ROPES

Ropes are an important component of cage aquaculture. They are used for the mooring lines, the grid system and for the netting frame (such as the rib-lines and down-lines, which distribute the forces on the cage net).

Ropes are generally divided into two types (Figure 35):
Twisted rope with an S or Z torsion (either clockwise or anticlockwise twist), and usually composed of 3, 4 or 8 strands. Each strand consists of several twisted yarns. The tighter the twisting, the better the abrasion resistance, and the longer- lasting the rope. A softer twist is generally preferred if splicing is needed. Soft- medium twisting is mostly used in cage net production, owing to their being readily sewn by machine.
Braided rope composed of a braided coat with 12, 16, 24 or 32 yarns, and ant inner core made with twisted rope or braided yarns. Some braided rope can have a double coating in order to improve the abrasion resistance. Braided rope without any core is generally used when it is necessary having a good elasticity and resistance to torsion.

Indicative breaking loads and weights of main rope types

Tables 21-24 show the weight (in kilograms per metre) and breaking load (in kilograms) of main rope types for ropes of different diameters.