"before the breaking point of the rope itself is reached"

When a knotted rope breaks it always breaks at the knot, presuming some other part of the rope is not compromised.  A rope breaks because you exceed its tensile strength.  A knot breaks because you exceed the ropes shear strength.  Shear is exactly what it sounds like. It is a force that is perpendicular to the length of the rope and shears the rope in half.  Shear strength, to my knowledge, is always lower than tensile strength.  But, how much lower depends a lot on the material.  For things like mono filament lines (fishing lines for instance) the shear strength can be surprisingly low and thus the best knot tries to minimize this shear be spreading it over many turns, but no mater how good you are at tying those lines the knot is always where they fail.  A simple over hand knot often will break at no more than 25% of the lines tensile strength.  The high tech invisible lines fly fisher people use on the tippet is notorious for terrible shear strength.  Kevlar is even worse.  A Kevlar single filament that would cut a finger off before breaking in tensile will break at a one ounce or lower pull on a simple over hand knot.  Kevlar has a tensile strength higher than steel of the same diameter and basically no shear strength at all.  The best knot will also depend on the elastic properties of the rope.  Nylon is stretchy so a knot in nylon tends to compress into itself making it much harder to untie than the same knot in sisal rope or poly propylene rope if the knot is highly loaded.  So, the best knot for a given application also depends on the chemistry of the line being knotted.  I have found natural fiber ropes are a lot more friendly than synthetic plastic ropes in general.  Better on your hands most of the time, less prone to take a set after being loaded and simply more reliable overall.  If you are going to use a synthetic at least use a woven rope as they have fine fibers that are easier on your hands and less prone to take a set under load.

The bowline is a good knot but sailors often tie nothing else other than a clove hitch.  There are many applications, even on a sail boat, where other knots are much better.

Dick

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