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The new smart trawl doors

In engineering the new Twister smart trawl doors, Vónin started from the same principles as the highly successful Tornado design, and have in addition to that incorporated shutters that allow the lift force from the flow to be altered on the lower and upper part of the trawl door.

The new Twisters have already proven that they surpass previous designs in terms of spreading force, and are prepared for an active control system that will make these the first ever smart doors.

The Twister trawl door is equipped with a shutter system
New Shutter System


The new Twisters have already proven that they surpass previous designs in terms of spreading force, and are prepared for an active control system that will make these the first ever smart doors.

One fantastic advantage of the Twister trawl doors is the shutter system, which allows the spreading force of the doors to be altered very simple. One man can adjust the trawl doors from the setting for surface fishing to going deep in a matter of minutes with a straightforward adjustment of the shutters.

Høgni Hansen, skipper of Høgaberg

Exceptional spreading force
with minimal drag

The Twister doors were put through a tough testing process to ensure that they did everything the calculations had predicted – and they did, generating even better spreading force than the Tornado doors.

These highly effective new doors are designed for low drag, high efficiency, and high spreading force using and improving on the same flow booster principle that has worked so well before. The spreading force of the Twister doors has been shown in extended sea trials to be exceptional and the doors square away fast as soon as they hit the water.

The CL of the Twister doors at 4.39 is believed to be the highest of any trawl doors on the market, and the CL/CD value varies between 3.16 and 3.60, depending on the shutter settings and the angle of attack. The shutter settings have very little effect on the CL/CD values of the doors, meaning that the Twister will be lighter to tow when lift (CL) is decreased.

“We have been using the new Twister trawl doors on herring, mackerel and blue whiting fisheries. We have towed them at depth and at the surface. I have to say that we are very happy with the performance of the Twister trawl doors.

These 11m2 Twister doors have a much higher spreading power then our previous 13m2 trawl doors. The stability of the trawl doors is excellent, as we can see that the trawl maintains its shape and full opening while turning.”

Høgni Hansen, skipper of Høgaberg


The skippers who put the Twister doors through their paces during the long testing process were particularly impressed with the stability of these doors, allowing them to take turns during a tow that would not be possible with any other doors.

The Twister trawl door being lowered into the ocean for full scale testing
Twister trawl door

Max CL: 4,39 (Sintef)

AOA can range as much as 25 degrees

Great stability while turning


The stability of the Twister doors goes with a high flexibility range. These have been used across several pelagic fisheries, from working on highly dispersed fish at depth, to chasing elusive marks of fast-moving mackerel just a few metres beneath the surface.

Twister doors offer a significant variation in spreading force, depending on the attachment point and shutter settings, offering CL values across a range from 2.65 all the way up to 4.39. This flexibility means that Twister doors are suitable for use with a variety of trawl types and sizes.

Significant variation in spreading force (CL) from 2,65 to 4,39

The twister trawl doors on the Icelandic trawler “börkur”
Newbuilding Börkur was the first Icelandic trawler to go for the Twister trawl doors
Twister on the Faroese trawler “Tróndur í Gøtu”
The Twister trawl doors on faroese trawler Tróndur í Gøtu


Vónin’s Twister doors are built to last. The doors are made from high-quality high-yield steel, with fully welded seams on all joints and all welding procedures are certified.

Steel: Strenx 700, Hardox, ST355

6,0 m22100
7,0 m22475
8,0 m22850
9,0 m23225
10,0 m23650
11,0 m23975
12,0 m24350
13,0 m24725

Read more
Icelandic pelagic trawler Vilhelm Þorsteinsson
is using the Twister trawl doors


The flexibility of the Twister doors is due to the versatile shutters that alter the flow of water passing between two of the sets of foils, with each door fitted with upper and lower shutters. This offers settings for greater or lesser spreading force, while also providing options for the doors to be set to seek up or down in the water column.

A straightforward crank arrangement allows the shutters to be adjusted easily by a single crewman with the doors at the stern. This patent-pending arrangement means that there are no shackles that need to be moved to adjust the doors.

The shutters are a key element of Vónin’s smart doors concept.

Going for the smart option

Vónin has its own approach to controllable trawl doors with the Smart concept. Twister doors are already prepared for the installation of this Smart system in which the doors poll each other for spread. Combined with depth sensors, the doors have a situational awareness that enables them to respond according to their programming, with setting options for various fisheries.

The skipper can manage door setting from a smartphone or tablet app, and by making the doors capable of responding to changing circumstances autonomously, there is no need for a hull-mounted transducer and no ship-to-gear communication challenges.

Vónin Twister articles

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