Thursday, 5 May 2011

SOLO CREVASSE CROSSING.Part-3.(Alternative Ice Anchor System.)

In Blog-2, I demonstrated two simple retrievable anchor systems for a solo crevasse crossing. The first employed a sack "hip belt" around a snow or ice bollard, or embedded in a curved trench (similar to an ice-axe belay system). The second employed multiple Abalakovs threaded with "tape or tat-rope" on a hard-ice dry glacier.
Rob and fellow ABMSAC member Phil practising crevasse rescue on Chessjen Glacier, Saastal.

The third method here depicted simply employs the climbing rope on its own, around an ice or snow bollard. It is comprised of up to five turns of the rope taken from the "middle" of the rope to form a large "Sheepshank" Knot. This picture is of a 2-metre length Sheepshank held with four half-hitches, each secured with an Overhand Knot on a bight. Each hitch is taken completely around the main coil and then secured with the Overhand Knot.
The standard use of a Sheepshank is of marine origin, where a long rope needs to be shortened without resorting to cutting it.
In this instance we are using the Sheepshank to distribute the shock load of a falling climber around an ice/snow bollard-belay, in the same way the "hip-belt" was employed in Blog-2.
The principle of rope and anchor retrieval remains exactly the same after a safe crossing, with the whole system being pulled in on the "sack-attachment" side of choice.

The one disadvantage of this system is that it requires a shortening of the climbing rope to construct. Any shortening of the climbing rope will of course limit the safety margin of the climber's crevasse-crossing distance. Its advantage is that it requires no equipment, other than the rope.
The amount of rope used to construct the width of a Sheepshank anchor depends entirely on the climber's skill and experience to read the effective snow and ice consistency of the bollard belay.

Good climbing,