Author Topic: Open Helix loop  (Read 2626 times)

Mobius

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Open Helix loop
« on: August 26, 2015, 01:05:03 PM »
This knot started it's life as a bowline attempt, with a typical closed loop turNip. It looked promising until I loaded it and ended up with the secure loop that is shown in the bottom image. This rather flat, plait style, loop has been repeatedly loaded and untied to 50%+ MBS (>315 kg) and it appears to hold very nicely and is very easy to untie.

The top image shows the knot in expanded form, with it's open helix in the nub segment following from the standing part. It is disconcerting not to see a closed loop here, however, despite this, it works! The returning leg does provide a closed binding loop and this is what keeps the knot together in my opinion.

We are so used to seeing a tight nipping turn from the standing part promoted here as prerequisite for a loop it was interesting to me that this knot does not seem to need one.

The knot is PET and TIB, however I don't think many (including me) will want to tie a knot with an open helix instead of a turNip, even if it does appear to work. It was interesting to me though, so I thought I would share it.

Cheers,

mobius


xarax

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Re: Open Helix loop
« Reply #1 on: August 26, 2015, 01:26:35 PM »
   Read what has been written in the thread about "Helical loops", and in the references therein.
   http://igkt.net/sm/index.php?topic=4949.0
   The first Helical loop I have tied was when I was trying to figure out a mid-line / mid-span bend, at :
   http://igkt.net/sm/index.php?topic=3020.msg21688#msg21688
   Try to find TIB ones.
   
 
This is not a knot.

Mobius

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Re: Open Helix loop
« Reply #2 on: August 26, 2015, 01:56:18 PM »
   Read what has been written in the thread about "Helical loops", and in the references therein.
   http://igkt.net/sm/index.php?topic=4949.0
   The first Helical loop I have tied was when I was trying to figure out a mid-line / mid-span bend, at :
   http://igkt.net/sm/index.php?topic=3020.msg21688#msg21688
   Try to find TIB ones.
   
 

Thank you xarax. The knot I came up with might be more interesting than I first thought, it is very easy to tie and it is TIB. It loads very well and distorts very little from the times I have loaded it.

I viewed my knot as a somewhat 'failed' bowline, however after a quick read from the start of one of the links you provided maybe it has potential after all.

Cheers,

mobius
« Last Edit: August 26, 2015, 02:05:21 PM by mobius »

Mobius

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Re: Open Helix loop
« Reply #3 on: August 27, 2015, 08:48:12 AM »
To tie this knot it is probably easiest to pretend it is a bowline with an 'Eskimo' start. If you tie it this way and then snug it like a bowline then it settles into a really nice stable open helix form after loading. Remember, the loading I show here is high (>50% MBS) and the nub retains a nice shape in my opinion. One that is apparently stable and easy to untie.

Cheers,

Mobius

Edit: > not <
« Last Edit: August 28, 2015, 02:51:36 AM by mobius »

Dan_Lehman

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Re: Open Helix loop
« Reply #4 on: August 28, 2015, 05:28:40 PM »
We are so used to seeing a tight nipping turn from the standing part
promoted here as prerequisite for a loop it was interesting to me that
this knot does not seem to need one.

The knot is PET and TIB, however I don't think many (including me) will want
to tie a knot with an open helix instead of a turNip, even if it does appear to work.
It was interesting to me though, so I thought I would share it.
Cheers,
mobius
As X. notes, you are following where others have gone,
and as for having an "open helix" (which might be seen
by that adjective to acknowledge that the turNip also
is a helix --which even in the venerable bowline sometimes
somehow gets well open, nearly straightened!),
YMMV per material & circumstance.

But I've dropped my thoughts that the open helix leads
to a nice gradual curvature and greater strength, though
there might be something to that.  It comes down to
relying too much, IMO, on knowing the behavior of the
particular cordage and then setting the knot just right
for that --just anticipating its particular elongation, sliding
of material-over-material but yet being "fixed" as an eye,
to be impractical.

Still, there are many such knots that at least start with
the reentry of the just-formed-the-eye tail on that opposie
side of the foundation loop (to open more helically) that
are fine.  And whereas this initial reentry done as for the
bowline makes an overhand at that point --so, will
then be not-TIB--, going the opposite way leaves TIB
potential.


--dl*
====

Mobius

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Re: Open Helix loop
« Reply #5 on: August 29, 2015, 06:01:32 AM »

As X. notes, you are following where others have gone,
and as for having an "open helix" (which might be seen
by that adjective to acknowledge that the turNip also
is a helix --which even in the venerable bowline sometimes
somehow gets well open, nearly straightened!),
YMMV per material & circumstance

A turNip is a closed loop, still a helix to be sure, however that it remains closed under load is a defining point to me. If a bowline starts collapsing under load and becomes an 'open helix' nip turn then I don't think it deserves to be called a bowline. So my use of 'open' was deliberate.

Quote
But I've dropped my thoughts that the open helix leads
to a nice gradual curvature and greater strength, though
there might be something to that.  It comes down to
relying too much, IMO, on knowing the behavior of the
particular cordage and then setting the knot just right
for that --just anticipating its particular elongation, sliding
of material-over-material but yet being "fixed" as an eye,
to be impractical.

I believe the strength of a loop, in terms of where it breaks and at what %MBS, has very little to do with the curvature of the helix nip turn, or whether that helix be closed or open. One advantage of the cordage and test materal I have used a lot (white braid and a black marker) is that I can mark it at ~60%+ MBS and then get a really good idea of where the knot breaks. One of the many more formal studies I have in mind is a presentation of different loops and showing that loops do not break where some (perhaps many) believe they do.

Quote
Still, there are many such knots that at least start with
the reentry of the just-formed-the-eye tail on that opposie
side of the foundation loop (to open more helically) that
are fine.  And whereas this initial reentry done as for the
bowline makes an overhand at that point --so, will
then be not-TIB--, going the opposite way leaves TIB
potential.


--dl*
====

Yes indeed, exactly my experience with trying to tie many TIB bowlines. I was trying to introduce a bowline that has a binding loop before the collar so that the collar remains relatively loose and is your access point for undoing the loop. Note that a 'collar' to me is the loop around the neck of a bowline (collars go around necks), other loops that get called collars are just binding loops to me. My experince to date is that getting a TIB bowline with the "Eskimo" entry into the nip turn then binding loop is a lot easier than entry into the foundation loop from the 'normal' side and then binding loop.

Cheers,

mobius
« Last Edit: August 29, 2015, 06:04:31 AM by mobius »

xarax

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Re: Open Helix loop
« Reply #6 on: August 29, 2015, 07:56:01 AM »
   Regarding the "open helical" nipping structure tied on the Standing Part before the eye, we had discussed about the term and the issue about if such structure should characterizes a "bowline" ( or not ), back at Jan. 2012. At the end of the day, it all comes to d e f i n i t i o n s :
 
   According to my definition,
   
   this loop should be described as a bowline-like loop.... 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 !
   
   Find a better definition!
   
   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.)

   http://igkt.net/sm/index.php?topic=3233.msg21697#msg21697
   http://igkt.net/sm/index.php?topic=3020.msg21688#msg21688
This is not a knot.