Alpine butterfly knot

:"Alpine butterfly" redirects here. For the actual butterflies, see Alpine."Knot-details
name=Alpine butterfly knot


caption=An alpine butterfly knot with a carabiner.
names= Alpine butterfly loop, Lineman's Loop, Butterfly Loop
type= loop
strength= 53% with both ropes loaded
67% with loop loaded
origin= Ancient
related= Farmer's loop, Artillery loop, Span loop
releasing= Non-jamming
uses= Used by climbers, mountaineers and cavers. Can be used to isolate a worn section of rope.
caveat=
abok_number=#331, #1053

The Butterfly Loop, also known as the Lineman's Loop or alpine butterfly loop, is a "non-jamming loop on the bight": a loop which may be tied in a rope with two fixed ends, and can take loads on both ends of the original rope, and on the loop. The alpine butterfly loop is a symmetrical and more secure version of the butterfly loop.

Usage

The Butterfly Loop has a high breaking strength and is regarded by mountaineers as one of the strongest knots to attach climbers to the middle of a rope, such that they have room to move around even when the main rope goes tight, and they can be supported in either direction from the main rope. The loop is typically attached to a climbing harness by carabiner.

It can also be used to isolate a worn section of rope, where the knot is tied such that the worn section is used for the centre of the loop (which of course does not receive a carabiner or bears any loads in this case).

Advantages

* Does not reduce the strength of the rope by very much
* Will not slip (after initial settling)
* Allows for the knot to be loaded three ways (each end of the main line and by the loop)
* Relatively easy to undo after loading (more difficult if wet)
* Very easy to adjust the size of the bight
* If multiple knots are tied in one rope, the climber can form a ladder, assisting in aid climbing

Disadvantages

* Difficult to tie one-handed
* Difficult to casually inspect
* Requires some training/practice to master

ee also

*List of knots

External links

* [http://www.geocities.com/roo_two/butterflyloop.html Butterfly Loop]
* [http://www.animatedknots.com/alpinebutterfly/ Butterfly Loop animation]
* [http://www.caves.org/section/vertical/nh/50/knotrope.html Knot Strengths]