Tow Cable; Installing A Winch And Pulley (If Used); Securing The "Soft" Tow Cable (If Used); Attaching The Towfish - C-Max CM2 User Manual

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CM2 Sidescan Sonar User Manual

3. Installing the System

Tow Cable

Put adhesive tape markers on the tow cable, a few metres above the terminator, to warn when the towfish is

close to the vessel.

The tow cable should run directly from the top of the winch drum to a suitable pulley or fairlead.

Any pulley or fairlead must be no smaller than the cable's recommended minimum radius, preferably

considerably larger. A pulley is better than a rigid fairlead.

The pulley should normally be suspended above the stern or stern quarter, able to move freely in any

direction, and positioned so that neither the towfish nor the tow cable is in danger of fouling the vessel's

propeller or rudder or any other structure. A central position minimises tow cable heave caused by the

vessel's roll, but may be too close to the propeller wash.

The winch should be mounted as far forward (away from the pulley) as practical, to reduce the maximum off-

axis angle of the cable. Also the winch should be located directly ahead of the pulley to minimize the tilting of

the pulley and side force on the pulley rim. The winch mounting must be able to withstand the shock of the

towfish striking the bottom.

The mounting "footprint" of the CM2-WIN-300 winch is shown in Section 16.

Securing a "soft" Tow Cable (if used)

Make sure that enough cable is flaked out on the deck so that the towfish can reach its operating depth

without the need to disconnect the inboard end of the tow cable. Provide a method of securing the tow cable.

One method is to use a loop of 5-6mm diameter rope, one end secured to the deck and the other terminated

in a "prusik" knot with 2 or 3 turns around the tow cable. The cable will slip through the hitch until the

operator starts to tighten its grip.

To prolong the life of the cable, avoid sharp bends, twisted loops, and shock loads.

Securing a Soft Tow Cable with a Prusik Knot

Straighten out the end of the tow cable and, if it is a steel-armoured cable, ensure that there is no more than

a half-turn of inherent twist in it.

Version 3.6 (2008)

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