Author Topic: Butterfly bend eye knot  (Read 3006 times)

Dan_Lehman

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Re: Butterfly bend eye knot
« Reply #15 on: March 01, 2018, 01:04:19 AM »
I tied the butterfly bend ...
Here is the first problem, which most people gloss over
(such as the ensueing discussion here) :: there is no "the"
knot, but some commonly formed ones and others of a
similar construction but with different dressing.

To begin : since the butterfly --unlike a quite lookalike
Ashley #1408-- is asymmetric, there are two *knots*
(structures with a loading profile) to consider re loading
--i.e., which end will bear tension while the other dangles?
Before this, there is the matter of how the knot is oriented
via dressing --e.g., do the eye legs (or in this common
eye-from-end2end relation, and eye leg & the tail) cross?
(Most presentations of the butterfly do not cross them
(but maybe it's best if the parts are crossed).)

Making an eye knot from a given end-2-end knot as you have
done is the common way of relating these types of knots; but
it is not the only one --another, which I'm currently exploring,
entails tying a bight's twin legs to a single strand in the way
of making the end-2-end knot, and then seeing how the tail
from the single strand can be *fused* with one of the bight's
tails to result in a corresponding eye knot for that bend.
This latter correspondence better preserves the workings
of the end-2-end knot, in some cases (though in being
roughly end-2-DBL_end it of course has that difference).

> Is this eye knot an already known and named knot?

One might say simply that the relation --the way of deriving
the eye knot-- is understood and so exists for any end-2-end
knot (though some won't result in good eye knots (e.g., the
square knot)!).

Quote
So despite Mr Delaney's assertions - the Butterfly does jam!
I recall his assertions about Ashley's #1452 jamming, and how
it took some persistent pressure from me to discover that he
was tying the knot in a version different from others in which
jamming was prevented; I suspect that there might be a like
issue with your butterflies, which as aforementioned begin
with a dressing choice upon which then comes the loading one.

Meanwhile, someone reported a jammed zeppelin knot,
so never say 'never" on that.
(Dynamic rope probably has the greatest potential for jamming,
as with such great stretch comes diminished diameter and
great knot compression (potentially) to fill the voids of
disappearing bulk; then, if material swells outside of the
knot (recovering towards original diameter & length) but
cannot gain entry past the tight constriction at entry,
... jam!)

As for "SPart loading", by definition one typically loads
a (if not more than "a") SPart.  "End-2-end" or "through"
loading is what's meant, here in the mid-line eye-knot case.
And the issue re asymmetry points to the duality of
potential SParts for the eye.

And what is seldom (ever?) tested is the behavior of
whatever loading AFTER the knot has been otherwise
loaded (not merely "dressed & set"), which might be
how a practical circumstance delivers force.  (Watching
some arborist fellow's loading the butterfly qua eye knot
and seeing how the collar around the unloaded end collapsed
was pretty eye-catching; how the knot would then perform
on through loading is a question, with that so-tightened
collar.  (Although forces were probably well higher than
some practical likelihood.)


--dl*
====


agent_smith

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Re: Butterfly bend eye knot
« Reply #16 on: March 01, 2018, 01:37:06 AM »
Quote
the butterfly... is asymmetric, there are two *knots*
(structures with a loading profile) to consider re loading
--i.e., which end will bear tension while the other dangles?

Indeed - I agree.
This is a factor in 'eye loading' (as opposed to SPart loading).
As far as I am aware, no one has tested (in proper test lab environment) #1053 Butterfly in eye loading in both directions; and then comparing test results. This asymmetric structure has been something I have given thought to over the past year - but it is hard to find someone willing to invest time and effort to conduct the testing.
I have contacted Richard Delaney (rope test lab) a few times about other knots (eg #1410 Offset overhand bend) - but he declined.

Quote
Meanwhile, someone reported a jammed zeppelin knot,
so never say 'never" on that.

I have tried to induce jamming of the Zeppelin bend but as 'yet' - have failed.
My last attempt involved a forklift truck - I created a rope sling which was built from two Zeppelin bends in 19mm diameter yachting double braid rope.
I lifted a 10 ton crane counter-weight - then lowered it back down (due to the effect of the sling - each knot only experienced 50% of the load).
The Zeppelin bends were both easy to untie.
I admit this was not a scientific experiment - it was just a home-brew test.
I am curious about the 'someone' who managed to jam a Zeppelin bend. There must have been very specific conditions for this to occur...

Quote
As for "SPart loading", by definition one typically loads
a (if not more than "a") SPart.  "End-2-end" or "through"
loading is what's meant, here in the mid-line eye-knot case.

In the case of #1053 Butterfly (TIB midline) - the #1053 derived bend and the #1053 derived eye knot (end-line) - one has to be careful in specifying loading profiles.

In indoor climbing gyms, eye loading of #1053 Butterfly (TIB midline version) is commonplace. And in this type of loading profile, I can confirm that it jams.
I have not tested - nor have I seen test results for eye loading of #1053 derived Butterfly eye knot (the corresponding eye knot derived from Butterfly bend).

In what I referred to as 'SPart loading' of #1053 Butterfly - yes, it is a 'through-loading' and this would be a nice descriptor particularly for loading a series of Butterfly knots (TIB midline) tied in the one length of test rope. This is what we did a number of years ago... 2 Butterfly knots tied in series - and we pulled to MBS yield point.
I was able to untie (by hand) the surviving Butterfly knot - but, some of the others could not (they didn't have sufficient hand/finger strength). They tried first then gave up - then I tried and succeeded (without tools). The rope was EN892 dynamic and it was very old & worn (quite 'stretchy' rope if I recall correctly).

This is why I think the matter of #1053 derived Butterfly bend in terms of its jam resistance - is not fully resolved.
I think more testing needs to be carried out and peer reviewed.
« Last Edit: March 01, 2018, 01:43:10 AM by agent_smith »

Harold Kahl

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Re: Butterfly bend eye knot
« Reply #17 on: March 02, 2018, 01:36:47 AM »

I have not seen or known that it is possible to create the Butterfly eye knot with tail outside the eye.

Would this qualify?
https://youtu.be/xVeDZ3IOM3E

agent_smith

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Re: Butterfly bend eye knot
« Reply #18 on: March 02, 2018, 02:52:28 AM »
No.

Can you please closely study my attached image of the structure of #1053 Butterfly (TIB mid-line version).

Compare this to your video.

Notice anything?

Harold Kahl

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Re: Butterfly bend eye knot
« Reply #19 on: March 02, 2018, 03:33:06 AM »
Back to the drawing board.

agent_smith

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Re: Butterfly bend eye knot
« Reply #20 on: March 02, 2018, 03:57:52 AM »
Harold, I admire your tenacity.
Although you seem to focus your attention on my work (why?).

...

If you would like a real challenge - one that will put you squarely in the history books - try this one...

Can you test #1410 Offset overhand bend (aka 'EDK')?

Test as follows:
1. Test #1410 in its 'mid-rotation' state
[ ] determine the load threshold which triggers instability.

2. Test #1410 in its 'rotated' state.
[ ] determine the load threshold which triggers instability.

The control for the test is #1410 in its 'mid-rotation' state.

For background info on #1410 and its various rotation states - please down my 'Offset knots' paper.

Alan Lee is also testing #1410 and its various rotation states.

HYPOTHESIS:
#1410 in its rotated state will be less vulnerable to instability (eg a capsizing event).
It is hypothesized that a simple rotation of #1410 will trap and hold the tails - and also reduce the tendency to capsize due to a re-alignment of load closer to the axis of tension.
We just need testing to either confirm or reject this hypothesis.

We desperately need this data.

Help me Obi Wan Harold :)

« Last Edit: March 02, 2018, 03:59:10 AM by agent_smith »

Harold Kahl

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Re: Butterfly bend eye knot
« Reply #21 on: March 02, 2018, 05:13:21 AM »
Is this better?
https://youtu.be/lUZIkN8SFqE


Mark, I'm not stalking you, honest. This just happens to be what interests me at the moment.
Sorry, I don't really have any equipment for testing knots.

agent_smith

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Re: Butterfly bend eye knot
« Reply #22 on: March 02, 2018, 06:22:12 AM »
Quote
Mark, I'm not stalking you, honest.
Hmmmm, not convinced!

Anyhow - No cigar I'm afraid.

Nice try - but it isn't a proper functional eye knot.
Surely you must have realized that?
Did you try loading the eye? If not, please do so and watch what happens. The core collapses in a kind of implosion.

What you have created is a 'reversed derived Butterfly' (for want of a better name).

I say 'reversed' because what used to be the SParts are now eye legs.

What used to be the 'eye' is now an SPart and and a tail.

...

NOTE: Some will argue that technically - what you have created is a #1053 derived Butterfly eye knot. And they would be technically correct.
But, I think you have done a Jim Kirk and cheated Kobayashi Maru test by simply reversing a standard #1053 Butterfly eye knot. Kudos to you!
« Last Edit: March 02, 2018, 06:35:29 AM by agent_smith »

Dan_Lehman

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Re: Butterfly bend eye knot
« Reply #23 on: March 03, 2018, 10:25:32 PM »
Quote
Meanwhile, someone reported a jammed zeppelin knot,
so never say 'never" on that.

I have tried to induce jamming of the Zeppelin bend but as 'yet' - have failed.
...
 There must have been very specific conditions for this to occur...
It's much a matter of >>cordage<<.  I've found it to be
less than *easily* untied (if not jammed) once or so (not
specifically looking).

--dl*
====

Dan_Lehman

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Re: Butterfly bend eye knot
« Reply #24 on: March 03, 2018, 10:32:41 PM »
Is this better?

Heck, I have trouble keeping straight which is which,
but I THINK that you've there put the knot into the
form --w/crossed eye legs-- that was recommended
by Wright & Magowan's 1929 Alpine Journal article,
and which seems good (for through / end-2-end loading;
for eye loading, not sure which end would make the
better SPart (and how to judge "better" : stronger
or more-easily-untied!?).

Thanks,
--dl*
====

agent_smith

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Re: Butterfly bend eye knot
« Reply #25 on: March 14, 2018, 03:34:10 PM »
Quote
Heck, I have trouble keeping straight which is which,
but I THINK that you've there put the knot into the
form --w/crossed eye legs-- that was recommended
by Wright & Magowan's 1929 Alpine Journal article

The video is not good quality and his hands keep getting in the way but, upon scrutiny - it appears he tied the knot at far right (see attached image).
It s complete reversal of the #1053 Butterfly eye knot.

It appears to be prone to deforming in this reversed loading profile (what used to be the SParts is now in fact the 'eye').
« Last Edit: March 14, 2018, 03:34:58 PM by agent_smith »

Dan_Lehman

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Re: Butterfly bend eye knot
« Reply #26 on: March 14, 2018, 10:30:41 PM »
Quote
Heck, I have trouble keeping straight which is which,
but I THINK that you've there put the knot into the
form --w/crossed eye legs-- that was recommended
by Wright & Magowan's 1929 Alpine Journal article

 it appears he tied the knot at far right (see attached image).
And your butterfly versions do not have the crossed eye legs
as Wright&Magowan prescribed, which IMO give nice SPart
curves vs. the 1dia hard turns of the commonly parroted version.

--dl*
====

ps : I think I remarked, but will echo then here ... that
HNG Bushby mused the butterfly as an alternative knot
for the middleman, in consideration of the then-recommended
(by Alpine Club) fisherman's knot (which logically is a noose
on one SPart's loading (and which Bushby also remarked could
be simply anulled by putting in a 3rd overhand, which he smartly
noted could be done no matter the stage of tying --first/last!!)).

SOOOO, that gives us 1902 as earliest sighting;
but there could (should?) be something in linemen documentation
to support/further A. Burger's 1909 presentation of the knot as
used by them.

agent_smith

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Re: Butterfly bend eye knot
« Reply #27 on: March 15, 2018, 05:14:40 AM »
per Dan Lehman...
Quote
And your butterfly versions do not have the crossed eye legs
as Wright&Magowan prescribed

I was unaware that Wright and Magowan were considered to be authorities on how to tie a #1053 Butterfly eye knot (TIB midline)?
This 'prescribed' form - as you put it, is not the default (standard) form.

Indeed, I am unaware of any specific testing on the X variant in comparison to a 'control' (#1053 default version with no twist would be the control for the experiment). Maybe this is another possible test for Alan Lee to investigate?

This 'X' form - where the eye is twisted - may indeed provide an increased bending radius for the SParts when the knot is bi-axially 'SPart loaded'.
However, Eye loading may not see any real tangible benefits. Although it would be interesting to see if an 'X' variant is more jam resistant in eye loading.

Mark G

Edited...found a photo of the twist rotated in the opposite direction
« Last Edit: March 18, 2018, 12:15:05 AM by agent_smith »

Dan_Lehman

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Re: Butterfly bend eye knot
« Reply #28 on: March 15, 2018, 06:00:57 PM »
per Dan Lehman...
Quote
And your butterfly versions do not have the crossed eye legs
as Wright&Magowan prescribed

I was unaware that Wright and Magowan were considered to be authorities on how to tie a #1053 Butterfly eye knot (TIB midline)?
This 'prescribed' form - as you put it, is not the default (standard) form.
I'm unaware of any "standard" for the forms of knots
--though CEN & UIAA I think have standards for cordage
tests that require a particular knot (viz., fig.8 eye knot)

Quote
This 'X' form - where the eye is twisted - may indeed provide a reduced bending radius for the SParts when the knot is bi-axially 'SPart loaded'.
However, Eye loading may not see any real tangible benefits. Although it would be interesting to see if the 'X' variant is more jam resistant in eye loading.
You must mean "increased bending radius"; I do.

And there you go again with "the" vs. "a" ::  what you
present is but one of two "X" forms, and the wrong one,
naturally!   ::)
One can remember the butterfly's two-overhands structure
as having one "pretzel" and one where "SPart SPlits SPine"
--yep, SPit it out, like that.  There are three orientations:
eye legs abutt in a plane parallel w/axis of tension;
eye legs cross such that the pretzel's spine is UNsplit;
 < ditto > but with spine split.  (Other OH spine will
 always be split, by opp. SPart.)

The pretzel's spine is split in your case (by an eye leg),
but being so via eye leg it can be also unsplit when that
leg is around the other way.  IMO, it is how torsion will
want to place the eye legs if tying by the "twirly flop"
method.  (But when playing around expressly to note
this point, earlier today, my initial tying got an ugly
mess; though a later one, I thought the same way,
produced the result just described.)

Quote
SPart loading ...
However, Eye loading ...
HOW MIGHT THIS BE LOADED IN <what___?> PRACTICE?!

There is the use for a two-anchor joint, where the eye
serves as an attachment point --if not the entire bit--
for one of two anchors, and one end running to the other.
Loading here would be on all parts at once, with some
acute angle in the eye.  IF one or the other anchor then
failed, ... .  If the failure occurred on some significant
loading, you'd have a knot that had been hard set in
the initial state.

And otherwise I wonder at loading in practice :: might
it come in some sort of this-way then that-way manner?
--where after the initial loading, the knot takes a shape
well different (collapsed collar, say, after eye loading, of
the unloaded SPart if ...) from what one would normally
test!?

--dl*
====

agent_smith

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Re: Butterfly bend eye knot
« Reply #29 on: March 15, 2018, 10:07:19 PM »
Quote
You must mean "increased bending radius"; I do.

Take a breath Dan..its obviously a typo!

Quote
And there you go again with "the" vs. "a" ::  what you
present is but one of two "X" forms, and the wrong one,
naturally!
Did you read the accompanying text in the image? I clearly stated that the twist can also be made in the opposite direction - I only had a photo for one version...
And there is no A versus B in the corrupted sense you are implying.
I always try to provide something readers can compare with...so you provide a default form and then you provide a variation. Doing so side-by-side allows readers to compare differences visually.
I would have thought that this is common sense?
Sort of like showing a common Bowline and then an anti-Bowline next to it for comparison.

With reference to eye loading...
Quote
HOW MIGHT THIS BE LOADED IN <what___?> PRACTICE?

This remark demonstrates a surprising lack of knowledge on your behalf.
Eye loading is common!
1. it occurs in anchor systems
2. it occurs within indoor climbing gyms
3. it occurs in top-managed belay systems for abseiling (although I personally prefer to use an 8mm slide and grip hitch - 'klemheist' because it allows adjustment of position)

Refer to attached images...

Within indoor climbing gyms, eye loading causes the knot to jam.
The X variants may be worth investigating to see if the jamming threshold can be raised.
« Last Edit: March 16, 2018, 06:23:28 AM by agent_smith »