The latest pelagic trawl doors from Thyborøn Skibssmedie combine the functions of the adjustable Flipper doors with a new design, with some outstanding results both in trials on herring at the end of last year and more recently on horse mackerel and blue whiting.
The Type 22 Bluestream doors are designed around new developments in the body of the doors, and a new construction in the vents that reduces the overall drag while still giving better spread than the older pelagic designs, reports Hook & Net.
According to Ole Kjærgaard, the first pair of trial Bluestream doors were tested on board Hirtshals pelagic vessel Isafold on herring at the end of last year, with a 12 square metre pair of the new design replacing a 15 square metre pair of Flipper doors.
‘And they did the same job,’ he said.
Since then, pairs of 12 square metre Bluestreams have gone to Dutch pelagic vessels Frank Bonefaas SCH-72 and Afrika SCH-24, and now that the test period is over, the secrecy over the new doors has been lifted as half a dozen pairs of Bluestreams are being delivered.
‘We took the Flipper principle and transferred it to the Type 22 Bluestream doors,’ Ole Kjærgaard said, commenting that the door surface area can be reduced by 20% by opening all the flaps.
‘On Frank Bonefaas they showed that these doors could work with different settings with three different trawls, and now they’ll be using them for mackerel. The Bluestream doors are made with two flaps in each upper and lower section, and these can be either folding or sliding versions, or they can be made without the flaps if there’s no requirement for adjustment.’
According to Piet Hoek who skippers Frank Bonefaas, they tested the Bluestreams starting on night fishing for horse mackerel west of Ireland with all four flaps open to minimise the door size for the 1050 daytime trawl and the 1440 metre nighttime trawl.
‘There was a good spread on the 1050 metre trawl, five metres more than with our 12 square metre Type 15 doors, and resistance was lower with 14-15 tonnes on our Marelec trawl system and with a slightly higher towing speed that our colleagues with the same size trawl,’ he said.
‘At night we were fishing with a bigger trawl and had good spread and towing speed, and the doors are very stable in a turn.’
For the full story, take a look at Hook & Net.
