Difference between revisions of "AY Honors/Knot/Prusik"

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A '''Prusik (or Prussik or Prussic)''' is a [[friction hitch]] used in [[climbing]], [[canyoneering]], [[caving]], [[rope rescue]] and by [[arborist]]s to grab a rope (sometimes referred to as a ''rope-grab''). The term '''Prusik''' is used both for the knot, for the loops of cord, and for the action ('''to prusik''').  More casually, the term is used for any friction hitch that can grab a rope.
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{{Knot
 
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| name=Prusik knot
The Prusik hitch is named for its inventor, Austrian mountaineer [[Karl Prusik | Dr. Karl Prusik]]. It was shown in a 1931 Austrian mountaineering manual for rope ascending. It was used on several mountaineering routes of the era to ascend the final summit block of a peak; where a rope could be thrown over the top, one side anchored, and climbers could attain the summit by prusiking up the other side of the rope.
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| image= Prusikhowto4.jpeg
 
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| use = A '''Prusik (aka Prussik or Prussic)''' is a friction hitch used in climbing, canyoneering, caving, rope rescue and by arborists to grab a rope (sometimes referred to as a ''rope-grab''). The term '''Prusik''' is used both for the knot, for the loops of cord, and for the action ('''to prusik''').
== Advantages of a Prusik hitch ==
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A Prusik rope is a circular loop with a circumference of {{units|20 to 100 cm|8-40 inches}} depending on its intended use. Two Prusik ropes are tied to another rope which is anchored above. When the Prusik knot is under tension, it grabs the rope to which it is tied. When not under tension, it is easily moved. The climber places one foot into each loop, and shifts all of his or her weight to one of them, releasing the tension on the other. The rope without tension is then slid upwards on the vertical rope. The climber then shifts his or her weight to the other loop and slides the first one up. This is repeated until the rope has been ascended.
Climbers carry Prusiks mainly for emergency use, as they are lighter than other options.  Prusiks are fast to place on the rope, and with practice, can be placed with one hand. The loops of cord can be used as slings, and are thus multi-functional in a climbing environment.
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Prusiks will work around two ropes, even two ropes of different diameters. Prusiks provide a high-strength and relatively fail-safe (i.e., they will slip before damaging the rope or breaking) attachment, and are used in some rope-rescue techniques. Prusiks are good to use in hauling systems where multiple rope-grabs may be needed, and where mechanical rope-grabs are not available.
 
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Although the Prusik Climb technique may be called old-school by some, the US Army still includes it in its annual Best Ranger competition. Rangers in the competition routinely make it up a 90 foot rope in under a minute.
Prusiks will work around two ropes, even two ropes of different diameters. Prusiks provide a high-strength and relatively fail-safe (i.e., they will slip before damaging the rope or breaking) attachment, and are used in some rope-rescue techniques. Prusiks are good to use in hauling systems where multiple rope-grabs may be needed, and where mechanical rope-grabs are not available.
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| tying_instructions =
 
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The Prusik is tied by wrapping the prusik loop around the rope a number of times (depending on the materials, but usually 3-5 times), and then back through itself, forming a barrel around the rope, with a tail hanging out the middle. When the tail is weighted the turns tighten around the main rope and grab. When weight is removed the loop can be slid along the rope by placing a hand directly on the barrel and pushing. The trick is, if it grabs well, then it is hard to slide along the rope. '''Breaking''' the Prusik free from the rope after it has been weighted can be difficult, and is easiest done by pushing the ''bow'', being the loop of cord which runs from the top wrap, over the knot to the bottom wrap, along the tail a little. This loosens the grip of the hitch and makes movement easier.
Prusiks are far less likely to damage the main rope as opposed to mechanical rope-grabs (or jumars). A prusik which is overloaded will initially slip and, if loaded to excess, it will normally slide until the heat of friction between the ropes results in a physical failure of the prusik cord. Opposed to mechanical rope-grabs which will sometimes either damage the sheath of the rope it is attached to, or, on some cases, sever the rope entirely when overloaded.
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Image:Prusikhowto1.saa.jpeg|Step 1
Some Prusik hitches (dependent on which variant is used) have the advantage of working equally in both directions.  Most mechanical rope-grabs work like a ratchet, moving freely up the rope, but grabbing when a load in placed down on them.  Traditional Prusiks (such as those shown below) will grab when pulled by the tail, either up or down, and will slide when pushed by the barrel.
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Image:Prusikhowto2.saa.jpeg|Step 2
 
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Image:Prusikhowto3.saa.jpeg|Step 3
== Disadvantages of a Prusik hitch ==
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Image:Prusikhowto4.jpeg|Step 4
For climbing a rope, Prusiks are slow and inefficient.  Mechanical devices (such as [[jumars]]) to grab the rope are available that are easier and faster to use, but of course, heavier, more expensive and bulkier.
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Image:Prusikhowto5.jpeg|Locked while holding tension.
 
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Image:Prusikhowto6.saa.jpeg|Slides readily without tension.
== Related hitches and equipment ==
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The Prusik hitch is a specific hitch.  Other friction hitches can be used to create a rope-grab from small cord (i.e., cord that is smaller than the rope being grabbed) or [[webbing]] slings.  The two main alternatives are the [[Bachmann knot]] and the [[Klemheist knot]].  Each has its advantages and disadvantages, mainly in how easy they are to use for climbing a rope.  Another variation is the AutoBloc, used by some people as a backup knot while rappelling.
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A '''Purcell Prusik''' is a related cord popular among cavers and rope-rescue people.  A somewhat longer loop than the normal Prusik is used around the rope, then a second Prusik is used around the cord loop itself to form a foot loop.  The foot loop is then easily adjusted in length and position.
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{{#ifeq:{{#titleparts:{{PAGENAME}}|1}}|Adventist Youth Honors Answer Book|[[Category:Adventist Youth Honors Answer Book|{{SUBPAGENAME}}]]}}<!-- Use in [[knots]] -->
 
 
A '''Prusik-Minding-Pulley''' is common in rope rescue.  The rope to be pulled is passed through a pulley, and a Prusik is tied on the loaded side.  When the rope is pulled, the Prusik rides against the pulley and the rope slides through it, but when the rope is relaxed, the Prusik slides away from the pulley and grabs the rope.  Thus, the combination acts as a ratchet.
 
 
 
== Equipment ==
 
A Prusik hitch is tied using a loop of nylon accessory cord or a sling.  The length of this loop depends on the application it is being used for.  For instance, the loop used for an ''Auto-Bloc'' might only be 20 cm, whereas the foot loop for climbing a rope might work better with a length of 100 cm or more.  As a general rule, longer loops are preferable over shorter ones, as a loop can always be shortened (by tying a knot in it), but cannot be lengthened if the application changes.
 
 
 
The effectiveness of the Prusik hitch relies on the surface area between the hitch and the mainline, and the diameter of the cord used.  Normally the greater difference between the diameter of the cord used for the hitch and the mainline, the greater the ability for the hitch to hold.  It should be noted, however, that the smaller the diameter of the cord used the lower its safe working load. In addition, smaller diameter cords are often harder to work with as they often jam tight when placed under load, and the size of the rope makes them hard to handle when wearing gloves.
 
 
 
== Tying the Prusik ==
 
The Prusik is tied by wrapping the loop around the rope a number of times (depending on the materials), but usually 3-5 times, and then back through itself, forming a barrel around the rope, with a tail hanging out the middle. When the tail is weighted the turns tighten around the main rope and grab. When weight is removed the loop can be slid along the rope by placing a hand directly on the barrel and pushing. The trick is, if it grabs well, then it is hard to slide along the rope. '''Breaking''' the Prusik free from the rope after it has been weighted can be difficult, and is easiest done by pushing the ''bow'', being the loop of cord which runs from the top wrap, over the knot to the bottom wrap, along the tail a little. This loosens the grip of the hitch and makes movement easier.
 
 
 
{|
 
|[[Image:prusikhowto1.saa.jpeg|thumb|none|150px|Step 1.]]
 
|[[Image:prusikhowto2.saa.jpeg|thumb|none|150px|Step 2.]]
 
|[[Image:prusikhowto3.saa.jpeg|thumb|none|150px|Step 3.]]
 
|-
 
|[[Image:prusikhowto4.saa.jpeg|thumb|none|150px|Step 4.]]
 
|[[Image:prusikhowto5.saa.jpeg|thumb|none|150px|Locked while holding tension.]]
 
|[[Image:prusikhowto6.saa.jpeg|thumb|none|150px|Slides readily without tension.]]
 
|}
 
 
 
It is a matter of debate as to whether the rope grip can be increased by passing through the [[bight]] additional times:
 
 
 
[[Image:prusikthreeturn.saa.jpeg|thumb|none|250px|A variation of the Prusik knot with additional friction.]]
 
 
 
== Applications ==
 
In addition to being a useful rope-grab for rope-rescue applications, Prusiks are popular for:
 
 
 
*'''"Rappel Backup"/"Self-Belay Below The Device":''' A Prusik is placed below the descender and controlled with the brake hand.  It acts as an automatic 'dead man's handle' should the climber be incapacitated or require the use of both hands.  Careful setup of the [[rappel]] backup is critical, or it will not work.  An AutoBloc knot is most widely used in this application.  This technique is used by some rappellers, and not by others.
 
 
 
*'''"Rappel Backup"/"Self-Belay Above The Device":''' A Prusik is placed above the descender and controlled with the hand not being used as the brake hand. This configuration allows for easier and faster transition from rappeling to climbing the rope, but can also result in the Prusik locking tight as the amount of friction required to hold the load at that point is far higher than that experienced by a ''self-belay below the device''.
 
 
 
*'''"Prusiking" or ascending the line:'''  Two prusiks used in tandem can be used to climb a fixed rope. One prussik is attached to the "belay loop" sewn onto the front of a harness and the other is attached to a longer length of cord reaching to one foot.  With one loop attached to the rope above the other the climber can then stand up in the foot loop, slide the prusik hitch of the waist loop further up the rope and then "sit" down on it.  Once sitting, they can slide the foot loop up the rope and repeat the process.
 
 
 
*'''"Escaping the Belay": ''' In a lead-climbing situation, should the belayed climber become incapacitated in a position where they cannot be safely lowered to the ground, the belayer must ''escape the belay'' in order to effect rescue.  With the belay rope locked off with one hand, the belayer can tie a prusik to the rope with the other hand, and transfer the load to a fixed anchor;  thus allowing them to effect rescue or go get help.
 
 
 
*'''Various Rescue Applications''' Rope rescue teams such as in [[swiftwater rescue]] use a Prusik hitch as a 'pulley tender', to hold a line taut while tensioning a [[highline]] for a [[Tyrolean traverse]], or in ''boat-on-tether'' and similar rescue operations.
 
 
 
== When To carry (climbing) ==
 
Prusik cords are carried by some climbers and not carried by others. The decision over whether or not to carry prusiks is a matter of personal taste and training.  Prusiks are unlikely to be needed on short climbs where the climber can be lowered to the ground; conversely they may prove useful where the climber cannot be lowered (either due to the height of the cliff or due to a hazard underneath the climber). Contrary to popular belief, prusiks are not the sole preserve of [[Traditional climbing|Trad Climbers]] - [[Sport climbing|Sport Climbers]] on [[Multi-pitch climbing|multi-pitch]] routes sometimes also carry prusiks.
 
 
 
Prusiks can be improvised from other climbing equipment, such as slings, already carried by the climber.  Some climbers carry prusik-specific cords so that they are always easily and quickly available in an emergency.
 
 
 
Some sources recommend that three prusik loops be carried. The logic being that two are required to ascend a rope, and the third allows for one to be lost, damaged, or dropped.  Three loops also allow the climber to pass a knot in the rope should the need arise, a difficult task without a third loop.
 
 
 
'''WARNING:'''  Climbing is a sport with inherent dangers.  The techniques described require expertise, practice and judgement to apply safely.  Specific instruction by trained professionals is recommended.
 
 
 
==External links==
 
*[http://ozultimate.com/canyoning/knots/prusik/ Prusik Knot at OZultimate.com canyoning] with good pictures showing how it is tied.
 
*[http://fmg-www.cs.ucla.edu/geoff/prusik_knot.html Prusik Knot used in Sailing] for climbing a mast, with other notes.
 
*[http://www.iland.net/~jbritton/Friction%20Hitches.html Many Varieties of Friction Hitches]
 
*[http://storrick.cnchost.com/VerticalDevicesPage/Misc/RappelSafetyPost.html Discussion of Rappel Backups - Pros and Cons]
 
*[http://www.outdooridiots.com/features/200605/prusik/prusik.asp A detailed article, good pictures, several prusiks and ideas shown.]
 
 
 
[[Category:Knots]]
 

Latest revision as of 13:43, 8 September 2021

Prusik knot
Prusikhowto4.jpeg

Use: A Prusik (aka Prussik or Prussic) is a friction hitch used in climbing, canyoneering, caving, rope rescue and by arborists to grab a rope (sometimes referred to as a rope-grab). The term Prusik is used both for the knot, for the loops of cord, and for the action (to prusik).

A Prusik rope is a circular loop with a circumference of 20 to 100 cm8-40 inches depending on its intended use. Two Prusik ropes are tied to another rope which is anchored above. When the Prusik knot is under tension, it grabs the rope to which it is tied. When not under tension, it is easily moved. The climber places one foot into each loop, and shifts all of his or her weight to one of them, releasing the tension on the other. The rope without tension is then slid upwards on the vertical rope. The climber then shifts his or her weight to the other loop and slides the first one up. This is repeated until the rope has been ascended. Prusiks will work around two ropes, even two ropes of different diameters. Prusiks provide a high-strength and relatively fail-safe (i.e., they will slip before damaging the rope or breaking) attachment, and are used in some rope-rescue techniques. Prusiks are good to use in hauling systems where multiple rope-grabs may be needed, and where mechanical rope-grabs are not available.

Although the Prusik Climb technique may be called old-school by some, the US Army still includes it in its annual Best Ranger competition. Rangers in the competition routinely make it up a 90 foot rope in under a minute.

How to tie:
The Prusik is tied by wrapping the prusik loop around the rope a number of times (depending on the materials, but usually 3-5 times), and then back through itself, forming a barrel around the rope, with a tail hanging out the middle. When the tail is weighted the turns tighten around the main rope and grab. When weight is removed the loop can be slid along the rope by placing a hand directly on the barrel and pushing. The trick is, if it grabs well, then it is hard to slide along the rope. Breaking the Prusik free from the rope after it has been weighted can be difficult, and is easiest done by pushing the bow, being the loop of cord which runs from the top wrap, over the knot to the bottom wrap, along the tail a little. This loosens the grip of the hitch and makes movement easier.