At 15–30%, it has the highest elongation at break of the four materials but only a medium tensile strength of 800 N/mm2.
Polyamide (PA) is the most widely used material. A highly stretchy material can compensate for these tension peaks more so than a static material as the fibers subject to the most tension stretch, placing the load on additional fibers.įour materials are used for the textile fibers in ropes, slings, and accessory cords: The cross-section shape (round, rectangular) and dimensions together with the material's elongation at break affect the impact of the uneven load distribution due to the knot. Tension peaks occur in the material, which can break at these points when subjected to a certain load. The fibers in bent material are compressed, meaning that some are subject to less tension than others (see Figure 1). The knot's bend radius is a key factor and is influenced by both the knot type and the direction of the load on the knot. All gear should naturally hold, but how much safety reserve remains? Which textile with which knot is particularly ideal for which purpose? To answer these questions, we have tested the most important combinations.Įssentially, a knot reduces the strength of textile materials due to the imbalanced distribution of the load on the fibers. The material and construction, as well as the knot type and load direction on the knot affect the extent to which the strength of the starter material is reduced by the knot. Bourdon, creator of knots and hitches.Textile ropes, slings, webbing, and accessory cords are standard pieces of climbing equipment and almost always knotted when used. It Is Highly Recommended To Load A Rope Under 50% The “Maximum Load” Specified By The Manufacturer !!! Even less if the rope is not as good as new!ĭaniel M. It make sence since the pulling force squeezes the first loop in which the rope passes two times in it, i.e., 50% efficiency.īottom line.
Here, the chart rates a Bowline at 60% efficiency. We can apply this theory to the chart above. When the inner part of a bend reaches its maximum contraction, its acts as a fulcrum of a bubble ‘class one’ lever that stretches forcefully the circumference of the bend with an increasing mechanical advantage like breaking a stick with your two thumbs joined together.Īccording to rescue people, a loop looses 25% per width of the rope, e.g.: a loop of 3 times the width has 75% efficiency, 2 times the width has 50% efficiency, 1 times the width has only 25% and the efficiency of a very tight bend is next to zero. Reducing further the diameter increases the resistance.
Reduce the diameter very slowly until you feel a subtle resistance.Ĥ. Make a loop greater than 4 Times The Width Of The Rope.Ģ. You can verify that statement this way:ġ. Since a rope is flexible, it keeps its 100% efficiency until the diameter of a loop is less than 4 Times The Width Of The Rope. That means that the rope will snap at 60 kg. The chart above estimates the strength of a “Clove Hitch” at 60%. Say the Maximum Load is specified at 100 kg. A “Maximum Load” is always tested with a new rope before being rolled for packaging. The 100% efficiency (the strength) is the “Maximum Load” specified by the manufacturer that is written on the package or in the details on Internet. You’re not the only one who wonder about that ratio.
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