GB670222A - Improvements in trawl nets - Google Patents

Abstract

670,222. Trawl nets. LARSSON, K. H. Nov. 22, 1949, No. 29932/49. Class 48. A floating trawl net towed by a single boat comprising two trawl doors 15 has a plurality of shearing boards 18 pulling upwardly on the head-rope 16 and spaced therealong each attached thereto by a single cord, and a plurality of shearing boards 19 exerting a downward pull attached by single cords at spaced points to the foot-rope 17. The doors, which may be rectangular or shaped as shown in Fig. 7, have a pressure surface of circular or varying curvature and floats or.hanging weights 20 or boards with an upwardly or downwardly shearing effect are attached to the doors; alternatively weights 21 which drag along the sea bed are attached by wires 22 of adjustable length to the doors. In order that the doors may be inclined at a variable angle to the vertical two equal cables 25, 26 leading from the rear edge of the door are secured to two holes 28, 29 in a ring 27 and the net warp 13 is selectively secured to any one of a number of holes 30 in the ring. The equal cables 25, 26 may also be selectively attached.to holes 31 in the rear edge of the board. The towing warp 14 is connected to the central horizontal line of the door by a crow's foot which is arranged substantially at right angles to the crow's foot formed by the equal cables 25, 26 connecting the door to the net warp and which comprises a front chain 32 fixed to the door and a back chain 33 fixed to a coupling plate 37 having a row of equally spaced holes which cooperate for the reception of a lock pin with spaced aligned holes 39 in parallel rails secured to the door to give a vernier adjustment. The struts 11 at the wings of the net have plain front surfaces and curved back surfaces and the two fastening rings 45, 46 at each end are positioned so that the struts shear apart.