Author Topic: What defines a Bowline? - structure, characteristics, topology  (Read 131933 times)

xarax

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #225 on: September 25, 2011, 12:04:12 PM »
   First, I would not have said that "the SP is "collared" by its own continuation", even with two pairs of ditto marks...To my mind, collar ( "proper" or not ) and nipping structure do belong to different words, the former to the eye leg of the bight, the second to the eye leg of the standing part. As I have said before in this thread,
... do not confuse [a part of] the nipping loop with a collar : A structure is either a nipping loop or a collar, it can not be both of them, simultaneously !  :)
A collar has its second leg nipped by the nipping loop, and secured because of the action of the nipping loop on it ( which, after its turn around the tree, does not pull as hard as before, so the nipping loop has a much easier job to do...)
The collar is not any U turn of a segment of the rope...The collar is a U turn of the tail, it is a mechanism of the tail, a means of the tail to be secured easier by the nipping loop.
   Also, the nipping loop is not any 360 degrees turn of a segment of a rope...The nipping loop is a 360 degrees turn of the standing part around the tail, it is a constricting mechanism that nips the tail, a mechanism to secure the tail.
    It is absurd to talk about collars on the standing part, and nipping loops on the working end / tail !

   Now, regarding the first pair of two the loops posted at reply#224, the collar(a part of the eye leg of the bight) is U-turned around the standing part, in both loops. What differs is that the ""collar""(a part of the nipping structure, that is a continuation of the (first?) "turnip") is U-turned around the SP, in the first (1a) loop, but around the SP AND the collar( a part of eye leg of the bight), in the second (1b) loop. So, the collar of the tail of the loop makes a U-turn around one strand of the SP, in the first loop, but around two strands of the SP, in the second loop. As the two collars, the collar at the eye leg of the bight, and the ""collar"" at the continuation of the (first?) "turnip" are interwoven together in the second loop, that loop should be more secure than the first. Whether this second (1b) loop should still be considered a crossing-knot based bowline-like loop or nor, it is not obvious to me...
   We have a  similar, but even more complex, situation at the other pair of loops shown in reply#224. The second (2b) loop should perhaps be considered as a crossing-knot based loop, ( the continuation of the eye leg of the bight and the continuation of the standing end cross each other, dont thy ?), while the first (2a) loop looks more as a double interwoven-collars bowline. However, they are essentially the same knot, the Constrictor bowline, in its two variations.
    The situation is more clear in the case of the double, crossed-coils bowline shown at reply#225. We have a "proper" collar, indeed, and a double coils nipping loop - so, according to my definition, it IS a bowline... -, but the SP makes also a  U turn around itself - so, according to your definition, it is a crossing knot based loop...The similarity of this loop with the double bowline ( double-turn bowline) makes things worse for you, not for me !  Are you going to deny the inclusion of the double bowline into the bowline family, as you did for the Eskimo bowline -  while you accept the ABoK#1033 ? Whoa !   :) THAT is a position really difficult to defend !
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Dan_Lehman

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Re: Concepts and explorations of knotting : What defines a Bowline? - structure,
« Reply #226 on: September 27, 2011, 06:40:30 AM »
Describe those 2 pairs of knots using your words and terms,
and tell me if they are crossing-knot bowlines or not,
and, if some are but some are not, why is this so.

The first two I group as crossing=knot-based eye knots,
NOT bowlines --and though the tail makes a "proper collar",
the SPart nevertheless effects a collaring of itself in its turn
around itself, which distinguishes it from a turNip.

The latter two are not bowlines by my (current (!)) thinking,
either, as there again is no turNip feeding an eye leg
--rather, from the initial turn of the SPart the rope flows
back into further construction of the nub.
But here I can sense my position is on (at best?) diminishing
ground; you will want to thrust the oft'-cited "water bowline"
at me --its more-recently presented clove base being cousin
to these knots' constrictor bases.  I'm left defending my
position by pointing to *impurities* in the continuation of
the SPart from a turNip into <whatever> --where pure
continuation by reiteration of the turn is presumed acceptable,
but this deviation into the clove not.
(I have thought such structures should be considered
"false" --or some better term of amelioration-- "bowlines"
at best.)

--dl*
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xarax

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Re: Concepts and explorations of knotting : What defines a Bowline? - structure,
« Reply #227 on: September 27, 2011, 01:55:44 PM »
the SPart ... effects a collaring of itself in its turn around itself, which distinguishes it from a turNip.

   You do not need to use the term "collar" - as a noun, adjective or verb- to describe the U-turn of a "continuation" of the SP around itself, I believe. It blurs rather than clarifies your position.

from the initial turn of the SPart, the rope flows back into further construction of the nub.

   I see any turn, the "initial" or the following one(s), as part of the same nipping structure -  if it is located in the same place, of course : we can have more than one nipping structures, the one after the other. So, this "further construction"  can be just a part of the first nipping structure, or part of a second nipping structure.

...pure continuation by reiteration of the turn is presumed acceptable

  If that is so, the double (coils) bowline, (in the common, parallel, not-crossed coils form), should also be considered as a bowline. You have achieved a slight generalization - the FIST one, to my view... :) - by this clever use of the term "reiteration".

   If you want to remain so restrictive with what you accept as a "proper" bowline nipping structure,  with this image of the so-called "turnip" you have in your mind, I do not understand why you insist that the ABoK#1033 is a bowline...The images back at reply #49 (!), show that - at least in its capsized form - it is a crossing-knot based loop and not  a bowline, according to your  criteria. ( To me, it is not a bowline, not because it does not have a "proper" nipping structure - a "turnip", as you call it - but because it does not have a "proper" collar.)

   Now, there are some new candidates for this so desirable member-of-the- "royal"-bowline-family status - which is expected to remain desirable, if the blood that flows into the veins of a member should be as "pure" and  blue as the "turnip".  :) See the discussion at
http://igkt.net/sm/index.php?topic=19.msg20883#msg20883
and my opinion at
http://igkt.net/sm/index.php?topic=19.msg20890#msg20890
    It is  amusing that, although I feel the need to generalize the notion of the common s bowline s nipping loop - so it would include any TIB nipping structure tied on the standing part -, I am not ready to accept a similar, (and perhaps simpler) generalization for the common bowline s collar:) For me, a "locked" bowline- by any tight, secure hitch tied around the standing part, in place of the simple "proper" collar -  is not a bowline any more !   :) It might well be considered as a compound knot, but I believe that the spirit of the bowline has departed / is absent in such fixed end-of-line loops, however secure they might have become by the inclusion of such a "lock".   

« Last Edit: September 27, 2011, 01:59:28 PM by xarax »
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Dan_Lehman

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Re: Concepts and explorations of knotting : What defines a Bowline? - structure,
« Reply #228 on: September 27, 2011, 05:22:56 PM »
the SPart ... effects a collaring of itself in its turn around itself, which distinguishes it from a turNip.

   You do not need to use the term "collar" - as a noun, adjective or verb- to describe the U-turn of a "continuation" of the SP around itself, I believe. It blurs rather than clarifies your position.

?!  Rather, I think that you have an overly restrictive sense
of "collar", such that my use rubs it sore.  But what I point
to --by any name-- is that the pure circle of tightening that
is evident, quintessential in the turNip is broken by the Spart's
turning around itself --the loading from the tail-end will press
into the SPart and not purely constrict the nip (given friction).

Quote
from the initial turn of the SPart, the rope flows back into further construction of the nub.

   I see any turn, the "initial" or the following one(s), as part of the same nipping structure -  if it is located in the same place, of course : we can have more than one nipping structures, ...
...
but we needn't regard them as "bowlines" --that is the question.


Quote
...pure continuation by reiteration of the turn is presumed acceptable

  If that is so, the double (coils) bowline, (in the common, parallel, not-crossed coils form), should also be considered as a bowline. You have achieved a slight generalization - the FIST one, to my view... :) - by this clever use of the term "reiteration".

Whether this is a generalization of the structure, or, perhaps,
just a *2nd*, agreed acceptable structure to include, is debatable.
Framing it in this latter way ("2nd") is intended to deny "slippery slope"
charges, though it is a bit awkward.

Quote
I do not understand why you insist that the ABoK#1033 is a bowline...The images back at reply #49 (!), show that - at least in its capsized form - it is a crossing-knot based loop and not  a bowline, according to your  criteria.

Here I'm reminded of your frequent protest, "Read all of
my words, not every 30th one!" : for I expressly stated
that this knot has a range of orientations, some of which
qualify --rather obviously-- to being an eye knot based on
a turNip --which can be drawn up to otherwise be
a crossing=knot-based eye knot, like the Eskimo bowline.

Quote
It is  amusing that, although I feel the need to generalize the notion of the common's bowline's nipping loop - so it would include any TIB nipping structure tied on the standing part -, I am not ready to accept a similar (and perhaps simpler), generalization for the common bowline s collar:) For me, a "locked" bowline- by any tight, secure hitch tied around the standing part, in place of the simple "proper" collar -  is not a bowline any more !   :) It might well be considered as a compound knot, but I believe that the spirit of the bowline has departed / is absent in such fixed end-of-line loops, however secure they might have become by the inclusion of such a "lock".

Yes, that is peculiar.  I look to the SPart's treatment of the
knotted material as the essence, here, at least; how that
turNip's effect is secured then becomes the varying factor
that enumerates the group.

--dl*
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xarax

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Re: Concepts and explorations of knotting : What defines a Bowline? - structure,
« Reply #229 on: September 27, 2011, 06:06:39 PM »
you have an overly restrictive sense of "collar", such that my use rubs it sore.

   True. I wonder why...I suppose that, using the bowline, at some point I have decided - consciously ot not- to denote as "nipping loop" the essential part of the knotting operation at the first leg/stage of tying a bowline, and as "collar" the essential part at the second leg/stage. Two different names, for two structures that are tied in two different legs/stages...a seductive economy of notions.

the loading from the tail-end will press into the SPart and not purely constrict the nip (given friction).

  Evidently, but so what ? It will constrict the nipping loop nevertheless, so it will reinforce the initial gripping action of the nipping structure on the tail, too - that was the original purpose of the nipping loop in the first place. The fact that some of the internal tensile force will be "wasted" in this "pressing" of the standing part on itself, indeed, does not mean that any additional structure - besides the initial closed helical structure you call "turnip"-, by amy continuation of the standing part, will be condemned to be useless ! I have performed some home-made tests with the Constrictor and the Pretzel bowlines, and I have seen that the additional structure is noticably effective. Of course, we need detailed laboratory tests to be sure about it, and quantify the results.
 
I expressly stated that this knot has a range of orientations, some of which qualify --rather obviously-- to being an eye knot based on
a turNip

OK, I stand corrected. I have missed or I forgot that statement. ( Within/after 230 posts... :))
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xarax

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Is this thing a bowline ? If not, what is it ?
« Reply #230 on: January 08, 2012, 10:14:41 AM »
   According to my definition, this loop should be described as a bowline-like loop.... It has a "proper" bowline collar, not more complex than many Janus-like secure bowlines we have, Moreover, it has a nipping structure on the standing part before the tip of the loop, and, although this nipping structure is nothing more than a wide open helical nipping "loop" (?), nobody can deny that it nips the tail nevertheless - and it nips it in a most effective  way ! Indeed, as the interested reader would discover the moment he ties this loop, the grip of this combination of the simple nipping structure- complex Constrictor based collar, is so tense, that we can not possibly talk about having an "adjustable loop" here ! A noose, that is not, for sure. Moreover, although we can adjust this loop if we wish, when it is loaded it looks more as a completely fixed loop - so tight is the connection between the open helical nipping structure and the Constrictor collar. 
    I am not happy that this loop falls into my definition of the bowline...but what can I do ? I see no escape route here...However, for the time being I call this loop "Adjustable Constrictor loop", because I see some knot tiers around that are already weary a little bit ... :) If I take the liberty to call this thing a bowline, I am afraid they will be much-much more !
 
 Read also :
 http://igkt.net/sm/index.php?topic=3020.msg21688#msg21688
 
« Last Edit: January 08, 2012, 10:22:51 AM by xarax »
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Dan_Lehman

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Re: Is this thing a bowline ? If not, what is it ?
« Reply #231 on: January 08, 2012, 07:01:43 PM »
   According to my definition, this loop should be described as a bowline-like loop....
... I am not happy that this loop falls into my definition of the bowline...but what can I do ?

Find a better definition!

Quote
However, for the time being I call this loop "Adjustable Constrictor loop",
because I see some knot tiers around that are already weary a little bit ... :)
If I take the liberty to call this thing a bowline, I am afraid they will be much-much more !

This knot too directly is based upon a helix rather than a loop
--acknowledging that the distinction between them comes in
some arbitrary measure (as we have no perfect circle/loop).
(It's an old acquaintance from my seeking to create a
gradual curvature in the SPart.)


--dl*
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xarax

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #232 on: January 08, 2012, 07:34:55 PM »
Find a better definition !

   Well. I try, but i do not see much progress, after 234 posts...Perhaps one should reach 1234 ?


This knot too directly is based upon a helix rather than a loop
--acknowledging that the distinction between them comes in some arbitrary measure

    Correct, but make just another step, and tie it with another, second helical coil...and then another, and another...At some point, those coils will touch each other, and then we will suddenly have many loops ! When exactly do those helical coils cease to be helices, become loops ?   :)
   ( I have tied it with a two-coils helix, and I can not say that it was safer than the one-coil version, because the one-coil version seems to me to be as safe as it could possibly be ! Perhaps one should test it with a slippery spectra/dyneema rope...)
« Last Edit: January 08, 2012, 07:48:01 PM by xarax »
This is not a knot.

Dan_Lehman

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #233 on: January 11, 2012, 08:09:48 AM »
This knot too directly is based upon a helix rather than a loop
--acknowledging that the distinction between them comes in some arbitrary measure

    Correct, but make just another step, and tie it with another, second helical coil...and then another, and another...At some point, those coils will touch each other, and then we will suddenly have many loops ! When exactly do those helical coils cease to be helices, become loops ?   :)

It is not number except in that you have constrained
the space for them; the crux is that there is no boundary
line of geometry --except as we might define, by some
arbitrary imposition, for the sake of definition(?)-- to make
the distinction.  --reminds me of your insistence on seeing
"shear" in some cases and not others; the zeppelin can
e.g. be left loose on setting and then tensioning will see the
SParts' turns be that of bowline's and the nipped tails
much less disposed to visions of *shear* and compression
vs. nipping and tension.

I think we'll just have to accept that there is no boundary,
but that there ARE fairly distinct (end) cases between which
come a sequence of compromises & ameliorations of one
towards the other extreme.  (In trying to ensure good security
--under tension(!)-- for my seeking the "gradual curvature
in the SPart" playing with a helix, the later (farther along
into the knot from the SPart feed) turns would be more
nearly close & "loop" like, for this secure binding, so to
enable the SPart's initial passage to be more nearly
uncurved and presumed-to-be strong, friction building
upon the material gradually.  (Likely a pipe dream of real
effect in some actual usage, maybe only "strong" to the
test device, and maybe that only on slow-pull tensioning.)


--dl*
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xarax

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #234 on: January 11, 2012, 01:34:38 PM »
the crux is that there is no boundary line of geometry --except as we might define, by some arbitrary imposition, for the sake of definition(?)
I think we'll just have to accept that there is no boundary,but that there ARE fairly distinct (end) cases between which come a sequence of compromises & ameliorations of onetowards the other extreme.

 It would be great if there were, would nt it ? I do not feel comfortable wth loose knots or definitions of knots...

friction building upon the material gradually.

  I say something perhaps similar, when I insist that, if the working end/tail is nipped in more than one points into the knot s nub, it is better if it is nipped harder in the last points - the last line of defence against slippage - than at the first ones.This way the knot does not run the danger to slack, and some of the anti-slippage action on the last points be left unused.

P. S.
reminds me of your insistence on seeing"shear" in some cases and not others

   Reminds me of your insistence to put into people s mouth words never pronounced by them ! I had never said this, because that would be wrong : Shear forces exist everywhere, except in a straight tensioned line ! I said that the role of the shear forces was the primary role, in the complex function of knot s nub to secure the tail. If you have not got the difference between Zeppelin bend and the other interlinked overhands bends by now, I guess you will not get it ever... :) The fact that the Zeppelin s tails can work/be secured even with loose bights, is a proof you can not see, and the fact that any additional tension accumulates compression forces as well, can not cancel the reality of the first fact !  I rest my case !  :)
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xarax

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #235 on: January 19, 2012, 07:56:03 PM »
   there are some quite simple bowline extensions that do well to add security, maybe even a bump of strength--putting a 3rd or 4th diameter in the central nipping loop--, so that rope users can meet their needs with that knot.

   In relation to security, the most essential part of those bowline extensions is not the 3rd or the 4th diameter going through the central nipping loop, but the second collar around one of the three limbs of the initial knot. The positive contribution of the second collar is certain, while that of the 3rd ( and, to a greater degree, of the fourth) diameter is debatable, and has yet to be demonstrated. The nipping loop takes a more round, apparently more efficient nipping shape, that is true, but the nipping force on each rope diameter is reduced by 1/3... And we can be sure that the nipping action on each individual rope strand of a bundle of many strands will get less efficient after a certain number... but we do not know what this number is. I will not surprised if it turns out that 4 strands going through a nipping loop are in fact nipped not much more, or even less efficiently than 3... and I would love to be sure that 3 is better than 2, as I am sure that 2 collars are better than one.
This is not a knot.

Dan_Lehman

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #236 on: January 20, 2012, 06:25:24 PM »
   In relation to security, the most essential part of those bowline extensions is not the 3rd or the 4th diameter going through the central nipping loop, but the second collar around one of the three limbs of the initial knot.

We should remember that in the most modern materials
of HMPE (Spectra / Dyneema) and, I think, Vectran and
aramids (Kevlar / Technora / Twaron), there is inadequate
security when tensioned/loaded of the bowline (and have
seen the double bowline let rope just flow out through its
"doubled" nipping turns!!).  One needs to do something with
the SPart in order to preclude such insecurity/slippage (and
the clove-hitch("water") bowline is one solution to that).

But the important security when slack, loosening vulnerability
of the bowline --which is critical for kernmantle-rope users
(and, I should think, some applications with springy polypropylene
cordage, e.g.)--, might be redressed by the extensions that take
the tail through the knot further.


--dl*
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agent_smith

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #237 on: June 26, 2012, 08:48:02 AM »
At risk of doing the wrong thing..I've revived this topic.

I read the warning notice re no posts in this topic for 120 days.... I did consider starting a new thread but, it seemed logical to continue.

Anyhow, this is to advise that I have updated my paper on Bowlines.
Go hear to download it: http://www.paci.com.au   then click on 'public downloads'.

Click on knots and knotting concepts from the list. Its a PDF file - so you need Adobe Acrobat reader to open and view the file.

All articles and papers on the site have been made free to the public.

I would welcome any considered and constructive feedback on my theoretical proposition regarding Bowlines.

I must advise that I am bound to acknowledge the hypothesis of Derek Smith - as my work draws heavily on this.


Mark

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #238 on: June 26, 2012, 11:48:19 AM »
   I would nt describe the following comment as "exciting"  :)....  I am not even sure that it makes any sense, in relation to the security of a bowline.
   What happens in a bowline if, intentionally or by accident, one of its two essential elements, the collar, cease to exist altogether ? Will this half-bowline still be capable to hold some loading ? This is a somewhat far-fetched measure of the security of the bowline, but I think that is not completely irrelevant. The thought that a knot would still function adequately well - at least for some brief moments. and when loaded with a small only percentage of its maximum capacity - even if/after it is severely de-structured, brings piece to mind...
   One secondary, yet essential function of the collar, is to keep the nipping loop retain its closed loop shape - and prevent it to run the danger and degenerate into an open helix and, subsequently, unwind completely. Some double bowlines ( with two collars, the one after the other ), use this assistance from their collars less than other secure bowlines. So, their nipping loops will remain closed, and they will continue to nip the tail hard and prevent it from slipping out, even without the help of the collar (at least to some degree, for some brief time and for some light loading ). We may conjecture that these bowline will be more effective that the others in their complete form too - just as they were in their half-untied form.
   The most well known examples are the Water bowline and the Girth-hitched bowline. Without their collar, they look like the configuration used by Captain Mullins (ABoK#160 ), or a "Hitch series" (1)- so they do hold adequatelly well. Even without detailed experimental testings, we may suppose that, with their collar on, AND with a second collar and the tail going through both nipping loops for a third time ( three rope diameters nipping loops), their security will be enhanced as much as possible, yet they will remain easy-to-remember-how-to-tie and easy-to-untie end-of-line loops. ( " Mirrored bowline" ).

1)   http://storrick.cnc.net/VerticalDevicesPage/Ascender/KnotPages/KnotHitchSeries.html

Dan_Lehman

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #239 on: June 26, 2012, 09:11:05 PM »
   I would nt describe the following comment as "exciting"  :)....  I am not even sure that it makes any sense, in relation to the security of a bowline.
   What happens in a bowline if, intentionally or by accident, one of its two essential elements, the collar, cease to exist altogether ? Will this half-bowline still be capable to hold some loading ? This is a somewhat far-fetched measure of the security of the bowline, but I think that is not completely irrelevant. The thought that a knot would still function adequately well - at least for some brief moments. and when loaded with a small only percentage of its maximum capacity - even if/after it is severely de-structured, brings piece to mind...

Such as the fabled sheepshank, which sports a "collar"
only as seemingly peripheral decoration, yet could hold
such important loads as might be drawn from a ship?!

Quote
One secondary, yet essential function of the collar, is to keep the nipping loop retain its closed loop shape - and prevent it to run the danger and degenerate into an open helix and, subsequently, unwind completely.

Indeed, and I maintain that there isn't anything "secondary"
to this, but that IT is the quintessential aspect of a "bowline"!
To the point that I find the following item in the paper's definition
to put the cart before the horse:
Quote
3. That all Bowlines fundamentally consist of a bight component that is held and stabilised by an encircling nipping turn component.
No, rather, the relationship is the other way 'round :
bight stabilizes (serves) the nipping loop (master).
Further, I don't insist on a bight component at all, and thus
accept the so-called "Myrtle" eyeknot as a *bowline* .


--dl*
====