This summer Scanmar is launching a new clump sensor in the SS4 sensor generation, providing 100% accurate distance measurements between the clump(s) and both trawl doors.
Scanmar says that this gives the skipper the opportunity to correct the trawl’s geometry to an optimum for efficient fishing.
The geometry of the trawl is affected by a number of factors, such as side current, towing speed, height of the trawl opening, the doors’ distance and angle, and the fill rate of the cod end.
To avoid an asymmetric and inefficient trawl it is important to keep the clump in line with the doors. Information about the trawl doors’ and the clump’s position in relation to each other is therefore essential. To find the correct wire length of the centre wire many use geometrical and mathematical tables, but in many situations these methods are not accurate and don’t take into account factors as side currents, tension in the wires etc.
The clump’s actual position in relation to the centre line is measured independently of the length of the wire, side currents etc. With the accurate distance measurements the skipper is able to optimise the trawl’s geometry by adjusting the length of the wires so that the clump and doors are in line. The data is presented graphically on the Scanmar’s bridge system.
With a transponder on the clump, the estimated distance between the clump and starboard door is only correct if the clump and doors are in line.
