TYPES OF NATURAL FIBER LINES

Vegetable fibers commonly used in the manufacture of line include manila, sisal, hemp, coir, and cotton.

Manila

Manila is a strong fiber that comes from the leaf stems of the stalk of the abaca plant, which belongs to the banana family. The fibers vary in length from 4 to 12 feet in the natural state. The quality of the fiber and its length give manila line relatively high elasticity, strength, and resistance to wear and deterioration. A good grade of manila is cream in color, smooth, clean, and pliable. Poorer grades of manila are characterized by varying shades of brown. In many instances, the manufacturer treats the line with chemicals to make it more mildew resistant, which increases the quality of the line. Manila line is generally the standard item of issue because of its quality and relative strength.

Sisal

The next best line-making fiber is sisal. It is made from two tropical plants-sisalana and henequen. The fiber is similar to manila, but lighter in color. It is grown in the East Indies, Africa, and Central America. Sisal fibers are usually 26 to 40 inches (65 cm to 1 m) long but are only about 80 percent as strong as manila fibers. Sisal line withstands exposure to seawater exceptionally well. It is frequently used in towing, mooring, and similar purposes.

Hemp

Hemp is a tall plant that provides useful fibers for making line and cloth. It is cultivated in the United States, Russia, Italy, and South America. Hemp was used extensively before the introduction of manila. Throughout the Navy the principal use is for small stuff, ratline, marline, and spun yarn. Since hemp absorbs tar much better than the hard fibers, these fittings are invariably tarred to male them water resistant. The term small stuff is used to describe small cordage that a layman may call string, yarn, or cords. Tarred hemp has about 80 percent of the strength of untarred hemp. Of these tarred fittings, marline is the standard item of issue.

Coir

Coir line is a light line made from the fiber of coconut husks and is light enough to float on water. A resilient rough line, it has about one fourth of the strength of hemp; therefore, the use of coir is restricted to small lines.

Cotton

Cotton line is a smooth white line that stands much bending and running. Cotton is not widely used in the Navy except, in some cases, for small lines.

TYPES OF SYNTHETIC FIBER LINES 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.

FABRICATION OF LINE

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.

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