Author Topic: Offset Ring Bend (Euro death knot) - testing and a proposal  (Read 15467 times)

agent_smith

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Offset Ring Bend (Euro death knot) - testing and a proposal
« on: January 02, 2009, 02:50:49 AM »
Dan, I pulled this info from the following site: http://www.xmission.com/~tmoyer/testing/EDK.html

Quote
My opinions:

I have personally used the flat-overhand on some rappels where I thought pulling the ropes across an edge might cause problems. Otherwise, I use a figure-eight follow-through knot with grapevine safeties. Most of the people I know use the flat-overhand, including Chris Harmston, who co-wrote the high-strength cord paper with me. I don't believe the flat-overhand will ever fail under body weight if it is tied well.

The flat-overhand is clearly better than the flat-figure-eight. The flat-eight is represented three-to-one in the accidents despite (to the best of my knowledge) many more climbers using the overhand. The flat-eight also starts flipping at a lower load (750 lbs vs 1400 lbs for well-tied, 110 lbs vs 200 lbs for badly tied) than the overhand, and it eats two to three times as much tail in each flip.

I think both knots are a bad choice for tying slings. Why would you need the pulling advantage of an asymmetrical knot in a tied sling? And why would you be willing to put up with the uncertainty in the strength? Tie a real knot. I use a water-knot (see my water-knot testing and cautions) for slings I plan to untie later, and a single or double-fisherman's for slings I don't plan to untie - like slings that I leave at an anchor.

I also think both knots are a bad choice for more than body-weight, for use as a moving knot during a lowering, or to hold dynamic loads. I think to use them for a rescue lowering or belay is to invite an accident. There are a few rescue teams who use them for lowering, and they have had no accidents yet that I know of. One team that I spoke to about my testing has now changed their protocols and discontinued their use of the knot.

Adding a safety by tying a second overhand on top of the first is probably a good idea. This likely helps prevent flipping (I haven't tested it yet). It does sacrifice some of the cleanness of the knot, but at least it's all still asymmetrical. Dan Lehman has also proposed some variations of the overhand to me that look very promising. They keep the asymmetry and are all probably much harder to flip than the overhand. If I get any spare time I will test these and post the results.

Its the last bit of reference to Dan Lehman that got my attention!

Can you elaborate on the 'proposed variations' to the offset ring bend (ORB).

Am very curious...


agent smith


PS By the way, I am about to purchase some kernmantel accessory cord for break testing. I am thinking 4.0mm diameter cord so that I dont have to generate huge forces and risk personal injury. I could go as high as 5.0mm though...your thoughts?

Dan_Lehman

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #1 on: January 02, 2009, 06:10:00 AM »
Dan,  ...
PS By the way, I am about to purchase some kernmantel accessory cord for break testing.
I am thinking 4.0mm diameter cord so that I dont have to generate huge forces and risk personal injury.
 could go as high as 5.0mm though...your thoughts?

After I saw that Yosemite finish in my EBDB, I was thinking "... personal injury".    ;D

I'm not sure how relevant the small cord will be--issues of percentage of surface
contact, sheath/core balance, and so on.  Naturally, this (conjectured) thinking
would move towards the nearer (here, larger) size to what is of issue (8-11mm).

But what of the issues you've raise much concerns strength (hence, breakage)?
Esp. re abseil-rope joints, strength is much a non-issue (unless you want to abseil
on that 4mm cord)  (use parachute cord:  with parachute attached!)

--dl*
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Dan_Lehman

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #2 on: January 04, 2009, 07:15:37 AM »
Quote
Adding a safety by tying a second overhand on top of the first is probably a good idea. This likely helps prevent flipping [aka "flyping"]
...Dan Lehman has also proposed some variations of the overhand to me that look very promising. They keep the asymmetry
and are all probably much harder to {flype} than the {Offset} overhand.

It's the last bit of reference to Dan Lehman that got my attention!
Can you elaborate on the 'proposed variations' to the offset ring bend (ORB).
Am very curious...

While I'm not sure of all that I sent to Tom, at least one obvious one is simple
to explain and to effect, and it's likely the surest solution.  While I've *designed*
(= *directed discovery* ?!) some symmetric offset bends, it later occurred
to me that frequently--perhaps most often--the two lines to be joined are not
*symmetric*, i.e., of unequal natures (e.g., often it is a thin, low-elongation haul
line tied to a full-size dynamic climbing line).  So, the best solution is probably
an asymmetric knot, with guidance to tie it with the thinner line HERE,
and the thicker THERE.  (And then one can worry whether that distinction
implies a risk where it's ignored.)

Firstly, consider the image here:  www.ukclimbing.com/images/dbpage.html?id=13909

For this knot to flype, the darker blue w/red rope must be pried out around
the other (or the other forced through the first).  To my thinking, thus, the
thicker rope should be in the "other" position, and be by size alone an
impediment to this particular failure mode of flyping.  To Tom's first-indicated
security measure of tying a 2nd/back-up Overhand, I say "... IN THE THINNER
ROPE AROUND THE THICKER TAIL"--this looks pretty good, as it arrests
the early draw of thinner end out of the knot as that line's *choke* of the
SParts is strained.

A better resitance however comes from a simple modification:  make a full,
round turn with the thinner line before following the thicker line out through
the loops formed for the Overhand (so, the darker line would wrap again
around the SParts--the image would show two strands--and then be tucked out).
This full circle of material greatly resists being pried open.  (It quite possibly
weakens the knot by forcing a sharper bend of the SParts; but the concern
in Abseil-Rope-Joining knots is security, not strength; they are typically
bearing just HALF of the weight of an abseiler.)
The extra/full turn in the should-be-the-thinner line makes a Fig.9 in it
(should you stop to notice that).  No, an offset Fig.9 is NOT thus a better
idea (and certainly no thinking of working in some Yosemite finish!! :-) ;
were the full wrap made in BOTH lines, the helix angle of the closing
near-circle(s) spiral would be more open and less effective; the extra
bulk of material if anything would make the knot less secure.

There are some other orientations an extra turn can take, in one case
making a Dbl.Oh / Strangle form in the thinner line.

One can also make just an extra HALF wrap, resulting in a Fig.8 in the
thinner line; the characteristic visual aspect of this, call it "Offset Eight-Oh Bend"
is that the ends point in opposite directions.  I think that this knot is more
resistant to flyping than the now infamous Offset Fig.8, because of the
lesser material (given one rope making only an Overhand) and the
exit of the ends in opposite directions (as it is hard to force material
over/around these protuding ends).  Note that the opp.-direction-ends
make for a distinctive appearance.

------------------

It is worth reiterating here that many of these offset bends can be tied
and then given a setting in any position in the range of 180 degrees in
regard to the plane of a surface over which the knot is placed.


E.g., in the URLink'd image cited above, the light blue rope enters the knot
and makes backward loop, and the dark blue rope makes a forward arc;
without untying the knot, and even after some setting, perhaps even usage
for abseil, one could grasp the knot and rotate it from this one extreme
to where the two lines equally enter the knot and move to viewer's right
and then curve around ... , or the opposite extreme where the light blue
rope makes a forward arc and the dark one makes the backward loop
--the rotation here would be with the ends going away from the viewer.

There needs to be some exploration as to the effect of these orientations
on vulnerability to flyping.

--dl*
====
« Last Edit: January 04, 2009, 06:17:59 PM by Dan_Lehman »

alpineer

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #3 on: January 20, 2009, 07:36:01 AM »
 A rolled ABOK #1452 seems to have the same advantage as the Offset Ring Bend regarding it's ability to slide over terrain easier (although slightly more bulky), and may have the advantage of greater security. If the knot rolls or flips it forms ABOK #1452, a very secure knot. However, it is not as simple to tie as ORB.
« Last Edit: January 20, 2009, 07:37:02 AM by alpineer »

Dan_Lehman

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #4 on: January 22, 2009, 01:04:02 AM »
A rolled ABOK #1452 seems to have the same advantage as the Offset Ring Bend
regarding it's ability to slide over terrain easier (although slightly more bulky),
and may have the advantage of greater security. If the knot rolls or flips it
forms ABOK #1452
, a very secure knot. However, it is not as simple to tie as ORB.

You're speaking Greek to many, but I happen to know what you mean (I think),
and you're half right (variously per circumstance):  flyping an offset variation of
Ashley's Bend #1452 can  come in a half-done manner--i.e., ONE rope
before the other, and ... pffffft , the knot spills !!  And as one paradigm use
is for mixed-nature ropes (7mm low-elongation haul line + 10.2mm dynamic
climbing line), such a vulnerability kills this knot's candicacy (before it kills an
abseiler).  I learned this by accident, fortunately of the test-knot-in-hand sort.

--dl*
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alpineer

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #5 on: January 22, 2009, 08:17:23 AM »
Hi Dan,

I'm not entirely certain we're on the same page here, but if we are, your point is well taken. So, in the "offset variation" example using two ropes of mixed nature, are you loading the two lines which exit the knot in the same direction and parallel to each other?
 

Dan_Lehman

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #6 on: January 22, 2009, 09:57:37 PM »
So, in the "offset variation" example using two ropes of mixed nature, are you loading the two lines [that] exit the knot in the same direction and parallel to each other?

Yes (otherwise it wouldn't be offset).  This knot is in Ashley as a lanyard knot (78x, IIRC), btw.
There are various other ways to produce an offset bend that is symmetric,
but, again, considering that a frequent situation is with non-*symmetric* cordage,
symmetry is arguably a bad thing.

The Offset Ring Bend should be oriented such that the thinner or more flexible rope
of the pair is what makes the sure *choke* of the entering lines, as it will be harder
for their loading to prise this rope (possibly less elastic, if haul line) out around the
thicker one.  A full round turn by this rope, here (rendering a "Fig.9" form), will
assure security; or tying off the thinner end in an Overhand around the thicker
end and snug to the ORB body should also arrest the slippage of the end from
the knot that enables flyping.

But, WOW, I am so glad to have found that 1452 weakness the *easy* way!
Otherwise, that thinking you espoused--if it capsizes, it does so into a secure knot--
is quite appealing!  What a great "back-up" that would be.  It certainly wouldn't
have occurred to me that the capsizing could occur in such a one-sided way
(I think I was at a table, stressing with leg/foot, and banged my hand up into
the table when the knot spilled!)

--dl*
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alpineer

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #7 on: January 23, 2009, 07:20:38 AM »
Hey Dan,

Thank You so much for all that beta. Glad you survived the experiment. A brilliant example of serendipity. And you may have saved MY life in the process! Who would have thought that a knot with such potentially beautiful properties for this particular application could betray the applier in such a cruel manner. It drives the point home that any knot which might be considered for a certain use where personal injury or life is "on the line" must be analyzed with great rigor (even ongoing), and sometimes luck, with an end to minimizing or managing any risk related to it's use, even discontinuing it's use.

Thanx again Dan

Dan_Lehman

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #8 on: January 23, 2009, 08:17:12 PM »
Thank You so much for all that beta. Glad you survived the experiment. A brilliant example of serendipity.
And you may have saved MY life in the process! Who would have thought that a knot with such potentially
beautiful properties for this particular application could betray the applier in such a cruel manner.

Exactly!   - -  w h e w ! ! - -

Quote
It drives the point home that any knot which might be considered for a certain use where personal injury
or life is "on the line" must be analyzed with great rigor (even ongoing), and sometimes luck, with an end to
minimizing or managing any risk related to it's use, even discontinuing it's use.

Here I'll take issue w/details, although sympathetic to the general thrust.

I think I was lame (we were ...) to have not been suspicious of the symmetric knot tied
in *asymmetric* materials--in my case, I think that the slightly thinner cord was much
more flexible, and maybe also slick whereas the other was frictive.  Nicely, the lesson
to be had was offered w/o injury.

I'm STILL lame in not enumerating a aspects-to-analyze  checklist, to collect and hold
the collective wisdom.  Such a checklist can be made general with qualifiers such as
"If this is an EyeKnot, how does it behave on abnormal loadings:
 a. through-loading
 b. bend-loading
 c. ring-loading
Is the intended application likely to generate any abnormal loading?"  (One might argue
I think correctly that rockclimber tie-in with a relatively small eye is not; if that eye is later
used as a belay-loop anchor, ring-loading is involved.)

Your point of "even  ongoing" scrutiny has direct merit/application in the recent acceptance
of HMPE (Spectra, Dyneema) cordage by rockclimbers:  that material had some extra issues
re core slippage (security) and stiffness and shock generation--the mighty "cordelette" being
hyped for great strength in the material w/o notice (until recently, by many) of its considerable
reduction of force absorption (well, I guess this is more an issue not w/belay anchors, where
still there's dynamic rope in the system, but in short slings which might be dropped upon
--daisy chains).
And it shows, to some degree, with the different results Lyon Equipment found in testing
Clove Hitches in low-elongation ("static") SAR/caving rope vs. one dynamic rope they
tested--only the latter held to rupture, the others slipped at various loads.  A knot used
successfully in one field, is brought into a seeming similar one (re material--both using
like-sized kernmantle ropes, i.e.), but with potentially different results.  (I should note
that the issue of Clove Hitches holding is under debate for climbing materials,
interestingly--YMMV even within dynamic cordage?)

But, I'm comfortable with some cases of untried knots being considered safe, given the
proper inspection:  e.g., I have not the slightest qualms about the bowline extensions
(in part, "extension" indicates a lot of why ...) in consideration being used; we should
be able to see that they just don't introduce problems.

And we need to ask How does the <whatever> testing relate to the intended use?
Agent_Smith is doing break testing; but the concern re Bowline use is with security
--what sort of test can we do for that?  (Maybe make some high-energy dance dependent
upon using rope & an eyeknot!  What great promotion for knot tying  (and bring the kinky
aspect of bondage into hip dancing seems like an appealing marketing gimmick)!

 :D

DerekSmith

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #9 on: February 11, 2009, 02:10:06 PM »
A most important point Dan.

Perhaps we should consider a thread on 'Aspects to consider when putting a knot through its paces, with thoughts on how to evaluate them'.

It might also be a good thread to make into a 'sticky'.

Derek

JNZ

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #10 on: March 01, 2009, 11:58:33 PM »

'I think both knots are a bad choice for tying slings. Why would you need the pulling advantage of an asymmetrical knot in a tied sling? And why would you be willing to put up with the uncertainty in the strength? Tie a real knot. I use a water-knot (see my water-knot testing and cautions) for slings I plan to untie later, and a single or double-fisherman's for slings I don't plan to untie - like slings that I leave at an anchor.

I also think both knots are a bad choice for more than body-weight, for use as a moving knot during a lowering, or to hold dynamic loads. I think to use them for a rescue lowering or belay is to invite an accident. There are a few rescue teams who use them for lowering, and they have had no accidents yet that I know of. One team that I spoke to about my testing has now changed their protocols and discontinued their use of the knot."



And why would anyone want to be using slings for dynamic loads?! Water knot is the accepted knot in tape slings- but its a good idea to stich the ends if used permamently (or tape them) and leave plenty of tail on temp knots as the knot can "walk"

Dan_Lehman

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #11 on: March 04, 2009, 08:43:32 AM »
Quote
Can you elaborate on the 'proposed variations' to the offset ring bend (ORB).

Ah, yes, I can!

Discussions & debates about the thus infamous "EDK" arise frequently
on various climbing/caving/canyoneering--and, who knows, maybe
even knitting ("Eleanor broke several good yarns that way!")--forums.
For years I've urged some simple remedies to the perceived weakness
of the knot; but words have mostly failed me (actually, others' loss
more than mine).

So, vioci, here are some images, to accompany the words, at last.
In the first, I present the Offset Ring Bend (aka "EDK") with an Overhand
stopper in the "nipping" line's end tied around the other end.  The ropes
are 8mm (orange) and 11mm (gold); the thinner rope is put in the
position of making the binding constraint on the entry of the ropes into
the knot, and its end is what is first pulled out by loading--hence, the
stopper in it improves stability and resistance to "rolling".
And with the thinner  rope in this position it will be more difficult for
loading to force it out and around the thicker rope
--added resistance!

Please note that the same "knot" is shown in two orientations--the
extremes of how the knot body can be rotated in the surface plane
(should the knot lie on a surface):  in the lefthand knot, the orange
rope enters the knot and makes a backwards loop to the gold's forward
arc; in the righthand side, the trajectories are switched.  (And in
between these extremes lies the case where the two ropes seem
to abut each other and rise up together (with the ends, thus, not
at right angle to the axis of tension but parallel to it).  I've not
done enough playing around to figure how much this variance
matters in terms of the knot's vulnerability to flype.  And this
orientation can be adjusted under at least light load, even, by
just rotating the knot body.
Btw, the pictured knots were subjected to loading via me and
a crummy 5:1 pulley (though I didn't give full force, but some),
so are showing the state of a pretty serious load (vis-a-vis one
half of an abseiler's weight).


The 2nd photo shows two simple ways to improve on the stability
of the ORB without using a stopper:  the upper knot is what I call
the "Offset 9-Oh", as a Fig.9 & Overhand are used, the former
doing the binding work (nb:  I put this knot is in that "in-between"
orientation--ends abutting, neither arcing/looping); the lower knot
is the "Offset 8-Oh", which by this simple nomenclature denotes
the use of a Fig.8 & Overhand (note that here the ends exit in
opposite directions; this helps resist flyping).  These are loaded knots.


www.postimage.org/image.php?v=PqAodEJ


www.postimage.org/image.php?v=PqAoxBS

It should be noted that Franz Bachmann proposed using an Offset Grapevine,
and this was tested in equal & diff-sized ropes by Edelrid, and did well;
Heinz Prohaska & (separately) Jost Gudelius proposed using alternating
(re ropes) Overhands--what could be called an "Offset (single) Fisherman's
Knot + Overhand back-up (or *guard*!)"
--; Edelrid tested this, too, and
it sufficed for rapping purposes.  (There are actually a variety of ways
one might position the Overhands.)  Re the Offset Grapevine, that is
a bit more than is needed:  the extra turn in the rope making the binding
is what gets one resistance against flyping (though I think that the Fig.9
structure is better focused for this); that of the other rope is just extra
bulk w/o real benefit--it is just being pulled into the other component.
[ cf.  http://www.gudelius.de/spst.htm  , but PLEASE ignore
Jost's crazy "TFK" name!  :-]

--dl*
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knudeNoggin

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #12 on: November 01, 2009, 05:24:40 AM »
Funny not, it looks as though PostImage is tired of that task?

Let us put here independently the pretty pictures of some
offset knots for abseil-ropes joining.  The point to all of these
knots is manifold:
1) to join ropes of sometimes different natures (diameter, condition)
in an "offset" way that enables easy pulling of the knot over rough
surfaces (especially as is encountered in rockclimbing abseils);
2) to be easily tied and easily untied and easily inspected;
3) to prevent "flyping" (being pulled open & inverted) and so
do away with advice given often for the "European Death Knot"
to "leave tails long".

The first photos show also how the knot body can vary in its
position vis-a-vis the axis of tension for the same knot (!).
(The knots should be secure in all possible orientations.)

*kN*
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[Inkanyezi] gone

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Re: Offset Ring Bend (Euro death knot) - testing and a proposal
« Reply #13 on: November 06, 2009, 08:46:09 AM »
At reading through the Edelrid report (in German), I noticed that I speed-read one sentence wrong, and afterwards I came to wonder whether the word-play is intentional?  "er erfordert aber einen ausreichenden Seilschwanz; die Lehrmeinung "das 10-fache des Seildurchmessers" reicht nicht". What I read was not Lehrmeinung (teaching sentence), but Leermeinung (emty sentence). Both are pronounced exactly the same in German.

I'm also puzzled that people might even think of using an offset fig8, as it readily demonstrates its flippiness.

The Edelrid test was undertaken with rope of about the same diameter, but reported failure of the ORB suggest that it is often used for different diameter/type rope, which might be more prone to failure. Hence, it would be interesting to see the test performed on offset grapevine knot in different diameter rope. My opinion is that when life is at stake, the relative difficulty of the knot should not be an impediment; it just has to be learned.
« Last Edit: February 17, 2010, 09:22:23 AM by Inkanyezi »
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