Author Topic: Constrictor bowlines - which is easier to unte ?  (Read 5033 times)

X1

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Constrictor bowlines - which is easier to unte ?
« on: July 23, 2013, 06:45:59 PM »
  There is a "reversed" form of the Constrictor-as-double-nipping-structure bowline - "reversed" in just the same way  there is a "reversed" form of the Clove-as-double-nipping-structure bowline ( = the Water bowline ).( To the time being, " Analysis of Bowlines" shows only the "reversed" form ). In the "reversed" forms the Clove or the Constrictor, which play the roles of the double nipping turns, are rotated 180 degrees vertically, in relation to the standard, non-reversed ones, and if there are, to chose the easier to untie.
  As the Constrictor is what its name suggests, i.e. a very tight hitch, it is expected that we should not worry about the nipping power of it on the legs of the encircled bight component ( collar structure ). And it might also be expected that one or both of those bowlines would be difficult to untie. However, one of the great advantages of the secure bowlines in comparison to the fig.8 eyeknot is just the easiness with which they can be untied, even after hard strain. So, we wish to find if there are any differences regarding this characteristic between the two forms.
   It turns out that there are, indeed. The reversed form, shown in "Analysis...", can be untied much easier than the non reversed one. Therefore I believe that it is more suitable as a secure bowline, that could possibly replace the hard-to-untie fig.8 eyeknot.
   I have tied and tried those bowlines on the two ends of the same 7mm rope, hanged from a pipe end on the ceiling of my laboratory ( kitchen)  :) . I had submitted  them to a moderate, for their size, but alternating loading ; my own body weight, jumping on the one or the other eye !
   The careful reader will distinguish, at the attached pictures, that the "lower" nipping turn / collar around the eye leg is much smaller=tighter in the case of the non-reversed form ( at the right side of the attached pictures ) than in the case of the reversed one ( at the left side). Although the "higher" collars of both forms can be released very easily, the "lower" collar of the non-reversed form tend to clinch very hard, around the eye leg, because it is fed directly by the tensile forces coming from the Standing Part. On the contrary, in the 'reversed" form, the Standing part makes a U turn, and then turns upwards, so much of the tensile forces transported through it are "uploaded" and dissipated at the point of this U turn.
   Provisional verdict : The Constrictor bowlines have a very efficient double nipping turn ( we knew that... ), so they present no weakness whatsoever regarding security. However, only one of them, the "reversed" form ( the one shown in "Analysis..." ) is very easy to untie. The other can jam at the point the "lower" nipping turn collars the eye leg of the Tail side ( by just examining the structure per se, we might had expected that, but now we have more "evidence" ).
   
« Last Edit: July 23, 2013, 10:35:53 PM by X1 »

Dan_Lehman

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Re: Constrictor bowlines - which is easier to unte ?
« Reply #1 on: July 26, 2013, 07:40:26 AM »
IMO, these knots are a "too-clever-by-half" sort
of extravagance over the mirrored bowline and
others like that --complexity that looses.

Quote
As the Constrictor is what its name suggests, i.e. a very tight hitch,
it is expected that we should not worry about the nipping power of it on the legs
of the encircled bight component ( collar structure ).
Noope, it's a binder not a hitch --hitch loading in fact
is a method to loosening for untying--, and it nips
less well than the clove hitch, whose nipping parts
aren't impeded in flow by any crossing section such as
distinguishes the constrictor --and which serves
no useful function here, methinks.

Still, the intriguing way in which the constrictor form
works qua noose knot (i.e., the knotted part of a noose)
invites one to such ventures here.  But the eye knot
loading doesn't sit so well.


--dl*
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X1

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Re: Constrictor bowlines - which is easier to unte ?
« Reply #2 on: July 26, 2013, 10:16:35 AM »
IMO, these knots are a "too-clever-by-half" sort of extravagance over the mirrored bowline and others like that --complexity that looses.
   
   Perhaps you are right. The Constrictor is the last of the series of the four TIB "double" hitches/binders/whatever = complex nipping structures that can replace the single nipping turn of the bowline : double nipping turn, Clove, Girth , Constrictor. ( They should be TIB, in order the eye-knot be PET. The Strangle, for example, is non applicable ).
   As such, it is on the limits - I do not doubt that one can find it unreasonably / unnecessarily complex. However, we so accustomed with the Constrictor, it can be formed very easily, the working end can be driven through its two openings in one stroke also very easily, that the "extravagance" characterization becomes an extravagance itself.

Quote
As the Constrictor is what its name suggests, i.e. a very tight hitch,
it is expected that we should not worry about the nipping power of it on the legs of the encircled bight component ( collar structure ).
Noope, it's a binder not a hitch --hitch loading in fact is a method to loosening for untying--, and it nips less well than the clove hitch, whose nipping parts aren't impeded in flow by any crossing section such as distinguishes the constrictor --and which serves no useful function here, methinks.
   Still, the intriguing way in which the constrictor form works qua noose knot (i.e., the knotted part of a noose) invites one to such ventures here.  But the eye knot loading doesn't sit so well.
   
   We have been talking about this the other day - personally, perhaps erroneously, I consider anything that can attach the end of one or two lines around a pole or through a ring as a hitch - including some hitches that can work as tight adjustable nooses, and so they are also binders ! If somebody would come up with a precise definition of those three knotting terms ( hitch, noose, binder ), that can classify / sort all the known knots used as such, I would be glad to follow his terminology. For the time being, I see nobody around... :)
   In the Constrictor s case, the noose knot loading or the "eye knot loading" depends also upon the orientation of the collar : the left-hand and the right-hand Constrictor-based noose and double nipping structure "sit" a little bid differently.

[ the crossing section of the Constrictor s ] nipping parts... serves no useful function here, methinks..

   1. The magnitude of the nipping force is not the only thing we expect to enhance by utilizing a complex nipping structure. The stability it offers to this structure, so that it will not run the danger to degenerate into an open helix, is also of paramount importance. A weaker, simpler collar can prevent the opening of a stable nipping turn, while a stronger, more complex one can fail in the case of a nipping turn which is not so stable in the first place, by itself. The Constrictor is a most stable platform, in its non-reversed as well as in its non-jamming, reversed form ( the one shown in "Analysis...").
   2. Although the crossing of the two legs of the two nipping structure absorb some portion - and so diminish the total available amount - of the tensile force turned into nipping force transferred by the 100% load of the Standing part, it binds the two openings / nipping turns of the double nipping structure together - and that is beneficial to its integrity and stability.
   3. My point in my previous post was that this diminishing if the nipping force of the nipping structure is, in fact, beneficial to the structure of the whole eye-knot - because it does not jam ! The reversed Clove hitch-based structure jams, the non-reversed Constrictor-based nipping structure jams - and, interestingly, in the same way, and in the same point, the "lower" nipping turn / collar -, but the reversed Constrictor does not ! The crossing section of its two nipping turns turn a lethal constriction into a friendly hug. The total nipping force remains moderate, the Constrictor loses its ratchet-ly squeezing nipping character, and it does not jam any more.
   I believe that the safe bowline based on a reversed Constrictor, as shown in "Analysis...", is a good knot : easy to tie, stable, safe, non-jamming. Its drawback is that the flow of lines is ...well, almost a mess, so it can not inspected easily, and it can not win in any beauty contest. However, as the end of line in the series of gradually more complex double nipping structures : single, double, Clove, Girth , Constrictor, I think that it is worth mentioning. It is an example of a general knotting principle that is applied on the Common bowline to make it safer, and as such it has a much greater value than the particular knot it represents.
 
 
 

 
 
« Last Edit: July 26, 2013, 10:31:04 AM by X1 »

Dan_Lehman

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Re: Constrictor bowlines - which is easier to unte ?
« Reply #3 on: July 26, 2013, 05:14:57 PM »
Quote
As the Constrictor is what its name suggests, i.e. a very tight hitch,
it is expected that we should not worry about the nipping power of it on the legs of the encircled bight component ( collar structure ).
Noope, it's a binder not a hitch ...
If somebody would come up with a precise definition of those three knotting terms
( hitch, noose, binder ), that can classify / sort all the known knots used as such,
I would be glad to follow his terminology. For the time being, I see nobody around... :)

But I did this a long time ago, and echo'd that more recently.
A *hitch* (basic) comprises 1 POFM around an object
and is loaded on one *end* --a binder, on none.
A *noose* is a knotted structure in which the POFM
turns around the object and then is *hitched* to
itself, loaded on the unknotted *end* of the *structure*.
This much seems simple.

Now, "noose" might need some further working,
to account for --not necessarily (actually, unlikely!?)
under the same word-- such things as reeve eyes
(running bowline), in contrast to 2 half-hitches,
in contrast to poacher's noose.  I'm inclined towards
distinctions based one structure rather than effect
because the latter can be variable across materials/forces;
there will be some need to account for that, when needing
to speak of effect, but in a classification system I think
one does better to classify irrespective of behavior.

Note that I added the parenthetical "basic" in recognition
of more complex structures (a round turn vice turn, or
some further such complication).


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X1

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Re: Constrictor bowlines - which is easier to unte ?
« Reply #4 on: July 26, 2013, 06:15:42 PM »
   A *hitch*...is loaded on one *end*

   One, or two - climbing hitches and hitches able to withstand lengthwise pull may be loaded on both ends - in the more strict or in the broader sense where the two ends are tied connected together just out of the knot s nub.

   A *noose* is a knotted structure in which the POFM turns around the object and then is *hitched* to itself, loaded on the unknotted *end* of the *structure*.
   This much seems simple.

   It may seem so, but it is not !  :)
   In the case of the slide-and-grip hitches, for example ( like the "lockable" arthroscopic hitches ), the knot starts as a noose, with the noose s nub sliding on the knotted end of the structure, and ends up as a hitch, where there is a switch of the load, and the previously unloaded knotted end becomes now the one which carries the load. - while, at the same time, the previously unknotted end becomes knotted, too ! Simple, indeed ! Some more of this "simplicity", and the noose/hitch Janus-faced knot will become a straight line !   :)

   I'm inclined towards distinctions based one structure rather than effect because the latter can be variable across materials/forces; in a classification system I think one does better to classify irrespective of behaviour.

   Welcome to the Universe where there are individual objects, like apples or knots, about which we can speak - without reference to the worm inside the apple and the apple s "edible material", or the "knotted material ".
   Now, you may argue that you are speaking about classification, and not examination, and that, when we examine a "knotted material", the classification does not matter. If that is so, I will tell you that your classification system is worthless, as it can not help you "connect the dots", and predict something that you were not already aware about. When people connected the dots of the Periodic table of elements ( the archetype of a classification system of natural objects ), they made new discoveries ! They predicted new elements, and new unknown qualities of already known elements. If you "see" objects in another way than the one you "sort" them into categories, you should either "close" your old classification system, or "open" your eyes ! 
   A classification of knots according to their structure ( i.e., the consideration of each individual knot per se ), can reveal, to a large degree, their practical value regarding simplicity, stability, non-jamming-ness, and strength. There will be surprizes - and there are plenty of elements in the periodic table with some surprizing, unpredicted, even unexpected qualities. However, the basic scheme stands. A knot can be examined per se - without references to the knotting material and the loading pattern-, and that is exactly why it exists, re. us, in the first place, as an individual object, and does not remain another indiscernible part of the cosmic soup !
   If the classification of knots should based on their structure, that means that the principal quality of their existence, and the quality which has to be examined first, is their structure - or that we have to change our classification system, or that we have to discover the deeper relations between qualities of knots and their structures we still miss.
 
P.S.
    A personal experience, which, although it has taken place decades ago, is still vivid in my memory. I was 17 and about to participate in difficult exams in order to be admitted to college, and I had never ever opened ONE page of the thick chemistry books. A teacher noticed that, and volunteered to give me some private lessons - not more than 10, as I remember. In those lessons he systematically taught me how to predict most of the chemical properties of a chemical element, where the only thing I knew about it was its place in the periodic table - and then, knowing how this element behaves as a chemical substance, to be able to write long blah blah expositions about it, figure out how to predict possible industrial uses, solve chemical problems, etc. In the test, I got 32 out of 40, and I still remember the feeling of learning how a key of nature works, and using it on one s behalf.
    That is the classification scheme of knots I wish : something that would not only be a catalogue, but a system, and which will allow us not only to remember, but to imagine as well. 
   
 
 
 
« Last Edit: July 26, 2013, 06:40:53 PM by X1 »

X1

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Re: Constrictor bowlines - which is easier to unte ?
« Reply #5 on: July 26, 2013, 07:11:20 PM »
   Another observation which further complicates attempts to distinguish the differences between "hitches" and "binders", is that many "tight" hitches ( hitches where the Standing part is also locked by the knot s nub, just as the Tail ) can serve as binders.

X1

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Re: Constrictor bowlines - which is easier to unte ?
« Reply #6 on: July 30, 2013, 05:49:34 PM »
   We can use the Clove or Constrictor not as a more complex double nipping turn, but as a more complex double bight component - and tie corresponding bowlines.
   It is the adoption of the midspan bend solution suggested by dfred, extended in the case of PET eyeknots. See the midspan case in (1), and the eye-knot case in (2), (3). See also the attached pictures.
   
Here's a fairly simple midline bend ...[ which ] has a nice perpendicular lead. 
Many variations are possible here, including a constrictor instead of a clove hitch.  I didn't identify anything simpler and less bulky than a clove hitch though.
   
   The use of the Constrictor instead of the Clove hitch might not be so necessary, indeed, in the case of the midspan bend, as dfred says - but in the case of the eye-knot, it offers a significant advantage we can not ignore : It binds the two collars together ( the "higher" one, around the Standing Part, and the "lower" one, around the eye leg of the Standing Part ), so the whole knot becomes less prone to "open up". As the nipping turn in this bowline retains this almost vertical orientation, the danger of opening up and degenerating into a open helix is more severs than in most other cases of bowlines, where it is more inclined.
   I was curious to see if I could make the double ( = double collar ) bowline, based on a Constrictor double crossed-bight component, to jam, as I have done with the non-reversed Constrictor bowline discussed in this thread. So, I visited my "laboratory", and I started jumping over the "experimental devise" with my full body weight, twice as many times as I did when I tested the non-reversed Constrictor bowlines. With such moderate to heavy loading of the small rope I used, if the knot was to jam, it would had jammed after fewer jumps, than the 64 that I tried !  :)  The strands were flattened at the turns, the knot was compactified to the limit, yet it was so easy to untie by just a light twist of its collars !
   The explanation of the difference between the two cases may be simple : In the Constrictor bowline, where the Constrictor is used as a complex double nipping turn, the one end of it would be loaded by 100% of the total load, and the other by 50%. In the case of the bowline where the Constrictor is used as a complex bight component, its two ends are loaded by 50% and 0%, respectably, of the total load. Biiig difference, indeed.
   So I conclude that the Double bight component bowline ( double = two Myrtle-like crossed-bight components, the one after the other, tied around the SP and the eye leg of the SP ), is a very secure bowline, very easy to remember how to tie, to actually tie and to inspect, which not only does not jam, but it can also be untied very easily. 

1.  http://igkt.net/sm/index.php?topic=3020.msg17965#msg17965
2.  http://igkt.net/sm/index.php?topic=19.msg20905#msg20905
3.  http://igkt.net/sm/index.php?topic=19.msg20922#msg20922
« Last Edit: July 30, 2013, 05:50:57 PM by X1 »