Author Topic: What defines a Bowline? - structure, characteristics, topology  (Read 134706 times)

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #285 on: December 14, 2012, 04:10:11 PM »
   Thank you SS369,

   So, for you the "Eskimo" bowline is not a bowline ? Because, if it is a bowline, this one should also be a bowline :  The nipping loop on the standing part is there, in the same location, the eye-leg-of-the-bight enters into it through the same orientation as it enters into the nipping loop of the standard "Eskimo" bowline, and then it encircles the eye-leg-of-the-standing-part at the same location, too. Then, instead of making a "proper" "Eskimo" bowline collar, it makes a sort of a "Myrtle" collar, i.e., it crosses the nipping loop for the last time without penetrating it. Is this one and only factor the decisive factor ? Is the type of the collar, the specific way the last part of the tail is secured by the nipping loop, such an importand thing ?
   I do not wish to abandon the name "bowline" for the "Eskimo" bowline too easily... I think I had managed to reduce the number of "bowlines", by defining the "crossing knot " loops ( or, at least, a large subset of them ) and then excluding them from the family - but the "Eskimo" bowline I wish to remain part of it, if it is possible ? 

   P.S. I have tied two Forms of "Janus" bowlines, that can illustrate the ( slight ? ) difference between the "prorer" "Eskimo" collar, and the collar of the Sheet bend "Eskimo" bowline-like loop shown in this last post. See the attached pictures. Woudnt it be a little far fetched, to deny that the "Fontus" bowline is so different than the other "Janus" bowlines ?
« Last Edit: December 14, 2012, 04:26:38 PM by X1 »

SS369

  • Global Moderator
  • Sr. Member
  • *****
  • Posts: 1868
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #286 on: December 14, 2012, 04:43:30 PM »
Hi X1.

Yes, it has the parts, but not the orientation. I would call it bowline-esque.

As tied in the accompanied picture (yours hopefully used with permission). I find it lacking security as compared to the (let's say) original bowline, tied in static 11mm rope. I tied the two in identical rope (the ends of the single rope), dressed and snug, and then just beat them around hitting the floor and whatever. The "normal" stayed secure where as the Eskimo nip loosened.
Not very scientific, but for a quick test it shows me some things.
I am not diss-ing the knot here I just don't think we need to call it a bowline.

Maybe I am being too critical, but I think an eye-loop just doesn't have to have "bowline" in the name.

I tied a loop knot the other day in front of a co-worker. It was just a overhand slip loop and he beamed with recognition and called it a Bowline! lol

Maybe the others can be called "Stern-lines". 
;-)))

SS

Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3894
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #287 on: December 14, 2012, 05:19:43 PM »
Hi X1.

Yes, it has the parts, but not the orientation. I would call it bowline-esque.

We need context here : your reply follows an X1 msg. posted
after a prior post-&-reply, but nevertheless you seem to be
referring to the earlier and not immediately-above knots
--for those in the pure orange rope nearest above cannot
be faulted for orientation.

Quote
Maybe I am being too critical, but I think an eye-loop just doesn't have to have "bowline" in the name.

"eye loop" I deem a pleonasm : "eye knot" is my term
vice "loop knot"/"loop" --"loop" being so overloaded as
to be problematic, "eye" IMO w/o such issue (as used
e.g. in "eye splice", with no such "loop splice" around).

 ;)

Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3894
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #288 on: December 14, 2012, 05:25:53 PM »
   Definitions do reduce ambiguity, that is true, but, unfotunately, they can not reduce doubt... :)
  So, is this knot a (-) bowline, or not ? ?

You mean the top, colored-rope knot?

Hmmm, I'd say that these knots (both) too much break
there being any real/in-effect loop part, with their
structure forcing that into more of a helix than it should
be for the category.


--dl*
====

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #289 on: December 14, 2012, 06:44:14 PM »
I would call it bowline-esque.

   I keep the bowline-like term to signify the PET feature of it. However, is there anything beyond this, that makes it akin to an (Eskimo) bowline ? That is the question.

I find it lacking security
I think an eye-loop just doesn't have to have "bowline" in the name.

   So, are we going to call "bowlines" only the knots that do not "lack security"  ? Are we going to name a knot depending upon its supposed or proved qualities - or lack of qualities -, independently of its structural characteristics ? That is a very slippery road !  :) Knots would be named and re-named, if they hold or not on some specific materials, under some specific circumstances, patters of loading, etc.
   I search for the characteristics of the mechanism, not for the qualities of it. A nut ans a bolt are a nut and a bolt, even if they are made by a very soft material ( boiled spangetti ? )  :)
   

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #290 on: December 14, 2012, 07:00:59 PM »
You mean the top, colored-rope knot?

I mean the knot shown in the post where this question was asked, the Sheet bend "Eskimo" bowline-like loop. ( See the attached pisture )

Now, if you try to name a knot, either the one shown in Re# 286, or the two shown at Re#288, based upon pottential quantities ( forcing it "more" or "less" to degenerate to a helix ), you do the same mistake as SS369 did : you judge the knot by its supposed or proven perfomance, not by its structure. ( And you forget what you have said elsewhere : what characterizes a structure being a "collar structure", is its ability to keep the balance of the nipping loop, to prevent it from degenerating into an open helix. There are collar structures which achieve this better than others - but we can not name as "collar structure" only the most efficient collar structure, as we can not name "a knot" only the most efficient knot ! :) )
« Last Edit: December 14, 2012, 07:05:23 PM by X1 »

SS369

  • Global Moderator
  • Sr. Member
  • *****
  • Posts: 1868
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #291 on: December 14, 2012, 09:00:22 PM »
Hi X1.

Yes, it has the parts, but not the orientation. I would call it bowline-esque.

We need context here : your reply follows an X1 msg. posted
after a prior post-&-reply, but nevertheless you seem to be
referring to the earlier and not immediately-above knots
--for those in the pure orange rope nearest above cannot
be faulted for orientation.

Quote
Maybe I am being too critical, but I think an eye-loop just doesn't have to have "bowline" in the name.

"eye loop" I deem a pleonasm : "eye knot" is my term
vice "loop knot"/"loop" --"loop" being so overloaded as
to be problematic, "eye" IMO w/o such issue (as used
e.g. in "eye splice", with no such "loop splice" around).

 ;)

I was replying to the instance of the "eskimo" bowline and not the previous knots specifically. There was an edit (X1) afterwards in which the Janus had been added.

My apologies for the pleonasm. It sometimes happens. Yes "loop" is overworked as is "eye",  so in my mind I threw them together as a slam dunk. ;-)

SS

SS369

  • Global Moderator
  • Sr. Member
  • *****
  • Posts: 1868
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #292 on: December 14, 2012, 09:17:29 PM »
I would call it bowline-esque.

   I keep the bowline-like term to signify the PET feature of it. However, is there anything beyond this, that makes it akin to an (Eskimo) bowline ? That is the question.

I find it lacking security
I think an eye-loop just doesn't have to have "bowline" in the name.

   So, are we going to call "bowlines" only the knots that do not "lack security"  ? Are we going to name a knot depending upon its supposed or proved qualities - or lack of qualities -, independently of its structural characteristics ? That is a very slippery road !  :) Knots would be named and re-named, if they hold or not on some specific materials, under some specific circumstances, patters of loading, etc.
   I search for the characteristics of the mechanism, not for the qualities of it. A nut ans a bolt are a nut and a bolt, even if they are made by a very soft material ( boiled spangetti ? )  :)
 

Bowline-like term is OK as a descriptor, but, I don't think "Bowline" has to be part of the name. It is overworked.

The mention of the lack of security (I qualified that in part) is not significant to the naming.
Naming is subjective and has to pass muster throughout all the languages.
I do not think that some attribute of the knot in the name is a bad thing, e.g., Slipped Bowline, Running Bowline,etc. At least that can inform us of something.
Eskimo Bowline really tells me nothing.

I digress into knot naming, but that is part of the challenge here.

I stand by the statement that if the loop knot/eye knot has the basic form and orientation of the common bowline (ABoK#1010) then that is what I consider the bowline realm.
Those parts and that orientation are what do the work. Addons can enhance the knot as a whole, in some way or another.

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #293 on: December 14, 2012, 11:26:18 PM »
Eskimo Bowline really tells me nothing.

  I was under the impression we should keep this name, if for nothing else, at least out of respect to "tradition" (?). However, I really do not know how "common" is this name, neither when it was first introduced, etc.
  If it is decided that this name is not so deeply/well established, and we abandon it, then we can use the name/term "anti-bowline', proposed by dL, to denote the bowline-like (PET) end-of-line loops where the direction the working part has as it enters into the nipping loop is opposite to the direction it follows in the standard bowline, 
   ( I believe I am less attached to any name than anybody !  :) I see complex "things"  as merely sets of physical characteristics, compiled by us for a purpose - as mental tools, as descriptions of experimental set ups, etc. They do not have any objective existence, other than the one our brain wish to endow them, to help us better adapt to our environment. So, a name is a tool of a tool of a tool - not so importand a thing, after all !  :) )
« Last Edit: December 15, 2012, 12:29:30 AM by X1 »

SS369

  • Global Moderator
  • Sr. Member
  • *****
  • Posts: 1868
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #294 on: December 15, 2012, 12:09:55 AM »
If the name "Bowline" (which is misleading anyway or doesn't describe the loop at all) will continue to be the nomenclature for the ABoK # 1010, then words (tools of communication) should be used to describe that knot accurately. Perhaps the parts in order of tying from the Standing Part to the Working End.(?)
Then we will have a definition, characteristics and topology. imo

Personally I am fine with retaining this particular name for this particular loop knot #1010). It is burned into memory and to unlearn is much harder. But, for newer knots to come (even) we can do better.
I think.

SS


kd8eeh

  • Exp. Member
  • ****
  • Posts: 159
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #295 on: December 16, 2012, 02:20:52 AM »
I'd just like to mention that X1's sheet bend-bowline like knots are simply a standard eskimo bowline (with what would be the tails on the inside of the loop) but loaded by what is usually the tail instead of what is usually the standing part.  For that reason, I would say it is a variant of a sheet bend, being that there is no true nipping loop in the in the standing part.

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #296 on: December 16, 2012, 02:57:18 AM »
[the] sheet bend-bowline like knot [is] simply a standard eskimo bowline... but loaded by what is usually the tail instead of what is usually the standing part.

   Yes, so we could well refer to this knot as the "reversed" /" inversed" form of the Eskimo bowline. However, there are 4 variations of "the"(?) Eskimo bowline - and the mechanism of this particular knot is similar to the mechanism of the Sheet bend, and the Sheet bend bowline-like loop, presented elsewhere. That is why I chose to use this name - which, indeed, may sound a little odd...

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
What prevents the "walking" of the nipping turn along the Standing Part ?
« Reply #297 on: July 18, 2013, 01:50:24 AM »
   Regarding what prevents the "walking" of the nipping loop downwards, towards the tip of the eye, I had made the following "thought experiment" - in an effort to isolate and reveal the very mechanism that prevents it :  
  Imagine that you glue the two legs of the bight component ( the collar structure) together - but nowhere else. Now, the eye leg of the Tail side can not pull the Tail itself around the "capstan" of the Standing end, and out of the nipping turn.
  Imagine also that, in between those two glued legs of the bight component and the rim of the nipping turn, you place a ball bearing, which prevents the slippage of the two legs of the bight component through it, on the one hand, but allows their rotation relatively to the rim of the nipping turn, on the other. That is, imagine that the nipping turn can prevent the bight component to slip through it, to be translated, but not to revolve within it, to be rotated.    
    Load the eye of the bowline. What will happen ?    The bight component, as a whole ( because its two legs are now glued together ), will tend to slip downwards. The friction forces at the Standing end - collar contact area are very small, and can not prevent this type of motion by themselves. Slipping downwards, the bight component will push the nipping turn from above, by the bulk of its collar, AND it will drag it along with it, by the friction of their mutual contact area -  because we have supposed it can revolve within it, but it can not slip through it - so the nipping turn, pushed from above, from its "head", and dragged by its rim, by its "waist", will start to "walk". The bight component will push and drag the nipping turn, but it can not / it will not follow its walking / rotating - for two reasons : First, nothing forces it to rotate ! : Even if/when the nipping turn rotates, as it starts "walking",  the ball bearing can not transfer this rotation from its outer ring, which is attached to the nipping turn, to the inner ring, which is attached to the legs of the bight component. Second, even if the bight component was forced to rotate, it would had not, because it could had not : we should never forget that the bight component can not rotate around its axis / revolve within the nipping turn, because the standing end that penetrates it, as a pin, at the region of the collar, does not allow this type of motion.  
  So, nothing will prevent the "walking" of the nipping turn, which, together with the bight component, will move downwards, and will consume the eye leg of the standing part side till the eye itself disappears altogether !    
   What prevents this from happening in the real bowline ? The friction between the nipping turn and the bight component, which, on top of everything else it achieves, it also prevents the nipping turn from rotating relatively to the bight component, and so it prevents if from "walking" - because the bight component itself is hindered by the standing end and can not revolve. It is the friction between the two elements of the bowline, the nipping turn and the bight component, what prevents the nipping turn from "walking'" - a potential movement of the nipping turn that people do not question why it does not become actual -  so they do not search for the mechanism that does not allow it to happen in the first place.    
  In this picture, I made a simplification, for the sake of the argument...There is also another mechanism that prevents the "walking" of the nipping turn, albeit a secondary one . The crossing point of the nipping turn is a "point" ( a small area )  where, for various reasons, the one leg of the nipping turn is squeezed on the other. For the nipping turn to be able to "walk", those two legs should be free to dis-engage and re-engage on each other, like the dents of two engaged gears, because the one feeds the Standing part, and the other is fed by it. During the "walking", the segment of the Standing part "above" the nipping turn is unwinding from its rim, and the segment "below" is winding around it. If those two segments, which meet at the crossing point of the nipping turn, are squeezed upon each other, and "bite" each other hard, and if they can not be dis-engaged and re-engaged again, the friction forces at this area will be enhanced, and the two segments will not be allowed to "walk" on each other - so the nipping turn itself, as a whole, will not be able to "walk" either.
« Last Edit: July 18, 2013, 09:44:41 PM by X1 »

Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3894
So, nothing will prevent the "walking" of the nipping turn, which, together with the bight component, will move downwards, and will consume the eye leg of the standing part side till the eye itself disappears altogether !    
   What prevents this from happening in the real bowline ? The friction between the nipping turn and the bight component, which, on top of everything else it achieves, it also prevents the nipping turn from rotating relatively to the bight component, and so it prevents if from "walking" - because the bight component itself is hindered by the standing end and can not revolve. It is the friction between the two elements of the bowline, the nipping turn and the bight component, what prevents the nipping turn from "walking'" - a potential movement of the nipping turn that people do not question why it does not become actual -  so they do not search for the mechanism that does not allow it to happen in the first place.    

Except that, in fact, such slipping can be observed
in the real world --esp. in HMPE cordage, such as on
the video I've linked to elsewhere; but also, to some
lesser degrees, in other circumstances.  It is something
to consider for some of the more complex bowlines
in which increased number of parts returning to the
turNip imply a diminished proportion of load
--in theory, disregarding friction-- upon the SPart-side
eye leg (or eye-leg part, which might not feed
directly into the eye).


--dl*
====

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
...in fact, such slipping can be observed in the real world --esp. in HMPE cordage, such as on the video I've linked to elsewhere; but also, to some lesser degrees, in other circumstances.
   Exactly ! :)   In the real world, when there is less friction between the two legs of the bight element and the rim of the nipping turn than it is required  /adequate to prevent this "walking" of the nipping turn under heavy loading of the eye, this "walking" will take place, indeed !
" It is the friction between the two elements of the bowline, the nipping turn and the bight component, what prevents the nipping turn from "walking'" .
   Under heavy loading, when there is less friction, there is more "walking". When there would be no friction ( as in my "thought experiment" described previously, with the bearing inserted between the legs of the bight component and the rim of the nipping turn ) this "walking" would transport the nipping turn to the tip of the eye in no time.

increased number of parts ...imply a diminished proportion of load - in theory, disregarding friction
   Not "disregarding friction" !
   Friction theory tells us that friction force is independent  of the number of parts, i.e., the total contact area : Amontons' Second Law : " The force of friction is independent of the apparent area of contact."  However, my theory  :) :) :)  is that, with objects whose surface can be deformed under compression, creating "dents", things are even worse ! The less the area, the deeper the dents, the greater the enhancement of the "normal" friction force, described by Ammonton s laws. In particular, when two straight strands of rope are squeezed upon each, the friction force between them depends upon the angle they meet : Under the same squeezing force, the greater the angle, the less the area, the deeper the dents, the greater the obstacles to any slippage, the greater the "enhanced" ,by the deformation of the surface area, normal friction forces. In fact, it is not only a theory : I have seen this happening in real ropes, although I had not measured it. The greatest angle, the right angle, is the angle when the two ropes "bite" each other the deepest, so, regarding our intention to prevent slippage, it is the right angle, indeed.
    So, when we wish to block slippage, multiplying the contact area by multiplying the number of parts in contact to each other is not beneficial to the enhancement of friction forces, and, most probably, it is detrimental to it ! The "increased number of parts" can slide on each other rather freely, because there are no deep dents, so the normal friction forces are not enhanced at all. No wonder that when the angle two adjacent ropes is almost zero, i.e. the ropes are almost parallel to each other, they can slide on their extended mutual contact area much more than in any other case.
   
   So, what should we do ? : Two things :

1. Keep the number of parts as small as possible. In particular, I believe that a nipping turn encircling two rope diameters is blocking the slippage of any of them more efficiently than if it was encircling three rope diameters. However, we need the three rope diameters for other reasons, that are related to strength, not to security. A nipping turn that is encircling three rope diameters is almost circular, that is, it is more round, with fewer "weak" points of smaller curvature which can diminish the strength of the rope. ( Also, any one of the three strands that would be squeezed upon each other inside a nipping turn, would have a greater chance to meet an other at a greater angle - so to block more efficiently any one of them which will attempt to slip out ).

2. Make the parts meet each other at as a great angle as possible. The best we can do is to have them settled in a stable position inside the knot s nub, where they will meet at the right angle, the right angle.
 
« Last Edit: July 18, 2013, 09:56:16 PM by X1 »