Assessment of resistance of trawl cod-ends with netting T0, T90

The difficulty of trawl design is due to the fact that its characteristics must take into account not only the distribution and behavior of the object to be fished, but also match the trawler's and the trawler's propulsion. For this purpose, the designer must calculate as accurately as possible the resistance of the trawl system, which consists of the resistance of: rope-net part, rigging parts, trawl boards, varers, etc. The purpose of the present work is to determine the resistance of trawl cod-end for the 18/95 m trawl with different rotation of the diamond-shaped netting: T0, T90, where T0 is the standard position of the mesh, T90 is the mesh rotated by 90°. For this purpose, the author of the work carried out experiments in the hydrochannel of “Fishering Service”. The model of a trawl cod-end, fixed on a hoop, which provides opening with a given fit ux, was located in the research and experimental sector, and the water flow moved towards it. The flow velocity was set between 1.2 and 2.5 m/s. Once the flow velocity became constant, the author ensured that the trawl cod-end took the correct shape and then used strain gauges to determine the resistance of the model. The experiments in the hydro-cone included: visual observation of mesh opening and cod-end shape changes and obtaining experimental data to determine the hydrodynamic drag coefficient for each trawl cod-end. The netting obtained showed that when the netting is rotated by 90° the mesh’s are opened more than in the standard position and due to this the hydrodynamic coefficient of the trawl cod-end with T90 mesh is smaller than with T0.