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From Wikipedia, the free encyclopedia

A knot is a method for fastening or securing linear material such as rope by tying or interweaving. It may consist of a length of one or more segments of rope, string, webbing, twine, strap, or even chain interwoven such that the line can bind to itself or to some other object—the "load". Knots have been the subject of interest for their ancient origins, their common uses, and the area of mathematics known as knot theory.

Contents

Usage

There is a large variety of knots, each with properties that make it suitable for a range of tasks. Some knots are used to attach the rope (or other knotting material) to other objects such as another rope, cleat, ring, or stake. Some knots are used to bind or constrict objects. Decorative knots usually bind to themselves to produce attractive patterns. The ability to choose the right knot for the job is a core skill of knot-tying. However, if memory is limited, three of the most useful knots are the bowline, the sheet bend, and the clove hitch.[1]

Learning

Sailors learning knots and ropework in the early 20th century

The number of books, websites, videos, and other resources about knots attests to their interest and value. While some people can look at diagrams or photos and tie the illustrated knots, others learn best by being shown. Knot tying skills are often transmitted by sailors, scouts, climbers, cavers, arborists, rescue professionals, fishermen, and surgeons. After one has mastered a few basic knots, diagrams and pictures become easier to interpret. As one learns more knots, one starts to discern patterns in their structure and tying method. Learning knots demands practice and patience.

Applications

Knots are essential in many industries, hobbies and domestic activities. Even simple activities such as running a load from the hardware store to home can turn into disaster if a clumsy twist in a cord passes for a knot. Truckers in need of securing a load may use a trucker's hitch, gaining mechanical advantage. Knots can save a spelunker from finding himself buried under rock. Learning well-tested knots prior to engaging in hazardous activities such as sailing or rock-climbing is a critical safety measure.

Knots can be applied in combination to produce complex objects such as lanyards and netting. In ropework, the frayed end of a rope is held together by a type of knot called a whipping knot. Many types of textiles use knots to repair damage. Macrame, one kind of textile, is generated exclusively through the use of knotting, instead of knits, crochets, weaves or felting. Macramé can produce self-supporting three dimensional textile structures, as well as flat work, and is often used ornamentally or decoratively.

Properties

Strength

Knots invariably weaken the rope in which they are made. When knotted rope is strained to its breaking point, it almost always fails at the knot or close to it, unless it is defective or damaged elsewhere. The bending, crushing, and chafing forces that hold a knot in place also unevenly stress rope fibers and ultimately lead to a reduction in strength. The exact mechanisms that cause the weakening and failure are complex and are the subject of continuous study.

"Relative knot strength," also called knot efficiency, is the breaking strength of a knotted rope in proportion to the breaking strength of the rope without the knot. Determining this number is hard because many factors can affect a knot efficiency test: the type of fiber, the style of rope, the size of rope, whether it is wet or dry, how the knot is dressed before loading, how fast the knot is loaded, whether the knot is repeatedly loaded, and so on. Most common knots' efficiency range between forty and eighty percent.

While some rope splices can nearly maintain the rope's full strength, in most situations, when forming loops and bends conventional knots are far more practical. Thus the prudent knot user will always allow for a large safety margin in the strength of rope chosen for a task due to the weakening effects of knots, aging, damage, shock loading, etc. In general, the safe working load is often specified as between 10% and 20% of the rated breaking strength of the rope being used.[1] For life-threatening applications, many other factors come into play which are beyond the current scope of this article. Experienced practitioners should always be consulted before using ropes and knots when safety of life, limb, or property is involved.

Security

Even if the rope does not break, a knot may still fail to hold. Knots that hold firm under a variety of adverse conditions are said to be more secure than those that do not. The main ways knots fail to hold are:

Slipping

The load creates tension that pulls the rope back through the knot in the direction of the load. If this continues far enough, the working end passes into the knot and the knot unravels and fails. This behavior can worsen when the knot is repeatedly strained and let slack, dragged over rough terrain, or repeatedly struck against hard objects such as a masts and flagpoles.

Even with secure knots, some slippage may take place as the knot is first put under real tension. This risk can be mitigated by leaving plenty of rope at the working end outside of the knot, and by dressing the knot cleanly and tightening it as fully as possible before loading. Sometimes, the use of a stopper knot or, even better, a backup knot can prevent the working end from passing through the knot; but if a knot is observed to slip, it is generally preferable to use a more secure knot. In life critical uses, backup knots are often added to already secure knots in order to maximize safety.

Capsizing

Bowline (PSF).jpg

Capsizing (or spilling) a knot refers to changing a knot's form and rearranging its parts, usually by pulling on specific ends in certain ways. When used inappropriately, some knots tend to capsize easily or even spontaneously. Often the capsized form of the knot offers little resistance to slipping or unraveling. For an excellent example of a knot that capsizes dangerously, see the discussion of the reef knot used as a bend.

Sometimes a knot is intentionally capsized as a method of tying another knot, as with the "lightning method" of tying a Bowline. Some knots, such as the Carrick Bend, are generally tied in one form then capsized to obtain a stronger or more stable form.

Sliding

In knots that are meant to grip other objects, failure can be defined as the knot moving relative to the object being gripped. While the knot itself does not fail, it ceases to perform the desired function. For instance, a simple Rolling Hitch tied around a railing and pulled parallel to the railing might hold up to a certain tension, then start sliding. Sometimes this problem can be corrected by working-up the knot tighter before subjecting it to load, but usually the problem requires either a knot with more wraps or a rope of different diameter or material.

Components

Knot components
A: Turn
B: Round turn
C: Two round turns

Bight

The center part of a length of rope, string, or yarn—in opposition to the rope's ends.

  • A "bight" is any curved section, slack part, or loop between the ends of a rope.
  • The phrase "in the bight" implies that a U-shaped section of rope is used in making a knot. Many knots can be tied either with the end or in the bight.

Bitter end

More a ropeworker's term than a knot term, it refers to the end of a rope that is tied off, hence the expression "hanging on to the bitter end". A bitt is a metal block with a crosspin used for tying lines to, found on docks. In fact the bitter end is the end of the Anchor "Cable" that connects to the Anchor Bitts in the cable locker under the forecastle or poop using the bitter pin. (British nautical usage). Other uses may be borrowed from this derivation.

Loop

A full circle formed by passing the working end over itself. Note that the term 'loop' is also used to refer to a category of knots (see 'Categories' below).

Elbow

Two crossing points created by an extra twist in a loop.

Standing end

The end of the rope not involved in making the knot, often shown as unfinished.

Standing part

Section of line between knot and the standing end (seen above).

Turn

  • A turn or single turn is a single pass behind or through an object.
  • A round turn is the complete encirclement of an object; requires two passes.
  • Two round turns circles the object twice; requires three passes.

Working end

The active end of a line used in making the knot. May also be called the 'running end' or 'live end'.

Working part

Section of line between knot and the working end.

Categories

The list of knots is extensive, but common properties allow for a useful system of categorization. For example, loop knots share the attribute of having some kind of an anchor point constructed on the standing end (such as a loop or overhand knot) into which the working end is easily hitched to using a round turn. An example of this is the bowline. Constricting knots often rely on friction to cinch down tight on loose bundles; an example is the Miller's knot. Knots may belong to more than one category.

Bend 
A knot uniting two lines (for knots joining two ends of the same line, see binding knots or loops). List of bends.
Binding 
A knot that restricts object(s) by making multiple winds. List of binding knots.
Coil 
Knots used to tie up lines for storage. List of coil knots. Another handy coil is here.
Decorative knot 
A complex knot exhibiting repeating patterns often constructed around and enhancing an object. List of decorative knots.
Hitch 
A knot tied to a post, cable, ring, or spar. List of hitch knots.
Lashing 
A knot used to hold (usually) poles together. List of lashing knots.
Loop 
A knot used to create a closed circle in a line. List of loop knots.
Plait (or Braid)
A number of lines interwoven in a simple regular pattern. List of plait knots.
Slip (or Running) 
A knot tied with a hitch around one of its parts. In contrast, a loop is closed with a bend. While a slip knot can be closed, a loop remains the same size. List of slip knots.
Seizing 
A knot used to hold two lines or two parts of the same line together. List of seizing knots.
Sennit 
A number of lines interwoven in a complex pattern. List of sennit knots.
Splice 
A knot formed by interweaving strands of rope rather than whole lines. More time-consuming but usually stronger than simple knots. List of splices.
Stopper 
A knot tied to hold a line through a hole. List of stopper knots.
Trick 
A knot that is used as part of a magic trick, a joke, or a puzzle. List of trick knots.
Whipping 
A binding knot used to prevent another line from fraying.

Basic useful knots

Knot theory

A trefoil knot a mathematical version of an overhand knot.

Knot theory is a branch of topology. It deals with the mathematical analysis of knots, their structure and properties, and with the relationships between different knots. In topology, a knot is a figure consisting of a single loop, abstracted from any physical rope or line, with any number of crossing or "knotted" elements. As such, it has no proper ends, and cannot be undone or untied. Various mathematical techniques are used to classify and distinguish knots. For instance, the Alexander polynomial can be used to distinguish the trefoil knot from the figure-of-eight knot and the unknot (a simple loop).

See also

References

Footnotes

  1. ^ Cassidy 1985, The Klutz Book of Knots

Notations

  • Clifford W. Ashley The Ashley Book of Knots. Doubleday, New York. ISBN 0-385-04025-3
  • R.S. Lee. All The Knots You Need. Algrove Publishing. ISBN 0-921335-47-4
  • Raoul Graumont. Handbook of Knots. Cornell Maritime Press/Tidewater Publishers. ISBN 0-87033-030-6
  • Cyrus L. Day. Knots & Splices. International Marine/McGraw-Hill Companies. ISBN 0-87742-252-4
  • Geoffrey Budworth (1999). The Ultimate Encyclopedia of Knots & Ropework. Annes Publishing Limited. ISBN 1-55267-986-1
  • John Cassidy (1985). The Klutz Book of Knots. Klutz Press, Palo Alto, California. ISBN 0-932592-10-4
  • Des Pawson(2001). Pocket Guide to Knots & Splices. Produced for Propsero Books by RPC Publishing Ltd., London. ISBN 1-55267-218-2
  • Brion Toss. The Complete Rigger's Apprentice. International Marine/McGraw-Hill Companies. ISBN 0-07-064840-9
  • Allen Padgett and Bruce Smith. On Rope. National Speleological Society. ISBN 0-9615093-2-5
  • J.C. Turner and P. van de Griend (ed.) (1996). History and Science of Knots. World Scientific. ISBN 981-02-2469-9

External links

Knots at the Open Directory Project


Bible wiki

Up to date as of January 23, 2010

From BibleWiki

Some form of quipu or knot-alphabet appears to have been adopted in Biblical, or, at least, in Talmudical times, to judge from the form taken by the ẓiẓit. Whether any mystical influence was connected therewith is uncertain, but tefillin are not knotted, except with the permanent knot of the head phylactery. It was even disputed down to the time of R. Tam whether the head knot should be tied afresh every day (Responsa, No. 132). To the rigid Sabbatarians of the Talmudic period, to make a knot was an act of labor, and, therefore, forbidden on the Sabbath (Shab. 111b), and this forms part of the Jewish law to the present day. Not alone is the making of a knot forbidden, but also the loosing of one. Consequently ultra-Orthodox Jews who will not carry a handkerchief except in the form of a girdle merely twist it around and do not tie it in a knot. Children, however, might go out on the Sabbath with stalks of madder knotted together, seemingly as an amulet (Shab. 66b). In the discussion on the restriction of martyrdom some of the extremists held that one should suffer martyrdom rather than tie even the knots of one's shoes like the Romans (Sanh. 74b). It is stated that Ex 33:23 really means that God showed Moses the knots of the tefillin (Ber. 7a); the passage, however, is interpreted by Ibn Ezra (ad loc.) as referring to the knowledge of the physical laws of nature (comp. Maimonides, "Moreh," i. 35).

In Jewish folk-lore knots play a certain part, though how far the folk-lore is Jewish in origin generally remains uncertain. Among the children of Kiev one of the ways of determining who shall be "it " is to tie a knot in a handkerchief; the children pick out the corners, and the one selecting the knotted corner is "it." In Kovno, when a wart isremoved, a knot is tied around it with a thread, and this knot is placed under the threshold. To cure a person who is possessed one counts nine knots ("Sefer Ḥasidim," § 1159): this seems to be German (comp. Wuttke, "Deutscher Aberglaube," p. 157).

Bibliography: Levy, Neuhebr. Wörterb. iv. 399-400; Güdemann, Gesch. ii. 205.

This entry includes text from the Jewish Encyclopedia, 1906.
Facts about KnotRDF feed

Simple English

For the unit of speed, see Knot (unit)
File:Alpine Butterfly Bend
A knot from a blue and red string

A knot is a fixed looping of a piece of string or rope. Knots are often used for binding things together. While a knot is often made from rope, it can also be made from many other things. In fact, a knot is actually the condition a long flexible object is in. For example, hair can be tied in a knot. The ends of balloons are tied in a knot to prevent the air from escaping. The average person over 5 or so years of age is likely capable of tying a knot; most of these knots people tie are probably with their shoelaces. Ribbons are also tied in a knot so as to appear pretty, as when wrapped around a gift. In addition, knots are also made by sailors in many different forms and for many different purposes. There are even people who have adopted knot-making as a hobby.

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