Author Topic: #582 adjustable eye  (Read 4805 times)

agent_smith

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#582 adjustable eye
« on: July 07, 2015, 10:34:14 AM »
Last week, I was thinking about Xarax's conspiracy theory in relation to the so-called Zeppelin bend and why it is absent from ABoK.

#582 is a remarkable structure - and it surprises me that Ashley did not report its resistance to jamming - and to further explore variations (which might have led to the discovery of the Zeppelin bend).

Anyway, I thought that if I fed the tail through the central core/nub - perhaps it might afford adjustability while gripping securely under load.

Try it and see what you think... :)

xarax

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Re: #582 adjustable eye
« Reply #1 on: July 07, 2015, 01:03:38 PM »
while gripping securely under load.

   Noope... Same old thing : a too convoluted surrounding nub, which functions as a (protective) chain mail rather than as a (constricting) corset around the returning/second eye leg  :) :) . It absorbs ( and redistributes all over the rest of the nub ) a significant portion of the tensile forces coming from the Standing End and the ongoing/first eyeleg, which otherwise would had been able to be channelled straight to the gripping / nipping area. I use to say that this portion of the tensile forces is "wasted", and it is not contributing to the gripping / nipping action as much as it could.
   We need a direct contact between the penetrating line ( the continuation of the returning/second eyeleg ) which is the line we want to immobilize, from the one hand, and the Standing Part s first curve, which is the most heavily tensioned part of the nub, from the other ( because the 100% of the tensile forces running through the Standing Part s first curve have not yet been absorbed by the other segments of the nub ).
« Last Edit: July 07, 2015, 01:09:27 PM by xarax »
This is not a knot.

agent_smith

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Re: #582 adjustable eye
« Reply #2 on: July 07, 2015, 01:10:07 PM »
Xarax, I hope you withdrew all your money from the bank...and that Greece will still be afloat next week.

As for #582 gripping and holding the penetrating line (to set a desired length/eye size) - I found it works for me. I weigh 100kg (6 foot 4 inches tall) - I also found it to be rather efficient in terms of the amount of cord required to form the knot nub/core. It is jam resistant.

Did you actually try to apply body weight to the eye?

Admittedly, the force I applied was only my own body weight bouncing... and my intended application was to use it as an adjustable foot loop/stirrup for fixed rope ascending. I probably should have disclosed my intended application...

Mark G
« Last Edit: July 07, 2015, 01:12:25 PM by agent_smith »

xarax

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Re: #582 adjustable eye
« Reply #3 on: July 07, 2015, 02:31:39 PM »
   Well, let us agree that your adjustable loop "works" as well as Greek economy !  :) :)
   I happen to have some experience on adjustable loops, because I always wanted to learn how secure a fixed loop can be if it does not utilize a collar, so I had tried many "similar" constricting nubs ( See, for example, the ones shown at (4)(5). Also, I had tried such nubs in an effort to improve the Gleipnir binder.
   In a few words, I had concluded three things :
   1. The simplest AND the most secure "locking" mechanism is no other than the well-known opposing bights mechanism we use to secure the Trucker s hitch (0). In order to apply it in the case of an adjustable loop, we should use, as our first bight, the Standing Part s first curve ( tensioned by the 100% of the load ), and then we should figure out which would be our second bight. The optimum solution would be to utilize, for this role, the returning/second eyeleg s first curve ( tensioned by the 50% of the load ), but this is not easy : the constricting nub should not only be gripping/nipping, but also stable/balanced in mid air...
   2. The nub should be as simple as possible : If it is more convoluted than required, it would be less efficient, because some portion of the available tensile forces would be "wasted" within the turns and the twists of many other segments, which do not contribute to its gripping / nipping / immobilizing action. In an adjustable loop, simplicity is a functional requirement !
   3. To maximize friction forces between two tensioned segments which are squeezed upon each other, we better arrange them so they meet each other at the right angle : the "right" angle ( 90 degrees ). If those two segments meet each other at an oblique angle, the contact area tends to be more extended, more shallow and less saddle-shaped, so they not "bite" each other so deeply. On the contrary, they tend to slide on each other s surface.
   Of course, at the end of the day, the proof of the pudding is on the eating. Compare your adjustable loop to the Pretzel loop, the double-overhand-knot based one (6), or the recent adjustable loops tied by Luca (1) and Alan Lee (2)(3). And, of course, examine how much loading they can withstand - not if they can withstand 100kg or not !

0. http://igkt.net/sm/index.php?topic=4906.msg33365#msg33365
1. http://igkt.net/sm/index.php?topic=5383.msg36215#msg36215
2. http://igkt.net/sm/index.php?topic=5383.msg36262#msg36262
3. http://igkt.net/sm/index.php?topic=5383.msg36472#msg36472
    http://igkt.net/sm/index.php?topic=5383.msg36474#msg36474
4. http://igkt.net/sm/index.php?topic=3315.msg19887#msg19887
5. http://igkt.net/sm/index.php?topic=3315.msg19890#msg19890 
6. http://igkt.net/sm/index.php?topic=5322.msg35761#msg35761

P.S. I do not apply weight to the eye itself ! I wrap the eye around a freely rotating pulley, and I apply/hang the weight on this pulley - because, otherwise, the returning/second eyeleg may remain less loaded than the ongoing/first one.
« Last Edit: July 07, 2015, 02:45:05 PM by xarax »
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Dan_Lehman

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Re: #582 adjustable eye
« Reply #4 on: July 07, 2015, 07:33:17 PM »
Last week, I was thinking about Xarax's conspiracy theory in relation to the so-called Zeppelin bend and why it is absent from ABoK.
Because it just happened to not come across
Ashley's mind, and wasn't otherwise presented
to general awareness!?  And because Ashley had
already discovered some good (better) interlocked
overhands knots --viz., #1408, #1452 (& IMO
#1425 quite good in slack-security).

Quote
#582 is a remarkable structure --and it surprises me
that Ashley did not report its resistance to jamming--
and to further explore variations (which might have
led to the discovery of the Zeppelin bend).
Yes, with that image in hand/mind, it would be
conceivable that one could think of it to work
qua end-2-end knot.  We might guess that Ashley
simply passed over the structure w/o such attention,
focused in the moment on "lanyard knots" about
which many aspects just aren't of issue.

For your use qua "adjustable loop," I find this to
be far from as good as we can do, and Xarax's point
about oppose-bights nipping should take one to e.g.
#525 (what I call "symmetric fig.9" --though there
is another geometry giving symmetry to the 9),
where the tail can be brought back through the nub
to be nipped by both the S.Part's & its own U-turns
--works great, but beware any *biased loading* of
just the tail : then, the S.Part's nip w/o partner
will likely fail to hold.

As for
Quote
1. The simplest AND the most secure "locking" mechanism
is no other than the well-known opposing bights mechanism
we use to secure the Trucker s hitch (0)
"We" don't do that, as it detracts from our hauling
force with gratuitous friction (of that nipping, opposed
bight)!  In "Paul Bunyan" circumstances, one can ignore
the friction and enjoy the quick, self-locking; but that's
not the norm for trucker's hitch applications.


--dl*
====

xarax

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Re: #582 adjustable eye
« Reply #5 on: July 07, 2015, 09:22:29 PM »
"We" don't do that, ...
 that's not the norm for trucker's hitch applications.

  I mean, "we", the knot tyers, not "we", the truck drivers:) :) :)
  Personally, since I had found, almost by accident, that method of securing the Tail End, and had implemented it in many other knots ( especially in "tight hitches", as the TackleClamp hitch and the Double Cow hitch ), I had never looked back... Not that the other methods are less secure, of course ( two half hitches are always enough...), but, once one has applied it in a variety of knotting applications, all those methods look less "clever"...
This is not a knot.

Dan_Lehman

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Re: #582 adjustable eye
« Reply #6 on: July 08, 2015, 04:21:08 PM »
"We" don't do that, ...
 that's not the norm for trucker's hitch applications.

  I mean, "we", the knot tyers, not "we", the truck drivers:) :) :)
...
//
once one has applied it in a variety of knotting applications, all those methods look less "clever"...
But the point is that looks don't rise to the level
of importance as function, and encumbering the
transfer of applied hauling-tight force by gratuitous
friction is a bad thing --often surprisingly so.

Frankly, all this "adjustable eye" discussion strikes me as
a solution looking for a problem : there is in most of the
offered structures a need to begin with an approximation
of size and in that sense quite a limit on adjustability
--in contrast to tying off with a friction hitch, wherever
it's needed (as one can tie such a thing in the bight,
easily enough --meaning a regular such knot where one
lets the one side of the "bight" accumulate to the side
of the usual structure, coming into play only at the final,
closing part).


--dl*
====


ps : Btw, Agent_Smith, are you looking for "bunny ears"
to discuss in your document?  --the quick8 provides
a good base for revising the fig.8 use to form such.

xarax

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Re: #582 adjustable eye
« Reply #7 on: July 08, 2015, 07:22:40 PM »
... encumbering the transfer of applied hauling-tight force by gratuitous friction is a bad thing

   I do not think so - simply because that is what happens in knots ( into knots, within knots ), all the time ! In a non-local "knot", an "extended" rope mechanism, as the Trucker s, the TackleClamp and the Double Cow hitches, this mechanism is just more easily visible = more obvious... Hauling force becomes inner tension, which is transformed into friction, which encumbers the transfer of more tension, which encumbers the generation of more friction, and so on, until the whole mechanism settles in a state of mechanical equilibrium. Friction is always present, and "gratuitous" - there is no reason whatsoever one should not utilize it, when he can, and when, at the end of the day, he will, the one or the other way... In practical knots, all we do is to try to utilize the offered, "gratuitous" friction as effectively as we can, in order to increase the security of the knot, so we will not need more friction, which can only be generated by more tension, meaning a more tightly woven = less easily untiable knot...   
   We should also keep in mind that, in the case of the Trucker s hitch, we "bury" the Tail End under the one of the two opposing bights ( i.e., in between the two opposing bights ) only at the very end of the hauling process - so we can not say that some of the force we apply in order to tension the hitch is "wasted", because it is "encumbered" by the locking mechanism. In the cases of the TackleClamp hitch and the Double Cow hitch, the hauling force is not absorbed by the locking mechanism, because the two opposing bights are left free to move towards and squeeze each other, and so immobilize the penetrating line, only AFTER it is not applied any more.     
   I do not understand what you try to say - but, frankly, I believe that you just try to say something... :)

   
... all this "adjustable eye" discussion strikes me as a solution looking for a problem : there is in most of the
offered structures a need to begin with an approximation of size and in that sense quite a limit on adjustability

   So what ? ? The moment we tie the whatever TIB loop we decide to use in a Trucker s hitch, we also set a limit of adjustability... The same "problem" exists in the two-nub binders, but that does not mean those knots are worthless ! 
   What those adjustable eyeknots ( or the two-nub binders ) do offer, perhaps it is not realized/understood beforehand, but it becomes crystal clear when we try to immobilize a tensioned line by other means : The gripping / nipping nubs of the adjustable loops and of the two-nub binders are tensioned from both ends, with the 100% of the load from the one end and with the 50% of the load from the other - and so they become able to work as efficient constricting, "nipping structures". On the contrary, when such a "nipping structure" is tied at the end of a single line ( or at the tip of a fixed eye, as it happens in the case of binder#34 (1)), both its ends are tensioned by 50% of the load, so its efficiency is cut by half...  That is why a single or a double nipping loop ( like the double loop used in binder#34, for example ), tied at the one end of a single line, can not grip / nip / immobilize efficiently the other end, which will be tensioned by the 100% of the load.
   
1. http://igkt.net/sm/index.php?topic=2981.msg17780#msg17780
« Last Edit: July 08, 2015, 11:27:49 PM by xarax »
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xarax

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Re: #582 adjustable eye
« Reply #8 on: July 09, 2015, 10:04:53 AM »
   In knots, adjustability and security seem to belong to two different worlds. The moment you enter into the one, you have to abandon all hope  :) you will still savour what was offered by the other.
   The Blackwall bend (1), for example, was meant to serve as a bridge between those two worlds... However, although the security of the Blackwall hitch the one link of this bend incorporates is remarkable, its adjustability ( especially under even a light loading ) is questionable.
   The climbing slide-and-grip friction hitches, for example, can not grip before they slide, indeed  :) :) - but slide towards the opposite direction of which we would had wished ! Mark the point of the main line where a not yet "locked" climbing hitch has been slid, and then load it fully as instantly as you can, to see what I mean. When we speak about an "adjustable" knot, we mean a knot which can be "adjusted" by us ( not by itself ! ), at the exact point of the main line we wish, and remain at this same point after it will be fully loaded.
   As I had noticed in my previous post, the adjustable loops can serve as efficient one-nub mid-air binders, because their nubs are so tightly woven around the line we wish to immobilize - and they become so tightly woven, because they are tensioned by the 100% of the load from the one end and the 50% of the load from the other. That is my explanation about the fact that all my efforts to figure out a decent adjustable one-nub gripping / nipping knot, tied at the end of a single line, have failed... See, for example the knot shown at the attached picture, tied within an overhand loop : it is secure, and it can become even more, by increasing the number of the helical wraps - but is it "adjustable " ? 

1. http://igkt.net/sm/index.php?topic=5314.
« Last Edit: July 09, 2015, 10:08:18 AM by xarax »
This is not a knot.