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knudenoggin
Mar 2, 2009, 7:24 AM
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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.
[In theory, this post SHOULD have a small image clickable to get larger;
but this isn't working (op. error--it was done in another thread, in a reply
re the ELET?), and one will have to make the link the ol'-fashioned way.]
http://www.postimage.org/image.php?v=PqAodEJ
http://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! :-]
*knudeNoggin*
(This post was edited by knudenoggin on Mar 2, 2009, 7:27 AM)
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knudenoggin
Mar 15, 2009, 4:05 AM
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Aric, these are knots that The Lab should see tested to
say 1,000# in a variety of orientations and rope combos,
ideally stringing together two or more (could you get 3
on either side of a closed loop/sling), putting a ton of
force on this, and noting what slippage (or not!) occurred.
Given my conjecture that the particular orientation of the
thicker/thinner ropes shown above if beneficial, it makes
sense to check the reverse, which should put the geometry
of the knots to greatest test. Oh, and tying off the wrong
end in the stopperd ORB (1st-shown), which I see Luebben's
Rockclimbing Anchors book doing in the photos
on p.227.
*kN*
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ja1484
Mar 15, 2009, 4:16 AM
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I guess this goes here:
http://www.bdel.com/...p_archive.php#123008
Knude, I love all the dillying you do into this stuff (and at such a level of detail to), but I have to wonder if at many points you wander past practical purpose and into pedantism.
(This post was edited by ja1484 on Mar 15, 2009, 4:16 AM)
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kobaz
Mar 15, 2009, 5:46 AM
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I use the edk as my rappel knot. But, always tie two edk's.. one about a foot from the ends, one about 3 inches past the first. I've heard some horror stories of the edk rolling... if for some reason the first one starts to roll, the second will surely stop it.
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knudenoggin
Mar 15, 2009, 8:53 PM
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ja1484 wrote: Knude, I love all the dillying you do into this stuff (and at such a level of detail to), but I have to wonder if at many points you wander past practical purpose and into pedantism.
ideas put forward meet the examination of many; whatever
survives the critiques, the different perspectives, ought
to be pretty Good Stuff.
In this case, I think these are quite simple and helpful;
as noted below, it's even a little LESS in some cases.
(The Offset 8-Oh being weaker in qualities perhaps, but having
some theoretical import (and adding the full round
turn at the throat as done to make the EDK an Offset 9-Oh
will secure that, soundly.)
Consider that people have accepted using the Offset Fig.8 bend
w/o good examination of it; and apparently one British climber
died (though we don't know for sure of the cause; and
those ropes were quite stiff). And some years back the Offset
Fig.9 was tested as a surer alternative, and then by Bachmann
the Offset Grapevine bend, again, with what I'll say is half-thorough
thinking--point being that the offset nature of the knot
needs only ONE rope to make the sure binding at the throat, and
having the other rope share this structure (adjacently) only reduces
the effect and add at best gratuitous bulk--esp. where the extra
knotting/wrapping can be done in a thinner rope. (E.g., with the
Offset Dbl.Fish, the one Strangle-knot half will be resisting the
prying-open forces; the other will be simply jammed into the first
qua stopper knot, and there an Overhand will suffice so the bulk
can be reduced to that vs. dbl.overhand (Strangle).
And there are other offset bends to be found, including some symmetric
ones; but as often the nature of the ropes will be *asymmetric*
(thick-2-thin), an asymmetric geometry is actually a better fit.
In reply to: but, always tie two edk's.. one about a foot from the ends, one about 3 inches past the first. I've heard some horror stories of the edk rolling... if for some reason the first one starts to roll, the second will surely stop it.
[edit: that was a hastened comment as my computer time expired!]
The point here is this: putting the back-up/stopper knot at
some remove from the main one is:
(1) giving the back-up a chance to loosen (for it's untensioned but for manual setting);
and (2) giving room for the main knot to roll;
and then (3) tying off BOTH ropes in the Overhand, which is more bulk.
Whereas--and this is what I tried to show, above--what should
work much
better is (-3) tying off just the particular ONE rope (the thinner one, if using a haul line e.g.) which yields
a smaller knot, and which
will (-2) arrest the rolling ("flyping"--like inverting a sock) at its start, and in doing so
(-1) tension-tighten this smaller back-up Overhand.
That looks like a grand slam (not to be confused with a "slam dunk")
*kN*
(This post was edited by knudenoggin on Mar 16, 2009, 3:59 AM)
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patmay81
Mar 15, 2009, 9:39 PM
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kobaz wrote: I use the edk as my rappel knot. But, always tie two edk's.. one about a foot from the ends, one about 3 inches past the first. I've heard some horror stories of the edk rolling... if for some reason the first one starts to roll, the second will surely stop it.
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rocknice2
Mar 15, 2009, 11:21 PM
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kobaz wrote: I use the edk as my rappel knot. But, always tie two edk's.. one about a foot from the ends, one about 3 inches past the first. I've heard some horror stories of the edk rolling... if for some reason the first one starts to roll, the second will surely stop it.
I have heard the same but never have I seen it happen with an EDK. It's always the Fig8 that rolls faster than a cheap whore.
Bla Bla Bla.....strenght of knot. It's use for rapping not FF2's
IMO it's the best knot for rapping
low profile
doesn't roll
doesn't rub over rock
easy to untie
50% strenght reduction!............so what my ass isn't that big. Anyone that can get thier ass up a climb, this knot will get you down
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acorneau
Mar 16, 2009, 3:20 PM
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I also use an EDK with a second overhand snugged right up against the first, with about 6-8" tails after that.
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kobaz
Mar 22, 2009, 10:04 PM
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patmay81 wrote: it could really suck to pull a knot that bulky, it seems like it could have a serious tendancy to catch on any constriction or horn/loose block on the way down.
I don't find any pulling or bulk problems and here's why. The knot itself is pretty low profile and has a Y form, where 75% of the surface area around the knot, isn't actually the knot. So when your putting the rope over an edge, the rope will tend to twist around and the "flat" part of the edk will pop over the lip, leaving the knot part of the edk facing away from the wall. The second edk isn't in contact with the wall.
If you say, use a fisherman's or figure 8 rope join, you're stuck with 100% of the surface area of the joined section being a big bulky knot.
If you use a single edk, and it isn't perfectly dressed or for some reason it loosens (renegade badgers messing with it?), you risk a roll with nothing to stop it.
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