User guide

FS 20/25 Operators Manual 901-10037001/1.1
FS 20/25 Installation, System Set-Up and Test Page 4.9
Kongsberg Simrad Mesotech Ltd.
Port Coquitlam, BC - Canada
4.3 ASSEMBLING OF TRAWL UNIT
Assembling the trawl unit for the first time should be conducted in the wheel house
where the surface unit electronics have been mounted. This will facilitate testing the
trawl unit using the test cable.
4.3.1 FS 20/25 Configuration
The FS 20 trawl configurations all consist of an FS3300, or TS10, or TS15, or a TS
15S sonar head, an FS 3300 sensor module and the FS900 polyurethane housing.
The FS 20/25 will have an additional FS925 sonar head, an FS 900/925
polyurethane housing, mounting and assembling hardware, and a strain relief. The
trawl unit also contains a catch receiver unit. Assembly of the unit involves correctly
locating the sonar head, attaching strain relief to trawl cable, proper routing and
connection of cable to the sonar head and bolting the polyurethane housing
together. This section describes the connection and locating of the sonar head, the
sensor module and catch receive transducer; final assembly is illustrated in Part 6
“Drawings”.
The FS sonar heads should have been supplied from the factory with two retaining
rings (collars) and a locating pin or guide bracket already installed. If not, these
parts will be included with the sonar head and should now be attached.
A stainless steel locating pin threaded into one the tapped holes located in the
connector end of the housing or a guide bracket is used to prevent the sonar head
from rotating. Only one pin is required and it can be placed into the positioning hole,
as shown in the assembly drawing in Chapter 6, of the bottom half of the trawl unit
housing. The pin location should be such that the diaphragm housing that protrudes
from the sonar head housing will be located to one side (normal convention has
polyurethane housing half with metal serial number plate being used as the top).
Correct location of the pin will be determined during initial test of the system.
The first retaining ring is mounted on the sonar head housing flush with the transducer
end of the housing, and the second retainer ring is mounted approximately 25 mm/1"
from the first. Final position (see Chapter 6 - Drawings) is determined by placing the
sonar head into one half of the trawl unit housing with the locating pin inserted into the
correct hole. The first retaining ring is then moved in tight against the outside of the
polyurethane housing and the second retaining ring is moved in tight against the inside
of the polyurethane housing outside wall. Both are fastened into place to prevent the
sonar head from moving back and forth.