Author Topic: Analysis of Offset Rope Joining Knots  (Read 14685 times)

Sweeney

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Re: Analysis of Offset Rope Joining Knots
« Reply #15 on: July 03, 2017, 07:14:53 PM »
There was a previous thread on offset bends  - http://igkt.net/sm/index.php?topic=4411.msg27806#msg27806 - in that thread  James Peterson suggested using the Bowstring Knot (ABoK 151) tied in 2 parallel cords and collapsed rather than used as a loop -http://igkt.net/sm/index.php?topic=4411.msg28635#msg28635. Perhaps worthy of inclusion even if not to be recommended?

Sweeney

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #16 on: July 04, 2017, 01:29:55 PM »
I have some spare time this week and will tie, assess and then photograph the suggestions from SS369 and Sweeney.
Thanks.

Mark

knotsaver

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Re: Analysis of Offset Rope Joining Knots
« Reply #17 on: July 04, 2017, 02:16:39 PM »
There was a previous thread on offset bends  - http://igkt.net/sm/index.php?topic=4411.msg27806#msg27806 - in that thread  James Peterson suggested using the Bowstring Knot (ABoK 151) tied in 2 parallel cords and collapsed rather than used as a loop -http://igkt.net/sm/index.php?topic=4411.msg28635#msg28635. Perhaps worthy of inclusion even if not to be recommended?
Sweeney

I notice only now that I didn't know this post and I showed this knot at
http://igkt.net/sm/index.php?topic=5555.msg38903#msg38903
starting from ABoK #523,
please notice that it is a reversed of a figure 9 knot.
Ciao,
s.

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #18 on: October 01, 2017, 10:59:25 AM »
Just announcing that the draft paper (VER 1.1a  01 OCT 2017) is now uploaded and live on the PACI website.

PACI website: www.paci.com.au  (click on 'public downloads' / 'knots and knotting concepts')

Direct link to page: http://www.paci.com.au/knots.php   (at #3 in the table)

Dan, can you please have a look a page 14?
I have re-photographed the neutral (no rotation) and rotated state...hopefully the neutral (no rotation) image is now of an acceptable standard?

Camera angles are tricky - and I am not a professional photographer - just trying my best to capture the salient features to showcase concepts.
Are you still in support of a rotation to induce a chocking effect to trap and crush the tails of #1410?

...

Scott, sweeney and 'knotsaver', I will be looking at your comments in detail probably tomorrow. Will try to incorporate your info as best I can and then upload another paper for comment. I appreciate any and all assistance received...thanks!

Mark Gommers

knotsaver

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Re: Analysis of Offset Rope Joining Knots
« Reply #19 on: October 02, 2017, 05:31:36 PM »
Hi Mark,
some comments/notes:
- p.9 the knot in the picture (bottom right) is not the #1410 but (your) "improved #1410".
- p.13 you could specify (in the picture) the thick and thin rope (yes they are visibly different).
- p.18 you could add an example with wrong knot and ropes of different color.
(- p.2 l.4 " ' " is missing: "whats in a name").
- please, explain why the tails should be of identical length (I think I know why but...)
---
Will you add/analyse other (offset) bends?
---
Ciao,
s.

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #20 on: October 03, 2017, 12:49:49 PM »
Knotsaver,

Made some amendments per your suggestions.

Quote
(- p.2 l.4 " ' " is missing: "whats in a name").
Unsure what this comment was actually referring to??

Hope all is okay now?

This is still a work in progress...

Mark Gommers

knotsaver

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Re: Analysis of Offset Rope Joining Knots
« Reply #21 on: October 04, 2017, 11:35:02 AM »
Quote
(- p.2 l.4 " ' " is missing: "whats in a name").
Unsure what this comment was actually referring to??

(- page2 line4 (the Contents page): " ' " is missing: "what's in a name")

I noticed it...

Ciao,
s.

Dan_Lehman

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Re: Analysis of Offset Rope Joining Knots
« Reply #22 on: October 04, 2017, 09:38:56 PM »
Dan, can you please have a look a page 14?
I have re-photographed the neutral (no rotation) and rotated state...

just trying my best to capture the salient features to showcase concepts.

I'm unsure of "neutral" : "middle-of-possible-rotational-range" is what
that one is --and it allows rotation opposite to what you chose for the
2nd orientation.  IMO, show all three ; let viewers see the whiter rope
making the loop, then the "neutral"/"middle" state where both ropes
go away from viewer, up into knot, then a less in-your-face(large) and
equal image of the other end of the range, where now the blue rope
loops to the white rope's "arc" (my terms).

Respectively of this trio of states, tails come AT viewer, run to left,
or go AWAY from viewer.  --all from the "same knot", one might think!


Quote
Are you still in support of a rotation to induce a chocking effect to trap and crush the tails of #1410?
Absent any much testing of this, still,
I'm yet leery of the middle orientation
vs. either of the ones w/a loop in them,
yes.  But that's a continued position devoid
of further testing to support ..., not one that
comes WITH such further support.
(Hoping that interested parties to this thread might
test their own materials with some kind of slow-loading
or bouncing/shock loading in variously tied/tightened
knots.

 - - - - - - - - - - - - - - -

Quote
Recent testing has demonstrated that ... the tails do not mysteriously slip.
I don't know what recent testing this is, but I can be pretty
certain that it hardly covered the myriad possible combinations
of ropes that might be joined for abseil --varied in firmness,
bending resistance, slick/frictive surface, sizes, & elasticities!

Now, you persist in putting up a strawman --or, at least
a weak substitute to what has been advanced to you by
me in this thread-- for attacking the "EDK-backed EDK"
(as colloquial/common parlance might put it) :: it is very
much a desirable *tool* in the knots kit on occasion that
all the important just-tie-it-right points cannot be done,
as is quite reasonable to anticipate via fatigue and other
stressful circumstances (and user error (my 'usERror' in fusion)!
And noting that this "back-up" EDK is loaded differently,
qua stopper, and more assuredly effective/safe thus,
and thereby ensuring ultimate security of the base knot.

As for "larger footprint", that, too, exaggerates likely effect
of the more material :: the 2 overhands will fit through
a slot about as likely as one, and the 2nd shouldn't affect the
offset qualities of the first in pulling down. (Beyond this one
can note some reports of lonnnnnnnnnng uses of only the
grapevine w/o all the troubles alleged of non-offset
knots.)

--dl*
====

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #23 on: October 11, 2017, 02:53:25 AM »
Quote
Quote

    Recent testing has demonstrated that ... the tails do not mysteriously slip.

I don't know what recent testing this is, but I can be pretty
certain that it hardly covered the myriad possible combinations
of ropes that might be joined for abseil --varied in firmness,
bending resistance, slick/frictive surface, sizes, & elasticities!

And this refers to my personal testing both in a test bench/lab environment and in actual field use.
I have just returned from a week long climbing trip to Mt Arapiles (Australia) where I had an opportunity to use #1410 (offset overhand bend) in a number of typical EN892 dynamic climbing ropes (different brands, different diameters, different sheath characteristics, some slick and some not so slick, etc) - in retrievable abseil systems.
NOTE: I use a modified #1410 - with an additional turn of one strand to bind and lock the structure.

I made approximately 10 multi-pitch abseil descents (as a means of descending to the ground after completing a route).

There were up to 4 climbers in my group - all descending one after-the-after.

There was no observable tail displacement or 'slippage' of tails at any stage.

I ensured that the tails were tied to identical lengths and then checked again at each intermediate belay ledge and then again upon reaching the ground. I could not discern any appreciable difference in tail lengths.

The point here is that if #1410 is properly and diligently cinched and dressed - with the nominal loading of a single person (100kg average) - you are simply not going to see any tail movement of statistical significance.
Keep in mind that in a typical double rope retrievable abseil configuration, the end-to-end joining knot (ie #1410) will only have 50% loading.

Quote
Now, you persist in putting up a strawman --or, at least
a weak substitute to what has been advanced to you by
me in this thread-- for attacking the "EDK-backed EDK"
(as colloquial/common parlance might put it) :: it is very
much a desirable *tool* in the knots kit on occasion that
all the important just-tie-it-right points cannot be done,
as is quite reasonable to anticipate via fatigue and other
stressful circumstances (and user error (my 'usERror' in fusion)!
And noting that this "back-up" EDK is loaded differently,
qua stopper, and more assuredly effective/safe thus,
and thereby ensuring ultimate security of the base knot.

As for "larger footprint", that, too, exaggerates likely effect
of the more material :: the 2 overhands will fit through
a slot about as likely as one, and the 2nd shouldn't affect the
offset qualities of the first in pulling down. (Beyond this one
can note some reports of lonnnnnnnnnng uses of only the
grapevine w/o all the troubles alleged of non-offset
knots.)

--dl*

My counter-point is that duplication of #1410 is simply an attempt to add security where none is required in the first instance (per certain conditions which I will try to elaborate).
Your proposition is one that is often quoted...ie; "tired", "mentally fatigued", "cant think straight", "oxygen starved", blah blah blah...) is your justification for knot duplication.

The list of things that could go wrong in the hands of mentally fatigued climbers is long..and is not just confined to knot tying errors.

Climbers (by definition) are conditioned to certain routine behaviours - like putting one foot in-front-of-the-other. Like coiling a rope - it is a conditioned behaviour.
The conscious act of climbing a big/long route means that they would have knowledge ahead of time that an abseil descent is a likely consequence of getting down safely. In other words, they would be aware ahead of time that joining 2 ropes together is a likely task. Such an act is not haphazard - they would already have a procedure in mind. Risk mitigation is something that many climbers takes seriously, so the act of joining 2 ropes together would not be a random/haphazard process. There would be a rehearsed or well practiced procedure - it would not be made up on-the-spot using a random tangle. So their minds are prepared...even in a stress situation, the process would be automatic/routine - like soldiers/paramedics/firefighters who train and practice for stressful events - skills become automatic, and appropriate decision making (in the 'fog of war') is still possible.

...

If you tie #1410 and then duplicate it by tying another #1410 (in a stacked configuration) which now creates a composite structure - you have increased the footprint of the original joining knot (which is obvious...and it should be obvious to you). Logically, the larger the footprint of a knot, the more likely that it might foul somewhere. Even if it is unlikely that any knot will foul - it is the principal of the matter...in that it is logical to keep things small and compact (the opposite view would be; makes things larger and less compact).

The central tenet of your argument is based on the premise that a fatigued climber could make a fatal error in joining 2 ropes together using #1410 by virtue of the fact that they do not have full use of their mental capacity.  #1410 is the simplest way of uniting 2 ropes. This knot was even found on the 'iceman' (some 5000 years ago) - and this humanoid likely had less mental processing power than modern humans. Even if there is a slight dressing misalignment - provided that all 4 rope segments are tightly cinched - there is little chance of anything going south (remember that the joining knot only has 50% loading).

Based on such an argument, we can perhaps see different classes of user groups of #1410.

Examples (not exhaustive):
[ ] User group A: Not mentally fatigued, not hypothermic, not starved of oxygen
[ ] User group B: Mentally fatigued, hypothermic, starved of oxygen

Your argument appears to require certain pre-existing conditions - for example, those conditions experienced by group 'B'.
Does this mean that group 'A' must also duplicate #1410 into a larger composite structure, regardless of conditions?

The other argument often touted in internet forums etc, is that duplication of #1410 by adding another #1410 in a stacked composite structure guards against potential tail slippage.
This argument has little real-world testing that proves #1410 is prone to failure (ie that #1410 is inherently insecure by virtue of tail slippage). This is largely a myth that is passed on by word-of-mouth. Also, there is a the fear-factor...such as when standing near the precipice of a massive cliff and about to put absolute trust in #1410... and then step backwards into the void and abseil down. Some may gain a psychological boost from a duplicated #1410?

I have personally used #1410 and its 'locked' variant (extra binding turn) for 30 years with many different ropes. Evidently I am still alive (because I am writing this post).
Those that have ran into trouble seem to have made a mistake..that is, they did not properly cinch and dress the knot. Now, this is a basic requirement of any mission critical knot - and not just confined to #1410. Eg...a tie-in knot to a harness for lead climbing.
Mistakes might also have been the miss-tying of #1410 into some other knot species...eg #1411 in its 'offset' form.
A miss-tied harness tie-in knot can be just as fatal as a miss-tied end-to-end joining knot.


Mark G

[Grammar edits...]
« Last Edit: October 13, 2017, 12:58:57 PM by agent_smith »

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #24 on: October 13, 2017, 01:02:31 PM »
New update has been uploaded...

Link to knots page: http://www.paci.com.au/knots.php
Now VER 1.2

[ ] Major updates to pages 14+15 (effect of rotation)
[ ] Also revised page 16 (tying duplicate #1410 as a 'backup')
[ ] Page 17 is a work in progress...

Mark G

Dan_Lehman

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Re: Analysis of Offset Rope Joining Knots
« Reply #25 on: October 13, 2017, 09:47:12 PM »
Quote
Quote

    Recent testing has demonstrated that ... the tails do not mysteriously slip.

I don't know what recent testing this is, but I can be pretty
certain that it hardly covered the myriad possible combinations
of ropes that might be joined for abseil --varied in firmness,
bending resistance, slick/frictive surface, sizes, & elasticities!

And this refers to my personal testing both in a test bench/lab environment and in actual field use.
I have just returned from a week long climbing trip to Mt Arapiles (Australia) where I had an opportunity to use #1410 (offset overhand bend) in a number of typical EN892 dynamic climbing ropes (different brands, different diameters, different sheath characteristics, some slick and some not so slick, etc) - in retrievable abseil systems.
NOTE: I use a modified #1410 - with an additional turn of one strand to bind and lock the structure.
NB : then you missed the point of my remark.
Especially, I'm thinking of cold or wet ropes,
where stiffness might keep too loose the knot
and make slippage possible (or a smaller, more
flexible-slick strand).

Quote
Keep in mind that in a typical double rope retrievable abseil configuration, the end-to-end joining knot (ie #1410) will only have 50% loading.
And keep in mind that the cyclical ratcheting slippage
observed by Tom Moyer and a corresponder to his tests
found slippage only under relatively light loads!


Quote
Quote
Now, you persist in putting up a strawman --or, at least
a weak substitute to what has been advanced to you by
me in this thread-- for attacking the "EDK-backed EDK"
(as colloquial/common parlance might put it) :: it is very
much a desirable *tool* in the knots kit on occasion that
all the important just-tie-it-right points cannot be done,

as is quite reasonable to anticipate ...

--dl*

Climbers (by definition) are conditioned to certain routine behaviours
And doing again immediately what one just did
in this conditioned state is a much surer thing
to ask be learned than making one of our more
efficient, well-intentioned *improvements*.

Quote
[failures have come because...] that is, they did not properly cinch and dress the knot.
Again, to my point about removing most vulnerabilities.


Quote
Does this mean that group 'A' must also duplicate #1410 into a larger composite structure, regardless of conditions?
You seem to be hearing me as advancing an *either or*
choice, vs. promoting a should-be-known tool for use.


Quote
If you tie #1410 and then duplicate it by tying another #1410 (in a stacked configuration) which now creates a composite structure - you have increased the footprint of the original joining knot (which is obvious...and it should be obvious to you).
IMO, a *footprint* is much a 2-dimensional thing,
a matter of area, presence --not so much so volume.
And the issues regarding knots being hung up during
abseil-ropes pull down is one of rope-movement
impediment (the rationale for "offset" knots!),
and sometimes crack-filling stoppage (stopper effect).
In neither case does a back-up OWK IMO pose
adding much risk --as noted, if the base knot can
fit through the crack, it can bring the other along
with it (the line won't be running through holes
after all!).

Quote
Even if there is a slight dressing misalignment - provided that all 4 rope segments are tightly cinched - there is little chance of anything going south (remember that the joining knot only has 50% loading).
This is a tough thing to test : "... misalignment" being just
a "NOT <aligned>" wide open, broad designation; and
on that, one is advised IMO to feel some doubt!
The best I can come up with re testing the challenged
knot of our debate would be to actively strive to form
badly aligned/dressed knots, thinking that such structures
lie farther from good than anything better done.
AND, I think that the debated knot will survive;
this makes it commendable to be known.


--dl*
====

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #26 on: October 14, 2017, 12:14:57 AM »
New update has been uploaded...

Link to knots page: http://www.paci.com.au/knots.php
Now VER 1.2a

[ ] Corrected error on page 15 (references to image 'C' was incorrect)
[ ] Minor revision to page 16 (primary knot is under maximum tension but duplicate 'backup' is not under tension and simply tails along)
[ ] Page 17 is a work in progress...

Dan, my response to duplication of #1410 (to create a 'backup') is that the primary #1410 knot is under maximal load. However, the duplicate #1410 is not under maximum tension. The primary #1410 always has a tendency to self-align and translate over an edge. My concern is that the tailing duplicate #1410 backup is increasing the overall footprint and could conceivably cause issues downstream (it does not self-align in the same manner as the primary knot).

...

Since you appear to be a strong advocate for duplicating #1410, I would like to include commentary in the analysis paper supporting your view.
I can pull quotes directly from your posts in this thread or you could write some supporting argument. Please advise...

...

Also, I have significantly improved pages 14+15 (re orientation)...I am reaching the limits of what a photo can convey - camera angles are tricky to get right. Any further comments?

Mark G

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #27 on: October 14, 2017, 01:05:37 PM »
New update has been uploaded...

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

[ ] Page 17 (long tails) has been updated.

Mark G

Dan_Lehman

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Re: Analysis of Offset Rope Joining Knots
« Reply #28 on: October 14, 2017, 04:34:38 PM »
New update has been uploaded...
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!
(There might be something to the conjecture (mine,
on this writing) that by having two "pry-up" "arcs" in the
SParts, the mid-range orientation raises greatest vulnerability
to capsizing; the orientations with a "loop" (+ arc in opp.SPart,
of course) have this bit of resistance !?
)

(FYI, I go further in dressing & setting the owc : I pull
the choking line's tail *up into* the expected curve of the
SParts, anticipating their draw on this important part by
setting it most in opposition/distance from where the draw
will rotate it --so, e.g., one would see NO slit of gap/space
at knot nub center as one can see in your mid-range image.
)
Quote
Dan, my response to duplication of #1410 (to create a 'backup')
is that the primary #1410 knot is under maximal load. However, the
duplicate #1410 is not under maximum tension. The primary #1410
always has a tendency to self-align and translate over an edge. My
concern is that the tailing duplicate #1410 backup is increasing the
overall footprint and could conceivably cause issues downstream
(it does not self-align in the same manner as the primary knot).
"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.

In any case, one can imagine somehow that dangling tails
get slipped into mischief?  --never heard of such, though.
I don't think that the knotted bulk (vs plain length of ropes)
invites anything bad; it won't need to "self-align", as it won't
be so oriented to snag (as the aligned base knot will lead to
the back-up from its top, away from edge/surface).


Quote
Since you appear to be a strong advocate for duplicating #1410,
Maybe esp. in cases of stiff ropes and mitten'd hands,
though perhaps in such an alpine situation there'd be
less advantage to offset aspects!?
(Tom Moyer also suggested by his limited testing that
the grapevine can be poorly tied but yet work;
tensioning the knot IS presumed, at least.  Forming an
offset water knot and then with tails OR with SParts
forming a 2nd, and setting to reasonable tightness & closeness
I'm surmising is a measure surer than tying many things;
the grapevine's ability to be tied in halves (each rope
strangle-ing the other) remotely/clearly apart
(un-interfering; not requiring intricate interlacing)
is a good attribute similarly.
)

Quote
I am reaching the limits of what a photo can convey - camera angles are tricky to get right. Any further comments?

I was looking at some of those top-/tails-down views
and thinking "my, this can show how a thicker rope in the
choking position (bad) has a lot of material half way to
coming out around the thinner --which if in the choking
position might not be visible from under its thicker twin!?

 - - - - -

Hmmm, some of us should perhaps go out into the wilds
and do a batch of drop-tests --can we muster up some
weight about 50-100# (noting as you do that the knot
is usually taking half a climber+pack's weight) !?

--do some shock-loading short drops;
--do some mild, like-during-abseil "bounces" to see if
  anything worrisome appears to be happening (under
  this relatively light, but cyclical loading)!?
--in a mixture of ropes (not only likely offset-knot users),
  and tying goodness.

Maybe a quick-&-dirty batch of tests so done would at least
point to some orientation as indeed looking worse, as taking
a step farther from desired snugness & so on!?


Thanks,
--dl*
====
« Last Edit: October 15, 2017, 08:00:48 PM by Dan_Lehman »

agent_smith

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Re: Analysis of Offset Rope Joining Knots
« Reply #29 on: October 15, 2017, 01:16:38 AM »
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).


Quote
(FYI, I go further in dressing & setting the owc : I pull
the choking line's tail *up into* the expected curve of the
SParts, anticipating their draw on this important part by
setting it most in opposition/distance from where the draw
will rotate it --so, e.g., one would see NO slit of gap/space
at knot nub center as one can see in your mid-range image.

Dan, virtually all of the photos in this 'analysis' paper are loosely tied, and with deliberate short tails. Part of the reason for this is trying to get all of the knot to fit within the narrow field-of-view of the macro camera lens. The other reason is to show details. So the slit/gap you refer to is a deliberate act on my behalf (sort of my attempt at creating an 'X-ray view').

I will add remarks to this effect to further emphasize these salient points.
I re-assert that I am reaching the limits of what can be done with a camera. I am not a professional photographer - I am an amateur - and working with a very limited budget. Be that as it may, I want to get this right and I am very motivated in this regard.

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?


Quote
.....[OP comment...per duplication of #1410]... Maybe esp. in cases of stiff ropes and mitten'd hands,
though perhaps in such an alpine situation there'd be
less advantage to offset aspects!?

I am happy to add any personal commentary from you regarding your 'official' position re adding a duplicate #1410 to serve as a 'backup'. I just need some relevant words to that effect and I can insert it into the paper.
I would like to hear some well considered argument to support the duplication of #1410 - and I am sure any potential readers would also be interested.


Quote
Hmmm, some of us should perhaps go out into the wilds
and do a batch of drop-tests --can we muster up some
weight about 50-100# (noting as you do that the knot
is usually taking half a climber+pack's weight) !?

--do some shock-loading short drops;
--do some mild, like-during-abseil "bounces" to see if
  anything worrisome appears to be happening (under
  this relatively light, but cyclical loading)!?
--in a mixture of ropes (not only likely offset-knot users),
  and tying goodness.

Maybe a quick-&-dirty batch of tests so done would at least
point to some orientation as indeed looking worse!?

Indeed.

I am a huge fan of well thought out testing. As long as it isn't just the usual mind numbing MBL yield/break testing. The spacial orientation of the knot per inducing a choking effect should be near the top of the test criteria. And different diameter ropes - to investigate the effect of altering the relative positions of the different diameters.
In addition:
[ ] instability threshold/range
[ ] jamming threshold
[ ] icy ropes
[ ] very stiff ropes versus supple ropes

Maybe that fine fellow who responded re the 'Prusik Hitch tests' (ITRS symposium)?

Mark G
« Last Edit: October 15, 2017, 01:19:55 AM by agent_smith »