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, but not pushing). Rope is thicker and stronger than similarly constructed cord, line, string, or twine.
Construction
Common materials for rope include natural fibers such as manila hemp, hemp, linen, cotton, coir, jute, and sisal.
Synthetic fibers in use for rope-making include polypropylene, nylon, polyesters (e.g. PET, LCP, HPE, Vectran), polyethylene (e.g. Spectra), Aramids (e.g. Twaron, Technora and Kevlar) and polyaramids (e.g. Dralon, Tiptolon). Some ropes are constructed of mixtures of several fibres or use co-polymer fibres. Rope can also be made out of metal. 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 fiber used to make decorative rope.
Usage
Rope is of paramount importance in fields as diverse as construction, seafaring, exploration, sports and communications and has been since prehistoric times. In order to fasten rope, a large number of knots have been invented for various uses. 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 a load and multiply the force applied to the end. Winches and capstans are machines designed to pull ropes.
Climbing Ropes: Climbing ropes have a "kernmantle" construction consisting of a braided core, which supplies most of the rope's strength. The core is covered by a woven sheath. Kernmantle ropes are durable and easy to knot. More importantly, they are dynamic. They stretch. When falling, say 50 feet, the rope will stretch five to seven feet (average) to gradually absorb the impact. By applying the brakes this way, a climbing rope catches the climber gently, lessening the force on the climber as well as his/her gear. "Static" ropes used in caving and sport rappelling hardly stretch at fall. Fall on one of these and the jolt it delivers could break the climber's gears or even the climber him/herself. The UIAA (Union Internationale des Association d'Alpinisme) in concert with the CE sets climbing-rope standards and oversees testing. Any rope bearing a UIAA or CE certification tag is fine for climbing. Despite the hundreds of thousands of falls climbers suffer every year, there is not a single recorded instance of a climbing rope breaking in a fall. Climbing ropes, however, do cut easily when they are weighted. Keeping them away from sharp rock edges and old worn carabiners is imperative. Ropes come with either a designation for Single, or Double(Twin) use. A single rope is the most common and it is intended to be used by itself, as a single strand. Single rope range in thickness from roughly 9mm to 11mm. Smaller ropes are lighter, but wear out faster. Double ropes are thinner ropes, usually 9mm and under, and are intended to be used as a pair. These ropes offer a greater margin or security against cutting, since it is unlikely that both ropes will be cut, but complicate belaying and leading. Double ropes are usually reserved for ice and mixed climbing, where there is need for two ropes to rappel.
History
The use of ropes for hunting, pulling, fastening, attaching, carrying, lifting, and climbing dates back to prehistoric times and has always been essential to mankind's technological progress. It is likely that the earliest "ropes" were naturally occurring lengths of plant fiber, 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. Fossilised fragments of "probably two-ply laid rope of about 7 mm diameter" were found in one of the caves at Lascaux, dating to approximately 15,000 BC.[1]
The ancient Egyptians were probably the first civilization to develop special tools to make rope. Egyptian rope dates back to 4000 to 3500 B.C. and was generally made of water reed fibers. Other rope in antiquity was made from the fibers 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 B.C., rope made of hemp fibers was in use in China. Rope and the craft of rope making spread throughout Asia, India, and Europe over the next several thousand years.
In the Middle Ages (from the thirteenth century to the eighteenth century), from the British Isles to Italy, ropes were constructed in so-called rope walks, 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 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 diameter 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 unable to support the required weight.
Leonardo de Vinci drew sketches of a concept for a ropemaking machine, but just like many other of his inventions, they never got built. Nevertheless, remarkable feats of construction were accomplished 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 1700s several working machines had been built and patented.
Some rope continues to be made from natural fibers such as coir and sisal, despite the dominance of synthetic fibers such as nylon and polypropylene which have become popular since the 1950s.
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A German ropemaker, around 1470 AD -
Public demonstration of historical ropemaking technique
Styles of rope construction
Laid or twisted rope
Laid rope, also called twisted 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. One naming convention uses the uppercase letters Z and S 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-laid rope is said to be "right-handed", and S-laid to be "left-handed". Traditionally, a three strand laid rope is called a plain or hawser-laid rope. A four strand rope is usually called shroud-laid, and a larger rope formed by twisting together 3 or more ropes is called cable-laid.
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. On the other hand, rope constructed in this manner untwists under tension, which is the cause of spinning, kinking, hockling and stretching. 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. One of the drawbacks of this construction is that every fiber is exposed to abrasion numerous times along the length of the rope. This means that the rope can degrade to numerous inch-long fiber fragments, which is not easily detected visually.
Braided rope
Braided ropes are generally made from nylon, polyester or polypropylene. Nylon is chosen for its elastic stretch properties and good resistance to ultraviolet light. Polyester is about 90% as strong as nylon but stretches less under load, is more abrasion resistant, has better UV resistance, and has less change in length when wet. Polypropylene is preferred for low cost and light weight (it floats on water).
Single braid consists of 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 fiber is chosen for strength while the outer braid fiber 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 fibers in the center, with a braided outer sheath or mantle of woven fibers. 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, the core fibers are usually twisted, and chopped into shorter lengths which makes the rope more stretchy. Static kernmantle ropes are made with untwisted core fibers and tighter braid, which causes them to be stiffer in addition to limiting the stretch.
Braided ropes (and objects like garden hoses, fiber optic or coaxial cables, 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.
Other types
Plaited rope is made by braiding twisted strands, and is also called square braid. 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 fibers 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 the most popular rope for anchoring and can be used as mooring warps. This type of construction was pioneered by Yale Cordage.
Handling rope
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 unraveling, the ends of a rope are bound with twine, tape, or heat shrink tubing. The ends of plastic fiber ropes are often melted and fused solid.
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.
The average rope life-span is five years. Serious inspection should be given to line after that point.
When preparing for a climb, it is important to stack the rope on the ground or a tarp and check for any "dead-spots".
Avoid stepping on rope, as this might force tiny pieces of rock through the sheath, which can eventually deteriorate the core of the rope.
Line
A piece of rope that has a specific purpose is called a line, especially in nautical usage. Examples include clothesline, chalk line, anchor line, stern line, fishing line etc.
See also
- Flogging
- International Year of Natural Fibres 2009
- Jump rope or rope skipping
- Knot
- List of spans
- Rope bondage
- Rope splicing
- Ropework
- Single Rope Technique
- Tight-rope walking
- Twaron
- Whipped rope
References
- ^ J.C. Turner and P. van de Griend (ed.), The History and Science of Knots (Singapore: World Scientific, 1996), 14.
Sources
- Gaitzsch, W. Antike Korb- und Seilerwaren, Schriften des Limesmuseums Aalen Nr. 38, 1986
- Gubser, T. Die bäuerliche Seilerei, G. Krebs AG, Basel, 1965
- Hearle, John W. S. & O'Hear & McKenna, N. H. A. Handbook of Fibre Rope Technology, CRC Press, 2004
- Lane, Frederic Chapin, 1932. The Rope Factory and Hemp Trade of Venice in the Fifteenth and Sixteenth Centuries, Journal of Economic and Business History, Vol. 4 No. 4 Suppl. (August 1932).
- Militzer-Schwenger, L.: Handwerkliche Seilherstellung, Landschaftsverband Westfalen-Lippe, 1992
- Nilson, A. Studier i svenskt repslageri, Stockholm, 1961
- Pierer, H.A. Universal-Lexikon, Altenburg, 1845
- Plymouth Cordage Company, 1931. The Story of Rope; The History and the Modern Development of Rope-Making, Plymouth Cordage Company, North Plymouth, Mass.
- Sanctuary, Anthony, 1996. Rope, Twine and Net Making, Shire Publications Ltd., Cromwell House, Princes Risborough, Buckinghamshire.
- Schubert, Pit. Sicherheit und Risiko in Fels und Eis, Munich, 1998
- Smith, Bruce & Padgett, Allen, 1996. On Rope. North American Vertical Rope Techniques, National Speleological Society, Huntsville, Alabama.
- Strunk, P.; Abels, J. Das große Abenteuer 2.Teil, Verlag Karl Wenzel, Marburg, 1986
- Teeter, Emily, 1987. Techniques and Terminology of Rope-Making in Ancient Egypt, Journal of Egyptian Archaeology, Vol. 73 (1987).
- Tyson, William, no date. Rope, a History of the Hard Fibre Cordage Industry in the United Kingdom, Wheatland Journals, Ltd., London
External links
- Ropewalk: A Cordage Engineer's Journey Through History History of ropemaking resource and nonprofit documentary film
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