Bowline meets Zeppelin

[xarax]

@Valentine post:6

In the first post, I said, "The inserted overhand knot forms a zeppelin-like rope hinge around the bowline’s nipping turn and standing part … As shown below, that is precisely what’s going on here.

No, it does not. We are not talking about the topology of overhand knots here, but about their geometry. The links of the Zeppelin bend are, topologically, overhand knots, but they work differently than the links of the Hunter s bend, for example - which are, topologically, overhand knots, too. The overhand knot in your loop is hooked to = hooked within the nipping turn of the nipping loop of the eyeknot, as the one link of the Hunter s bend is hooked to = hooked within the other. Moreover, an overhand knot, in general, where the one end ( its Standing end ) is pulled and the other end ( its Tail end ) is made fast somewhere else, is NOT a hinge. The Tail end of this overhand knot, in particular : 1, makes a second turn, a collar, around the Standing end of the eyeknot, and, 2 : it is nipped by the nipping loop of the eyeknot. So, as the eye of the eyeknot is loaded and the returning eyeleg is pulled, this overhand knot can only contract, and constrict / strangle / choke everything that penetrates it, including its own tail : a hinge does not choke the pivot. Each ring of the hinge does not constrict the pivot from every direction, because it does not need to do this. On the contrary, the rings can rotate freely around the pivot = the pivot can rotate freely inside the rings, but this does not mean that the pivot can slip through the rings : The pivot does not slip through the hinge because it feels shear forces, not because it feels compression and friction forces. In a hinge, the mechanism works even if the rims around the pivot remain loose, because the fact that the pivot does not slip through the rim does not depend on the compression forces, and the generated friction forces, applied on it. On the contrary, in this particular overhand knot applies compression and friction forces to the lines that go through it, including its own tail, rather than shear forces.
Anyway, this particular overhand knot does not work as the overhand knots of the Zeppelin bend. To see some eyeknots that are more Zeppelin-like, see (1). To see a Zeppelin-like bend, where the pivots do not slip even when the rings off the hinge are very loose, see (2).

1. http://igkt.net/sm/index.php?topic=4095.0
2. http://igkt.net/sm/index.php?topic=3716.msg21527#msg21527

@Valentine post:6

1. As in the Zeppelin knots, the overhand knot constricts on the tail when loaded, helping to lock it in place.
2. I don’t know what you mean by “rope-made hinge”

1. No, the tail does not remain in place because it is constricted by the overhand knot - as I tried to explain previously, yet another time.
2. Evidently ! But do not bother, you are not alone… The exact opposite might well be true : I may be the only one who understands what I am talking about. However, believe me, I am talking about something, that exists, even if I can not explain it to other people. I know knot tyers with dozens of years of knotting experience who had never thought about this almost obvious fact, and who, even now, can not understand it ( or refuse = are afraid to understand it, but that is another matter ). I believe that manipulating a Zeppelin bend in one s own hands for some time, rotating the two not-hooked =parallel rims around the pair of tails, will offer the feeling my wording evidently fails to convey.

@Valentine post:6

the attributes required of a knot rather than a general assessment of the knots’ “authenticity”.

A friendly advice, coming from an old man : Do not underestimate authendicity, never. The authentic is true, by definition, the rest my well be imitations (Fr.) / fake = false. A knot, like anything else, has to be authentic = true, above all. ( This applies to knot tyers, too… :))

@Valentine post:6

Like many other such loops, half the knot is more complicated than it has to be for a loop, but it still works fine.

Like which other such loops ? If a knot is more complicated than it has to be for a loop, do not tie it ! Every complicated enough tangle of rope “works” - iff by “working” you mean that it dies not slip…
Moreover, as I had explained elsewhere, and I believe you have read it, it does not even work well ! The one overhand knot closes up and locked before the other, making half of the knot obsolete, and forcing the other half to bear the total of the loading forces - not a good thing for the strength of any knot.

@xarax post:10

I have seen that as the “main” first overhand knot, which is tied on the Standing part, is loaded first and more forcefully, it also “closes” and “locks” first, well before the second overhand knot, which is tied on the Tail. Consequently, this second overhand knot can well remain slag, with half of its structure not participating / contributing in the locking mechanism of the knot at all. The most evident result of it is a very tight, compact, rock solid first overhand knot, that has immobilized the eye leg of the Tail without any involvement of the second loose overhand knot, which is locked before / without been able to lock. The interested reader who will load the eye-knot to its limits, will see this discrepancy between the two links, the second one remaining almost absent of the mutual entanglement. It is this lack of “balance” that characterizes even many secure bowlines. where the one, only, of the two links bears most of the strain - one can easily imagine what that will mean for the overall strength of a two links knot, which will depend on half of the available material.

@Valentine post:6

A wider, rounder loop is stronger and generally preferable, but that’s not where a bowline typically breaks…

A knot does not break in the point of maximum tension. A wider, rounder loop can, supposedly, distribute and dissipate the tensile forces along a greater portion of the knot. That does not mean that a three-rope-diameters nipping loop will not break , and a two-rope-diameters will. Both knots will break at another point, probably outside the nipping loop, but the one will, supposedly, break after the other.

@Valentine post:6

…without another pass through the nipping turn, the tail experiences greater pressure locking it in place (similar force over a smaller area), which I would expect to be advantageous in resisting shocks and cyclic loading.

You may well be right on this. That is a debatable issue about which only NUMBERS ( = detailed, laboratory tests = experimental data ) can tell :).