Rope

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A coil of right-handed laid three-strand rope Cordage en chanvre.jpg
A coil of right-handed laid three-strand rope
Construction of cable Constriction of rope.png
Construction of cable

A rope is a group of yarns, plies, fibers or strands that are twisted or braided together into a larger and stronger form. Ropes have tensile strength and so can be used for dragging and lifting. Rope is thicker and stronger than similarly constructed cord, string, and twine.

Contents

Hawser-laid rope (Seaman's Pocket-Book, 1943) Hawser-laid rope (Seaman's Pocket-Book, 1943).jpg
Hawser-laid rope (Seaman's Pocket-Book, 1943)

Construction

Three-strand natural fiber laid line SuperMacro Rope.JPG
Three-strand natural fiber laid line

Rope may be constructed of any long, stringy, fibrous material, but generally is constructed of certain natural or synthetic fibres. [1] [2] [3] Synthetic fibre ropes are significantly stronger than their natural fibre counterparts, they have a higher tensile strength, they are more resistant to rotting than ropes created from natural fibers, and they can be made to float on water. [4] But synthetic rope also possess certain disadvantages, including slipperiness, and some can be damaged more easily by UV light. [5]

Common natural fibres for rope are Manila hemp, hemp, linen, cotton, coir, jute, straw, and sisal. Synthetic fibres in use for rope-making include polypropylene, nylon, polyesters (e.g. PET, LCP, Vectran), polyethylene (e.g. Dyneema and Spectra), Aramids (e.g. Twaron, Technora and Kevlar) and acrylics (e.g. Dralon). Some ropes are constructed of mixtures of several fibres or use co-polymer fibres. Wire rope is made of steel or other metal alloys. Ropes have been constructed of other fibrous materials such as silk, wool, and hair, but such ropes are not generally available. Rayon is a regenerated fibre used to make decorative rope.

The twist of the strands in a twisted or braided rope serves not only to keep a rope together, but enables the rope to more evenly distribute tension among the individual strands. Without any twist in the rope, the shortest strand(s) would always be supporting a much higher proportion of the total load.

Size measurement

Because rope has a long history, many systems have been used to specify the size of a rope. In systems that use the inch (Imperial and US customary measurement systems), large ropes over 1 inch (25.4 mm) diameter – such as those used on ships – are measured by their circumference in inches; smaller ropes have a nominal diameter based on the circumference divided by three (as a rough approximation of pi). In the metric system of measurement, the nominal diameter is given in millimetres. The current preferred international standard for rope sizes is to give the mass per unit length, in kilograms per metre. However, even sources otherwise using metric units may still give a "rope number" for large ropes, which is the circumference in inches. [6]

Use

Bollard and mooring line HK TST Star Ferry Victoria Harbour Mooring Rope.JPG
Bollard and mooring line

Rope has been used since prehistoric times. [7] It is of paramount importance in fields as diverse as construction, seafaring, exploration, sports, theatre, and communications. Many types of knots have been developed to fasten with rope, join ropes, and utilize rope to generate mechanical advantage. Pulleys can redirect the pulling force of a rope in another direction, multiply its lifting or pulling power, and distribute a load over multiple parts of the same rope to increase safety and decrease wear.

Winches and capstans are machines designed to pull ropes.

Rock climbing ropes

Dynamic kernmantle rock climbing rope with its braided sheath cut to expose the twisted core yarns and core yarn plies Kernmantle climbing rope dynamic Sterling 10.7mm internal yarns and plies.jpg
Dynamic kernmantle rock climbing rope with its braided sheath cut to expose the twisted core yarns and core yarn plies
Section through kernmantle rope Kernmantle climbing rope dynamic Sterling 10.7mm cut end.jpg
Section through kernmantle rope

The sport of rock climbing uses what is termed "dynamic" rope, an elastic rope which stretches under load to absorb the energy generated in arresting a fall without creating forces high enough to injure the climber. Such ropes are of kernmantle construction, as described below.

Conversely, "static" ropes have minimal stretch and are not designed to arrest free falls. They are used in caving, rappelling, rescue applications, and industries such as window washing.

The UIAA, in concert with the CEN, sets climbing-rope standards and oversees testing. Any rope bearing a GUIANA or CE certification tag is suitable for climbing. Climbing ropes cut easily when under load. Keeping them away from sharp rock edges is imperative. Previous falls arrested by a rope, damage to its sheath, and contamination by dirt or solvents all weaken a rope and can render it unsuitable for further sport use.

Rock climbing ropes are designated as suitable for single, double or twin use. A single rope is the most common, and is intended to be used by itself. These range in thickness from roughly 9 to 11 mm (0.35 to 0.43 in). Smaller diameter ropes are lighter, but wear out faster.

Double ropes are thinner than single, usually 9 mm (0.35 in) and under, and are intended for use in pairs. These offer a greater margin of safety against cutting, since it is unlikely that both ropes will be cut, but complicate both belaying and leading. Double ropes may be clipped into alternating pieces of protection, allowing each to stay straighter and reduce both individual and total rope drag.

Twin ropes are thin ropes which must be clipped into the same piece of protection, in effect being treated as a single strand. This adds security in situations where a rope may get cut. However new lighter-weight ropes with greater safety have virtually replaced this type of rope.[ citation needed ]

The butterfly and alpine coils are methods of coiling a rope for carrying.

History

Ancient Egyptians were the first to document tools for ropemaking Ancient Egypt rope manufacture.jpg
Ancient Egyptians were the first to document tools for ropemaking

The use of ropes for hunting, pulling, fastening, attaching, carrying, lifting, and climbing dates back to prehistoric times. It is likely that the earliest "ropes" were naturally occurring lengths of plant fibre, such as vines, followed soon by the first attempts at twisting and braiding these strands together to form the first proper ropes in the modern sense of the word. The earliest evidence of true rope making is a very small fragment of three-ply cord from a Neanderthal site dated 50,000 years ago. [8]

A 40,000-year-old tool found in Hohle Fels cave in south-western Germany, originally suggested to be a musical instrument or a religious object, was identified in 2020 as very likely to be a tool for making rope. It is a 20 cm (8 in) strip of mammoth ivory with four holes drilled through it. Each hole is lined with precisely cut spiral incisions. Plant fibres would have been fed through the holes and the tool twisted, creating strong ropes and twines. The spiral incisions would have tended to keep the fibres in place. [9] After this object was identified as a likely rope-making tool, other 15,000-year-old objects with holes with spiral incisions, made from reindeer antler, found previously in Cheddar Gorge, Somerset, England appear to have been used to manipulate ropes, for purposes still unclear, but now thought to be for making or manipulating ropes. They were originally named "batons", and thought possibly to have been carried as badges of rank. [9]

Impressions of cordage found on fired clay provide evidence of string and rope-making technology in Europe dating back 28,000 years. [10] Fossilized fragments of "probably two-ply laid rope of about 7 mm [0.28 in] diameter" were found in one of the caves at Lascaux, dating to approximately 15,000 BC. [11]

The ancient Egyptians were probably the first civilization to develop special tools to make rope. Egyptian rope dates back to 4000 to 3500 BC and was generally made of water reed fibres. [12] Other rope in antiquity was made from the fibres of date palms, flax, grass, papyrus, leather, or animal hair. The use of such ropes pulled by thousands of workers allowed the Egyptians to move the heavy stones required to build their monuments. Starting from approximately 2800 BC, rope made of hemp fibres was in use in China. Rope and the craft of rope making spread throughout Asia, India, and Europe over the next several thousand years.

From the Middle Ages until the 18th century, in Europe ropes were constructed in ropewalks, very long buildings where strands the full length of the rope were spread out and then laid up or twisted together to form the rope. The cable length was thus set by the length of the available rope walk. This is related to the unit of length termed cable length . This allowed for long ropes of up to 300 yards (270 m) long or longer to be made. These long ropes were necessary in shipping as short ropes would require splicing to make them long enough to use for sheets and halyards. The strongest form of splicing is the short splice, which doubles the cross-sectional area of the rope at the area of the splice, which would cause problems in running the line through pulleys. Any splices narrow enough to maintain smooth running would be less able to support the required weight.[ citation needed ]

Leonardo da Vinci drew sketches of a concept for a ropemaking machine, but it was never built. Remarkable feats of construction were accomplished using rope but without advanced technology: In 1586, Domenico Fontana erected the 327 ton obelisk on Rome's Saint Peter's Square with a concerted effort of 900 men, 75 horses, and countless pulleys and meters of rope. By the late 18th century several working machines had been built and patented.

Some rope is still made from natural fibres, such as coir and sisal, despite the dominance of synthetic fibres such as nylon and polypropylene, which have become increasingly popular since the 1950s.

Styles of rope construction

Laid or twisted rope

Illustration of the S and Z naming convention Yarn twist S-Left Z-Right.png
Illustration of the S and Z naming convention

Laid rope, also called twisted rope, is historically the prevalent form of rope, at least in modern Western history. Common twisted rope generally consists of three strands and is normally right-laid, or given a final right-handed twist. The ISO 2 standard uses the uppercase letters S and Z to indicate the two possible directions of twist, as suggested by the direction of slant of the central portions of these two letters. The handedness of the twist is the direction of the twists as they progress away from an observer. Thus Z-twist rope is said to be right-handed, and S-twist to be left-handed.

Twisted ropes are built up in three steps. First, fibres are gathered and spun into yarns. A number of these yarns are then formed into strands by twisting. The strands are then twisted together to lay 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. It is this counter-twist, introduced with each successive operation, which holds the final rope together as a stable, unified object. [13]

Rope making using the twisted rope method on a 1928 Metters Rope Making Machine Metters rope serpentine vtm.jpg
Rope making using the twisted rope method on a 1928 Metters Rope Making Machine

Traditionally, a three strand laid rope is called a plain- or hawser-laid, a four strand rope is called shroud-laid, and a larger rope formed by counter-twisting three or more multi-strand ropes together is called cable-laid. [14] Cable-laid rope is sometimes clamped to maintain a tight counter-twist rendering the resulting cable virtually waterproof. Without this feature, deep water sailing (before the advent of steel chains and other lines) was largely impossible, as any appreciable length of rope for anchoring or ship to ship transfers, would become too waterlogged – and therefore too heavy – to lift, even with the aid of a capstan or windlass.

One property of laid rope is partial untwisting when used. [15] This can cause spinning of suspended loads, or stretching, kinking, or hockling of the rope itself. An additional drawback of twisted construction is that every fibre is exposed to abrasion numerous times along the length of the rope. This means that the rope can degrade to numerous inch-long fibre fragments, which is not easily detected visually.[ citation needed ]

Twisted ropes have a preferred direction for coiling. Normal right-laid rope should be coiled clockwise, to prevent kinking. Coiling this way imparts a twist to the rope. Rope of this type must be bound at its ends by some means to prevent untwisting.

Braided rope

A rope braiding machine at the Arbetets Museum (Museum of Work) in Norrkoping, Sweden Braiding machine arbetes museum.jpg
A rope braiding machine at the Arbetets Museum (Museum of Work) in Norrköping, Sweden

While rope may be made from three or more strands, [16] modern braided rope consists of a braided (tubular) jacket over strands of fiber (these may also be braided). Some forms of braided rope with untwisted cores have a particular advantage; they do not impart an additional twisting force when they are stressed. The lack of added twisting forces is an advantage when a load is freely suspended, as when a rope is used for rappelling or to suspend an arborist. Other specialized cores reduce the shock from arresting a fall when used as a part of a personal or group safety system.

Braided ropes are generally made from nylon, polyester, polypropylene or high performance fibers such as high modulus polyethylene (HMPE) and aramid. Nylon is chosen for its strength and elastic stretch properties. However, nylon absorbs water and is 10–15% weaker when wet. Polyester is about 90% as strong as nylon but stretches less under load and is not affected by water. It has somewhat better UV resistance, and is more abrasion resistant. Polypropylene is preferred for low cost and light weight (it floats on water) but it has limited resistance to ultraviolet light, is susceptible to friction and has a poor heat resistance.[ citation needed ]

Braided ropes (and objects like garden hoses, fibre optic or coaxial cables, etc.) that have no lay (or inherent twist) uncoil better if each alternate loop is twisted in the opposite direction, such as in figure-eight coils, where the twist reverses regularly and essentially cancels out.

Single braid consists of an even number of strands, eight or twelve being typical, braided into a circular pattern with half of the strands going clockwise and the other half going anticlockwise. The strands can interlock with either twill or plain weave. The central void may be large or small; in the former case the term hollow braid is sometimes preferred.

Double braid, also called braid on braid, consists of an inner braid filling the central void in an outer braid, that may be of the same or different material. Often the inner braid fibre is chosen for strength while the outer braid fibre is chosen for abrasion resistance.

In solid braid, the strands all travel the same direction, clockwise or anticlockwise, and alternate between forming the outside of the rope and the interior of the rope. This construction is popular for general purpose utility rope but rare in specialized high performance line.

Kernmantle rope has a core (kern) of long twisted fibres in the center, with a braided outer sheath or mantle of woven fibres. The kern provides most of the strength (about 70%), while the mantle protects the kern and determines the handling properties of the rope (how easy it is to hold, to tie knots in, and so on). In dynamic climbing line, core fibres are usually twisted to make the rope more elastic. Static kernmantle ropes are made with untwisted core fibres and tighter braid, which causes them to be stiffer in addition to limiting the stretch.

Other types

Plaited rope is made by braiding twisted strands, and is also called square braid. [17] It is not as round as twisted rope and coarser to the touch. It is less prone to kinking than twisted rope and, depending on the material, very flexible and therefore easy to handle and knot. This construction exposes all fibres as well, with the same drawbacks as described above. Brait rope is a combination of braided and plaited, a non-rotating alternative to laid three-strand ropes. Due to its excellent energy-absorption characteristics, it is often used by arborists. It is also a popular rope for anchoring and can be used as mooring warps. This type of construction was pioneered by Yale Cordage.

Endless winding rope is made by winding single strands of high-performance yarns around two end terminations until the desired break strength or stiffness has been reached. This type of rope (often specified as cable to make the difference between a braided or twined construction) has the advantage of having no construction stretch as is the case with above constructions. Endless winding is pioneered by SmartRigging and FibreMax.

2D images / sections

2D flight-throughs/sections

3D renderings

3D flight-throughs/sections

Handling

Cordage aboard the French training ship Mutin Cordages-mutin.jpg
Cordage aboard the French training ship Mutin

Rope made from hemp, cotton or nylon is generally stored in a cool dry place for proper storage. To prevent kinking it is usually coiled. To prevent fraying or unravelling, the ends of a rope are bound with twine (whipping), tape, or heat shrink tubing. The ends of plastic fibre ropes are often melted and fused solid; however, the rope and knotting expert Geoffrey Budworth warns against this practice thus: [18]

Sealing rope ends this way is lazy and dangerous. A tugboat operator once sliced the palm of his hand open down to the sinews after the hardened (and obviously sharp) end of a rope that had been heat-sealed pulled through his grasp. There is no substitute for a properly made whipping.

If a load-bearing rope gets a sharp or sudden jolt or the rope shows signs of deteriorating, it is recommended that the rope be replaced immediately and should be discarded or only used for non-load-bearing tasks. [19] [20]

The average rope life-span is 5 years. Serious inspection should be given to line after that point.[ citation needed ] However, the use to which a rope is put affects frequency of inspection. Rope used in mission-critical applications, such as mooring lines or running rigging, should be regularly inspected on a much shorter timescale than this, and rope used in life-critical applications such as mountain climbing should be inspected on a far more frequent basis, up to and including before each use.

Avoid stepping on climbing rope, as this might force tiny pieces of rock through the sheath, which can eventually deteriorate the core of the rope.

Ropes may be flemished into coils on deck for safety, presentation, and tidiness.

Many types of filaments in ropes are weakened by corrosive liquids, solvents, and high temperatures. Such damage is particularly treacherous because it often invisible to the eye. [21]

Shock loading should be avoided with general use ropes, as it can damage them. [22] All ropes should be used within a safe working load, which is much less than their breaking strength.

A rope under tension – particularly if it has a great deal of elasticity – can be dangerous if parted. Care should be taken around lines under load.

Terminology

"Rope" is a material, and a tool. When it is assigned a specific function it is often referred to as a "line", especially in nautical usage. A line may get a further distinction, for example sail control lines are known as “sheets” (e.g. A jib sheet).

A halyard is a line used to raise and lower a sail, typically with a shackle on its sail end. Other maritime examples of “lines” include anchor line, mooring line, fishing line, marline. Common items include clothesline and a chalk line.

In some marine uses the term rope is retained, such as man rope, bolt rope, and bell rope.

See also

Related Research Articles

Knot Method of fastening or securing linear material

A knot is an intentional complication in cordage which may be practical or decorative, or both. Practical knots are classified by function, including hitches, bends, loop knots, and splices: a hitch fastens a rope to another object; a bend fastens two ends of a rope to each another; a loop knot is any knot creating a loop; and splice denotes any multi-strand knot, including bends and loops. A knot may also refer, in the strictest sense, to a stopper or knob at the end of a rope to keep that end from slipping through a grommet or eye. Knots have excited interest since ancient times for their practical uses, as well as their topological intricacy, studied in the area of mathematics known as knot theory.

A whipping knot or whipping is a binding of marline twine or whipcord around the end of a rope to prevent its natural tendency to fray.

Timber hitch

The timber hitch is a knot used to attach a single length of rope to a cylindrical object. Secure while tension is maintained, it is easily untied even after heavy loading.

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| header =  | direction = vertical | image1 = Nuba woman2.jpg | caption1 = A woman wearing braids | image2 = Classic French Braid (2).JPG | caption2 = A young girl with a French braid

The common whipping is the simplest type of whipping knot, a series of knots intended to stop a rope from unravelling. As it can slip off the rope easily, the common whipping should not be used for rope ends that will be handled. This whipping knot is also called 'wolf' whipping in some parts of the world. The 'Hangman's knot' is a variation of this whipping knot.

Matthew Walker knot Knot, useful to keep the end of the rope from fraying

A Matthew Walker knot is a decorative knot that is used to keep the end of a rope from fraying. It is tied by unraveling the strands of a twisted rope, knotting the strands together, then laying up the strands together again. It may also be tied using several separate cords, in which case it keeps the cords together in a bundle. The traditional use of the knot is to form a knob or "stopper" to prevent the end of the rope from passing through a hole, for instance in rigging the lanyards which tension the shrouds on older sailing ships with standing rigging of fibre cordage.

Cordage may refer to:

Rope splicing Rope merging

Rope splicing in ropework is the forming of a semi-permanent joint between two ropes or two parts of the same rope by partly untwisting and then interweaving their strands. Splices can be used to form a stopper at the end of a line, to form a loop or an eye in a rope, or for joining two ropes together. Splices are preferred to knotted rope, since while a knot typically reduces the strength by 20–40%, a splice is capable of attaining a rope's full strength. However, splicing usually results in a thickening of the line and, if subsequently removed, leaves a distortion of the rope. Most types of splices are used on 3-strand rope, but some can be done on 12-strand or greater single-braided rope, as well as most double braids.
While a spliced 3-strand rope's strands are interwoven to create the splice, a braided rope's splice is constructed by simply pulling the rope into its jacket.

Whipcord is the name for either a fabric or a form of braided cord.

Kernmantle rope is rope constructed with its interior core protected by a woven exterior sheath designed to optimize strength, durability, and flexibility. The core fibers provide the tensile strength of the rope, while the sheath protects the core from abrasion during use.

Parachute cord

Parachute cord is a lightweight nylon kernmantle rope originally used in the suspension lines of parachutes. This cord is now used as a general purpose utility cord. This versatile cord was used by astronauts during the 82nd Space Shuttle mission to repair the Hubble Space Telescope.

Wire rope

Wire rope is several strands of metal wire twisted into a helix forming a composite rope, in a pattern known as laid rope. Larger diameter wire rope consists of multiple strands of such laid rope in a pattern known as cable laid.

Fid

A fid is a conical tool traditionally made of wood or bone. It is used to work with rope and canvas in marlinespike seamanship. A fid differs from a marlinspike in material and purposes. A marlinspike is used in working with wire rope, natural and synthetic lines, may be used to open shackles, and is made of metal. A fid is used to hold open knots and holes in canvas, and to separate the "lays" of synthetic or natural rope for splicing. A variation of the fid, the gripfid, is used for ply-split braiding. The gripfid has a jamming cleat to pull a cord back through the cord split by the fid's point.

A ropewalk is a long straight narrow lane, or a covered pathway, where long strands of material are laid before being twisted into rope. Due to the length of some ropewalks, workers may use bicycles to get from one end to the other.

Eye splice

The eye splice is a method of creating a permanent loop in the end of a rope by means of rope splicing.

Worm, parcel and serve

To worm, parcel and serve a line is to apply a multi-layered protection against chafe and deterioration to standing rigging. It is a technique not usually used on modern small boats, but is found extensively on traditionally-rigged sailing ships. Worming, parcelling and serving —referred to collectively as "service"— is traditionally applied only to traditional twisted rope, either natural fiber or steel wire-rope, not the braided line almost exclusively used on modern vessels, but some traditional vessels now use modern high modulus braided lines in place of wire rope and serve the line to maintain the traditional appearance. It can be applied to the entire length of a line, such as a shroud, or selectively, to specific parts of a line, such as over the spliced ends of a stay, where the chafe on the middle section of the stay precludes complete protection.

Tarring (rope)

Tarring Is protecting some types of natural fibre and wire rope by coating it with tar. Hemp rope, which was typically used for standing rigging, requires tarring. Manila and cotton ropes were used for running rigging and were not tarred as this would make the rope too stiff to run easily through blocks. Regular tarring at sea was required when sailing ships used hemp rope - once every 6 months for a ship on a long voyage.

String (structure)

String is a long flexible structure made from fibers twisted together into a single strand, or from multiple such strands which are in turn twisted together. String is used to tie, bind, or hang other objects. It is also used as a material to make things, such as textiles, and in arts and crafts. String is a simple tool, and its use by humans is known to have been developed tens of thousands of years ago. In Mesoamerica, for example, string was invented some 20,000 to 30,000 years ago, and was made by twisting plant fibers together. String may also be a component in other tools, and in devices as diverse as weapons, musical instruments, and toys.

References

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  9. 1 2 McKie, Robin (1 August 2020). "Take a tusk, drill holes, weave a rope – and change the course of history". The Guardian. Article has photograph of the Hohle Fels rope-making tool.
  10. Small, Meredith F. (April 2002), "String theory: the tradition of spinning raw fibers dates back 28,000 years. (At The Museum).", Natural History, 111 (3): 14(2)
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  14. G.S. Nares (1865), Seamanship (3rd ed.), London: James Griffin, p. 23
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  16. Kyosev, Y (2015). Braiding technology for textiles. Cambridge, UK Waltham, MA, USA: Elsevier/ Woodhead Pub. ISBN   978-0-85709-135-2.
  17. Boating. June 1965.
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  19. "Air Winch Safety Info". AirWinchSafety.com. Retrieved 10 October 2012.
  20. "Wire Rope Inspections". U.S. DOL, OSHA. Retrieved 10 October 2012.
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Sources

Further reading