Simrad ES120-7C - REV D, Installation Manual, Page: 74 / 98

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Slamming
Slamming happens if the vessel hull climbs out of the water in heavy seas. The force of
the water when the hull falls down may push the transducer up, and may cause damage
both to the transducer and to its mounting. This is especially important for low frequency
transducers with large faces. The effect of slamming can be reduced by mounting the
transducer as deep as possible on the hull.
Note
Kongsberg Maritime AS takes no responsibility for any damages to the transducer, the cable
or the mounting arrangement, caused by slamming.
Avoid protruding objects near the transducer
Objects protruding from the hull will generate turbulence and flow noise. This will reduce
the ES120-7C performance.
Protruding objects may be zinc anodes, transducers or even the vessel's keel. Holes and pipe
outlets are also important noise sources, as well as rough surfaces caused by bad welding.
Even traces of sealing compound, sharp edges, bolts or empty bolt holes will create noise.
All these protruding objects may act as resonant cavities amplifying the flow noise at
certain frequencies.
Do not place a transducer in the vicinity of protruding objects, and especially not close
behind them. Make sure that the surface of the transducer face, the hull plating and putty
around the transducer is as even and smooth as possible. Mounting screws or bolts must not
be extruding from the transducer, the installation hardware or the hull plating. If necessary,
grind and polish all surfaces.
Mount the transducer at forward part of hull to
minimize the effects from the flow boundary
water layer
The upper water layers of the sea contain a myriad of small air bubbles created by the
breaking waves. When the hull moves through water it will cause a disturbance, and this
will generate friction. The friction zone is called the
flow boundary layer .
The flow in this boundary layer may be laminar or turbulent .
• The laminar flow is a nicely ordered, parallel movement of the water.
Simrad ES120-7C Installation Manual