Slings, made with lengths of webbing that are sewn or knotted into a closed loop, are essential pieces of climbing equipment that you use every time you go rock climbing. Slings work with carabiners, quickdraws, cams, nuts, and a climbing rope to make a safe climbing system.
Slings Work Hard
Slings do lots of climbing jobs, like attaching yourself to anchors, creating equalized anchor systems, tying off natural protection like trees and wedged chockstones, for making an autoblock knot, and clipping into the rope and gear to reduce rope drag.
First Slings Were Knotted Rope
The first slings used by climbers were simply short pieces of thin rope and cord that were knotted into a closed loop. The use of strong nylon webbing in the 1960s, however, created better, stronger, and lighter slings for climbers. By the mid-1970s, climbing gear manufacturers began sewing slings by overlapping the two ends of a length of webbing and sewing them together.
Spectra and Dyneema Slings
Slings now are made with either nylon webbing or Spectra and Dyneema. The ideal sling material is Spectra and Dyneema, which are both light, flexible, strong, and durable. Both Spectra and Dyneema are polyethelene arranged as parallel fibers, giving it a slick surface which makes it impossible to tie and hold a knot. The fibers won’t accept dye so they’re white. Colored yarn is woven into the fibers so that it can retain a knot. Slings made from these materials are always sewn for maximum strength. They’re also more resistant to ultraviolet damage from the sun. The main negative characteristic is that they are less elastic and dynamic than nylon webbing, so they don’t absorb as much energy when shock loaded in a fall.
Nylon Webbing Slings
Nylon webbing is either flat or tubular. The flat woven webbing is lightweight and inexpensive, while tubular webbing is more durable but bulkier and more expensive. Nylon webbing is ideal for constructing Swiss seat harnesses, long slings for tying off trees or boulders for top-rope anchors, for leaving at equalized rappel anchors, and for making knotted slings of various lengths.
Modern Sewn Slings
Modern slings are made from lengths of ½-inch or one-inch webbing that are either tied or sewn together in lengths from one to four feet long. Climbers commonly use two-foot-long slings. Sewn slings are stronger than tied ones. The sewn bar tacking on the webbing overlap of a sling is extremely strong, as strong as most carabiners.
Tie Slings With a Water Knot
Tied slings can be made to various lengths and of different material including cord rather than webbing. Always tie the ends of sling together with a water knot, also called an overhand trace knot. Knotted slings that fail under a load or a fall usually break at the knot.