Installing the Trawl Unit
Before you can put the FX80 system to work, you need to mount the Trawl Unit onto your fishing gear.
Prerequisites
•  It is easiest to mount the Trawl Unit after the cod end of the trawl has been deployed.
•  You will need an ample supply of mounting materials (wires and ropes, hooks and shackles).
•  The third-wire trawl cable must enter the Trawl Unit using an external strain relief with the proper dimensions. This item is not provided by Simrad.
•  The fourth-wire cable must be connected with proper slack, and with a dedicated safety rope to accept the tension. Connections and splices cannot take any strain.
Context
Firstly, no matter how the Trawl Unit is mounted on the gear, the most important task will always be to keep it from falling off during use.
Secondly, you must always mount the unit so that the acoustic beams from the Sonar Head hit and reflect from the targets you wish to see. Make sure that you position the Trawl Unit while considering the tensions on the fishing gear once it has been deployed.
The same tensions may also cause the Trawl Unit to be tilted or pitched. In most cases, if you cannot see the expected targets on the sonar screen, there is nothing wrong with the sonar. Check the pitch and roll values. Is the sonar beam pointing in the right direction? Keep in mind that when the footrope hits the bottom, or the cod end is filled with fish, the location of the footrope may change.
Note
There are many different ways to do this installation, and many vessels have established their own procedures and “best practices” for these tasks. This procedure explains one method suggested by Simrad.
Simrad will not take any responsibility for any loss of or damage to equipment, even if our general installation and/or mounting procedures have been followed.
Image
A Third-wire trawl cable
B Fourth-wire cable (allow for plenty of slack)
C Non-stretchable rope attached to the fourth-wire cable
D Rope secured to the headrope to take up the tension
Procedure
1 Place the Trawl Unit on its chosen location on the fishing net.
This may, for example, be immediately behind the headrope, or on a kite.
2 Make sure the Trawl Unit is facing the correct way — the Sonar Head must face aft.
3 Make sure that the Trawl Unit is positioned so that the sonar beam is pointing in the right direction.
4 Secure the Trawl Unit using a minimum of four wires or ropes from the Trawl Unit’s mounting shackles to the headrope or kite.
Tip
Make sure that the mounting takes into consideration the various tensions applied to the fishing net once it has been deployed. Once deployed, these tensions may cause the Trawl Unit to pitch and roll. They may also cause the footrope to move forward or backward and then “out of reach” for the sonar beam.
5 Unless you keep it connected all the time, connect the third-wire trawl cable to the Communication Hub prior to or during the deployment of the trawl.
6 Connect the fourth-wire cable to the Communication Hub prior to or during the deployment of the trawl.