Author Topic: What defines a Bowline? - structure, characteristics, topology  (Read 126684 times)

X1

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #315 on: July 29, 2013, 04:35:51 AM »
Reply #315 has been edited, hoping for clarity.
   The " Z Common bowline", although it is Conveniently represented, indeed, clearly it can not be tied with a Common right-handed bolt / working end. The S bowline can be tied by a Common right-handed S bolt / working end that enters into a Common right-handed S nut / nipping turn - and the Z Eskimo bowline can be tied by a not-Common left-handed bolt / working end that enters into a not-Common left-handed Z nut / nipping turn.
   I  believe that my re-written post, I had explained it with clarity.
 
« Last Edit: July 29, 2013, 04:39:20 AM by X1 »

X1

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #316 on: July 29, 2013, 05:03:35 AM »
  It makes no sense to me to eliminate - in your starting assumptions - half of the bowline population in order to solve (half) a problem. That's an inconvenient convenience. :)
 
  I do not have to eliminate half of the bowline population - I have to eliminate the three quarters of it !  :)
  First, from the 4 possible bowlines, I eliminate the ones in which the nut / nipping turn does not have the same handedness as the bolt / working end. So, from the 4 I go to 2. Then, I eliminate the ones that are not Conveniently represented. So from the 2  I go to the 1. I want a one-to-one correspondence / relation, and that is a convenient way to achieve this.
  Remember, we only want to distinguish the Common from the Eskimo bowlines, with another label that uses a more "balanced" pair of terms than the bowline / anti-bowline one. We do not wish to classify the mirror-symmetric bowlines, as the two "Common" bowlines you show. In mirror symmetric knots the handedness is reversed, so there is no way one can retain a relation that includes handedness in it.
   I do not say that all "Common" bowlines are right-handed, of course, I say that the "Common" bowline, in general, per se,  :) , is related to the S helix because of the fact that an eye leg of the Tail entering into an S nut / nipping turn as an S bolt, can only tie a "Common" bowline. By the same token, the "Eskimo" bowline, in general, per se, is related to the Z helix, because of the fact that an eye leg of the Tail entering into a Z nut / nipping turn as a Z bolt, can only tie an "Eskimo" bowline.
« Last Edit: July 29, 2013, 05:08:07 AM by X1 »

alpineer

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #317 on: July 29, 2013, 09:25:02 AM »
Now this is much better than the bloated mess of your previous posts on this matter, and I can receive and accept it. You've anticipated some questions and responded in an informed and logical manner. So, yes, under those restrictive terms one can relate the common and Eskimo bowlines to specific handedness. While I concur with the unambiguous implications of your exclusive initial assumptions, I might not ascribe importance to those implications because of the restrictive nature required of the initial assumptions to arrive at them. Still, I can appreciate what you are trying to do here.     
« Last Edit: July 29, 2013, 12:10:37 PM by alpineer »

X1

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #318 on: July 29, 2013, 11:18:21 AM »
   Thank you alpineer,
   It seems that writing and re-writing the same thing, consumes time of sleep, but it is useful after all !  :)
   However, this experience also showed to me that people would probably jump to the ( obviously wrong ) conclusion, that all "Common" bowlines are right-handed, and all "Eskimo" bowlines are left-handed... The nut-and-bolt trick was meant to protect the reader from this misconception, by requiring the nut = nipping turn AND the bolt  = working end / eye leg of the Tail be BOTH S or BOTH Z. Perhaps a "SS" - "ZZ" labelling ?
   I have also realized that people confuse the Convenient way or representing the bowline, with ONE particular side of the nipping turn, be it a right-handed or a left-handed. Let me emphasize this point :
 
    The "Common" bowline is more conveniently represented when tied in a nipping turn where the Standing Part goes "over" the eye leg of the Standing Part, be it a right-handed or a left-handed one. This way the crossing point area of the nipping turn is not hidden underneath the two legs of the bight component. Similarly, the "Eskimo" bowline is more conveniently represented when tied on a nipping where the Standing part goes "Under" the eye leg of the Standing Part, be it a right-handed or a left-handed one. We should reverse the "over" / "under" way  the Standing part meets the eye leg of the Standing part at the crossing point of the nipping turn, in order to achieve for the "Eskimo" bowline the same thing we seek for the "Common" bowline : an as less as possible hindered by the two legs of the collar view / aspect of the nipping turn - which nipping turn in the most important of the two components of every bowline, the other one being the bight component / collar.
   
« Last Edit: July 29, 2013, 11:34:56 AM by X1 »

Dan_Lehman

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #319 on: July 30, 2013, 05:31:09 AM »
   Thank you alpineer,
   It seems that writing and re-writing the same thing, ...
EsPECiALly if it's this stuPid
" the eye leg of the Standing Part",
nomenclature --which I'll hope has been wrung out of
Agent_Smith's pen, lest it find itself against a mightier
sword!

Quote
Similarly, the "Eskimo" bowline is more conveniently represented
when tied on a nipping where the Standing part goes "Under"
...
AND one of the great benefits or frustrations,
depending on how bent one is on these matters
(I feel the pain),
is that with the "Janus" forms in which "one good
collaring deserves another" cover both halves of
the argument and so are equally half-full/-empty
no matter!
= a tie.
Heck, yeah, a darn good tie(-on)!

 ;D

alpineer

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #320 on: July 30, 2013, 08:05:34 AM »
"eye leg of the Standing Part" is improper syntax as it implies that the eye leg is part of the S.Part
"Standing Part Side eye leg" is proper syntax as it implies that the eye leg has an association of proximity to the S.Part

X1

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #321 on: July 30, 2013, 10:31:14 AM »
"eye leg of the Standing Part" is improper syntax as it implies that the eye leg is part of the S.Part.

  Is nt it ? To my view, anything ante the tip of the ey , is Standing Part... Anything we can form a second, or third, etc. nipping turn on, and pass the eye leg of the Tail through it, after we pass it through the main nipping turn, belongs to the Standing part.
  I will follow whatever agent_smith decides - because we should have a common ground to understand each other, and the "Analysis...." offers such an opportunity...The next one may well come after 60 years. Will I live till then ? I doubt it... :)

X1

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #322 on: July 30, 2013, 04:07:09 PM »
you are washing your hands by pointing to agent_smith 
   I am not "washing hands", I have my own opinions and I express them whenever I can, as my tons of blahing blahing in this Forum prove -- so, evidently,  I am not afraid to do this !   :)  I wonder how one can think I am the kind of person that is not willing to bear the consequences of expressing what he believes, by hiding himself behind others !
  My own collection of bowlines, my terminology and my views of how they work, were and still are not the same as agent-smith s - but I have no problem to follow his choices, or anybody else s choices, for the sake of finding a common ground, when I am convinced they are about as near the truth as mine s.
  The " Analysis ..." is published for 4 years now. I do not think they have established any de facto standard - regarding knots, in general, and bowlines, in particular, we are still living in the Tower of Babel ! I do not see much consensus on much things, I do not even see many people that have studied the previous versions...What makes you think that they are gong to swallow the present one, without any criticism ?
« Last Edit: July 30, 2013, 04:10:12 PM by X1 »

X1

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #323 on: July 30, 2013, 05:01:39 PM »
   It is not even like this !  :)  It is "eye leg of the Standing part s side", and the "eye leg of the Tail side " ...
  However, I have not seen any better alternative, so, for the time being, we are left with this. Imagine that I write this looong phrase each and every time I am writing about bowlines - and I have to admit that I write about bowlines a lot !  :)  Place your bets / faites votre jeu..

Dan_Lehman

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #324 on: July 30, 2013, 06:51:56 PM »
   It is not even like this !  :)  It is "eye leg of the Standing part s side", and the "eye leg of the Tail side " ...
  However, I have not seen any better alternative, ...

But you have, and it has been explained.
The focus of the language is on the eye and on
Which side/leg, therefore the proper grammar is
to refer to the eye and qualify that noun.
Agent_Smith's terminology is bassackwards, referring
to either SPart or Tail and modifying IT to denote part
of the eye.  How clumsy can you get?  Well, that's too
harsh : this challenged terminology can be seen as
"nub"-centric, looking out from where there is a SPart
& tail into the eye.  But, practically, I think we're best
oriented upon the eye and then qualifying; after all,
the eye here is a key element, joining human to safety!

Improvement might be seen, in actual diction, using
"tail" & "through" as modifiers : the SPart side is the
latter, as forces --and indefinite distance-- run "through"
the nub, in contrast to that on the tail's side, where
there is the end of things.  (Woe be unto us and the
mid-line eyeknots, "with no end in sight"!)


--dl*
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xarax

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #325 on: March 25, 2014, 09:50:46 AM »
   Recently, Alan Lee has tied some fine, secure bowline-like PET eyeknots where either the first (1) or the second (2) leg of the collar do not penetrate the nipping loop ! ( The only instance I have seen something remotely resembling this, but not so radical, is at the Fontus bowline (3) : a Janus-like bowline where the Tail End does not penetrate the nipping loop - but, regarding the first or the second leg of the collar, I had never questioned the need to go through the nipping loop...). The problem arises instantly : Should they be considered / defined as bowlines, or not ?
   I have to admit that I have been tying "ordinary" bowlines for too long, during most of my life, so I can not judge this matter objectively. I still find it "difficult", mentally, to tie those loops without looking at their pictures, although I have tied them many times till now. That is, I have been brain-washed by the "working end going through the nipping loop before and after the collar" pattern, and, being an old dog, I can not really learn the new trick... Younger and fresher knot tyers would perhaps be more able to have a say on this matter.   

   1. http://igkt.net/sm/index.php?topic=4125.msg31307#msg31307
   2. http://igkt.net/sm/index.php?topic=4125.msg31273#msg31273
   3. http://igkt.net/sm/index.php?topic=1202.msg19317#msg19317
This is not a knot.

agent_smith

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #326 on: February 15, 2016, 09:15:55 AM »
The Capstan Effect:

Does it exist and is it measurable?
Can a test rig be devised which can reliably and consistently detect it? And if so, could others repeat the experiment to verify it?

The test rigs I have used thus far have not revealed a capstan effect in a standard #1010 Bowline.

While toying with some ideas - it occurred to me that perhaps it may be possible to detect a capstan effect in #1431 Sheet bend.

In advancing my Analysis of Bowlines paper, I have posited that there is no nipping loop in a Sheet bend because it is not loaded at both ends. The compressive force of the nipping loop in a standard #1010 Bowline effectively grips and crushes both legs of the bight - removing any detectable capstan effect.

But the core of a Sheet bend should not produce the same compressive force as a Bowline because only the SPart is loaded. And therefore I surmise that it might be possible to detect a capstan effect. A few quick tests by hand did indicate some promise...

If a capstan effect can be demonstrated in #1431 Sheet bend - this would provide strong evidence that the core function of a Sheet bend does not produce the same level of compressive force as a nipping loop in a Bowline. And this in turn would support the definition that a nipping loop must be loaded at both ends.

Mark G


DerekSmith

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #327 on: February 18, 2016, 05:47:47 PM »
The Capstan Effect:

Does it exist and is it measurable?
Can a test rig be devised which can reliably and consistently detect it? And if so, could others repeat the experiment to verify it?

Mark G

The capstan effect is real and it is an absolutely critical part of knot operation.  For example, in #1010, the capstan effect is responsible for transmitting SPart load into the bight legs and thus into the 'return' loop leg.

The capstan effect is present and active every time one cord passes around another and has a loading differential one end to the other.  This includes the situation found in the Sheetbend where one end of the turn is loaded and the other is simply clamped.

However, no capstan effect is generated when neither end is loaded or when both ends are loaded equally.

I believe this issue though, came about over the suggestion that the Bight collar in #1010 expresses a capstan effect, and this helps prevent the WE from being pulled through the nipping helix.

The simplest test rig we can set up to demonstrate the presence or absence of this effect in the working (i.e. loaded) is shown in this image made by Mark.



If there was any capstan load shedding around the SPart, then one of the legs would be more loaded (and therefore straighter) than the other.  We can see clearly from this image that neither of the legs are loaded, and so it is impossible for there to be any capstan load shedding in this part of the knot.

This situation however, does not hold true for extreemly low CF cordage.  In very strong, low CF cord, some of the load on the loop can escape the grip from the nipping helix and progress into the collar area, where, because the WE is clamped, it can start to set up a slight capstan load shed around the SPart.  However, because of the low CF and the presence of only one and a half radians of turn, only an insignificant capstan load shedding force is generated.

Of far greater significance however, is the negative cogging present in the legs of the bight component.  It is generally presumed that there is no load on the WE.  In reality the negative cogging is able to transfer load from the outgoing loop leg into the WE, essentially generating an effective WE load and contributing towards overall knot function and stabilisation.

Derek

Dan_Lehman

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #328 on: February 18, 2016, 08:08:00 PM »
The Capstan Effect:
...
But the core of a Sheet bend should not produce the same compressive force
as a Bowline because only the SPart is loaded.  And therefore I surmise that it
might be possible to detect a capstan effect. A few quick tests by hand did indicate some promise...

If a capstan effect can be demonstrated in #1431 Sheet bend - this would provide strong evidence that the core function of a Sheet bend does not produce the same level of compressive force as a nipping loop in a Bowline. And this in turn would support the definition that a nipping loop must be loaded at both ends.
Why are you reaching so desperately for something here
re the alleged "capstan effect"?!  I don't see great promise
for this pursuit, esp. vis-a-vis the bowline.

As you note, the end-2-end knot differs significantly,
but you've only remarked about one side/end's
difference : the bight's side differs in that what would
be the "returning eye leg" bears full load in the
end-2-end knot, not in the eye knot; so there is not
only less nipping as you suggest, but more need.
That the end-2-end knot has been reported to slip
in some kernmantle ropes (the Dave Richards report,
once hosted by NSS but removed for silly reasons)
only goes to confirm these differences.


--dl*
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Dan_Lehman

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #329 on: February 18, 2016, 08:21:19 PM »
I believe this issue though, came about over the suggestion that the Bight collar in #1010
expresses a capstan effect, and this helps prevent the WE from being pulled through the nipping helix.

The simplest test rig we can set up to demonstrate the presence or absence of this effect
in the working (i.e. loaded) is shown in this image made by Mark.
//
If there was any capstan load shedding around the SPart, then one of the legs would be
more loaded (and therefore straighter) than the other.  We can see clearly from this image
that neither of the legs are loaded, and so it is impossible for there to be any capstan load
shedding in this part of the knot.
I disagree that this image proves anything, much.  As I've
previously said --in another thread?--, this image shows
so much bending of the collar's legs that one can suggest
a capstan effect at this point / in the turNip, nevermind
needing anything further, at the bight's head/collar!
And I surmise that the situation is different where the collar
is reasonably sized much smaller and the bight legs more
nearly aligned with the axis of tension.  And it might be
that one could load and measure --somehow-- tensions
of either side of the collar (or maybe observe slight slippage
of the returning eye leg into the eye?) which would give
weak support to the alleged effect.

But I think that the alleged effect is being exaggerated
in significance.  It seems to consume a great deal of the
latest draft of the Bowlines document, to no benefit and
much diminution of the overall presentation, IMO.

Meanwhile, Derek has raised a valid point about how the
central nipping turn can be stabilized w/o a collar, and in
that point I've indicated one knot (which came by his
recipe though his verbal description ran off incomprehen-
ably to me), and which has other knots to rely on such
non-bight stabilization, too.  --where the opening of the
nipping loop="tightest helix" requires the bending of
nipped parts anchored on one side, and esp. in firm cordage
will work with good stabilization, I think.

As for calling the loops through & around the nipping loop
a "collar", I'm thinking "no, they're not" --or what would
NOT be, if they are?!  Yes, they do stabilize, but ... !?


--dl*
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