Rope

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). more...

Common materials for rope include manila, hemp, nylon, and steel. Sometimes woven straps or chains are used where rope could be used, especially in securing loads to vehicles. Rope is also known, depending on size and application, as cord, line, string or twine. In traditional nautical usesage, pieces of rope used in the rigging of a ship or boat are called lines. The only rope on a sailing ship was the bellrope used to ring the ships bell and the boltropes sewn into the edges of some sails.

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. Ropes have been constructed of other fibrous materials such as silk or wool and even dental floss, but such ropes are not generally available.

Rope has been an essential tool since prehistoric times. In the late 19th century, steel wire_rope, or cable, largely supplanted fiber rope in high load applications because of higher tensile strength, but modern synthetic materials can now equal or exceed the strength of steel of the same diameter. Rope is essential to 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.

Pulleys are used to redirect the pulling force to another direction, and may be used to create mechanical advantage, allowing multiple strands of rope to share to load and multiply the force applied to the end. Winches and capstans are machines designed to pull ropes.

Styles of rope construction

Twisted ropes and hawsers

Twisted rope, also called laid rope, 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.

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