Starting with this chapter, we explore another major area of steelworking skills-the erection and assembly of steel structure. Steelworkers require tools to hoist and maneuver the steel members into place to erect a structure of any magnitude. These hoisting tools range from uncomplicated devices, such as tripods and gin poles, to more complex mechanisms, such as cranes and motor-powered derricks. Whatever the case, one of the most important components of these hoisting mechanisms is the fiber line or wire rope that must be attached to and hold the load to be hoisted and maneuvered. Before you, as a Steelworker, can become skilled in the supervision of hoisting devices, you must first understand the use and maintenance of fiber line and wire rope.
This chapter and the next are designed to familiarize you with the different types of fiber line and wire rope commonly used by Steelworkers. We also discuss knots, bends, hitches, clips, and fittings and describe how they are used. Other topics discussed include the handling and care of fiber line and wire rope, making splices in fiber line, and methods of determining safe working loads.
Vegetable fibers commonly used in the manufacture of line include manila, sisal, hemp, coir, and cotton.
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.
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 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 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 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.Continue Reading