AY Honors/Knot/Prusik

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A Prusik (or Prussik) is a friction hitch used by Climbers, Canyoneers, Cavers, Rope Rescue people and Arborists to grab a rope (as a rope-grab). Two may be used to climb a rope. The knot is tied using a loop of (for example) 6mm cord around a 9mm rope. 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.

Advantages of a Prusik Hitch

Climbers carry Prusiks mainly for emergency use, as they are lighter than many 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.

Rescue teams such as 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.

Prusiks will work around two ropes, even two ropes of different diameters. Prusiks provide a high-strength and fail-safe (ie, 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 enough mechanical rope-grabs may not be available.

Prusiks 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. Prusiks will grab when pulled by the tail, either up or down, and will slide when pushed by the barrel.

Disadvantages of a Prusik Hitch

For climbing a rope, Prusiks are slow and inefficient. Mechanical devices to grab the rope are available that are easier and faster to use, but of course, more expensive and generally bulkier.

Related Hitches and Equipment

The Prusik hitch is a specific hitch. There are other friction hitches that can be used to create a rope-grab from small cord (ie, cord that is smaller than the rope being grabbed) or webbing slings. The two main alternatives are the Bachman knot and the Kleimheist. 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.

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.

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 tied into a loop about 30cm in length. It can also be tied with slings of a similar size. Most people use 6mm cord for climbing ropes of 8mm to 11mm diameter. The cord must be smaller than the rope climbed, or it does not grab well. Cord smaller than 6mm is usually too weak, and can be easily damaged.

Tying the Prusik

The prusik is tied by wrapping the loop around the rope 3-5 times (depending on the materials) 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 against 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.

Step 1.
Step 2.
Step 3.
File:Prusikhowto5.saa.jpeg
Locked while holding tension.
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:

File:Prusikthreeturn.saa.jpeg
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": A prusik can be used as a self-belay during a rappel descent. Placed below a descender and controlled with the brake hand, it can act 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. (Controversy:) Use of a rappel backup knot is not widely accepted, but fervently promoted by those who believe it adds to one's safety.

"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 waist loop up and "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, then 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, transfer the load to a fixed anchor, allowing themselves to effect rescue or go get help.

History

The Prusik hitch was invented by Austrian mountaineer 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.

When To Carry (Climbing)

Prusiks are carried by some climbers and not carried by others. The decision over whether or not to carry a prusik is determined by the nature of the climb - they are unnecessary on a short climb where the climber may always be lowered to the ground; conversely they may be neccessary where the climber cannot be lowered (either due to the height of the cliff or due to a hazard underneath the climber). Despite popular belief, prusiks are not the sole preserve of the Trad Climbers - Sport Climbers on multi-pitch routes may also carry prusiks.

Choosing to carry prusik loops is a personal choice, and does not differentiate more-skilled or more-prepared climbers from less-skilled or less-prepared, though proponents and opponents may argue otherwise. The uses of the prusik may be improvised from other equipment the climber normally carries - some climbers may choose to rely on this improvisation rather than carry a dedicated piece of equipment. Similarly, there are situations where the climbers personal sefety is dependent on speed, not fail-safe equipment and prusiks will slow down the climber.

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.

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