Major milestone achieved for controllable trawl doors
Notus Electronics Ltd of Canada and Polar Trawl Doors of Iceland have partnered to develop controllable trawl doors that are wirelessly controlled from the ship.
A major milestone has been achieved in the project, as the controllable trawl doors have been used in active fishing operations onboard an Icelandic trawler.
Over the last number of years, Polar has developed controllable trawl doors. The doors are constructed from aerodynamic shaped wings. The upper section has three wings and the lower section has three wings. By moving the wings, water flow can be changed which allows control over: spreading force, trawl depth and trawl position. Polar needed a partner that could develop a remote for the doors so that the wings could be moved while fishing. Polar partnered with Notus to use its unique two way wireless technology.
In April, FV Vestmannaey tested the Poseidon 4m controllable doors for bottom fishing and to control the doors’ distance from bottom. Both a bobbin trawl and footrope trawl were used at depths of 40-90 while towing at 3.5-4.0 knots. The doors were controlled by the Notus remote. Notus also supplied sensors to monitor warp length, spread and door angle.
Adjustments in the wings had a direct impact on the trawl. The left graphic (click to enlarge the image at the bottom of the page) shows the door heeling outward at -30⁰ and doors spreading 30 Fa. Commands were sent to the door to alter the position of the wings. The right graphic clearly indicates the difference from altering the wing’s position, the door stood up an additional 19⁰. As a result, the spread increased 23% to 37 Fa.
While fishing in a side current, the outer door was higher in the water column. By closing the wings of the upper section, the door moved to the same vertical position as the opposite door. Various other wing adjustments were made to increase spread and control the roll on the doors.
Skipper Birgir Thor Sverrisson of the Vestmannaey was pleased with the doors. “We changed position from high roll, increased spread, reduced spread and rolled the doors out to use less trawl warps. It looks very promising”.
The next step is to use the doors in the Icelandic mackerel fishery this summer.
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