Simrad EQ60 - Manual (Page 196)

Simrad EQ60
184
857-164342 / Rev.C
Centre board
The use of a centre board with the purpose of stabilising the
vessel is well known. A centre board is also a superior platform
for transducers. Such instrument keels have been built, mainly
on research vessels, with a length of 3 m, protruding also 3 m
below the hull, see the figure below. At that depth, the water is
free of air bubbles up to very high sea states. The vessel is then
able to perform reliable acoustic measurements in open sea a
larger part of the year.
(CD3003)
Instrument
keel shaft
Lower position
Bottom view
Figure 26 Deep centre board/instrument keel