Using the offset overhand bend for double rope rappelling has been controversial in some circles. My question is not whether the knot is safe or not, but rather what are the ‘best’ alternatives to it for this purpose if one doesn’t want to use it? For instance, would the Butterfly bend do?
I think an excellent alternative is the Zeppelin Bend. It’s slimmer than the European Death Knot, which is better for slipping through crevices or vegetation. Also, one side has a natural slope built in which is good for tensioned travel around a corner. If you get the non-optimal side by chance, it may be difficult to twist the bend over from a distance, however.
The right angle tails also prevent any hooking action.
Many of the same points can be made for the Butterfly Bend as well, but I have a slight preference for the properties of the Zeppelin Bend.
There have been fatal accidents involving the offset figure eight bend, which could be argued to be a consequence of the use of the European Death Knot, as many non-experts may reasonably, but mistakenly, think that the offset figure eight bend should be a step-up from the European Death Knot.
Using the offset overhand band for double rope rappelling has been controversial in some circles.Only controversial in the 'circles' of the ill-informed and/or the misinformed. And this circle of misinformation appears to be most prevalent in the climbing/canyoning community.
My question is not whether the knot is safe or not, but rather what are the 'best' alternatives to it for this purpose if one doesn't want to use it?The precise circumstances of the situation are crucial. Your question is framed in the context of a knot used in life critical applications. 'Best' is a relative term - and the circumstances of the situation determine what is 'best' (I would re-formulate 'best' as [i]optimal for the situation[/i]). One might also give attention to differing rope diameters...which can influence the security of an 'end-to-end' rope joining knot.
For instance, would the Butterfly bend do?Again - circumstances are important. For example, if the 'end-to-end' rope join had to translate around a [u]90 degree edge from low anchors[/u], then only an [b][i]offset [/i][/b]knot geometry will be optimal. The derived 'Butterfly bend' (corresponding to #1053) is not [i]offset[/i]. Offset knots translate easily around a 90 degree edge (and indeed, any type of 'edge'). If there is no 'edge' - and this would imply a very strategically positioned anchor - creating a clear and unobstructed pathway for the rope(s) - then your choices of what is 'optimal' are broader.
I would recommend that you carefully read my technical paper on offset rope joining knots.
Link: http://www.paci.com.au/knots.php (at #5 in the table).
Cheers for that! For the record, I also found another convincing analysis of offset bends here. There is a by-email link to a longer report on the testing and observations at the end of the article.
Hmmm, convincing in what way? --in putting higher
than likely loads per test device on candidate knots?
Firstly, be clear on the design goals for a good ARJ
(abseil ropes joint) :
-
joining different-sized/-nature ropes within a reasonable
range of 6-11mm; -
secure! --through sometimes varied loading,
some rubbing of a surface,
and surfaces contact when pulling down the joined ropes; -
enabling easy flow over rough surfaces, including
over an edge; -
able to be tied quickly and surely (or to offer
safety over imperfect tying!) -
non-jamming.
Well, that seems a good list.
Note that “strength” doesn’t occur above (!).
Well, sure, we don’t want the knot to break;
but in the likely materials and loads, there should
be a wide margin between actual forces and what
would break these ropes.
As Agent_Smith says, there is a pretty clear need
that the knot be “offset” (sadly called “flat” in common
parlance, but we hope to rectify that!), which enables
the joint to “flow” over rough surfaces pretty well.
(It is NOT a matter of merely having tails exiting
the knot together --which I presume is what moves
people to bring up the Butterfly (which they do in
ignorance of Ashley’s #1408 & 1452).)
The cited OverTheEdgeRescue quickly seen testing
report shows some cursory testing done on various
offset knots; but it doesn’t show the exact knots as
tied for testing. There are subtleties in dressing and
setting which could affect results, methinks ; and which
should thus be seen as notes of warning (should they
be done “wrongly”)!
Consider : if a knot “rolls” in the test device,
one common result is that the force on the knot
DROPS until the constant-rate-of-pull device
catches up … ; whereas if it’s your butt dropping
with the rolls there will likely be a bit of shock loading
for the just-rolled knot to sustain.
As I think Agent_Smith’s PACI paper articulates,
there are various ways some of if not most of the
offset knots can be set vis-a-vis the departure of
their SParts. E.g., for the well known “EDK” (offset
water knot), one can set it in 3 general states :
rope-1 makes arc to rope-2’s loop;
vice versa;
and in-between, ropes abutting and jointly turning
perpendicular to the axis of loading, and then into
their turn towards tucking out.
I’m MOST SURPRISED at the reports of the backed-up
(“stacked”) joints having, nevertheless, multiple (!) ROLLS!?!??
Huh, that is exactly what the back-up (loaded thus qua stopper)
knot is supposed to prevent! Okay, maybe at such high, push
comes-to-shove forces one might squeeze in ONE “roll” of a
sort; but 2-5?! I gotta SEE this.
Is there more info you’ve seen in the e-mailed report, to share?!
As Roo notes, the offset fig.8 has been seen sometimes
to perform worse than the OWK. There was at least one
tragic loss of life in a Zion; but a person familiar with those
ropes said “they were like cables” --meaning stiff. Still, one
needs to tie correctly, to set well.
.:. IMO, every canyoneer/climber should know about
the EDK-backed-EDK (“stacked overhand”),
or “Stoppered Offset Water Knot” --which naming challenge
is that one could see it as an EDK guarded by the same,
or else backed-up by same,
though in fact it’s not really fully “the same” as the loading
differs! (for those of us who note such fine points)
FOR USES UNDER DURESS, where tying CLOSEnuff to the
desired knotting will yet work! --i.e., I think that one can
botch various ideals of tying (thick & thin positions, crossing
strands, semi-tightened, leaving too short tails (for knotting:
so, knot 2nd knot IN FRONT of first-tied one), and still have
a joint that works. And knotting the simple OH once, and
once again --simple both times: 2 x simple = still simple!!
For calmer circumstances, there is this variety … .
–dl*
The actual report includes almost 200 pages of individual test reports with Force vs. Time curves and photographs of the knots after failure. Single EDK without backup seems to roll off the ends (20 cm long) around some 5 kN (or 500 kgf). If this is sufficient for the purpose only the one hanging from it should decide, I would think.
For the stacked EDK, only the first one rolled and the second prevented slipping - the rope broke at about twice the load required to slip the single EDK.
The report will be emailed to you if you enter your email at the end of the web summary. If you can’t get it, I’ll provide the link.
Just as I was going to muse some more, I discovered this thread (which started well but seemed to have gone sideways at some point…).
In conclusion: is the stacked EDK the pinnacle of offset bends with SParts exiting the bend together?
For awareness, casual lurkers are going to very perplexed when they go to Google “SParts”. Anyway, as always, there is a personally-weighted decision to be made. If you have a circumstance with lots of 90 degree corner pulls and no crevices, vegetation or other obstructions, I could see maybe choosing the rather large double stacked European Death Knot if you were afraid of the European Death Knot.
It does seem like a somewhat remote scenario.
In conclusion: is the stacked EDK the [i][b]pinnacle [/b][/i]of offset bends with SParts exiting the bend together?Your question is both complicated and also 'leading'.
You haven’t provided a context - eg is the ‘end-to-end’ rope join going to be used in a life critical application?
Or is it going to employed in some other non life critical application?
Stacking #1410 (offset overhand bend… or, offset water knot) doubles the footprint.
In my view, one of the objectives of forming a knot join is to try to keep the ‘footprint’ as small as reasonably practicable.
(and this is particularly important in climbing/canyoning activities).
The nominal load that will be applied to the joining knot would also be a key factor.
In climbing/canyoning activities, the nominal load is one (1) person… lets say 100kg.
In a doubled rope configuration that is set to be retrievable, only 50% of that load will be transmitted to the joining knot (ie approx 50kg).
Within these loading parameters, #1410 is stable and secure (the load threshold beyond which instability becomes likely is somewhere around 3kN in EN892 ropes).
In my technical paper, I have given examples of other choices of joining knots.
For example, I routinely use my ‘offset bound overhand bend’ (for more than a decade). Since I am typing this post, evidently I am still alive - and so that might constitute empirical evidence that the knot works as intended.
And another possibility is the ‘8Oh’ (a combination of an ‘8’ inter-wined with a simple overhand knot. With the right geometrical arrangement, this is very stable and secure (but more fiddly to achieve - and so it likely wont gain widespread popularity amongst climbers).
Just for fun, as this may be too complicated for practical use (but it’s actually relatively compact) and may not be that good at all, here is an idea: how about reversing the loading on the strands of the Cask/EHL loop (this time with the loop cut)? In other words, what were the SParts of the Cask loop now become tails, and the strands of the loop now are the Standing parts.
It forms an offset bend with two standing parts exiting from the same spot and, if anything, should be easier to untie than any version of EDK. As for security, strength, and rolling, I have no idea yet, but maybe somebody more experienced could take a look at this prototype or maybe tweak it if it holds any promise?
p.s. I tried the same maneuver with the Butterfly, but it doesn’t seem to be a good idea.
Yeah, I think you may be right about the level of complication. I don’t think many would like to be tasked with checking it for correctness. I did give it quick challenge with some bungee and it did OK at first, but I was able to make it flip. I don’t make any claims about how that might translate into normal rope.
I do sometimes wonder how much of the motivation for the use of the European Death Knot really came from plain ease of tying that also happens to be a major driver for so many other knots. It’s hard to think of an end joining knot that’s quicker and simpler.
I have no reason not to believe you (although with the advances in AI bots… 
Climbers use EDK and they are not falling like flies, so no contest here.
However, since you’ve quoted potential tension values to compare with some 3kN (maybe a bit more) threshold of the EDK instability, there is one interesting issue I’d like to point out to.
Let say that you still weigh some 100 kg but you don’t double the rope and descend on a single one, joined to another with an EDK (such as in this scenario). That’s around 1 kN. Every time you sit on the harness, you momentarily double the rope tension until the rope elasticity reacts to it (it’s a zero fall factor dynamic load on top of your weight - see this paper, p.3 or my rough approximation of dynamic loads calculator based on this paper). That’s some 2 kN already without any extra rope jerks, ‘micro falls’, or safety margins. That’s not that far from 3 kN…
Here is an interesting video with actual tension measurements that illustrates the above - she weighs some 60 kg.
Check the design goals : this doesn’t look to be all so good
with mixed diameters. At least I found myself doing much
fiddling with some few attractive results (for the knot, though
per Roo not for the tying),
then only later realized that the often needed joint for say
10mm & 7mm ropes would breach my ideals of symmetry
in what I’d fiddled.
(I recall one naming of “Mickey Mouse” per the “like ears”
aspect of something similar to what you present; another
was a “bee hive”.)
But, really, so far as the practical needs of folks who need
such a knot are concerned, I think we’ve adequate solutions
unlikely to be improved. Maybe if someone needs greater
strength AND an offset knot, it will be a chance to break out
the drawing board … ! 
Oh, and partly I think a problem arises from the LACK
of smarts doing SETTING :: i.p., that one should usually
be pulling the SParts TOGETHER IN OPPOSITION TO KNOT
BODY (so, that qua stopper),
before the SParts go there opposite directions upon the
set knot. --also, when to set hard the tails …
–dl*
A level-headed article (with testing data, observations as to the mode of failure, and an un-opinionated analysis and advice) by Tom Moyer. I imagine most people interested in the topic are familiar with it (Dan Lehman is even mentioned in it), but I wasn’t…
Another summary on the same topic.
Among other tests, in the midsts of this video there are several sequences of the EDK rolling under tension. It’s fascinating to watch.
Thanks much for this.
Alas, we don’t get GOOD views of the capsizing/rolling
Offset Water knot. Perhaps one could force a perspective
by having clear plexiglass on either side and so the Tails
would keep the orientation of the knot pretty constant?!
(We also don’t get a good look at the knot’s dressing
& setting prior to loading :: this might seem a “well,
hey, at least …” sort of missing nicety; but it maybe
should be taken as the testers not having the right
appreciation of important aspects of a knot!
Quite fascinating at 11:23 to see a Clove H. break
its sheath, as OH stopper comes up to knot (but
looks not to be much loaded?!), OUTSIDE of the knot!!
:: sheath breakage at about 3/4" outside the knot?!
I can’t figure out why this would be.
(I CAN imagine that the sheath was nipped/held
more firmly than the core, and so took a disproportionate
load; but why the break isn’t at knot-entry curve/binding,
but that far OUT, puzzles me.)
–dl*
The Italian video is good - and could have been much more if it changed its focus to the load thresholds where instability began to manifest (in #1410 Offset overhand bend).
Again, it ultimately appears that the testers were more interested in reporting the MBS yield (strength) achieved.
And again, we see that the testers are not aware of the the potential affect rotation has on boosting the instability threshold of #1410.
Same diameter cords were used - and then later we see dissimilar diameters. As with the vast majority of testers (of #1410) they appear to assume that the geometry of the knot core is ‘known’ to all and ‘assumed’ to exist in only one possible form - and so do not reveal with precision how the test specimens were oriented in some tests.
I explored this in my technical paper at my knots website http://www.paci.com.au/knots.php, but I have never seen any follow up technical papers investigating this issue.
My (limited) research shows that only one rotation state appears to have an effect. The way remains open for a serious investigator to definitively determine which rotations are most effective.
My discovery of the offset bound overhand bend (in 2011) was somewhat of a breakthrough - because the relatively minor addition of one simple binding turn significantly boosts the instability threshold. Meaning; you get a significant benefit from very little effort - and it works with differing diameters. In addition, there is only a small relative increase in overall footprint - a design goal of any rope joining knot for abseiling/rappelling/canyoning is to avoid creating a large volume/bulk.
One also has to factor in that the nominal weight on the joining knot is one (1) person. Depending on how the retrieval system is configured, the knot may only ‘see’ 50% of the load.
In canyoning, there is a growing trend to using a "Fiddle stick’ - which is essentially an open toggle in a double Marlinspike hitch. The ‘toggle’ is made of lexan polycarbonate and is remotely extracted via thin pull cord. There are no rope joining knots in ‘Fiddle stick’ systems.
I am currently conducting some research into the exact geometry of the double Marlinspike hitch - where care needs to be taken in how the hitch is formed in order to ensure no remnant line twists…
...using a "Fiddle stick'...
I had to look it up:
Looks scary, won’t do it, no matter how well you dress it - think of a malicious bear pulling the tongue depressor as soon as the line slacks.
An accident waiting to happen - the opposite of redundancy…