Simrad EQ 55, Operator'S Manual

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950-70017001/Iss 1.2 EQ-55 Operators Manual
Page 4.12 Installation Instructions for the EQ-55
Kongsberg Simrad Mesotech Ltd.
Port Coquitlam, BC - Canada
mixed into the boundary layer. The Boundary layer is thin underneath the
forward part of the vessel, and increases in thickness as it moves aftwards. If
the sides of the hull are steep, some of the air bubbles in the boundary layer may
escape to the sea surface along the vessel sides. It is our experience that a wide
and flat bottom, with a rising angle less than around 13 degrees, is prone to
giving air problems for the transducer. In any case a transducer location in the
forward part of the hull is preferred in order to minimize the influence of the
boundary layer.
Figure 4.1 Sketch of the boundary layer underneath the vessel.
4.3.4 Propeller Noise
The propulsion propeller is the dominant noise source on most fishing vessels,
research vessels, merchant vessels and pleasure crafts. The noise is transmitted
through the sea water. Therefore, the transducer should be placed far away
from the propeller, which means on the fore part of the hull. Positions 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 is
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
case at that side of the keel where the propeller blades move downwards.