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adnix
Jun 28, 2006, 7:24 PM
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In reply to: so I wrote this piece to try and come up with a solution that was as good as the "Euro death knot" , but would be used by those who prefer something that looks like a proper knot. |
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knudenoggin
Jun 29, 2006, 7:34 AM
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"Double Overhand Knot" is long taken to mean something quite different from
the object of this discussion (it's used sometimes as a stopper knot).
In reply to: Until the publishers of MFotH include the EDK it just isn't going to become widespread.
for inclusion in Clyde Soles's The Outdoor Knots Book (p.125ff);
he aptly names it "Offset Overhand Bend" (with alias "EDK" etc.), and
thereby takes a good step towards better knotting & nomenclature--as offset
hits the nail on the head for such knots (not so "flat" or "abnormal" or whatever
other nonsense has been advanced, IMHO). And some other climbers knots
books include, right--by John Long, Duane Raleigh (, & Leubben?)
And thus I'd think it will migrate into the next FoHills?
Perhaps along with a simple, more secure extension, described below.
There are several ways to skin this cat.
In reply to: I appreciate your criteria of easy tying and wanting to warn people of the real danger of the figure 8.
bad as has been asserted, if correctly tied. Moyer's results suggest this.
BUT, it can be worse than others if not, and with better alternatives, laying
the Offset Fig.8 aside is fine. For one thing, it has some variety of dressing
that needlessly complicates things. (Re that well-know tragedy at Zion with
the British climber, I hear that those ropes "were like cables"--not the sort
of material helpful to snugging up a knot! One of the folks who examined
the ropes even continued (a while?) to recommend that knot.)
For the most part, and esp. for abseiling, let's dispose of talk about comparative
knot strength--that is just irrelevant to the expected use, here! (Oh, it's
an easy and seemingly objective--but who examines the testing?--datum.
Rap forces are nowhere close to needing any special strength from the knot.)
In reply to: I find the EDK easy to tie, but hard to dress and difficult to inspect for proper dressing ...
EASIEST knots to tie, dress, set, AND inspect!! There really no simpler knot
in rope alone than the Overhand; tying this in twin ropes should only add the
issue of dressing, and the dressing should be pretty obvious AND easily seen
--parallel/twin strands all around! Perhaps you're put off by inspection
of it after the lines have been pulled apart (as opposed to immediately prior,
when one has dressed & set it)? That should be easy, too; but the orientation
of the knot body to the loaded lines can vary over a range of 180degrees
--it can be dialed, so to speak. --true for some other offset bends.
In reply to: Laugh if you want, but at my gym the staff has to tie figure 8's in all the ropes on a daily basis
them well tied (and jammed)?
In reply to: so climbers can clip in with 'biners --insurance doesn’t want people tying their own knots. You'd be surprised how often the knots are dressed improperly by staff who are experienced climbers. All the tests show that the EDK must be dressed properly to work.
of cross-loading or gate-opening. I guess that they require double 'biners,
greatly lessening the concern.
(For such application, I'll remark that climbing rope (even arborist rope, which
is supple but 1/2" thick(!) can be snelled to a 'biner to lock the attachment
in place (likely needing to attach to away end from gate to allow clearance
for gate opening). Then one needs to ensure that the user locks the 'biner.
(But this is for a single 'biner; I've not tried it w/a pair.))
I'm not at all surprised about the various dressings of the Fig.8 loopknot,
as one can see such things all over, in photos in climbing books/magazines
and on-line. (E.g., the aforementioned book by Clyde has an asymmetric Fig.8
loopknot on its cover! tsk, tsk) The Fig.8, thankfully, seems to handle this
inattention / variance well, at least for normal loading qua loopknot.
Re "properly dressed", unfortunately Moyer's tests lacked the case of an OOB
that is well set (tightened), but improperly dressed; but proper
dressing should be easy (even w/mitts & fatigue & dim light).
In reply to: AND the question about safe tail length is unanswered.
is weakened by the caveat "just leave long tails"! But better safe than sorry.
The suggested simple adjustment to the OOB below greatly diminshes
the risk of rolling (flyping).
In reply to: If you can tie a DFK than the DT-FK is no harder. It's 15% stronger than the EDK and has no failure mode other than breakage. Tail length is modest -- 10cm in the test, I think.
better moniker (so at once one knows its orientation & structure).
To assert that is has "no failure mode other than breakage" is to take a leap
of faith that the very small sample tested by Edelrid is broadly applicable.
Note that E. dismisses tying the knot poorly; by such constraints, other knots
lose some bad attributes too! But, I'll grant that setting the OGB is pretty
straightforward/obvious/easy, and the structure should prevent rolling.
Also note that the cited testings have been done with slow-pull devices,
which aren't exactly good models of the forces potentially realized in use
--where, were the knot to flype, it would receive a bit of a shock load,
not a slow building of force.
In reply to: And the TT-FK is the simplest of all the knots to tie. I could easily tie (AND DRESS) it with my heavy mitts on. It deforms, but doesn't roll, so tail length can be modest as well. And it's 40% stronger than the EDK. I think tying and dressing a double EDK with my mitts on would be much harder.
how about "Overhand-Guarded Offset Fisherman's Knot (OG-OFK)"? GOOD GRIEF!)
requires that one set either of the exterior Overhand knots well snug
into the structure (and preferably get the orientation of thick/thin ropes right;
so, too, really, does the OOB). Note that one cannot well set this knot by
pulling opposite ends, as done for the (Dble) Fisherman's knot--for the center
Overhand either loads against the end one OR ELSE the guard one,
but the exterior Overhands will in either case be pulled slightly farther apart!
(And then maybe one has to re-set whichever Overhand was not loaded
in opposition to the central one.)
And, besides, the part of the knot that runs along the surface isn't alls so
clean as in other offset bends (that partially capsized form isn't offset).
But against these interesting alternatives, the OOB has: ease of tying & checking;
compactness; & ease of untying. (and funny-sounding acronym)
http://www.xmission.com/...esting/knots_EDK.jpg
In Tom's image, the upper, lighter/grey end should be dressed to be lower
and set firmly in place thus, anticipating the draw of the loading that will
move it towards where it's shown in the image.
The simple revision to the OOB is to make a full wrap with the grey rope before
tucking it out to finish--yes, this forms a Fig.9 in that rope. The full wrap will
greatly resist being pulled open and moved around the other rope's Overhand
component. Also, in the case of different-sized ropes, the THINNER rope
goes in the position of the grey one (as it will be harder to move this out
around a thicker rope). (Many people somehow feel that the OOB is more
risky with different-diameter ropes; in fact, it's more sure, up to a point!)
Set this Offset 9-Oh & OOB(edk) if oriented as in Tom's image (a natural
form for a righthanded tyer, from holding the ropes in the left hand and
wrapping the twin ends around the fingers and then out through where the
fingers were), by bringing that lighter end down behind the darker, putting
the left hand on the knot so that the darker end is between the index &
middle fingers and the lighter end between index & thumb, and, having
already tensioned each of the ends pretty well, haul the lighter end towards
your body, pushing away on the knot.
-------
In reply to: Does anyone have any data of tying two ropes together using a butterfly knot?
strength is pretty much a laugh for a knot used on one side of a twin-rope
abseil line. Andy gives the relevant criteria well (though I'm having trouble
picturing this supposed one-handed tying!).
There are a zillion ways to join ropes; "butterfly" is a name, and so it comes
up, there are symmetric knots like this (interlocked Overhands) that seem
more desireable (Rosendahl's (Zeppelin) Bend, e.g.; Ashley's Bend (#1452),
and esp. Ashley's #1425 (the symmetric one like the Butterfly is #1408, btw)),
but all suffer the problem of non-offset knots in getting hung up moving over
a surface.
Btw, that Overhand-guarded "TT-FK" knot could be tied with the two Overhand
of the thinner rope adjacent, other rope's Overhand at the end.
The double overhands of the Grapevine can be reformed, too.
The doublee overhand (Strangle) of the away rope (green) could be just a
single overhand--no need for the extra wrap at this point, really (whereas
the red rope needs it to resist being pried apart--what Kim nicely shows in
building up the TT-FK; what I've described in my "Offset Nine-Oh" as the
reinforcing aspect for the OOB.
*knudeNoggin*
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heiko
Jun 29, 2006, 8:32 AM
Post #28 of 92
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I have a question here...
I live in Italy, close to the Dolomites. Some of my climbing partners here are fairly experienced chaps (10+ years on alpine rock, ice, etc. ) and every single one of them is using the normal EDK to rapell. The EDK is what the guides use. The EDK is what most everyone uses (except for the Americans that come over ;) )
So: leaving aside issues relating to rock formations, people in the US seem so utterly concerned about the EDK undoing, and are looking for the ultimate double-flying-fish-overhand-whatever knot, while here the EDK is simply the standard. Where does this aversion come from, and why don't we seem to share it? When was the last time that someone fell from a properly tied EDK that undid itself?
I love my life, and I dislike rapelling in general for many reasons, but my last concern has always been this knot. This whole discussion is leaving me puzzled.
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fabe
Jun 29, 2006, 10:52 AM
Post #29 of 92
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Seems like every country has his own rappelling knot! Here in Switzerland almost everyone uses the double figure eight....
I've been using this knot for more than 10 years now! Just leave a long rope tail (say 50-80 cm).
This is how the guides are thought in Switzerland. Of course this knot is dangerous if you leave a rope tail of 5cm..... but if it's long enough it's safe!
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sweetchuck
Jun 29, 2006, 12:27 PM
Post #30 of 92
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Great post knudeNoggin. I have been looking for some evidence that the EDK is safe for use on different diameter ropes. I have a 10.2mm and a 7mm line for rappelling. I’d love to use the EDK, but I want to be able to reassure partners that it is safe, and that takes data, or evidence. The method you mention keeping the thicker strand on the side where the rappel lines exit the knot seems like the way to go. Does anyone know of any studies of the EDK on different diameter ropes? I know I ask this on every thread I post, sorry. I am just really interested.
Your Offset 9, or whatever you call it, is confusing me. It would be great if someone can post a pic.
Last night I was fooling with the offset grapevine. I did it in a loop of a single rope, and found that it is possible to accidentally tie both grapevines in the same strand. It gives enough friction that you might think you tied it right, but the strand without the grapevines can pull right out. This probably isn’t a big deal with rappel rigging since the two ropes almost always look different. It should be easy to visually inspect.
Well, thanks for the posts, at any rate. This is something I have been thinking a lot about lately.
sc
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knudenoggin
Jun 29, 2006, 6:38 PM
Post #31 of 92
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In reply to: I have been looking for some evidence that the EDK is safe for use on different diameter ropes. I have a 10.2mm & 7mm line for rappelling.
about the Grapevine!). For the difference likely to exist with rockclimbers,
it should be fine, and as noted, even better ... , IFF tied correctly.
But that last point implies that the OOB will be sub-better if the position of
the diff.-dia. ropes is reversed! --doublEdged aspect, alas.
In reply to: I’d love to use the [OOB], but I want to be able to reassure partners that it is safe, and that takes data, or evidence. The method you mention keeping the thicker strand on the side where the rappel lines exit the knot seems like the way to go. Does anyone know of any studies of the [OOB] on different diameter ropes?
ropes, both cases of well-tied & -tensioned Offest Overhands Bends, and both
ran to nearly 1000# before flyping (also for an Offset Fig.8, which did better!)
It's not expressly stated as to the positions of the resp. thick/thin ropes,
but at least in having each size under "Rope 1" / "Rope 2" columns, we
might guess that both orientations were tried once, for the OOB.
In reply to: Your Offset 9, or whatever you call it, is confusing me. It would be great if someone can post a pic.
(positioned as you understand, now) before following the thicker line out
to finish the knot--really simple, it makes thus a full circle at the throat,
which is what gives it the resistance to opening there.
In reply to: found that it is possible to accidentally tie both [Dble.Overhand parts] in the same strand. It gives enough friction that you might think you tied it right, but the strand without the [knot] can pull right out. This probably isn’t a big deal with rappel rigging since the two ropes almost always look different. It should be easy to visually inspect.
Esp. since the setting of the Grapevine (name for ENTIRE knot, each half
of which is a Strangle/Dbl.Overhand) entails pulling one knot into the other,
which is impossible if they're in the same rope (which as I pointed out above
is the case for Jost's (& Heinz Prohaska's) "TT-TFK" (argh!) exterior Overhands)!!
People should beware that knots need to be looked at, tested for, various
perspectives: the mistied Offset Grapevine that you describe here might
in fact have sufficient friction grip on its unknotted rope end to hold, SO LONG
AS the knot isn't held by something; but were the knotted body to be
arrested (assuming knotting is in the away-from-loading rope) in moving
with the loading, the end could be whipped right out. Given the offset aspect
this is unlikely here, but consider the case where a Prusik H. is tied in the
away rope, and you're hauling down on the near rope, and the hitch hits
a rock--you could then pull the unknotted rope free of the hitch, which
absent tension on its main part would cease gripping.
Climbers are used to Clove hitches holding for them, maybe with some bit
of give on tightening; but Lyon Equip.'s testing of low-elongation ropes found
that none of them ultimately held in a Clove h., though one dynamic rope
did. Importing a belief about Clove h. security from the climbing use into
another field with slightly different material could lead to problems.
The Swiss favor an Offset Fig.8 Bend? But one can now point to various
studies that show this to have some risk, more than the simpler OOB,
which has broad usage. But in either case if one is called upon to join
a couple (or just one of the pair) stiff rope(s), both of these knots are suspect.
-----
Good testing of just one of these offset bends should include a good many
distinct test cases, IMO:
3 ways to orient the knot body;
3 ways to position ropes (thick-thin, thin-thick, even-even orientations);
different ropes (flexi-slick-new + hoary-stiffer-old rope (esp. for even-even),
climbing (maybe 2 sizes: 9.2, 10.7?) + haul line;
and various loading--steady, bouncy?
AND some deliberate checks of mis-tied knots.
As one can see, this amounts to a LOT of testing, for even ONE case per
condition (some of the material would be good to collect from the community).
*knudeNoggin*
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roy_hinkley_jr
Jun 29, 2006, 7:28 PM
Post #32 of 92
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In reply to: Until the publishers of MFotH include the EDK it just isn't going to become widespread.
It was included in the 7th edition, which came out in 2003.
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rgold
Jun 30, 2006, 5:15 PM
Post #33 of 92
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The EDK has been discussed ad nauseum here and indeed wherever climbers gather. And yet, it may be helpful to try to collect some of the information in one place. Those who feel bilious at the prospect of yet another EDK manifesto are urged to move on to other things.
Moyer's data indicates that a properly tied EDK can roll at tensions somewhat above 1000 lbf. Since the two strands of a rappel share the load, there would have to be roughly a 2000 lbf (or about 9 kN) load on the rappel to roll the knot, and this would require a factor 1 fall for the usual 80 kg rappeller. The only way to achieve this, short of a failure of part of the anchor, is for the rappeller to feed out a loop of slack before weighting the rappel and then jump off. Even then, a single roll does not mean failure of the knot, and if forces are really allowed to get up to 9 kN, the security of the anchor itself would in many cases be as much of a concern as the potential rolling of the knot.
I have read of two instances in which an EDK has failed. In one of these, the information is questionable; the rappellers were "sport rappellers" who had tied together two ropes with an "overhand bend" in order to do a long single-strand rappel. There is no information on the length of the tails, and no one except the inexperienced participants ever saw the knot. MOreover, the knot had to be fed through a figure-eight device, and failed on the second rappeller. The relevance of this accident to ordinary practice is far from clear.
The second accident is more worrisome. It happened to a guide on the Guide's Wall in the Tetons in 1997. The ropes were dry but of slightly different diameters, 10mm and 10.5mm, and the knot, which had joined the two ropes for six rappels already, was loosened, retightened, and rappelled on once before it failed on the second person down. There is no clear explanation for this failure if the various witnesses accounts are accurate. My guess is that the knot, after being loosened, was either not sufficiently tightened again and/or was not properly dressed, in which case Moyer's figures indicate rolling is possible at ordinary rappel loads.
By far the most authoritative study of the EDK and Double Fisherman's is by David Drohan, prepared for an Australian rescue group, Bushwalkers Wilderness Rescue. The paper and accompanying tables, are available in .pdf format at http://www.bwrs.org.au/research/index.html. Here are some of the points I find interesting, but there is much more than I refer to here.
1. Drohan is the only person I know of who has tried to quantify pull-down resistance of various knots. He found the EDK to require so much less pull-down force than the double fisherman's knot that the DFK was eliminated from further testing after the first round of comparative tests. The EDK is not just slightly better, it is vastly better whenever the rope must pass over distinct edges.
2. Drohan also found two features of the EDK that can significantly affect the amount of force needed for pulling. These seem to me to be little known and certainly deserve to be widely understood.
A. The EDK is significantly harder to budge initially if it is pulled up against the descending rings, so care should be taken move the knot away from the rings, at least by the last person down. This also means that those who use the knot to keep unequal diameter ropes from running are inadvertently making the initial pull much harder. On high friction surfaces, the position of the knot relative to the rap rings could make the difference between being able to retrieve the rappel and having ropes that won't budge.
B. The ability of the knot to roll over edges is affected by the orientation of the tails relative to the direction of pull, with the correct "tails leading" http://i3.tinypic.com/1694vig.jpg orientation requiring 24% less force going over 90 degree edges and 50% less force pulling past reverse edges. (Note: for clarity in the picture, I dressed the knot but did not fully tension it, and I used tails a bit shorter than the forearm-length tails I use for actual rappels.)
3. In addition to rolling the knot, which it seems to me is exceptionally difficult under ordinary circumstances, there is also the issue of tail creep. Drohan has measured this under the type of cyclic loading typical of rappelling, as well as for loads high enough to break the ropes. He found that after 15 weightings with 50 kg, the EDK tails crept about an inch.
One caveat about Drohan's strength and slippage results is that they are obtained using static ropes. The case of the clove hitch has shown us that knots in dynamic ropes can behave differently than they do in static ropes. A sceptic could wonder whether the results for dynamic ropes would be analogous.
The EDK is simple and dressing and tensioning it is easy. It appears to me to be plenty safe for ordinary rappels and, under normal circumstances, extra backups may make it harder to pull and/or more likely to hang up. However, based on Drohan's and Moyer's data, there are two times when I'd throw on a second overhand backup. One is with two wet ropes of unequal diameter, and the second is if more than one person will be weighting the rappel at the same time.
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csproul
Jun 30, 2006, 5:41 PM
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In reply to: B. The ability of the knot to roll over edges is affected by the orientation of the tails relative to the direction of pull, with the correct "tails leading" orientation requiring 24% less force going over 90 degree edges and 50% less force pulling past reverse edges. (Note: for clarity in the picture, I dressed the knot but did not fully tension it, and I used tails a bit shorter than the forearm-length tails I use for actual rappels.) |
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bluefunk
Jun 30, 2006, 6:14 PM
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What does every body think about rapping with the EDK when you have a smaller diameter static rope (9mm) and a larger diameter dynamic rope (10.5). Every time I've used the EDK it was with the same diameter dynamic ropes, but with a smaller slippery static rope I'm worried. Should I just back it up with another overhand or am I just being a baby? I've never used it but to me the DT-FK "looks safe" and should stay out of cracks like the EDK.
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reg
Jun 30, 2006, 7:06 PM
Post #37 of 92
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In reply to: What does every body think about rapping with the EDK when you have a smaller diameter static rope (9mm) and a larger diameter dynamic rope (10.5). Every time I've used the EDK it was with the same diameter dynamic ropes, but with a smaller slippery static rope I'm worried. Should I just back it up with another overhand or am I just being a baby? I've never used it but to me the DT-FK "looks safe" and should stay out of cracks like the EDK.
dlb fish w/tails is good'n tight - triple fish is better if your worried - i sometimes rap with a 9.5 static and a 10.5 dynamic with dlb over hand - I always use the edk with a backup knot on top of it - both dressed and backup knot tight against the edk - works great - i'm still here!
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knudenoggin
Jul 1, 2006, 6:06 AM
Post #38 of 92
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In reply to: The EDK has been discussed ad nauseum ...
And there can be more & better testing (more as in repeating to confirm,
better as in checking aspects not addressed previously).
In reply to: Moyer's data indicates that a properly tied EDK can roll at tensions somewhat above 1000 lbf.
what the slow-pull-device testing does NOT show, well, is how successive
rolls might occur--I'd guess that under a falling weight, they'd be more
likely than less, so some sort of testing with a weight would be new info.
In reply to: My guess is that the knot, after being loosened, was either not sufficiently tightened again and/or was not properly dressed ...
be snagged by some rock point; it was stated that the guy who started
to re-tie the knot but then re-set it also re-positioned it.
In reply to: By far the most authoritative study of the EDK and Double Fisherman's is by David Drohan
more useful information than Drohan's report. (As Drohan admits, on the break
tests, he used quite poor wording to say "loss of strength due to knot", when
in fact he doesn't establish the strength(s) of the used ropes of the study
(and does at least note this point in the report--i.e., that ageing might be
the cause (hard to find it stated that vendor strength ratings are
used to figure % lost by knot)).) However, Moyer's "Rope 1"/"Rope 2"
labels mean nothing--i.p., they don't indicate relative position of the ropes.
In reply to: 1. Drohan is the only person I know of who has tried to quantify pull-down resistance of various knots.
of comments about stuck ropes in practice suggests that the problem is
not all so great (Moyer openly wonders at this). I.p., Drohan's testing on
a real rock surface didn't have the great differences that he found on his
roof set-up, and, also, the rate of pull was constrained (slowed) so as to
be able to read values from the spring scale--which is kind of like looking
for a lost coin out of an alley because the light's better. Something to go
on, but as Drohan notes, it seems that natural pull rates are both faster
and with less disruption to rope flow.
In reply to: B. The ability of the knot to roll over edges is affected by the orientation of the tails relative to the direction of pull, with the correct "tails leading" http://i3.tinypic.com/1694vig.jpg orientation requiring 24% less force going over 90 degree edges and 50% less force pulling past reverse edges. (Note: for clarity in the picture, I dressed the knot but did not fully tension it, and I used tails a bit shorter than the forearm-length tails I use for actual rappels.)
that there would be a 2nd, parallel green strand on the left, the green
rope having been given a full wrap around the base of the knot
where the loaded strands enter (which full turn resists being pried open).
There are three main ways to orient the knot body relative to the loaded
strands in a range of 180 degrees (with all the in-between points, and some
shifting by distortion under increased load. At this time, I don't know
how much this orientation affects the vulnerability of the knot rolling.
But I'm pretty sure that users won't want to be bothered trying to achieve
any particular setting.
In reply to: It is possible to reverse the tail orientation by loosening the knot and "flipping" or "rotating" the strands---the knot does not have to be untied and retied.
but the "leading"/"trailing" orientation only comes from the mid-range
setting of the knot, and to obtain the same knot body orientation upon
putting the knot on the opposite side of the anchor DOES require re-tying.
Reference your image, above:
This is the mid-180deg-range orientation of body to loaded parts; the rope
enters the knot and arcs away from the viewer before turning down around
the ends.
You can turn ("dial") the body by bringing the ends towards the viewer,
in which case the red rope will make a loop, reversing direction upon
entering the knot, and the green will make a sort of forward rise & arc.
This is one extreme of the 180deg range.
The other extreme could be reached from here by--while holding the knot
body in place--swapping which rope runs through the anchor (!). This is
analogous to a person doing the splits, right leg front, left back, and then,
body not shifting, reversing the leg positions.
In either of these end-of-range positions, the tails will be perpendicular to
the loaded line--one side or the other--, at their exit.
But you cannot alter the knot body to point the tails leading or trailing
w/o re-tying the knot; the knot geometry doesn't allow it.
(Looking at Drohan's pics, it's not clear that his knot is so definitely at the
mid-range point, which isn't surprising, as it can shift a bit, etc.. Hmmm,
and is he tying it left-handed?)
In reply to: One caveat about Drohan's strength and slippage results is that they are obtained using static ropes. The case of the clove hitch has shown us that knots in dynamic ropes can behave differently than they do in static ropes. A sceptic could wonder whether the results for dynamic ropes would be analogous.
more than low-elongation, "static" ropes; in the case of offset knots, this
means that the rope gripping the base/throat/entry of the knot can give
more, opening more. And worn, frictive ropes can aggravate this by
the binding turns being more easily drawn by the loaded parts to open.
Thus, comes my (also in Soles's book, op cit) recommendation that the
thinner & less stretchy rope be in the position of the green rope above,
making the main/first grip at the entry. And thus I posit the case of joining
say an older, 10.5mm dynamic rope with a newer, 9.7mm one in the
reverse thin/thick orientation to what we've recommended as being
a greater risk of rolling than most other cases. (But w/o testing, yet.)
In reply to: However, based on Drohan's and Moyer's data, there are two times when I'd throw on a second overhand backup.
I see nowhere in Drohan a basis for your concern here, as he found no
rolling (save one partial roll "near failure"--so who cares?) in the OOB!
Now, his strength data should make you worry, but adding a back-up
knot isn't going to help you there!
In reply to: One is with two wet ropes of unequal diameter, and the second is if more than one person will be weighting the rappel at the same time.
of wet equal diameters for the OOB; for the Offset Fig.8, he did, and the
flyping occurred at a lower load (but then locked to rupture!?). I think
you're unfairly giving legs to the "unequal diameters" fear, here, that's all;
again, it might actually be a safer case, if properly oriented. That said, I like
a previous poster's suggestion to the OP to add just ONE Overhand for
a back-up; and I'd recommend it be in the rope in the green rope's
position, which should be the thinner rope if unequal diameters are used,
or the more flexible, slicker (newer) rope if different-condition ropes are
used (anyway, it is that rope that will pried open first, and so best
benefits from having the stopper).
Believe me?
Well, I hope at least one can see many aspects to consider/understand,
to put to test, which have previously seldom even been articulated!
*knudeNoggin*
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dirtineye
Jul 1, 2006, 1:33 PM
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fvck you very much, it's been fun
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adnix
Jul 2, 2006, 4:42 PM
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In reply to: Here's one little point: When ropes get stuck, you usually unstick them;when rappel knots fail, you usually die.
Quite many people have died while retrieving stuck ropes but there are only few cases of EDK failing.
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dirtineye
Jul 2, 2006, 5:17 PM
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fvck you very much, it's been fun
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knudenoggin
Jul 3, 2006, 3:39 AM
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In reply to: Back that up right now. Prove it. Prove that retrieving stuck ropes has caused death, and prove that it has caused more deaths then the EDK.
!! He gave just as much "proof" as you. RGold noted two cases of alleged
Offest Overhand failure--both well shy of sufficient information to draw
definite conclusions. Against this, above, are two reports from Over There
of the de rigeur use of either the Offset Overhand or Offset Fig.8
(which counts as likely that Brittish climber's death in Zion).
Beyond that, in this thread are a couple of simple ways to secure the knot,
while preserving its offset benefits & compactness, ease of tying/untying.
Even if NO cases of stuck ropes causing similar injuries are cited, 2-0 isn't
a compelling imbalance, given the scope of usage. (fine soccer score, though)
The Bowline comes with failure fears, too, but also desireable features and
ways to secure it in kernmantle ropes.
*kN*
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dirtineye
Jul 3, 2006, 12:18 PM
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fvck you very much, it's been fun
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cracklover
Jul 3, 2006, 12:53 PM
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In reply to: OH H3LL, here is the most offensive part: "Quite many people have died while retrieving stuck ropes but there are only few cases of EDK failing." If you can accept this statement without asking for proof, you are an idiot, plain and simple.
Hey Dirt,
You have to expect a certain amount of hyperbole and made up numbers from the folks here. Try to read between the lines. Here's what it boils down to:
1 - A stuck rappel rope can ruin my day, and maybe worse.
2 - An EDK, backed up the way I do it, simply will not roll off the end of the rope, and is less likely to get stuck when I pull it than a DF.
That's mainly what it boils down to. Throw in the convenience factors of easier to tie, easier to dress and inspect, easier to untie, and personal preference. All secondary to the two primary things I referenced.
Face it - the EDK is a weak bend, but it is strong enough for the application. That's all that's important.
GO
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dirtineye
Jul 3, 2006, 1:55 PM
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fvck you very much, it's been fun
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cracklover
Jul 3, 2006, 2:38 PM
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You (rightly) accuse others of making false claims, and then...
In reply to: With the EDK you HAVE to do it exactly right every time, no exceptions.
Nope. Two things bely the above assertion.
1 - Tom Moyer's tests. In the worst case scenarios, (crossed strands, loose, different diameters) the rope rolled a couple of times, and then would not roll any further except beyond the forces possible to generate under a rappeling or ascending situation.
2 - This has been the standard knot for joining rappel ropes in Europe for some time. You don't think all those thousands of European climbers do it exactly right every single time, no exceptions, do you?
By the way, my recollection of the accident you're referring to is that, while no-one saw it happen, the climber who fell was in the habit of tying the fig-8 version of the EDK, not the overhand version.
GO
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knudenoggin
Jul 3, 2006, 4:22 PM
Post #47 of 92
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In reply to: NO! Go back and read exactly what he says. Besides, after such a claim, the burden of proof is on him. OH H3LL, here is the most offensive part: "Quite many people have died while retrieving stuck ropes but there are only few cases of EDK failing." If you can accept this statement without asking for proof, you are an idiot, plain and simple.
to garner more documentation) calls for support (lacking); against this,
Moyer's remarks are a good counter. (I needed to (re-)read this!)
Hearsay from the RC.com grapevine is that occasionally stuck rap ropes have
been a pain. AND that such behavior seems to be only occasional--i.e., we
have testimony of decades-long use of the Grapevine bend w/o such troubles.
But from Europe, at least, is similar testimony to problem-free OOB (and,
egads, Offset Fig.8 bend!) usage; and UIAA, Petzl, Edelrid (old manual,
anyway) recommendation for the Offset OVERHAND Bend (not 8).
And the point re vulnerability of offest bends must be kept in mind.
That raises an issue in general: how dummied down, dummy proof, must
practices be? --assume inattention, mis-tying, mising, so recommend
as standard the use of back-up knots, etc.?
In reply to: Nope. Two things bely the above assertion. 1 - Tom Moyer's tests. In the worst case scenarios, (crossed strands, loose, different diameters) the rope rolled a couple of times, and then would not roll any further except beyond the forces possible to generate under a rappeling or ascending situation.
As I noted, the effects of a slow-pull load on the knot might not so well
model the behavior of a falling weight, when the knot rolls--the latter giving
a bit of shock to the system, the former not. Also, in some cases, the knot
might be rubbing rock, and one can have some concern about a snag on
it facilitating untying.
But the Offset Overhand IS pretty darn easy to DO RIGHT, and also to back
up with an Overhand knot in the (as above) green/thinner (if) rope. --and
to set well.
(And, yes, the DFK/Grapevine is pretty sure with even less attention. But
if used in offset orientation (that "TD-FK"), one wants closer attention
to setting.)
In reply to: 2 - This has been the standard knot for joining rappel ropes in Europe for some time. You don't think all those thousands of European climbers do it exactly right every single time, no exceptions, do you? By the way, my recollection of the accident you're referring to is that, while no-one saw it happen, the climber who fell was in the habit of tying the fig-8 version of the EDK, not the overhand version.
all so hard; orienting thin/thick ropes as recommended above IS likely
not so much observed, so there's a datapoint re that, I guess.
On the accident with the Brittish climber, yes, it was their practice (and we
should say, without prior problems for many uses!) to use an Offset Fig.8 bend;
moreover, one who saw the actual ropes said that "they were like cables"
--which would make setting the knot more difficult to do well.
Thanks,
*kN*
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knudenoggin
Jul 3, 2006, 4:25 PM
Post #48 of 92
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In reply to: NO! Go back and read exactly what he says. Besides, after such a claim, the burden of proof is on him. OH H3LL, here is the most offensive part: "Quite many people have died while retrieving stuck ropes but there are only few cases of EDK failing." If you can accept this statement without asking for proof, you are an idiot, plain and simple.
to garner more documentation) calls for support (lacking); against this,
Moyer's remarks are a good counter. (I needed to (re-)read this!)
Hearsay from the RC.com grapevine is that occasionally stuck rap ropes have
been a pain. AND that such behavior seems to be only occasional--i.e., we
have testimony of decades-long use of the Grapevine bend w/o such troubles.
But from Europe, at least, is similar testimony to problem-free OOB (and,
egads, Offset Fig.8 bend!) usage; and UIAA, Petzl, Edelrid (old manual,
anyway) recommendation for the Offset OVERHAND Bend (not 8).
And the point re vulnerability of offest bends must be kept in mind.
That raises an issue in general: how dummied down, dummy proof, must
practices be? --assume inattention, mis-tying, mising, so recommend
as standard the use of back-up knots, etc.?
In reply to: Nope. Two things bely the above assertion. 1 - Tom Moyer's tests. In the worst case scenarios, (crossed strands, loose, different diameters) the rope rolled a couple of times, and then would not roll any further except beyond the forces possible to generate under a rappeling or ascending situation.
As I noted, the effects of a slow-pull load on the knot might not so well
model the behavior of a falling weight, when the knot rolls--the latter giving
a bit of shock to the system, the former not. Also, in some cases, the knot
might be rubbing rock, and one can have some concern about a snag on
it facilitating untying.
But the Offset Overhand IS pretty darn easy to DO RIGHT, and also to back
up with an Overhand knot in the (as above) green/thinner (if) rope. --and
to set well.
(And, yes, the DFK/Grapevine is pretty sure with even less attention. But
if used in offset orientation (that "TD-FK"), one wants closer attention
to setting.)
In reply to: 2 - This has been the standard knot for joining rappel ropes in Europe for some time. You don't think all those thousands of European climbers do it exactly right every single time, no exceptions, do you? By the way, my recollection of the accident you're referring to is that, while no-one saw it happen, the climber who fell was in the habit of tying the fig-8 version of the EDK, not the overhand version.
all so hard; orienting thin/thick ropes as recommended above IS likely
not so much observed, so there's a datapoint re that, I guess.
On the accident with the Brittish climber, yes, it was their practice (and we
should say, without prior problems for many uses!) to use an Offset Fig.8 bend;
moreover, one who saw the actual ropes said that "they were like cables"
--which would make setting the knot more difficult to do well.
Thanks,
*kN*
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knudenoggin
Jul 3, 2006, 4:28 PM
Post #49 of 92
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Posts: 596
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In reply to: NO! Go back and read exactly what he says. Besides, after such a claim, the burden of proof is on him. OH H3LL, here is the most offensive part: "Quite many people have died while retrieving stuck ropes but there are only few cases of EDK failing." If you can accept this statement without asking for proof, you are an idiot, plain and simple.
to garner more documentation) calls for support (lacking); against this,
Moyer's remarks are a good counter. (I needed to (re-)read this!)
Hearsay from the RC.com grapevine is that occasionally stuck rap ropes have
been a pain. AND that such behavior seems to be only occasional--i.e., we
have testimony of decades-long use of the Grapevine bend w/o such troubles.
But from Europe, at least, is similar testimony to problem-free OOB (and,
egads, Offset Fig.8 bend!) usage; and UIAA, Petzl, Edelrid (old manual,
anyway) recommendation for the Offset OVERHAND Bend (not 8).
And the point re vulnerability of offest bends must be kept in mind.
That raises an issue in general: how dummied down, dummy proof, must
practices be? --assume inattention, mis-tying, mising, so recommend
as standard the use of back-up knots, etc.?
In reply to: Nope. Two things bely the above assertion. 1 - Tom Moyer's tests. In the worst case scenarios, (crossed strands, loose, different diameters) the rope rolled a couple of times, and then would not roll any further except beyond the forces possible to generate under a rappeling or ascending situation.
As I noted, the effects of a slow-pull load on the knot might not so well
model the behavior of a falling weight, when the knot rolls--the latter giving
a bit of shock to the system, the former not. Also, in some cases, the knot
might be rubbing rock, and one can have some concern about a snag on
it facilitating untying.
But the Offset Overhand IS pretty darn easy to DO RIGHT, and also to back
up with an Overhand knot in the (as above) green/thinner (if) rope. --and
to set well.
(And, yes, the DFK/Grapevine is pretty sure with even less attention. But
if used in offset orientation (that "TD-FK"), one wants closer attention
to setting.)
In reply to: 2 - This has been the standard knot for joining rappel ropes in Europe for some time. You don't think all those thousands of European climbers do it exactly right every single time, no exceptions, do you? By the way, my recollection of the accident you're referring to is that, while no-one saw it happen, the climber who fell was in the habit of tying the fig-8 version of the EDK, not the overhand version.
all so hard; orienting thin/thick ropes as recommended above IS likely
not so much observed, so there's a datapoint re that, I guess.
On the accident with the Brittish climber, yes, it was their practice (and we
should say, without prior problems for many uses!) to use an Offset Fig.8 bend;
moreover, one who saw the actual ropes said that "they were like cables"
--which would make setting the knot more difficult to do well.
Thanks,
*kN*
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dirtineye
Jul 3, 2006, 5:09 PM
Post #50 of 92
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Posts: 5590
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fvck you very much, it's been fun
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