Installing the transducer using a hull unit
A hull unit may be used to lower the ES18 transducer into the water for use. When not in use, the transducer is retracted into a protective installation trunk. A hull unit is commonly used on sonars.
Image
A Transducer shaft sleeve
B Installation trunk
C Transducer shaft
D Adapter
E Transducer
F Keel
The retractable hull unit is more expensive than a blister, but on vessels with a hull where it is difficult or impossible to install a blister, it may still be a cost effective solution.
Vessels without a keel and with a wide, flat bottom is an example where a retractable transducer using a hull unit can be the only acceptable method for bringing the ES18 transducer below the boundary layer.
Note
Several Simrad sonars are provided with hull units of various sizes. Any one of these hull units can be redesigned for use with a ES18 transducer. If this is a realistic option, call your dealer or Kongsberg Maritime for advice.