Slings (runners)

Sling, as a protection tool, is in mountaineering generally called a short rope or webbing connected by the knot or seam into a closed loop. Figuratively we use this name for all short rope or webbing parts of the climbing gear (1–2 m long ropes, webbing or auxiliary cords), whether or not they are tied into loop by a knot.

Besides that, strong eyelets created on the rope are also called sling, but that has nothing to do with protection tools. Slings tied with a knot on the rope are described in the first part of the textbook in a chapter Knots.

But let’s go back to a sling as a protection tool. Other shapes than a circle can be achieved by various ways of tying or stitching. The slings can be made into a figure eight or stitched into one strap with two closed loops at the ends used for attaching of carabiner (e.g. quickdraws).

According to a construction we divide the slings to:

  • Made of rope (either from part of dynamic rope or static rope, auxiliary cord)
  • Made of webbing (flat webbing or tubular webbing)
  • Quickdraw
Webbing slings sewn into a loop.

Webbing slings sewn into a loop.

Quickdraw

Quickdraw

We also divide the slings according to its use:

  • Looped sling – used for wrapping around something (e.g. rock horn) or for connection of any two parts of anything, circuit sling can be closed by a knot or stitched seam.
  • Gap (crack) sling – must be made with a knot which is inserted into a rock cracks and seams. Such a sling is used as a protection tool for creation of protection point in the terrain. Crack under the placed knot must get narrow in the direction of the anticipated load so the wider knot will not pass through. Carabiner clips into a sling’s loop protruding out of the crack.
Auxiliary webbing sling with sewn loop.

Auxiliary webbing sling with sewn loop.

Gap (crack) sling

Gap (crack) slings

How long the slings are?

It looks like a trivial question. But there is often a lot of confusion in this matter. Length of the sling can be taken as a “length of a rope or strand of webbing” (as is commonly understood in the shops, where a person buys measured piece of rope / webbing from the spool). It can also be seen as a length of a sling “after closing into a loop and under applied load” (which is more important for climber during an event, when he/she is creating protection in the terrain). Therefore, when we talk about length of the loop, we should clearly specify whether we mean “single-strand length’ or ‘length of closed loop”.

Auxiliary cords on spools.

Auxiliary cords on spools.

Design of webbing

There are two types of webbing – a) flat, b) tubular

If the webbing is made of the same material, the tubular is always stronger than flat. The tubular webbing is better when it is constructed in spiral manner. That means that strand of fibres passes smoothly from one side of the webbing over the edge to the other side of the webbing. Another construction option of tubular webbing is joining two flat straps by sewing its sides. Such connections are less durable, more prone to tear.

Sling’s material

Climbing slings are usually made of the same material as the rope, i.e. polyamide (PAD). However, they may be from other materials, so it is always good to check in the store what material was used for production of slings.

Polyamide (PAD) – Tensile strength, elasticity. Relatively small production costs, so it’s cheap. Water causes a small decrease in load capacity. Acids dissolve it. Solar and particularly UV radiation is detrimental. It melts at a temperature greater than 150°C.

Polyester (PES) – Tensile strength, elasticity. Not affected by water. It is more resistant to a rock abrasion. Solar and UV radiation is detrimental. It dissolves in alkaline solutions. It melts at a temperature greater than 150°C.

Polypropylene (PP) – Tensile strength, elasticity. Light, floats in water. Solar and UV radiation is strongly detrimental! Lower heat resistance, melts at a temperature lower then 150°C.

Aromatic polyamides (Aramids) – KEVLAR, NOMEX, etc. – High tensile strength, e.g. 5.5 mm cord can withstand load of 18kN (diameter of PAD rope would have to be 11 mm). Non-elastic. It substantially looses its strength at bends (in knots, during rappelling). Expensive. Can withstand a temperature greater then 150°C.

Oriented polyethylene (PE) – Maximal tensile strength, for example 5.5 mm cord can withstand load of approx. 22 kN. Damaged by heat, melts at temperatures just slightly above 100°C.

SPECTRA or DYNEEMA – Webbing only. Greater tensile strength. Resistant to cold tear (e.g. on the rock). Lower melting temperature; watch out for burning through by friction.

More in e-book.

Title Part 2Mountaineering Methodology – Part 2 – Gear and Accessories

ISBN 978-80-87715-08-6

MMPublishing, 2013

Available for download from Apple iTunes (in the Books section).

For example U.S. store – link

Another countries – look on the page Download

See layout.

Another possibility is Google Play. This version is a simplified (as PDF).

Title Part 2 GPMountaineering Methodology – Part 2 – Gear and Accessories

ISBN 978-80-87715-13-0

MMPublishing, 2014

Available for download from Google Play.