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Knot Strength Chart — 11 Comments

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  2. I think the important missing knot is “ROUND TURN & 2 half hitches”. Several tests (including modern ones like the RYA) show it is perhaps the only knot that doesn’t weaken the rope.
    The White Water rescue people have a “NO KNOT” which is the “ROUND TURN & 2 half hitches” without the 2 half hitches 😮 ie it’s just wrapping a couple of loops round a tree.
    Not sure if your tests are just the 2 half hitches which is a LOT weaker than “ROUND TURN & 2 half hitches”

    • I find it very strange that there is no up-to-date official information on knot strength. It really would not be too difficult to setup a machine and test all knots? Thanks for taking the time to view and also make a comment, very much appreciated.

    • The round turn & 2 half hitches is a safe knot and easy to tie – i have been down a cliff face after a faller on a hauser secured by a bowline round a tree trunk

  3. Great info! Thanks! What are the percentages relative to? Do they represent the strength of the knots as a percent of the TENSILE or WORKING strength of a <1" manilla rope?

    • Hi CC,

      You’re not the only one who wonder about that ratio. 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. A “Maximum Load” is always tested with a new rope before being rolled for packaging. They perform it on a straight rope.

      Say the Maximum Load is specified at 100 kg. The chart above estimates the strength of a “Clove Hitch” at 60%. That means that the rope will snap at 60 kg.

      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. You can verify that statement this way:

      1. Make a loop greater than 4 Times The Width Of The Rope.

      2. Reduce the diameter very slowly until you feel a subtle resistance.

      3. Measure the diameter.

      4. Reducing further the diameter increases the resistance.

      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.

      According 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.

      We can apply this theory to the chart above. Here, the chart rates a Bowline at 60% efficiency. It make sence since the pulling force squeezes the first loop in which the rope passes two times in it, i.e., 50% efficiency.

      Bottom line. 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!

      Daniel M. Bourdon , creator of knots and hitches.

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