Although natural fiber line is normally used, a number of synthetic fibers are also used to make line. The synthetic fibers used to fabricate line include the following: nylon, Kevlar, Orion, and Dacron.
Of the types of line made from synthetic fibers, nylon is the one used the most. The primary benefit of using nylon line is that the breaking (tensile) strength of nylon line is nearly three times that of manila line. An additional benefit of using nylon line is that it is waterproof and has the ability to resume normal length after being stretched and absorbing shock. It also resists abrasion, rot, decay, and fungus growth.
The fabrication of line consists essentially of three twisting operations. First, the FIBERS are twisted to the right to form the YARNS. Second, the yarns are twisted to the left to form the STRANDS. Third, the strands are twisted to the right to form the LINE. Figure 4-1 shows you how the fibers are grouped to form a three-strand line.
Figure 4-1. - Fabrication of line.
The operations just described are standard procedure. The product produced is known as a RIGHT-LAID line. The process is sometimes reversed, then you have what is known as a LEFT-LAID line. In either instance, the principle of opposite twists must always be observed. One reason for this is to keep the line tight or stable and prevent the elements from unlaying when a load is suspended on it. Another reason for twisting the elements of a line in opposite directions is to prevent moisture penetration.
There are three types of lays of fiber line with which you should be familiar. They are the HAWSER-LAID, SHROUD-LAID, and CABLE- LAID lines. Each type is shown in figure 4-2.
Hawser-laid line generally consists of three strands twisted together, usually in a right-hand direction.
Ordinarily, a shroud-hid line is composed of four strands twisted together in a right-hand direction around a center strand or core. This core is usually of the same material but smaller in diameter than the four strands. You will find that shroud-laid line is more pliable and stronger than hawser-laid line. You will also find that shroud-laid line has a strong tendency to kink. In most instances, it is used on sheaves and drums. This not only prevents kinking but also makes use of its pliability and strength.
Figure 4-2. - Lays of line.Continue Reading