FIBER LINE

Fiber line is commonly used to hoist and move heavy loads. Fiber line is constructed similar to wire rope. One difference is yarn. Yarn is used to make the strand in place of wire. Another difference is fiber line does not have a core.

TYPES OF FIBER LINE

The most common types of fiber line are manila, sisal, hemp, cotton, nylon, and Kevlar. The characteristics of these fiber lines are discussed below.

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 1.2 to 4.5 meters in the natural state. The quality of the fiber and its length give manila rope relatively high elasticity, strength, and resistance to wear and deterioration. In many instances, the manufacturer treats the rope with chemicals to make it more mildew resistant, which increases the quality of the rope. Manila rope is generally the standard item of issue because of its quality and relative strength.

Sisal

Sisal rope is made from two tropical plants that yield a strong, valuable fiber. These plants, sisalana and henequen, produce fibers 0.6 to 1.2 meters long with sisalana producing the stronger fibers of the two plants. Because of the greater strength of sisalana, these fibers are used to make the rope known as sisal. Sisal rope is about 80 percent as strong as high-quality manila rope and can be easily obtained. It withstands exposure to seawater very well and is often used for this reason.

Hemp

Hemp is a tall plant that provides useful fibers for making rope and cloth. Cultivated in many parts of the world, hemp was used extensively before the introduction of manila. Its principal use now is in fittings, such as ratline, marline and spun yarn. Since hemp absorbs tar much better than the hard fibers, these fittings are invariably tarred to make them water resistant. Tarred hemp has about 80 percent of the strength of untarred hemp. Of these tarred fittings, marline is the standard item of issue.

Cotton

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

Nylon

Nylon rope has a tensile strength that is nearly three times that of manila rope. The advantage of using nylon rope is that it is waterproof and has the ability to resume normal length after being stretched and/or absorbing shocks. It also resists abrasion, rot, decay, and fungus

When nylon rope is properly handled and maintained, it should last more than five times longer than manila line subjected to the same use. Nylon rope is also lighter, more flexible, less bulky, and easier to handle and store than manila line. When nylon rope is wet or frozen, it loses little strength. Additionally, nylon line defies mildew, rotting, and attack by marine borers. Nylon rope can hold a load even when many strands are abraded. Normally, when abrasion is local, the rope may be restored to use by cutting away the chafed section and splicing the ends. Chafing, and stretching do not necessarily affect the load-carrying ability of nylon rope.

The splicing of nylon rope is very similar to that of manila; however, friction tape is used instead of seizing stuff for whipping the strands and line. Because it is smooth and elastic, nylon requires at least one tuck more than manila. For heavy loads, a back tuck should be taken with each strand.

As with manila, nylon rope is measured by circumference. Nylon, as manila, usually comes on a reel of 600 to 1,200 feet, depending upon the size. Do not uncoil new nylon rope by pulling the ends up through the eye of the coil. Unreel it as you would wire rope. Avoid coiling nylon in the same direction all the time, or you could unbalance the lay.

When nylon rope is stretched more than 40 percent, it is likely to part. The stretch is immediately recovered with a snapbaak that sounds like a pistol shot.

WARNING

The snapback of a nylon rope can be as deadly as a bullet. Make sure no one stands in the direct line of pull when a heavy strain is applied.

This feature is also true for other types of lines, but overconfidence in the strength of nylon may lead one to underestimate its backlash.

The critical point of loading is 40-percent extension of length; for example, a 10-foot length of nylon rope would stretch to 14 feet when under load. Should the stretch exceed 40 percent, the linc will be in danger of parting.

If a nylon rope becomes slippery because of grease, it should be cleaned with a light oil, such as kerosene or diesel oil.

Do not store nylon line in strong sunlight. Cover it with tarpaulins. In storage, keep it away from heat and strong chemicals.

Kevlar

Kevlar is most popularly used to make bulletproof vests and knifeproof gloves. The characteristics of Kevlar line are similar to those of Nylon line except for one significant difference-Kevlar line does not snapback when it parts. This is an important safety feature, since parted nylon line has resulted in numerous deaths due to violent snapbacks.