Author Topic: Analysis of Offset Rope Joining Knots  (Read 3870 times)

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #30 on: October 15, 2017, 03:34:39 AM »
New update has been uploaded...

Link to knots page: http://www.paci.com.au/knots.php  (at #3 in the table)
Now VER 1.2c  (15 OCT 2017)

Password to open pdf document = thankyou
[Yes, I do believe this is necessary...a lot of time and effort goes into producing these documents...and you never seem to get much thanks).

[ ] added note about loose tying (X-ray view)
[ ] added commentary about long tails
[ ] added commentary about follow up testing of the different states of orientation
[ ] added some 'grim reaper' toon images (most people recognize this as a bad omen)

...

Dan, I need some feedback to advance this paper further.
Now is your chance!


Mark G
« Last Edit: October 15, 2017, 03:36:39 AM by agent_smith »

Dan_Lehman

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Re: Analysis of Offset Rope Joining Knots
« Reply #31 on: October 15, 2017, 08:20:49 PM »
Quote
It concerns me that you posit stability --as though something
needing minding-- to the trio of extreme/center orientations
of the offset water knot :: IMO, we just don't know enough
about their influence; but we do want to make their existence
known!

Ahhh a paradox! I am getting into a 'catch 22' situation. Damned if I do, and damned if I don't.
I can add wording to the effect that further testing/investigation is needed. I posit that the mid-rotation state does have a vulnerability to capsizing...indeed, this rotation state would appear to be the orientation most often tested (testers are not aware of this - they just orient the knot in this way by way of automatic, in-grained behaviour).
Well, you went further than anything I see as a basis
in making what appears to be your worst *rating* of
the 3rd-shown orientation (in which the white rope
makes the loop) --it gets a nasty thumb vs. a note
of dubiousness, whereas my current thinking (noting
w/o a firm basis) is that mid-range is likely worst.

It IS something to note any seeming preponderance
of an orientation; beyond this, those Australian Bush
Walkers asserted a point re direction of tails --and
wanted just this mid-range one for its aligning the
tails w/axis of tension!  Not that I've checked on
what a preponderance of orientation is, which should
indicate the most common tying method (with some
alteration via setting perhaps).

Quote
Quote
"Leaving long tails" --which is the commonly given advice--
can invite my challenge : "Rather, DO something with them
(with all that "left" material)!"   Because the common
advice is given in anticipation of some sort of capsizing/"rolling",
and I'm not comfortable with asserting that that will be limited
and so within some unknown though believed length of tails.

I concur here. I am not an advocate of long tails. It is largely providing a psychological boost (picture oneself standing on the edge of a very high cliff - about to step backwards into the void...add wind to that mix and you have all the sphincter valve-heart rate-breathing elevated inducements!
You say - 'Do something with those darn tails'!
I say, why have long tails in the first instance?
IIRC, while there haven't been reports of the owk failing
--beyond the old one w/"Karen" the victim--,
there have been some climbers citing "shorter tails"
upon completion of abseil, suggesting that there had
been some "rolling" of the knot --and that's their
grounds for the advice.  (Along with testing that shows
this, albeit typically at higher than expected forces.)


--dl*
====

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #32 on: October 17, 2017, 05:35:48 AM »
New update has been uploaded...

Link to knots page: http://www.paci.com.au/knots.php  (at #3 in the table)
Now VER 1.2d  (17 OCT 2017)

Password to open pdf document = thankyou
[Yes, I do believe this is necessary...a lot of time and effort goes into producing these documents...and you never seem to get much thanks).

[ ] amended page 15 per Dan Lehman feedback (Dan - please check and confirm if this is now acceptable?)
[ ] enhanced page 19 with further commentary re loading profile (compression up against anchor)

...

There is still time for interested parties to add commentary / feedback (but please be quick because I am starting to run out-of-time for this project).
What is needed now is some testing to investigate some of the concepts in the paper.

Mark G
« Last Edit: October 17, 2017, 05:43:45 AM by agent_smith »

alanleeknots

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Re: Analysis of Offset Rope Joining Knots
« Reply #33 on: October 17, 2017, 08:36:57 AM »

                  THANKYOU   謝謝
                  alanlee    謝謝

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #34 on: November 01, 2017, 11:13:23 AM »
New version has been uploaded...

Link to knots page: http://www.paci.com.au/knots.php  (at #3 in the table)
Now VER 1.3 (01 NOV 2017)

Password to open pdf document = thankyou
[Yes, I do believe this is necessary...a lot of time and effort goes into producing these documents...and you never seem to get much thanks).

Changelog:
[ ] new content on page 9 (photos and text about inherent tendency of offset knots to roll during retrieval process)
[ ] amended text content on page 15 (bottom of page)

...

Hoping Alan Lee can test the different orientation states of #1410 to see what affect this has on stability :)
Once I have these tests results (here's hoping) - they would be published in the paper...

Mark G

Dan_Lehman

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Re: Analysis of Offset Rope Joining Knots
« Reply #35 on: November 02, 2017, 12:56:08 AM »
If I can, I'll offer some re-wording for the EKD-backed-EDK
presentation, which is still underwhelming on its benefit.
(hint : the "2nd" knot --which could be first-tied!-- isn't
there for *back-up* but *stopp(er)ing* : it stifles any
pull-through.)

Steve Reid of NeedleSports introduced the knot upon some
unfortunate experience w/an offset fig.8 --a knot that
seems to yet retain or is it *regain* favor w/French, now?!
He thinks it was over a decade back.

Searching RC.com (now a slow-acting, largely ignored place)
for "knudeNoggin" --that sage commenter--, I see threads
remarking at the above presentation (presumably --citing
Steve R., at least, & site) in July 2006.  Andy Kirkpatrick
has further remarks at
https://andy-kirkpatrick.com/articles/view/the_ultimate_abseil_knot
and most notably a testimony to near failure --arrested
manually!!-- of the offset water knot (in thin wet ropes)!
THAT is why ... !  (tying w/gloves on, likely --& preferably!)

--dl*
====



agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #36 on: November 02, 2017, 04:44:27 AM »
New version has been uploaded...

Link to knots page: http://www.paci.com.au/knots.php  (at #3 in the table)
Now VER 1.4 (02 NOV 2017)

Password to open pdf document = thankyou
[Yes, I do believe this is necessary...a lot of time and effort goes into producing these documents...and you never seem to get much thanks).

Changelog:
[ ] page 17: amended and new content added... reference to Dan Lehman proposition that adding a duplicate #1410 (ie backup) acts to retard any risk of tail slippage
[ ] page 27: revised the conclusion and added some images

Dan, if you want specific changes/amendments - you will need to write and submit content. Please make it very clear as to precisely what you want changed/amended... I am starting to run out of time and energy on this particular paper. Need to draw it to a rapid close :)

Mark G

Dan_Lehman

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Re: Analysis of Offset Rope Joining Knots
« Reply #37 on: November 08, 2017, 10:03:58 PM »
New version has been uploaded...
Link to knots page: http://www.paci.com.au/knots.php  (at #3 in the table)
Now VER 1.4 (02 NOV 2017)
...
Dan, if you want specific changes/amendments - you will need to write and submit content. Please make it very clear as to precisely what you want changed/amended... I am starting to run out of time and energy on this particular paper. Need to draw it to a rapid close :)

In a bit of squeezed time (I feel your pain), here is what I've
just tossed together, which I think is an improvement in overall
thrust re the information, though writing-wise less smoothly put
than I'd like.  AND yet devoid of some further quick'n'dirty drop
testing of small masses to see how a well a sloppily tied "EDK=
backed-EDK"
performs.

Quote
SUGGESTED TEXT FOR MARK
--------------------------------------
Circa 2006, Steve Reid of Needle Sports reacted to the report of another
presumed failing of the offset figure 8 knot by introducing what he then
called the "double overhand knot" and which is better named, per its
construction, the "offset water knot with stopper(knot)" --and in the
common parlance among rockclimbers, "EDK-backed-EDK" will be an
even clearer communication of the knot.  In short, the fundamental
offset water knot which will take the main force has its tails --both--
tied in a 2nd overhand knot; this 2nd, "back-up" knot will not be
offset loaded but loaded as a "stopper" knot as its drawn to abut [edit : 'by'=>'but']
the main knot --and arrests any potential slippage of tails out of
that knot.
The current  [2017-11] reference for the NeedleSports article (dated 2015,
w/Lyon's test data) that presents this knot is:
www.needlesports.com/content/abseil-knots.aspx

Here is Steve's sage advice given in the aforementioned article:
Quote
"Of course we all know that knots shouldn't be tied sloppily, and that long tails
should be left, but as we said before, you're cold/wet/tired/frightened/distracted,
the weather has turned gnarly/you've run out of daylight/ you've bitten off more
than you can chew etc, or maybe you've just been distracted by the attractive girl/boy
sharing a stance with you.  Whatever the reason, we all tie our knots less than perfectly
on occasions, so it makes sense to use the safest knot available."

While adding a 2nd, like knot to stopper the first increases the knotted
bulk, it does so in a way that ought not to be any problem in general,
as this added knot will fit through slots and bounce over/around
impediments along with the main knot.  Moreover, it is a better thing
to do with the recommended "long tail's --i.e., to knot them-- than
merely have long tails.  At this point, it should be noted that the
two knot halves of this compound knot can be tied in either order :
once can tie a knot "with long tails" which then are used to make
the 2nd knot as a stopper, or if the tails come out not so long,
tie the 2nd knot in front of the first  --two ways to the same result.

Considering the more material-efficient knots recommended by
this paper, one realizes that their aptness often comes with making
a particular tying decision.  If one gets this wrong, results are not
necessarily good.  Consider the warnings about tying correctness
given above, pp. 13-16 (Vers. 1.4):
 "Correct Dressing is Critical " (cf. Vers. 1.4 p.13);
 "It is critically important to position the thinner rope underneath the thicker rope" (cf.  Vers. 1.4 p.14);
 And the uncertainty about the effects of radial orientation of the knot to the plane it is offset from (cf.  Vers. 1.4 p.15/16).
But to Steve's note above, indeed, it seems that one can violate many of the
preferred tying recommendations of dressing and orientation with this doubled
knot and the structure will still hold!  That is no small commendation for it,
at least under certain circumstances! It is a knot that should be known,
and sometimes used.

And "suggested text" is better taken as "some more words to
consider incorporating, as supplements or replacements (or
amendments).

Also, I find "Lehman posits that ... <the stopper knot will in
fact work qua stopper knot!>" pretty lame :: OF COURSE it
will, that should be pretty much w/o question, no?  (Okay,
some *no* in a case of a really loosely tied 2nd overhand
stopper, but ... .)  AND it can be noted that Moyer (et al.?)
have noted that the *capsizing*/flyping seen in the offset
water knot is rather apt of the colloquial "rolling" whereas
that in the offset fig.8 is more of a "jump" --a bigger flip
which consumes more rope.  So, stoppering the former
should be well assured, but perhaps an offset fig.8 could
partly capsize around a stopper knot (and then who
knows what transpires further)?!


--dl*
====
« Last Edit: November 23, 2017, 05:10:04 PM by Dan_Lehman »

Dan_Lehman

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Re: Analysis of Offset Rope Joining Knots
« Reply #38 on: November 10, 2017, 02:37:05 AM »
The other evening I was sitting fiddling with the
offset water knot tied in 8mm low-elongation,
"accessory cord" & 11(ish)mm low-elongation ("static")
kernmantles and a moderately well dressed & set
knot, under continual stressing & relaxing,
by hand (so, maybe 30# force?),
saw choking line ratcheted out of the knot!!
(And this is why you want even-length tails,
to make this imbalanced slippage evident.)

Whoa & wow!
Now, I've repeated this light loading a few times,
and not always with such dramatic, eye-opening
results.  And note that this was bit-by-bit upon
each surge of force, after relaxing (kinda like the
intermittent loading that can come from some
abseils), and so not the sort of continuous
slippage asserted by the famous Karen Turk
fall or the one posted to Andy Kirkpatrick's site
posted above (and elsewhere, to ukclimbing,
I think, too).
.:.  strange things can happen!

--dl*
====

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #39 on: November 23, 2017, 02:27:39 PM »
New version has been uploaded...

Link to knots page: http://www.paci.com.au/knots.php  (at #3 in the table)
Now VER 1.5 (23 NOV 2017)

Password to open pdf document = thankyou

Changelog:
[ ] page 17 + 18: complete re-write (added commentary from Dan Lehman)
[ ] page 28 + 29: new content added to conclusion
+ a few minor tweaks and enhancements here and there...

...

This is likely the last update for 2017 - and most likely for some months into 2018 - unless something is glaringly wrong or a crucial update is required.
Comments/feedback is always welcome :)

Mark Gommers
« Last Edit: November 23, 2017, 02:32:25 PM by agent_smith »

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #40 on: December 18, 2017, 12:56:54 AM »
In tracking down the history of the introduction into the USA of the unfortunate term Euro Death Knot ('EDK') - I stumbled across this forum in the USA:

Link: http://www.neclimbs.com/SMF_2/index.php/topic,9754.msg81122.html#msg81122

Copied and pasted here for quick view...

from Jeff Lea...
Quote
An excellent treatise-- I have only one slight disagreement : the author suggests early in his discussion that the term EDK to designate the Offset Overhand Knot originated after an accident in the Tetons in 1998. This knot was used by French guides in Chamonix in training at ENSA for their IFMGA certifications in the early 1980s, and British climbing friends of mine, who commonly tied their rappel ropes together end to end with either a double fisherman's bend or a retraced figure eight, referred to it by the term EDK. As the American delegate on the UIAA Safety Committee at the time, I had several discussions at meetings at ENSA with French guide instructors and learned of testing they had done to support the efficacy and safety of using the Offset Overhand Knot to join ropes for rappels, whether of equal diameters or not. I've used it consistently ever since for this purpose.
      I am impressed by the clarity of this paper and the quality of the photographs to support the written word. It deserves greater dissemination. I hope that its presentation here will contribute to that effect.

and this (also from Jeff):
Quote
Hmmmm--"at what point did this name enter into common/mainstream vernacular in the USA?" I'm afraid I can't answer that, other than to say that certainly it was commonly referred to in that manner among many climbers in New England of my acquaintance  who had also climbed in Europe and/or Great Britain prior to 1985. That is not to say I believe that it "had entered into the common vernacular". It was usually used in a jocular fashion, and often directed at those of us who had adopted the Offset Overhand Knot as our knot of choice for joining rappel ropes. I CAN say for certain that the first time I heard it was in Chamonix in the summer of 1982, after descending from the Aiguille de la Blaiti?re with a British partner, alongside a rope team of French Aspirant Guides, with whom we were sharing rappel anchors. This sharing may seem unusual to some who have climbed in the alps; my fluency in French as a career teacher of the language certainly helped our interaction, as did the fact that I had spent the previous week at ENSA representing the AAC at the meetings of the UIAA Safety Commission. As for citing me, you have my permission, since I have here clearly stated the limited level of my authority on the origins of the name "EDK".  Jeff Lea.

...

Mark G

Dan_Lehman

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Re: Analysis of Offset Rope Joining Knots
« Reply #41 on: December 19, 2017, 02:23:18 AM »
Nice to see some spreading of the good word/work!
And I'm glad he piped up.  I wasn't aware of your bogus "history"
of the "EDK" name --egadz, with a propensity to such dangerous
leaps like that deduction, stay well back from cliff edges!   :o

In regard to p.27's 3rd/lowest-shown end-2-end ARJ knot,
it c/should be named "offset 8-oh", the "8" in primary position
as that is the choking line's component, with the other line
making the ends-exit-altering overhand --and seeing the
exit of tails on each side as possibly adding some resistance
to flying.

And this *knot* just led me to a funny knot *invention* ::
 I'd tied this ARJ knot for some passing reason in a play
rope that had a new eye knot (derived qua corresponding
eye knot for the sheet bend, with the bight (not loop)
half of that asymmetric end-2-end knot taken as
the base (unlike the bowline's taking the (nipping) loop
as its base), ...
and later beheld the play rope with as holding TWO eyeknots
--i.e., regarding the closed-ring-via-offset 8-oh as not a ring
but an eye; the apparent SPart --i.e., the end leading some
ways to my intended eye knot-- was to the overhand.

It looks reasonably decent, secure-when-slack, and fairly
easily loosened after loading!?  Well, I loaded the half-inch
double-braid dock line to maybe 300# or so, as a check.

Ha, and that was inadvertent knot *invention*.  (Were one
to adopt the rigor of trying all possible loadings of each tangle
that some fiddled *new* knot provides, these things would
be found earlier; but so far, I've yet to be so tediously thorough.)

(Another just-now *new* discovery --though the tied knot has
been around w/me for years-- :: if one begins with the inline
/directional fig.8
eye knot and then takes its eye around
the tail SPart back up and out through the turns at the main
SPart --i.e., that part that is always a SPart, on eye- or
through-loading--, one gets an inline/dir. fig.9 !!
(Yes, the so-derived eye will now point the opposite way.)
[correction in red (vice "not")]


--dl*
====
« Last Edit: December 22, 2017, 01:57:55 AM by Dan_Lehman »

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #42 on: December 22, 2017, 12:47:48 AM »
New revision has been uploaded.
Now VER 1.6  (22 DEC 2017)
Link to knots page: http://www.paci.com.au/knots.php (at #3 in the table)

Change log:
[ ] pages 4+5 - added commentary from Jeff Lea re history of the term 'EDK'
[ ] page 13 - major re-write (hopefully better definitions and examples)

Quote
I wasn't aware of your bogus "history"
of the "EDK" name --egadz, with a propensity to such dangerous
leaps like that deduction, stay well back from cliff edges!

Refer to amended pages 4+5 which address your rhetoric  ;D



Quote
In regard to p.27's 3rd/lowest-shown end-2-end ARJ knot,
it c/should be named "offset 8-oh", the "8" in primary position
as that is the choking line's component, with the other line
making the ends-exit-altering overhand

See amended VER 1.6 at page 28, which addresses this point.

Happy Christmas to all :)
« Last Edit: December 22, 2017, 12:53:23 AM by agent_smith »

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #43 on: December 24, 2017, 02:57:01 AM »
New revision has been uploaded.
Now VER 1.6a  (24 DEC 2017)
Link to knots page: http://www.paci.com.au/knots.php (at #3 in the table)

Change log:
[ ] pages 4+5 - added commentary about Petzl and their 'RAD LINE' ( https://www.petzl.com/US/en/Sport/RAD-LINE-joining-knots )
[ ] page 19 - added commentary about Petzl testing of #1410 in their 'RAD LINE' system
[ ] page 30 - added commentary about Petzl and their testing to probe characteristics other than MBS yield.

...

Hopefully this paper is now complete?

Merry Christmas

Mark Gommers