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Rope
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Rope

Rope is also the title of a movie by Alfred Hitchcock


A rope is a length of fibers, twisted or braided together to improve strength, for pulling and connecting. It has tensile strength but is too flexible to provide compressive strength (i.e., it can be used for pulling, not pushing). Common materials for rope include: manila, hemp, hair, nylon, and steel. Sometimes woven straps or chains are used where rope could be used, especially in securing loads to vehicles.

Other fibrous plant materials sometimes used include cotton, linen, coconut-husk fiber (coir), jute, and sisal. Other synthetic fibers in use include various forms of polypropylene, polyethylene (e.g. Spectra ® a high modulus polyethylene), aramid (e.g. kevlar ®), and polyester (e.g. dacron ®). Some ropes are constructed of mixtures of several fibers or use co-polymer (mixed) fibers.

Rope has been an essential tool since prehistoric times. Today, steel wire rope has largly supplanted fiber rope in heavy construction and industrial applications because of higher tensile strength. Fiber rope is still used extensivly in light industry and in activities as sailing and climbing.

In order to fasten ropes, a large number of knots are used. Some rope material, like hemp, is stronger when wet with water.

A pulley is used to convert the pulling force to another direction, and multiple pullys may be used to increase the mechanical advantage, allowing the pulling or lifthing of heavy loads with limited force and strength of rope. Winches and capstans are machines designed to pull ropes.

Tension Technology International offers resources on rope fiber characteristics

Table of contents
1 Styles of rope construction
2 How to handle rope

Styles of rope construction

Twisted Ropes and Hawsers

Also called laid rope. This is historically the prevalent form of rope, at least in modern western history. Most twisted rope consists of three strands and is normally right-laid, or given a right handed twist. Large heavy duty ropes are sometimes called hawsers. Twisted hawsers were often made of 4 strands of right laid rope, laid left, or given a left handed twist, this was sometimes called cable-laid. More strands are sometimes used.

Twisted ropes are built up in three steps. First, fibers are gathered and spun to form yarns. A number of these yarns are then twisted together to form strands. The Strands are then twisted together to form the rope. The twist of the yarn is opposite to that of the strand, and that in turn is opposite to that of the rope. This counter-twisting helps keep the rope together. Any rope of this type must be bound at its end by some means to prevent untwisting.

Twisted ropes have a preferred direction for coiling. Normal right laid rope should be coiled "with the sun", or clockwise, to prevent kinking. Coiling this way imparts a twist to the rope. Braided ropes (and objects like garden hose, fiber optic or coaxial cable, etc.) that have no lay, or inherent twist, will uncoil better if coiled into "figure 8" coils, where the twist reverses regularly and essentially cancels out.

Before modern rope making machines were invented, these ropes were constructed in a "rope walk". This was a very long building where strands the full length of the rope were spread out and then "laid up" or twisted together to form the rope. A Cable length, in practical terms, was set by the length of the available rope walk.

Braided Climbing and Safety Ropes

These ropes are usually braided, which avoids a tendency to untwist under load, which causes the load to spin if not otherwise supported.

Ropes used for climbing can be divided into two categories: dynamic ropes and static ropes. Static ropes have very low stretch properties, they are used for carrying equipment, hauling equipment, and attaching pieces of equipment together. Dynamic ropes are stretchy; being stretchy is crucial in order to limit the maximum force experienced by a climber that falls when using one (and also the maximum force experienced by any piece of gear securing the climber to the rock or ice). The main ropes (called "lead ropes" when the climber is leading) that a climber uses are dynamic.

Climbing ropes are generally made from nylon and have kern mantle construction. There is a core, kern, of long twisted fibres in the middle, and an outer sheath, mantle, of woven coloured fibres. The kern provides most of the strength, the mantle protects the kern and generally affects the handling of the rope (how easy it is to hold, to tie knots in, and so on). Dynamic ropes are made by chopping the fibres in the kern to make them shorter which makes the rope more stretchy.

How to handle rope

Rope made from hemp or nylon should be stored in a cool dry place. It should be coiled and not twisted. If rope is found to be fraying you can melt some wax onto the end or in the case of nylon rope just melt the end so it fuses together. For fibre rope, fixing frayed ends can be more difficult. A strong cotton should be used to lash the end together; this will help the end from coming apart again and make tying knots easier. If a load-bearing rope gets a sharp or sudden jolt or shows signs of deteriorating the rope should be replaced immediately and should be discarded or only used for non-load-bearing tasks.