Fishing and Gear Technology

Unit 7 - Floats and sinkers

7.6.Steel wire rope
Steel wire ropes are used as trawl warps, sweeps and bridles and as foot rope and head rope in large trawl nets, as purse wire in purse seines. Steel wire ropes have high breaking strength and resistance to sustained loading with low elongation, unlike fibre ropes. Steel wire ropes are, however stiff and heavy. Steel wire ropes used in fisheries are generally manufactured from steel wires with a tensile strength of 1570-1770 N.mm-2. Most common construction used as trawl warps, sweeps and bridles is six strand ropes with a fibre core (6 x 19s-cf). There are 19 steel wires in each strand including a steel wire core (9-9-1). The diameter of the finished rope used for fishing gear construction generally ranges from 9 to 32 mm and the breaking strength from 43 to 497 Kg. Six-strand steel wire ropes with a central fibre core (6 x 24s cf) and each strand having 24 steel wires each with a fibre core (15-9-fibre core), ranging in diameter from 8 to 30 mm are in used as purse wires.

Construction of wire rope – The basic materials forming the wire ropes are small wires extending lengthwise in the rope. These wires are twisted into strands and these strands are twisted to form a wire rope.