Author Topic: What defines a Bowline? - structure, characteristics, topology  (Read 126225 times)

agent_smith

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This thread is about the Bowline.

Specifically: An entanglement of rope/cord that possesses form and structure under tension with characteristics that identify it as belonging to a class of knots known as the Bowline.

This thread is not about posting new discoveries - its about the structure of a Bowline.

At present, from what I can fathom, there is information/clues scattered about this forum - but no one coherent body of theory that defines a Bowline. So this is an attempt to bring together our collective knowledge into one place.

Obviously, this could be done for a few other knots as well...

Thus far, I have found the following information:-

Quote
The study of how the essential bowline structure can be employed/realized
in knots is helpful in finding "new" knots and understanding old.  To my
thinking, the sine qua non / essence of a bowline is the nipping loop;
I don't hold the bight collar to be key, just one way of forming a knot
using that loop.  And from a structural assessment, I find the
"double butterfly" (two eyes) to be a bowline variant (indeed, a good
candidate for the moniker "double bowline" !).

.:.  An easy-sounding question has more to it than one might suspect.

--dl*

and this (From DL):

Quote
Or is there some quintessential aspect of a *bowline* that qualifies
a knot to be so regarded (named "b." or not --a rose smells as sweet)?
This is a much better criterion, IMO, which will spare the minding of
Irish impostors and much of the nonsense coming from Hensel&Gretel's
make-believe land.....  The study of how the name "bowline" has been employed carries some
merit as a work in knotting history.  Unfortunately, it really entails a lot
of NEW work in trying to sort through the extant literature to figure out
which reports have any semblance of truth --a great deal of what's printed
amounts to hearsay from prior printed work.


and this - from xarax:

Quote
There are three, and only three elements that characterize a bowline, in relation to any other end of line loop:
  1. The knot tied on the standing part s leg, should be a slip knot. Any sailor will laugh with an end of line loop that is not completely untied like the bowline. Smiley
  2. This slip knot should include one, at least, nipping loop, which secures the tail.
  3. The tail should form one, at least, collar.


and this (from Derek Smith):

Quote
I would argue for the KISS principle where the Bowline is a small number of loop knots based on the SBCore, and that we might consider calling a knot a Bowline variant only if it clearly contains the SBCore + embellishments.

As for the Janus, it does contain the simple hitch (AKA nipping loop) snugly holding and held by a bight loop, so it can rightly claim to be a Bowline variant, although so far removed from the basic Bowline as for that claim to be almost irrelevant - and what is wrong with simply calling it 'The Janus Loop'?  Containing the SBCore is no great claim to fame or function...

Derek


and this (from TheKnotGuy):

Quote
The question still remains, ?How many Bowlines are there??  Does the structure define the knot?  Or do we define the knot because of the nipping loop or the bight collar?  Or does a ?true? Bowline need both a nipping loop and the bight collar?  Once again, I don?t know, but the question still needs to be asked.  

Some images to assist with identifying a Bowlines structure (Note: I am not suggesting that the so-called 'Janus' is in fact a Bowline - I am merely posting the image for thoughtful analysis)...





« Last Edit: July 12, 2011, 04:25:13 AM by agent_smith »

DerekSmith

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #1 on: July 12, 2011, 07:36:42 AM »
Hi Mark,

Rather than simply posting a personal declaration of what makes a Bowline, I believe that it is important to include the reasoning that supports that position.  To that end, I am reposting the whole of the post I referred to :-

Quote
The Sheetbend has two elements, a bight loop and a simple hitch (often called the 'nipping loop').

The Bowline is simply the Sheetbend 'wired up' as an end of line loop.  It has identical elements to the Sheetbend.  It would be inconceivable to describe the Sheetbend as 'a nipping loop  - with or without the bight loop', and I hold that it is incongruous to describe the Bowline in any way other than we would describe the Sheetbend.

There are four 'ends' from the basic Sheetbend core, and these can be 'wired up' to form 'L' and 'R' basic Bowlines and 'L' and 'R' Eskimo bwls. (the bwls. made by wiring up the SP to either of the bight legs are biased towards spilling and are ignored as practical knots).

Recapping - the 'Core' or 'SBCore' structure is a bight loop with a simple hitch, which can function as a loop or as a bend.

    SBCore

Beyond this, you are into variations - doubling, TIB with refold security, enhancing the bight, enhancing the hitch and securing the 'end'...   but in all cases, to be a variation it should still contain the two basic components - the co-embracing bight loop and the hitch - the SBCore.

So, for something to be 'Bowlinesque', I hold that it must contain the SBCore elements, any embellishment beyond this core and you are into variants which should be described as SBCore(B or E, L or R) + Variation

Give it whatever variations you like and call it whatever crazy name you like - Bobs Bonkers Bowline - the Triple B - but please, only give it the Bowline appellation if it contains the SBCore  - the co embracing bight loop and hitch.

This leaves us with just four simple or 'true' bowlines and as many variants as you would wish to waste use your life inventing.

snip...

Derek

Applying this to the four knots you posed and we can see they all fit this definition of either Bowline (1010) or Bowline + variations.

Derek
« Last Edit: July 12, 2011, 07:43:05 AM by DerekSmith »

xarax

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #2 on: July 12, 2011, 08:42:35 AM »
   The bowline does not have a hitch in it, like the Sheet bend.  
   The bowline is a close relative of the Gleipnir, not of the Sheet bend.
  
« Last Edit: August 12, 2011, 04:15:27 PM by xarax »
This is not a knot.

alpineer

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #3 on: July 12, 2011, 10:20:51 AM »
Very cool colour coding mods on agent smith's images Derek.

alpineer

agent_smith

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #4 on: July 12, 2011, 10:47:02 AM »
Hi Derek (the dunny man!!),

Nice to hear from you...

Can you apply your magic brush to the Karash double loop to indicate why it is does not meet the topological/structural requirements to be classified as a Bowline?

I'll also post a photo of ABoK #1080 tomorrow... I particularly want to compare #1080 against the Karash double loop with your colouring scheme.

Mark



« Last Edit: July 12, 2011, 10:48:00 AM by agent_smith »

DerekSmith

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #5 on: July 12, 2011, 03:28:04 PM »
  Derek, with all respect, I have to say that you make a mistake here. ( Of course, you might well succeed in persuading me to change my mind, as you have done in the case of the Carrick mat / bend !  :) )
   The bowline does not have a hitch in it, like the Sheet bend.  We can tie a bowline that holds satisfactory well, even if the collar is very loose. We can not do the same with a Sheet bend.
   The bowline is a close relative of the Gleipnir, not of the Sheet bend. In the bowline, we simply replace the 50 % mechanical advantage that is offered by the second line that goes through the nipping loop, with the 50 % capstain advantage that is offered by the collar.
   The Sheet bend does incorporate a hitch, just as the ABoK#1406, that is simply a doubled and symmetric Sheet bend (as such, it has two hitches.)
   I know that we can spend the rest of our lives arguing about this, but why? Is nt it much better, and interesting, and useful, just to make another walk in the Knotland, with the hope we meet some new knots ?  
  

Hi Xarax,

I can see that in order to make any headway here, I will have to demonstrate to your satisfaction that the  basic Bowline has the SBCore-i.e. that it incorporates a simple hitch...

I will start by conceding that under certain loading conditions the element in question is configured as a turned nip - as per the gripping element of the Gleipner, and in the Eskimo bwl the clamping function of the simple hitch is removed by the SP connection to the 'tail' of the hitch.  Having said that, it is when load is applied to the 'tail' of the hitch, that the very worse characteristic of the Bowline shows itself - i.e. loading on this leg of the loop risks an easy transformation from bwl to 'noose'.

In the spectrum of loadings that a Bowline will meet, the load will vary from 100% on the bight leg, right through to 100% on the 'hitch tail'.

When the load is full on the bight leg, the knot is working as a pure sheetbend and I hope you can agree, in that loading configuration, it IS a simple hitch.  At all other ratios of leg loadings, the hitch is functioning at some fraction as a simple hitch and some fraction as a 'turn-nip' - BUT - its function as the 'turn-nip' is the configuration we do NOT want to expose the bowline to.

Half convinced?

As for spending my life arguing about this - NO - not interested, but I can spare some time to share perspectives.

Derek


xarax

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #6 on: July 12, 2011, 08:21:06 PM »
  In the spectrum of loadings that a Bowline will meet, the load will vary from 100% on the bight leg, right through to 100% on the 'hitch tail'.

   The bowline is a loop, where the loading on each of the two legs varies, but, most of the times, very closely around the natural middle value, that is 50% of the total load for each of the two legs. It is THAT loading configuration which will make us decide if the bowline resembles more a Sheet bend, or a Gleipnir ( and/or ABoK#160, ABoK#161).The fact that, at some few and extreme cases, "the knot is working as a pure sheetbend"  indeed, does not prove your point. In MORE cases, with MORE realistic loadings, the bowline is working as a Gleipnir with a collar.
   In a bowline, none of the two legs of the collar are in a right angle with a segment of the standing part, as it happens with the Sheet bend ! In fact, they are almost parallel with it at the proximity of the nipping loop / the curved-around-360-degrees-segment of the standing end.
  
« Last Edit: August 12, 2011, 04:39:55 PM by xarax »
This is not a knot.

agent_smith

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What defines a Bowline? - structure, characteristics, topology
« Reply #7 on: July 13, 2011, 04:09:16 AM »
Images of the Karash double loop and ABoK #1080 for direct comparison...

Derek, can you apply your theorem to these 2 knots please?

Mark


knot4u

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #8 on: July 13, 2011, 07:54:05 AM »
To the definition of a Bowline, I'd add the working end (or working bight) first passes through the nipping turn in a way that makes the structure at that point topologically equivalent to an overhand knot.  For the case of a Double Bowline, a working bight passes through the nipping turn to form a structure that is topologically equivalent an overhand knot structure.

In contrast, in the Karash Double Loop, there is no overhand knot equivalent at the point where the bight first passes through the nipping turn.  Where the bight first passes through the nipping turn, the structure at that point is topologically equivalent to a Figure 8 knot.  Thus, the Karash Double Loop is eliminated from the Bowline definition.

Play around around with the structures for awhile.  Thank me later.  :)
« Last Edit: July 13, 2011, 08:35:49 AM by knot4u »

DerekSmith

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #9 on: July 13, 2011, 10:41:21 AM »
Images of the Karash double loop and ABoK #1080 for direct comparison...

Derek, can you apply your theorem to these 2 knots please?

Mark



Hi Mark,

I have to congratulate you on a skilful piece of educating you have done on me here.

While the Karash does not have a simple hitch and therefore is not a Bowline, it does have the co-engaged bight and hitch.  So, by my own definition I must concede that,  the Karash IS  a Bowline Variant and I withdraw my previous statement.

Well Done.

Derek

xarax

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #10 on: July 13, 2011, 12:47:25 PM »
   I believe that it is a self-evident truth, that has no need for any other justification :
   If part of a knot is a bowlne, the whole knot remains a bowline - albeit a more complex one.
   As part of the Karash loop is a bowline indeed, the whole double loop remains a bowline. Completing a knot can not erase a previously tied part of it, so, if a knot was a bowline, at one stage of its tying, it will remain a bowline, even after one adds some new parts on it.
« Last Edit: July 13, 2011, 01:45:32 PM by xarax »
This is not a knot.

xarax

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #11 on: July 13, 2011, 01:34:40 PM »
...  the structure at that point [is] topologically equivalent to an overhand knot.

   There are two ways one can read this sentence, and both reveal mistakes.

1) There is a structure topologically equivalent to the overhand knot, on the standing part :

   Of course not. Any knot that is tied on the standing part, with rope strands of the standing part, ( before the tail passes through it ), must be topologically equivalent to an unknot. ( that is what I mean by saying that it must be a slip knot : If we remove the segment of the line after the eye leg of the bight, the segment of the line before the eye leg of the standing part can, by pulling its two ends, be turned to a straight line, with no knotted structure on it. )

2)  We can speak of a structure topologically equivalent to a one line knot, even if we have two lines. So, even if there is no overhand knot tied on the first line, the standing part line, the local structure at the proximity of the nipping loop is topologically equivalent to the overhand knot, if we also consider the second line that passes through it - the segment of line after the eye leg of the bight.

   No. We can not speak of the same or equivalent topology of a one loop knot, and of a two loops link ! We can speak of geometrical identities or similarities. And considering those geometrical qualities and quantities, there is no difference whatsoever at the proximity of the nipping loop, between the simple, common bowline and the Karash double bowline.

Play around around with the structures for awhile.  Thank me later.  :)
 :)
« Last Edit: July 13, 2011, 01:46:39 PM by xarax »
This is not a knot.

knot4u

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #12 on: July 13, 2011, 07:09:37 PM »
You cannot tie a Karash Double Loop if you begin as if you are tying an Overhand knot (on a bight), but you CAN with every Bowline mentioned on this page:

http://www.paci.com.au/downloads_public/knots/02_Bowlines.pdf

In contrast, you begin the Karash Double Loop with a Figure 8 knot (on a bight).  For further explanation, I refer to my previous post.  In short, the Karash Double Loop is based on a Figure 8 knot, while the Double Loop Bowline and every other Bowline are based on an Overhand knot.  Even the Water Bowline?  Yes, even the Water Bowline.  If you don't see the Overhand knot, then keep looking.

As another example, the Double Dragon is also eliminated from the Bowline family because the working end does NOT enter the nipping turn such that the structure is topologically equivalent to an Overhand knot at that point.

Seriously, the term "Bowline" is already watered down enough.  Let's not water down the term even more to include knots that can be mathematically explained away.  Xarax, you can kick and scream all you want, but a Figure 8 is not equivalent to an Overhand.
« Last Edit: July 13, 2011, 07:25:16 PM by knot4u »

xarax

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #13 on: July 13, 2011, 07:25:23 PM »
the Karash Double Loop is based on a Figure 8 knot on a bight, while the Double Bowline is based on an Overhand knot on a bight.  

  I have read 29 more times your previous post, and I have not understood anything more than the first tme. So, my previous post stands as it is. You could possibly read it 30 times, to check if you could gain anything, but you will live without doing this, of course... :)

  The fact that you try to use the "overhand vs fig.8 " theory of yours to eliminate the Double Dragon (!) from the bowline family, or, fot this loop, any other theory, is an indication that you have not understood very well what a bowline is...Have you ever tied a Double Dragon on a ring, using the one end of the rope, while the other end is pulled by the boat that is pulled by the anchor chain ?  :)
This is not a knot.

knot4u

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Re: What defines a Bowline? - structure, characteristics, topology
« Reply #14 on: July 13, 2011, 07:36:18 PM »
Try these tasks:

Task A
1.  Tie an Overhand Knot on a bight.
2.  Without completely untying that Overhand Knot on a bight, can you tie a Karash Double Loop on that Overhand?
NO.

Task B
1.  Tie an Overhand Knot on a bight.
2.  Without completely untying that Overhand Knot on a bight, can you tie a Double Loop Bowline on that Overhand?
YES.

Task C
1.  Tie a Figure 8 Knot on a bight.
2.  Without completely untying that Figure 8 Knot on a bight, can you tie a Karash Double Loop on that Figure 8?
YES.

Task D
1.  Tie a Figure 8 Knot on a bight.
2.  Without completely untying that Figure 8 Knot on a bight, can you tie a Double Loop Bowline on that Figure 8?
NO.

...I submit the Overhand Knot structure is one defining structure within a Bowline that distinguishes the Bowline from other knots like the Karash Double Loop.  Again, the term "Bowline" is already watered down enough.  Let's not water down the term even more to include knots that can be mathematically explained away.
« Last Edit: July 13, 2011, 10:38:58 PM by knot4u »