Following extensive development, testing and refinement, Thyborøn Trawldoor’s auto height facility is now proving its value, maintaining the position of the doors at a constant distance from the seabed.
‘With the auto height feature you can maintain a given distance from the bottom,’ said Thyborøn Trawldoor area sales manager Henrik Andreassen, commenting that this results in minimised bottom contact, reduced fuel consumption, and simplified fishing operations.
‘It eliminates seabed contact at a time when there is strong focus on how fishing gear interacts with the marine environment. That makes this feature groundbreaking for the seabed.’
Pelagic trawler Kristin NC-336 has pioneered the auton height function during development across several of its fisheries.
‘In daytime sprat fishing in the North Sea, we use the auto height function set to one meter, and it’s excellent. We can turn and steer in spots without one of the doors lifting off the bottom or simply falling. In the evening, we can follow the sprat when it rises higher off the seabed by increasing the auto height as needed,’ reports says skipper Ola Hansson.
‘We no longer need to adjust any settings on the upper or lower back straps on the doors, which provides a safer working environment. The auto height feature has given us an additional way to increase control of the doors, and thereby the trawl.’
Ola Hansson has good reason to be satisfied with these new options that make fishing easier.
‘We can see that we have better control over the doors, and on the trawl sonar we can observe how just a few metres’ increase in auto height makes the trawl open more or less, and how the trawl tips work harder or softer against the bottom. This ensures the desired bottom contact with the entire trawl can be achieved – or avoided – as needed,’ he said.
The auto height facility is now available with Type 32 and Type 42 Bluestream controllable doors. The company states that these doors have already achieved savings of 5–25% in fuel consumption – depending on the equipment the new doors replace.
‘Lower fuel use means less CO₂ per kilo of fish caught – and a stronger bottom line. This feature has also proven invaluable on uneven seabeds, where precise clearance is critical,’ Henrik Andreassen said.’
‘On rough terrain, such as around a seamount, auto height really proves its value. You can fish with confidence, knowing the doors are maintaining the exact clearance from the seabed that you have set.’
He added that he benefits go further than this, as the doors no longer need to be lifted completely out of the water during a turn – saving time and increases efficiency, while keeping the doors clear of the seabed reduces wear and tear, which extends the life of the gear.
‘As quotas tighten and costs rise, fishermen need to catch efficiently, sustainably, and profitably,’ Henrik Andreassen commented.
‘Auto height isn’t just a feature – it’s the future of trawl doors.’
The auto height feature has come from Thyborøn Trawldoor’s in-house development department, where naval architecture, hydrodynamics, and practical fishing knowledge are combined. The team uses CFD flow simulations, extensive flume tank testing in Hirtshals, and multiple full-scale trials before a design reaches the market. As an example, the Type 42 trawl door design went through 14 model versions before the final version was built.
‘By keeping design and hydraulics in-house – and reinvesting a significant part of revenue into R&D – Thyborøn Trawldoor ensures it can stay ahead of the curve and deliver durable products that fishermen can rely on for years,’ he said.
