The CM2 product family
CM2 Accessories
The Towfish wing depressor Specifications
The CM2 Wing Depressor is an optional towfish attachment. It provides extra downforce to combat the drag of the tow cable, allowing the towfish to run deeper.
The wing, with clip-on tail, adds only 5kg to the launch weight; and recovery is aided by the wingtip handles. The efficient, high-aspect-ratio design of the wing allows it to generate 18kg of hydrodynamic downforce at 4kts. Download the specification here to see the effect that this has on the towfish depth.
This wing is significantly more efficient hydrodynamically than the V-fin type of depressor. It also does not suffer from the instability of the V-fin on launch. [Note that it is the unique design of the CM2 towfish, with its rear-mounted transducers, that allows an underslung wing to be used without interference with the acoustics; traditional towfish configurations are restricted to a top-mounted V-fin depressor.]
The wing clamps to the towfish using four screws. Attaching and detaching is a 2-minute job.
The CM2 Counting pulleys, standard and large types Specifications
Whilst it is possible to use a pulley or fairlead which may be already available on the survey vessel, it is normally better to use a purpose-designed pulley.
The advantage of using a C-MAX Counting Pulley is that the amount of tow cable paid out is continuously displayed to the sonar operator. This allows the operator to make estimates of layback (the horizontal distance of the fish behind the navigation reference point), to assess the vulnerability of the towfish to changes in ship speed, and to monitor the operation of the winch if it is being controlled by a deck crew.
The pulleys feature a quick release 'snatch block' configuration which allows simple fitting of the cable with no loose parts to get dropped.
The Counting Pulley includes a counting module with a PC-compatible RS232 link. The link transmits measured length in metres or feet, up to +/-10000m [32800ft]. Measurement resolution is 0.5 metre [1.7ft]. No batteries are required as power is extracted directly from the link. The standard link length is 10m [33ft] and other lengths are available to order.
The pulley is also available without the counting facility if required.
Pole mount
The Pole Mount allows the attachment of the towfish to a 50mm (2 inch) diameter pole for overside deployment in shallow water depths and is of stainless steel construction.
Towfish transit case
A purpose-designed clamshell transit case is available for both the CM2 Towfish and the DeepTow.
Cases are also available for the CM2 Winch, Wing Depressor and STR