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Working the Larsen Magic |
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Archives -
2007 Archive
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Written by A. Cross
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Monday, 21 May 2007 |
Believed to offer the best lift to drag ratio of any pelagic door design on the market, Injector’s new Stealth F15 trawl door demonstrates exceptional spread at minimal drag — promising high catch rates at low fuel consumption.
Injector trawl doors have made an undeniable impact on the fishing gear market since Helgi Larsen brought principles of aeronautical design to building trawl doors. Now based in Denmark but with roots in the Faroes, Injector contracts its manufacturing to specialists around the world, reducing manufacturing costs and delivery times.
The Injector Shark doors, introduced more than ten years ago, made an immediate impact and these are still to be seen adorning the sterns of trawlers across the Atlantic, but in recent years the company has brought out several new designs. The Scorpion, intended to replace the Shark, is selling “better than we could have hoped,” managing director Jan-Allan Müller says.
The company has fought long to establish a foothold in a tough market, but is now firmly established as a big player in this business. Last year a Danish business development fund purchased a stake in the company, allowing Injector to raise a stable base of capital, making it possible to focus increasing energy on research, development and marketing.
Another recent addition to the Injector range includes the SeaWolf. This is a lower-cost version model, with many of the advantages of the top-of-the-range designs, such as being unwilling to stick on seabed fasteners. The SeaWolf is aimed at smaller vessels, although it is made in sizes of up to 4600kg/11m2, with a tiny 100kg/1m2 door at the low end of the range.
From the outset, Injector has concentrated on demersal trawl doors for spreading groundfish gear, but increasingly the focus of development has been on high-aspect pelagic doors, alongside a general increase in pelagic trawling for a variety of species.
Newly introduced is an all-steel design, the Injector Stealth F9, which has so far been supplied to Faroese trawler Jupiter and Greenlandic vessel Erika, both of which target blue whiting, herring and other North Atlantic pelagic species. These doors have proved themselves to be stable and easy to work, in the same way that Injector’s demersal doors have a reputation for ease of use.
The new design that is set to open a few eyes is the Injector Stealth F15, a pelagic door made with a steel cover over a lightweight filling. Efficient lightweight doors may have been a trawl door designer’s dream for a long time, yet Injector claims to have achieved a breakthrough with the Stealth F15.
Tank testing has shown the door perform exceptionally well and Mr Müller says that this door has the best CL/CD (lift to drag) ratio of any pelagic door design on the market.
Injector was delivering a pair of these doors to Faroese pelagic vessel Fagraberg in May this year and Irish trawler Father McKee was to take a set in the summer.
The exceptional efficiency of the F15 doors is such that Mr Müller predicts that a pelagic trawler spreading its gear with a conventional pair of 15m2 doors would be able to downshift to 12 or even 11.5m2 F15 doors instead, a significant reduction in surface area that has implications for fuel consumption. The first pair of Stealth F15 doors, ordered for the Fagraberg, fit this example and the new doors, weighing 3.70 tonnes in air, have a weight in water of between 2.70 and 2.80 tonnes.
“Helgi Larsen has worked his magic on these doors, as he has done so many times in the past,” Mr Müller said. “The curves of the F15 really haul the doors out to square the trawl and this is done by maintaining a modest angle of attack to keep drag low, while still generating maximum spread and lift.”
An additional innovation with the Stealth is that adjustments can be made to the rigging with the doors still in the gallows.
“For a lot of pelagic vessels, the doors they use are now so big that they can’t be brought onto the deck, so making rigging adjustments is at best difficult, and can be dangerous, and sometimes simply can’t be done until the vessel docks and changes can be made with the gear on the quay.”
According to Mr Müller there has been tremendous interest in these doors so far and the performance of these first pairs of production trawl doors will undoubtedly be followed carefully by the skippers of other pelagic vessels when they hit the water.
Link to pdf presentation...
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