International Guild of Knot Tyers Forum

General => Knotting Concepts & Explorations => Topic started by: X1 on April 14, 2013, 10:31:02 PM

Title: Clove hitch- and Girth hitch-based adjustable loops.
Post by: X1 on April 14, 2013, 10:31:02 PM
  I had tied those two loops on the two ends of a 8 mm cord, and I had loaded them simultaneously, by my bouncing body weight.
  I have seen that the segments of the cord inside the knot s nub were much more squeezed / flattened at the Clove hitch ( = reversed Buntline hitch ) than at the Girth hitch. So, at first I had concluded that the strain around the returning eye leg was probably greater in the former than in the later - but how on earth can the same weight generate a different strain ? - which means that the tail, in the case the Clove hitch is used as a base for an adjustable loop, would be nipped much harder by the two nipping loops of the Clove hitch-based double nipping structure. However, by the same token, at the Clove hitch the standing part s first curve would suffer more than at the Girth hitch, so the ultimum strength of the corresponding loop would probably be lower. I have also seen that the Girth hitch does not "close" to a very compact shape, and it becomes easy to untie, the moment the load is released, while the Clove hitch becomes rock solid, and perhaps a little bid jammed. One would argue that this should have been expected, because the Girth hitch consumes a longer rope length than the Clove hitch, so the tensile forces are spread along a greater area. I do not believe that the difference in rope length is such that can explain the remarkable difference in strain, and/or the remarkable difference in the flattening of the segments within the nubs of the two hitches....
   My theory is this : At the Clove hitch, the standing part, as it enters into the nub, and the eye leg of the standing part, as it exits from it, meet and squeeze each other at an area where each one is pulling to a different direction - so this area behaves as a "lock",  a rope-made rachet device, that retains any tensile forces happen to be accumulated within the knot ( the tencile forves which were generated by the bouncing weight ). On the contrary, at the Girth hitch, the standing part and the eye leg of the standing part, at their contact area,  they are pulling towards the same direction - so, the moment the loop would not be tensioned any more, any tension from the previous loading(s)/ bounces would be free to escape. When we tie the Clove and the Girth hitches around a solid object, a pole, we can hardly notice this difference - but around a soft, compressible object, a segment of a rope, this racheting behaviour of the ends of the Clove hitch becomes evident.