The Zeppelin loop vs the F8 in pulls

[Constant Xarax]

Hi folks,

I am a new member of this Forum, so, please, excuse me if I have not yet learned to "do as the Romans do", i.e. to reply in a way compatible with what is accustomed here.
In the IGKT forum ( where I use to be a participant ), there was recently a long and heated debate about the test and the conclusions presented in this thread. I wish to state my humble opinion right away, using the very same words I had used there :

"ALL loops based on an overhand knot ( or, for that matter, on a fig.8 knot ) tied on the Standing Part ( so, loaded with 100% of the total load from the Standing End side, and with 50% of the total load from the eye leg side ) are NOT as easily untied as the bowline-like loops - which are based on nipping structures topologically equivalent to the unknot. Also, all these overhand knot- ( or fig.8 knot- ) based loops, should be untied in two steps : in order to get a clean, unknotted rope ( which will not run the danger to be caught somewhere ), one has to untie the "relic", remaining overhand knot ( or the remaining fig.8 knot ) from the Standing Part, after he has already untied the loop itself.
When tied on ordinary materials, there is no issue with the slippage of this non-Zeppelin eyeknot (*) - just as it happens with ANY other of the dozens of dozens interlocked-overhand-knot bends turned into eyeknots : on the contrary, one of the many disadvantages of this fake Zeppelin knot (*) is that oftentimes, after the first overhand knot ( the one tied on the Standing Part ) "closes", the second overhand knot ( the one tied at the returning eye-leg / Tail End ) does not - so, one can see that the degree of the complexity of this second part of the eyeknot is redundant. Even if it would had been entangled on a simpler than an overhand knot "nipping structure", tied on the Standing Part, an also simpler than an overhand knot "collar structure", tied on the returning eye leg, would had been enough."

" 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."

"With the start of the loading of the eye-knot, the overhand knot tied on the Standing part, which is pulled by both its limbs, "closes" faster than the overhand knot tied on the Tail, which is pulled by its one limb only. Therefore, at some point, the main overhand knot "locks" around the secondary one, before the later has given the opportunity to do the same around the former... The original genuine Zeppelin knot [ the Zeppelin bend ] works so well because the two links are in such a perfect balance the one in relation to the other, that they are loaded equally, they close around each other at the same time, they lock and they themselves are locked at the same time, and they suffer the strain of the tensile forces in tandem, re-distributing them along the common "pivot" made by the pail of tails. Nothing of the above is happening with the evil imposter of the Zeppelin family of knots - and its ugliness, its tying complexity, its asymmetric dressing... are only evidences of a knotting crime committed the moment some thought it would be so easy to kiss a prince, and do not transform it into a frog..."

"It turns out that an overhand knot ( or a fig.8 knot) can clinch too tightly, even when tied on the returning eye leg / Tail End - i.e., as a "collar structure", which is loaded only with 50% of the total load from the eye leg and with 0% of the total load from the Tail... If such a knot can be less easy to untie when it is loaded less, it will not become more easy to untie when it is loaded more ! "

Constant Xarax

 

[Constant Xarax]

However, the test presented in this thread, and the conclusions which it is claimed that are based on this test, are telling a different story. Which of the two stories is nearer to what is really happening ?
I have been very critical, and oftentimes harsh, to this test, for the following reasons :

1.
The number of specimen and trials is insufficiently small - no statistics can be based on just four numbers !
My not-so-well-informed opinion is that, regarding tests on tensile strength, one has to suppose that the data will, most probably, fit into a WeiBull distribution, also called "weak-link" distribution.
http://en.wikipedia.org/wiki/Weibull_distribution
However, with just four numbers, one can not use any distribution, I am afraid.
2.
Those numbers are not about / do not tell anything about the easiness to untie the ZL - either the relative easiness, in comparison to the fig.8, or the absolute easiness. I claim that the ZL is much more difficult to be untied than the Zeppelin bend - and, also, it is more difficult to be untied than ANY bowline-like loop. The reason is simple : Any overhand knot, or, for that matter, a fig.8 knot ( so, this applies for the fig.8 loop as well ), when loaded by both ends, clinches very hard around itself, in a ratchet-ing way. A single or double nipping loop / turn, on the other hand, like the loops / turns tied on the Standing Part of the bowlines, can not close and can not remain almost jammed as a loaded overhand or fig.8 knot does.
3.
The conclusions that were supposed to be based on numbers, or on any other information provided by the test ( no such information was presented neither in the first post, nor anywhere else...), are NOT corroborated by hard evidence. WHEN was the easiness to untie the ZL was tested, in which stage of the loading ? HOW this easiness was examined ( because, evidently, it was NOT measured, otherwise we would have had some numbers on it, like we have numbers for the actual breaking strength ).

4.
Last, but not least : WHERE, on earth , is this conclusion based on :

The ZL is stronger and just as secure, if not more so, than most bowlines and it's just as easy to untie. (sic)

WHO tested, WHERE, WHEN, HOW did he test the "most bowlines"(sic). As an old sailor, and for a hobby, I have been tying bowline-like loops half a century now ( dozens of dozens of different such loops ), and I can not claim I know "most" of them - so this "most of them" sounds like an empty speech to my ears.
However, one may argue that he knows "most bowlines", indeed. I would like to ask him, beg him, on my knees ! , to send me just a catalogue of them, and I will send him a catalogue of the ones I happen to know, and have published, with pictures, in the IGKT Forum. Then, I will ask him to show me the numbers , of the tests on strength and easiness to untie of them - so we can judge if this conclusion re-stated above is sound or not.
Of course, that will take some time - because there are literally hundreds of secure, easy to be untied bowline-like loops, which do not use an overhand or fig.8 knot tied on the Standing part ( so, they can also be tied and untied in one step, but that is a different advantage of them, and a different issue ). Until then, I would like to BET that this "conclusion" is not based on any measurement, against whoever question how I dare to claim this, without been able to present any detailed tests and numbers. The losers will pay for all the amount of rope we will need ( beware future losers ! It would be a lot ! ), and the winners will pay the cost of the required testing facility ( a universal testing machine - there are some cheap Chinese ones offered for sale in the web- so the winner will lose much less money...)
It is a very good, indeed, it is a GREAT thing, if we can base what we claim on hard evidence, on numbers produced by the "experimental method" called science. However it seems that it is also quite easy to cook some numbers, however few, and to present a salad which the clients are eager to buy and devour. Nowadays people are mesmerized by numbers and statistics, and they are ready to believe anything can entangle numbers and facts in any way, without examining the details. l am sure that the members in this Forum, and especially the tester, who love ropes and knots as tools, will not follow this fashion.
Personally, I do not test knots, simply because I can not, for various and many reasons. This does not mean that I can not have an opinion of what is a scientifically sound test, which is reliable, and repeatable, and which connects the data with the conclusions in a more sound way, than the data collected during the test were connected with the conclusions offered in the following presentation and discussion. I was enthusiastic about the tests by Paulo Bavaresko, for example, and I would be glad if the comparison of the ZL ( or the fig.8 loop ) to the bowline-like loops would be performed , in the future, in such a careful way.

Constant Xarax

(*) I characterise the ZL as a fake Zeppelin knot, because it lacks the unique property of the genuine Zeppelin knot, the Zeppelin bend, where the two first bights / curves are NOT hooked within each other ( like it happens in most bends ). They are parallel to each other, and work as two opposed bights who nip - and so block the slippage of - the pair of Tails which penetrates them. I like to say that the Zeppelin bend is a rope-made hinge, where the two tails play the role of the penetrating pivot. The ZL is not like this - and it could not be, because all loops have three loaded "limbs". However, there are more genuine Zeppelin-like loops ( although they are complex, and so not very practical ), as the ones shown at :
http://igkt.net/sm/index.php?topic=4095.msg24591#msg24591

Constant Xarax