Our wide range of semi pelagic trawl doors for all kinds of trawl fishing such as trawling on the bottom with single rig, twin rig, multi-rig systems and pelagic fishing. Some also uses the semi-pelagic doors for “flying off” the bottom.
In most situations we prefer the semi-pelagic trawl doors to be called or considered as a high aspect bottom door, since in the most cases and most fisheries these trawl doors are being used directly on the bottom.
In Thyboron Trawldoor we believe in more efficient and environmental fishing industry.
The newest development for the semi-pelagic door design is our patented BLUESTREAM technology. The BLUESTREAM technology is the key feature of the new trawl doors by Thyboron Trawldoor. By developing a door with a more fluent and efficient waterflow Thyboron Trawldoor has succeeded in bringing this revolutionary invention to the world’s fishermen. The concept is simple- a door that creates greater spread with less resistance. As the trawl doors are towed through the water, the double foiling system forces water through the foils at higher speed thus creating a greater amount of lift while at the same time reducing drag.
Spreading power and drag resistance of trawls doors can be measured operationally in a flume tank. To calculate the lift and drag ratios (CL-Lift Coefficient and CD-Drag Coefficient) trawl doors are tested at multiple angles of attack. The optimal angle of attack is the most efficient angle where CL is highest, and the CD is lowest.
As part of the trawl door designing and testing protocol once a door has been tested in a flume tank a full-scale model is built and tested at sea on a fishing vessel.
Flume tank tests have demonstrated that trawl doors can account for up to 25% of the total drag resistance of a bottom trawl when towed behind a vessel. By replacing traditional bottom doors with more efficient trawl doors and by flying the doors off the bottom (semi-pelagic) it is possible to significantly decrease the drag resistance made by the trawl doors.
Further, semi-pelagic doors significantly reduce seabed impact by limiting the contact the trawl doors make with the seabed. Increasingly, more areas around the world are restricting the use of bottom trawl doors because of the negative environmental impacts to the seabed.
As one of our patented features, the semi-pelagic trawl door designs TYPE 14 and TYPE 23 also comes as a FLIPPER model. With the flipper function it is possible to reduce the surface area of the trawl door by opening 1, 2, 3, or 4 flaps in the door. This offers a lot of adjustment possibilities for many different fishing setups and provides extremely high stability when fishing deep or fishing very close to the surface with a lot of turns. Furthermore, this feature can increase the efficiency of the trawl doors even more than with only the BLUESTREAM technology implemented.
All semi-pelagic trawl doors can be made in size and weight by customer request