The patented design called “Flipper door” has four flaps in the backend of the door. Two flaps on the upper part and Two flaps on the lower part that can be opened manually. By this, the effective surface area can be reduced up to 12,4% and the spreading power can be reduced up to 17%. At the same time, the door resistance can be reduced up to 25%. This design basically provides you with 3 door sizes in one. Furthermore, the pitch and roll of the trawldoor can be controlled. This feature will make it easier working the doors in deeper or shallow water or in strong tide.
The Type 20 VF “FLIPPER” pelagic trawl door is an all-round high aspect pelagic trawldoor. TYPE 20 VF is a further developed and improved version of the older TYPE 10. They are used for all kinds of pelagic fishing setups worldwide. They are also used for bottom fishing with the doors “flying off the bottom”. The aspect ratio and design of the TYPE 20 VF are the same as our well known TYPE 15 VF.
When fishing for pelagic species the TYPE 20 VF “FLIPPER” have shown extreme high stability during strong tides and rough weather conditions. The V shape of the TYPE 20 VF “FLIPPER” makes them much easier to control during different maneuvers when trawling. If fishing in deep water or close to the surface this design must be considered as one of the absolute most efficient trawl doors on the marked.
The most common usage of TYPE 20 VF is within pelagic fishing for species like mackerel, blue whiting, herring, or sprats. But they are also used for bottom trawling in some areas. The design of the TYPE 20 VF can be customized and a keel with wear shoes can be added to suit and last longer for bottom trawling.
The TYPE 20 VF was also implemented in bottom fisheries using a trawl running on the bottom and then the TYPE 20VF trawl doors was “flying off the bottom” using a flywire and chain weights at the end of the sweeps.
Spreading power and drag resistance of trawl doors can be measured operationally in a flume tank. To calculate the lift and drag ratios (CL-Lift Coefficient and CD-Drag Coefficient) trawl doors are tested at multiple angles of attack. The optimal angle of attack is the most efficient angle where CL is highest, and the CD is lowest.
As part of the trawl door designing and testing protocol once a door has been tested in a flume tank a full-scale model is built and tested at sea on a fishing vessel.
Type 20 comes in the following models:
- TYPE 20 VF FLIPPER
- TYPE 20 VF SLIDER
The weight can be custom made to suit customer requests.
Download technical specifications