Simrad TRANSDUCER - INSTALLATION GENERIC REV H Installation Manual page 22

Simrad Echo sounder transducers
20
Common guidelines
The best performance is obtained with a blister height of 40 cm
or more. A streamlined shape and rounded edges reduce the flow
noise. A vertical leading edge or front will guide the aerated
water to the sides of the blister. The orientation of the blister
should follow the water flow.
The interior of the blister must be filled with sea water. Use
drainage holes in the bottom and an air outlet on the top. The
water pressure behind the transducer will then compensate for
the outside pressure during vessel movements in rough sea.
Large diameter transducers must be fitted with a horizontal
U-shaped support bar. This bar can then be secured to the
mounting ring using threaded rods.
The transducer cable penetrates the hull in a stuffing tube. Leave
an adequate loop of the cable behind the transducer for easy
mounting or removal of the transducer.
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.
A
B
(CD17010C)
(A) = Keel
(B) = Blister
(C) = Toe-in angle
Physical location
The blister is placed on one of the sides of the hull, and the
distance from the keel is a trade off between a close distance
giving a turbulent flow of water in a narrow passage, and a large
distance bringing the transducer higher up and also more affected
by vessel roll. Normally a distance of approximately 1 m is a
good compromise.
C
851-160164/H