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CM2 Sidescan Sonar User Manual
18. Wing Depressor
18. WING DEPRESSOR
Introduction
The tow cable of a sidescan sonar is subjected to significant drag forces at normal survey speeds, causing
the towfish to rise. Therefore more cable must be veered or the tow speed must be lowered in order to keep
the towfish at the desired depth.
The purpose of the wing depressor is to tension the cable downwards, without attaching additional static
weight to the towfish or tow cable. Because almost all of the extra tension is generated dynamically,
launching and recovery are far easier than if static ballast weight is used. Also, the load on the winch motor
can be eased simply by reducing tow speed whilst heaving, an option that is not available with static ballast.
Fitting the Wing and Tail to the Towfish
Attach the wing to the towfish as shown in the illustration, with the wing clamp directly in front of the towfish
handle assembly. There should be no gap between the towfish handle assembly and the wing clamps. Use
the four 20mm M6 screws and washers to secure the wing clamps.
Check that the wing is tight on the towfish tube with no ability to rotate. (There should be a compressed
rubber strip inside the bottom clamp to grip the tube. If this is missing it needs to be replaced.)
Attach the tail using the 35mm drop-nose pin instead of the normal 25mm pin. Put the removed 25mm pin in
a safe place for future
CM2 Wing Depressor
Version 3.6 (2008)
39
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