Gollenes is fishing with a pair of Bluestream 32 trawl doors. These are the fully controllable variety that can be adjusted from the wheelhouse during a tow.
Article by Terje Engø
‘I have to say, the stability of the doors is just perfect,’ Frode Kvalsvik said. ‘But I have to add that we have only been using these doors for three months since Gollenes was delivered in April.’
This latest generation of doors, which utilise the Bluestream technology developed by Thyborøn Trawldoor, has a highly efficient water flow generated by the double foil that forces water through the doors at a higher speed to produce lift while also reducing drag.
‘Shooting these doors, especially during the sandeel fishery on relatively shallow water has been a fantastic experience. We haven’t once had the doors tilt because of contact with the bottom. This saves us time, fuel, and frustration. We are not out there to haul and shoot the trawl. We’re there to catch fish,’ Frode Kvalsvik said.
‘A common problem for trawlers is the doors tilting and falling flat in a turn. This hasn’t happened during the months Gollenes has been fishing with the new doors,’ he said, but added that right now there is a problem with the battery that results in a loss of contact with the doors.
‘But this doesn’t stop us from fishing, and the doors are still functioning very good. The battery problem will be fixed after landing. Then we’ll be going to Denmark for other reasons, and we’ll get the battery problem dealt with at the same time.’
Behind these doors is a long process of research, development and testing of the technology, including model testing in a flume tank before moving on to full-scale trials with a prototype. Getting doors off the bottom has been a central part of the development in recent years, as by flying the doors clear of the seabed there are efficiences to be made in reducing drag, as well as the benefits of minimising ground contact in semi-pelagic fisheries such as those Gollenes is part of.
‘As we speak, we’re trawling for Norway pout, and we have the doors very low, slightly touching the sea floor, but still with full control. We have been using the doors bottom trawling and for pelagic trawling for sandeel and herring. The doors have shown an impressive performance in several ways,’ he said.
‘We have until now been operating with a single trawl. After landing the catch this time, will we change to a double trawl system, using the same set of doors. This is the first time we are using doors which we can control from the wheelhouse. We can sit and follow the doors on the screens. Any changes to spread or to the depth are quick and easy. If we’re fishing for example for sandeel, we can change the towing depth by adjusting the doors to the depth we we see there’s fish,’ Frode Kvalsvik said.
‘We’re very proud of our Type 32 Bluestream design,’ said Thyborøn Trawldoor sales manager Henrik Andreassen. ‘This is the only trawl door on the market which has our patented moveable foils that can minimise the total area of the doors to adjust spreading power and resistance.’
He explained that the doors are made to suit the customer’s operating pattern.
‘Once the balance of weight has been calculated, the doors are constructed, and they are delivered as a package that include a HPU (High Pressure Unit), software, adjustable hydraulic foils, height sensor, hydrophones, WiFi antenna and subsea lithium batteries,’ he said
‘The software is an open-end design which can customised and adapted to a skipper’s specific needs or preferences.’
The system in the trawl doors is controlled via a wireless acoustic link from hull-mounted hydrophones, enabling the skipper to monitor the doors in the wheelhouse screen display and to fine-tune the doors’ performance remotely from the wheelhouse.
If the controllable trawl doors have caught your interest you are more than welcome to contact Thyboron Trawldoor for more information;
Henrik@Thyboron-trawldoor.dk
Allan@Thyboron-trawldoor.dk
Ole@Thyboron-trawldoor.dk
