing up on Transducer Location
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 of the hull at the water line, see Figure 4.2. If the vessel hull has a
bulbous bow, this may well be a good transducer location, but also here must be
taken into consideration the flow pattern of the aerated water. Often the
foremost part of the bulb is preferable as shown in Figure 4.3.