ACCESSORY CORDS

Cord specifications
Sewn prusik slings

Cord specifications

PMI accessory cords are attractive, high quality cords suitable for every purpose, in a range of sizes from 2 mm to 8 mm. Sizes 5 mm to 8 mm are available on convenient 50 metre spools, or can be cut to length to suit customer requirements.

ACCESSORY CORD SIZES
Size	Rating	Spool	Uses
2 mm	0.8 kN	100 metre	Lightweight cord
3 mm	1.8 kN	100 metre	Tent guys, draw-cords
4 mm	3.9 kN	100 metre	Boot laces, utility cord
5 mm	6.6 kN	50 metre	Lightweight prusik slings
6 mm	8.2 kN	50 metre	Prusik slings, nut slings, purcell prusiks
7 mm	10.5 kN	50 metre	Nut slings, haul rope, cordelettes, emergency rope
8 mm	15.1 kN	50 metre	Tandem belay slings, Aztek (edge kit) rope, jigger cord.

    Note: 1 kN = 102 kg

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Sewn cord slings

We supply sewn prusik slings in a wide variety of sizes and lengths, for a multitude of purposes, from back-up slings for abseiling to belay slings for rescue teams, using the cord sizes from 5 mm to 8 mm.

Sewn cord slings give test strengths which are about 50-70 % higher than the rating of the cord itself.  This means that even a 5 mm cord sling has a strength of over a tonne!

The strength in use will normally be less than the test strength. In tests of prusik slings on a rope, the sling usually breaks at the prusik knot. For example, in one test of a 6 mm cord tied on an 11 mm rope with a three-wrap prusik knot, the cord broke at the knot at 12.6 kN - below the sling strength rating, but well above the cord rating. Test results vary considerably depending on the test parameters.

The strength and failure mode depend on the cord size, rope size, and the type of knot. Some knots slip more than others - particularly the French prusik. For example, in one test a 5 mm cord on a 10.5 mm rope slipped when tied with a French prusik, the maximum load depending on the number of coils of the knot. With three coils, the knot slipped at 2.5 kN, with four coils at 3.3 kN, and with five coils at 9.7 kN. Neither the sling nor the rope suffered serious damage.

Specifications

Size	Cord rating	Sling rating
5 mm	6.6 kN	10 kN
6 mm	8.2 kN	14 kN
7 mm	10.5 kN	18 kN
8 mm	15.1 kN	22 kN

Sewn cord sling range

We supply a range of lengths to suit different applications in climbing and rescue. Generally 5 mm and 6 mm cords are used in climbing, and 6 mm and 8 mm cords in rescue.

Applications

Ratchet prusik:  (5mm or 6 mm) Used in rescue or hauling systems to block the movement of the rope in one direction through a pulley. Contact with the pulley allows the rope to move in the other direction.

Back-up sling:  (5mm or 6 mm) Used in climbing as a back-up when abseiling, but can be useful in all sorts of emergency situations. This length is short enough to be tied with a French prusik below the abseil device, or tied above the abseil device and connected with a cowstail or daisychain. If a longer back-up sling is preferred, the harness prusik can be used in this role instead.

Short prusik:  (6 mm) This is the sling used to connect to the harness when prusiking a rope. The usual knots are standard or triple prusik, or klemheist knot.

Long prusik:  (6 mm)  This is attached to the rope using one of the usual knots, and supports the legs when prusiking.

Short purcell:  (6 mm)  Purcell prusiks are a prusik-on-a-prusik - an adjustable prusik sling which is used in two differerent lengths by rescue teams for personal security, as well as for an adjustable prusik.

Long purcell:  (6 mm) This is the longer brother of the short purcell.

Short and long tandem: (8 mm) These are used as a set of short and long for belaying a resue load. The tandem prusik system has been found to be one of  the simplest and most reliable belay methods for heavy loads.

Cordelette: (7 mm)  A long sling used in climbing for equalising the load on several anchors.

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Copyright Aspiring Enterprises, revised 28 February, 2008.
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