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moose_droppings
Apr 25, 2008, 3:02 AM
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adatesman wrote: That said, are we talking about different knots here? In my mind its the same knot and just a question of which of the 4 strands coming out of it are being loaded.
Possibly semantics, but the motion you go through to tie it is an overhand. If its even a bend any more, I don't know, since a bend is tying two ends together, joining them.
PTFTW edit:
(This post was edited by moose_droppings on Apr 25, 2008, 3:03 AM)
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knudenoggin
Apr 25, 2008, 5:49 AM
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ja1484 wrote: My main curiosity with the ELET is that we know soft on soft is not the best attachment methods for runners and cords strength wise, but will the sheet bend attached runner prove stronger than just a plain ol' limiter knot in the same place.
ways. E.g., concerned with soft-2-soft, you could clip a sling into 'biners,
and use cord to tie off the 'biners and make the connecting side of the
ELET (as Aric shows, but absent 'biners at cord-2-tape joints). Or, a single
tape could be Clove hitched to the 'biners at the connection corners, and
separate material used to connect from 'biner to anchor.
I should expect that an equilateral triangle would be adequate in most cases,
and this will keep the connection corners from shifting to the powerpoint if
one side pulls out. (Aric's short sling doesn't achieve this; and the Triplette
was shown with an overly long connecting strand.)
And the Triplette is an implementation of the ELET, except that with the
connecting (single) strand nearly the same length as the paired strands
(which are clipped), it allows needless extension vs. limiting it--which I
see someone (Bill7) actually thought was a GOOD thing!?)
jt512 wrote: A couple of interesting details in there: first, that the strop hitch (which I'd never heard of) is stronger than the true girth hitch. Fooling around with a couple of Spectra slings just now, I suspect that we're usually connecting two slings together with strop hitches, and mistakenly calling them girth hitches.
The misnomer "Girth hitch" is bandied about w/o regard for the result,
sadly; one should in the climber-use case regard it as a tying algorithm,
the result of which can vary w/tyer, material, and maybe phases of the moon.
Double egads is that Kolin only once, apparently accidentally, shows what
I presume is the most common result of the algorithm--an asymmetric
geometry, in which one sling is pretty much unaltered (initially), and the
other bends around it--is "girth hitched" to it. You can see this form in the
climerware [sic--no 'b', contrary Kolin] site (and in Soles's Outdoor Knots,
p. 97).
In reply to: If I understand the strop hitch correctly, I have to try hard "de-symmetrify" it into a girth hitch.
symmetric form of the "Strop H." is what requires care--a departure from the
usual quickly made hitch, in which one sling is worked around the other
(and often I think w/o regard as to whether the result resembles what it
would around a rigid object ('biner) or with the bight tip fallen back over
the hitched-to sling).
In reply to: The other interesting detail is that pre-tensioning the strop hitch increases its strength against a dynamic load, presumably by decreasing slippage, and hence, heat, during loading.
Yeah, likely. And it's a worry to me about what I hope will be a better way
to join slings: to simply interweave them ("girth"-/"strop"-wise) a few times.
The thought is that with an extended section of twisted sling-sides, each
sling will dominate at its end of entry, and so take less initial bending,
off-loading force gradually. Such a structure is inevitably easy to untie,
as its center is a long slit between the entwisted sides. But your note about
the friction & benefit of a pre-set tight knot is a worry, as this extended
twisting is harder to set so tight.
*kN*
ps: majid wrote: GH knot naturally create a 2:1 mechanical advantages ...
on some irrelevant tangent connected only by the overloaded name "GH"
(you seem to be taking C.Connally's definition; it'snot that common a one,
and irrelevant entirely re joining slings).
pps: In reply to: ... and kN came along threating to set me on fire during the night as I slept.  Yeah, that'll learn ya!
(But we'd both much rather someonElse lit your fire during the night ... .)
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knudenoggin
Apr 25, 2008, 6:02 AM
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adatesman wrote: moose_droppings wrote: They aren't tied with a ring bend, they're tied with an overhand. There is a difference. If you tie an overhand in the middle of a rope and apply force to both ends, it cannot capsize. I agree that pulling on both ends won't be a problem, but if one side of the anchor fails you have an overhand/ring bend on top loaded correctly and one on bottom that's having the two strands on the same side pulled opposite directions, which is what leads to the rolling problem.
The knot in question is a an Overhand knot in doubled rope with another
strand run through it and tied off around the pair with a Strangle (a form
of Dbl.Oh). And the loading of it upon failure of its anchor will be that of
an offset Ring Bend (note the usefulness of Soles's term "offset")
with an extra strand to the Strangle, which also makes it conceivable as
an Offset "Half Grapevine", but it's not quite that.
To a good pull in 8mm low-elongation cord it looks stable so loaded;
but that's one quick check, at maybe 400#? (And just an Oh vice Strangle)
*kN*
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majid_sabet
Apr 25, 2008, 6:34 AM
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knudenoggin wrote: adatesman wrote: moose_droppings wrote: They aren't tied with a ring bend, they're tied with an overhand. There is a difference. If you tie an overhand in the middle of a rope and apply force to both ends, it cannot capsize. I agree that pulling on both ends won't be a problem, but if one side of the anchor fails you have an overhand/ring bend on top loaded correctly and one on bottom that's having the two strands on the same side pulled opposite directions, which is what leads to the rolling problem. The knot in question is a an Overhand knot in doubled rope with another strand run through it and tied off around the pair with a Strangle (a form of Dbl.Oh). And the loading of it upon failure of its anchor will be that of an offset Ring Bend (note the usefulness of Soles's term "offset") with an extra strand to the Strangle, which also makes it conceivable as an Offset "Half Grapevine", but it's not quite that. To a good pull in 8mm low-elongation cord it looks stable so loaded; but that's one quick check, at maybe 400#? (And just an Oh vice Strangle) *kN*
what is used to join these two cords?
That gray looking sling and red looking rope ?
[URL=http://imageshack.us]
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ja1484
Apr 25, 2008, 12:06 PM
Post #130 of 147
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knudenoggin wrote: ja1484 wrote: My main curiosity with the ELET is that we know soft on soft is not the best attachment methods for runners and cords strength wise, but will the sheet bend attached runner prove stronger than just a plain ol' limiter knot in the same place. The ELET is a general, triangular structure; this can be implemented in various ways. E.g., concerned with soft-2-soft, you could clip a sling into 'biners, and use cord to tie off the 'biners and make the connecting side of the ELET (as Aric shows, but absent 'biners at cord-2-tape joints). Or, a single tape could be Clove hitched to the 'biners at the connection corners, and separate material used to connect from 'biner to anchor. I should expect that an equilateral triangle would be adequate in most cases, and this will keep the connection corners from shifting to the powerpoint if one side pulls out. (Aric's short sling doesn't achieve this; and the Triplette was shown with an overly long connecting strand.)
The Trenchlette I use just has all three powerpoint strands the same length. Pick two to clip, which two doesn't matter.
As for adding in the carabiners, again, we're just bumping complexity of the rigging more and more. I like the Trenchlette, because it's nothing but an equallette with an extra strand on the PP (meaning you can use one less 'biner, so it's kind of a tradeoff complexity wise).
I think it's hard to state anything as having further advantages if they're negated by increased setup time or rigging complexity.
In reply to: And the Triplette is an implementation of the ELET, except that with the connecting (single) strand nearly the same length as the paired strands (which are clipped), it allows needless extension vs. limiting it--which I see someone (Bill7) actually thought was a GOOD thing!?)
Meh, the climbing community needs to get over extension. The tests by Jim Ewing at Sterling have basically shown it to be a non-issue in terms of load multiplication as long as the climbing rope is in the system.
FWIW, I think the SRENE acronym has been pretty much shown to be what an anchor rigger's exact order of priorities should be:
Strong first and foremost. Sacrifice any of the other three to get stronger until you're "good enough".
Redundant next. Sacrifice any equalization or extension limitations, but NOT strength, to get redundant.
Equalized third. No extension can be sacrificed to become more equalized, but you should NOT decrease strength or redundancy for more equalization.
Lastly, limit extension as much as you can, as long as it does not decrease the prior three properties.
(This post was edited by ja1484 on Apr 26, 2008, 12:45 PM)
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knudenoggin
Apr 25, 2008, 3:47 PM
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In reply to: what is used to join these two cords? That gray looking sling and red looking rope ?
the nice aspect of using the "Grapevine" nomenclature in that the overwraps
count matches the prefix ("dbl" = "2", vs. the "triple" w/"Fish")).
The knot joining the cord-to-sling is, absent anchor failure, a Reverse Becket
bend (or hitch, which name I'm favoring); upon achor failure, that of the
holding anchor becomes a fixed loopknot or sorts like the Eskimo Bowline,
and the one of the failed anchor becomes a reversed Rev.Becket Bend
--i.e., a Becket Bend.
Given the use of the sling, there are some tricks that can be done in tying
to it, should further security be wanted.
ja1484 wrote: The Trenchlette I use just has all three powerpoint strands the same length. Pick two to clip, which two doesn't matter.
to clip to stand out clearly, and you limit extension.
In reply to: As for adding in the carabiners, again, we're just bumping complexity of the rigging more and more.
repeatedly, variously tie your anchoring cord--no big deal, and perhaps more
easy than having to re-tie the entire structure per set-up.
In reply to: Meh, the climbing community needs to get over extension. The tests by Jim Ewing at Sterling have basically shown it to be a non-issue in terms of load multiplication as long as the climbing rope is in the system.
the belayer's mass is accelerated into static connections, which might be
an unlikely case.
But one might prefet to limit extension for other than force-generating reasons.
In reply to: Lastly, limit extension as much as you can, as long as it does not decrease the prior three properties.
Bingo!! So why make the connecting strand so gratuitously long?
--that's all I'm saying.
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adatesman
Apr 25, 2008, 4:13 PM
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moose_droppings
Apr 25, 2008, 5:43 PM
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I'd be more concerned about the sheet bend should one side give out since it is not generally considered to be very strong or reliable.
Anyway I guess someone can always add something to an already working mousetrap. As long as someone will use it and its safe, no foul no harm.
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moose_droppings
Apr 25, 2008, 5:48 PM
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adatesman wrote: Also hadn't heard of the Eskimo Bowline. Apparently preferred over the regular bowline when the two legs of the loop are pulled in opposite directions. Link -a.
Just looked that one up. Looks like it work great for snaring polar bears (wider working loop).
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trenchdigger
Apr 25, 2008, 5:56 PM
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knudenoggin wrote: In reply to: Lastly, limit extension as much as you can, as long as it does not decrease the prior three properties. Bingo!! So why make the connecting strand so gratuitously long? --that's all I'm saying.
Exactly. Plus the shorter strand makes it easier to clip. I have tied them with the short strand just the right length so it has no slack, but is basically untensioned with the anchor arms spread to 120 degrees - the max I'd accept in an anchor.
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knudenoggin
Apr 25, 2008, 11:26 PM
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trenchdigger wrote: knudenoggin wrote: In reply to: Lastly, limit extension as much as you can, as long as it does not decrease the prior three properties. Bingo!! So why make the connecting strand so gratuitously long? --that's all I'm saying. Exactly. Plus the shorter strand makes it easier to clip. I have tied them with the short strand just the right length so it has no slack, but is basically untensioned with the anchor arms spread to 120 degrees - the max I'd accept in an anchor.
The extension of the ELET is 1/2 the length of the connecting strand,
excluding any consideration for pendulum effects of spread anchors.
Joining two 2'(60cm) slings could yield an ELET that at 120deg., would
be an equilateral triangle w/6" extension, e.g. (the sling used for making
the hitching consuming half its length in knots & eyes, half left for the
connecting span).
------
"Becket Bend/hitch ("hitch" taken as the one side hitching to an eye]
differs from the Sheet bend in that both legs of the bight (u-part) are loaded.
(Although I think that the origin of the Sheet bend was for tying sheets to
an eye-like structure.)
*kN*
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ja1484
Apr 26, 2008, 2:27 AM
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kN/Trench:
I can respect wanting to limit extension for other reasons aside from prevention of "shock loading", and I totally get behind that.
That said, I like being able to just choose any two strands of the trenchelette to clip as my powerpoint. I'm willing to risk the extra 2- 4 inches of extension in the event of a leg failure for the versatility.
I suppose this is something everyone has to decide on per their preferences.
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jt512
Apr 26, 2008, 4:06 AM
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ja1484 wrote: ...I think the SRENE acronym has been pretty much shown to be what an anchor rigger's exact order of priorities should be[.]
I wonder to what extent, if any, that was John Long's intent; I don't recall his ever mentioning that he intended the order to have any significance. I, for one, merely assumed that the acronym was intended to be similar to the word "serene," implying that a SRENE anchor should give the climber peace of mind.
But I completely agree with you, now that you've pointed it out, that the priorities for an anchor are in the exact order of the acronym. I think you may be the first person to make this observation on the internet. I'm not one to lament the loss of trophies, but if we did have a means of rating posts, your simple, elegant observation would get the highest rating, at least from me.
You might want to think about working this up into an article for Climbing or R & I.
Jay
(This post was edited by jt512 on Apr 26, 2008, 4:08 AM)
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ja1484
Apr 26, 2008, 12:42 PM
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jt512 wrote: ja1484 wrote: ...I think the SRENE acronym has been pretty much shown to be what an anchor rigger's exact order of priorities should be[.] I wonder to what extent, if any, that was John Long's intent; I don't recall his ever mentioning that he intended the order to have any significance. I, for one, merely assumed that the acronym was intended to be similar to the word "serene," implying that a SRENE anchor should give the climber peace of mind. But I completely agree with you, now that you've pointed it out, that the priorities for an anchor are in the exact order of the acronym. I think you may be the first person to make this observation on the internet. I'm not one to lament the loss of trophies, but if we did have a means of rating posts, your simple, elegant observation would get the highest rating, at least from me. You might want to think about working this up into an article for Climbing or R & I. Jay
An article ain't a bad idea, even if it only ends up on here to educate.
And I agree, I'm not sure that's what JL had in mind, I just think with the evolution of anchor rigging and evidence disproving significant shock loading from extension, things kind of fell into place.
(This post was edited by ja1484 on Apr 26, 2008, 12:47 PM)
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knudenoggin
Apr 27, 2008, 8:09 PM
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jt512 wrote: ja1484 wrote: ...I think the SRENE acronym has been pretty much shown to be what an anchor rigger's exact order of priorities should be[.] I wonder to what extent, if any, that was John Long's intent; I don't recall his ever mentioning that he intended the order to have any significance. I, for one, merely assumed that the acronym was intended to be similar to the word "serene," implying that a SRENE anchor should give the climber peace of mind.
Before history gets revised much, let's read what VivaLargo/JL actually writes:
SRENE is an acronym for "Solid, Redundant, Equalized, and No-Extension"
first connived by professional guide Marc Chauvin, for use when teaching clients
anchoring fundamentals. Marc's first acronym was RENE; "S (Solid)" was later
added, resulting in SRENE, which was appropriated by the IFMGA (Int.Fed.
of Mtn. Guides Assoc.), and later by me in the first anchor book.
So making the originally absent "S" the most important factor turns this anchor
principle on its head, so to speak! It also changes "solid" into "strong", before
taking off w/rationalization.
But what is solid? Craig Connally's take on it sheds some light--to wit:
"'S' should mean 'strong & secure'. These are not the same." [Mnteering Hndbk]
And he also mentions "ERNEST" (which pops up in Craig (no relation) Leuben's
Climbing Anchors, a second point in anchor-acronym thinking that sorta
*determines the line*: "foremost, anchor acronyms must be pronounceable".
(And printable: the little-known "Foundation Using Cord for Kinetic Energy
Dispersal for Uber Protection" never left the publisher; it also has unfortunate,
unsettling connotations--as did "Bomber, Adjustable, & Duplicative", which
also did not find favor.)
So, the strength, or solidness, of arguing for Strong's prominence seems
weakened by a reflection on the origin of the principles. --or one might
counter-argue that the omission arose from taking it as so fundamental
that it did not in need stating.
In reply to: But I completely agree with you, now that you've pointed it out, that the priorities for an anchor are in the exact order of the acronym.
... which, to reiterate, were enumerated by ja1484 as:
In reply to: Strong first and foremost. Sacrifice any of the other three to get stronger until you're "good enough". Redundant next. Sacrifice any equalization or extension limitations, but NOT strength, to get redundant. Equalized third. No-Extension can be sacrificed to become more equalized, but you should NOT decrease strength or redundancy for more equalization. [ No-Extension] Lastly, limit extension as much as you can, as long as it does not decrease the prior three properties.
I take issue with the apparent assertion that it's all so simple as stated;
I'm also unconvinced with the asserted importance ranking.
Firstly, how does one evaluate Strong? Note that ja1484 qualifies this
(rightly) as "strong enough"; but what then is enough? To me,
this entails knowing the strength of the materials and anchor placements and
knots, all of which I surmise have variances not so easily perceived. (Mistakes
can be seen in the hype about how super-strong new hi-modulus fibres are, w/o
regard for their equally high loss of strength when knotted.) Are you sure that
the bolt (or the rock it's in) is good, is "strong enough"?
And implicit in Redundant is the answer "no" to the above question;
so one takes a precaution against the unknown weakness(es) by providing
a second, independent support.
One could suggest that Equalized is a fickle component of Strong,
in that by equalization one has halved the strong-enough threshold
--unless an anchor fails (and the other now must be strong enough alone)!
No-(/limited-)Extension was envisioned to also assist Strong, by lowering
a possible force surge upon an anchor failure. Fortunately, it appears that
the feared surge is unrealistic.
Absent from SRENE but in ERNEST is "timely", which seems to be on the
minds in discussion--some of the proposed structures mused as needing
an assembly team & special training/certification.
-------
But let's look at where any such compromises of the above qualities for one
another have actually occurred. And what field failures have occurred that
can put weight on any of these enumerated factors? --case histories?
In the simple case of the Sliding-X vs. S-X+limiters, one can suppose that
the limiter knots reduce Strength; but is it still strong enough?
Equalization is reduced in the X-clipping for the sake of redundancy;
but for the SXL structure, one could clip just one strand (and, the other strand
could be made a short, "connecting" strand to form an ELET). Now, many would
balk "then it's not Redundant, if that strand is cut ...", which is true also
of the original S-X. --and is true of the climbing rope, unless twin, in which
case though (unless Beal Joker or ...) one might challenge this coupled with
Strength if two strands are req'd for UIAA conformity.
*kN*, building finger strength through keystrokes
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spikeddem
May 29, 2008, 8:48 PM
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Here's an equalette with a 4 strand powerpoint, and just two knots. Additionally, the knots are standard, tested double fishermans. It eats up a bit of the cordelette, but if one really wanted some more, just buy longer cordelette (the two pictured are each 21 feet long).
Left: The setup before the knots are added (ignore the un-joined ends, I was lazy).
Right: Setup with double fisherman's knots. Clip the bottom four strands with a biner and voila.
The DB fisherman's knots do not join together when the four strands are loaded, because pulling on the four strands pulls them together and apart at the same time.
Now, I just made this up about twenty minutes ago, so it hasn't been tested in any true way, but it passes a good foot-and-hands tug test. I originally sat down to create a trenchelette, but I got side-tracked and made this  . The only way it is better, that I see, than the trenchelette is that it avoids a made-up, un-tested (although probably secure) knot, and is composed of half as many knots. (Edit: I just remembered that it was, in-fact, tested by the pull-tester. However, it hasn't been tested by time  )
What do you think?
Edit 2: Oops, I have no clue what would happen if a strand of the powerpoint was cut. Perhaps death. Someone else that thinks better in 3D could answer this. (No, I'm not testing it experimentally )
(This post was edited by spikeddem on May 29, 2008, 8:56 PM)
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spikeddem
May 30, 2008, 3:58 PM
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Apparently, if just one of the four strands is cut, it behaves no differently. If two of the strands are cut, then the double fisherman's knots join together, and the self-equalization properties are lost. Then again, if two of the strands are cut on the equalette or trenchelette, the anchor fails overall, so I'd consider the loss of self-equalization acceptable.
(Edit: Added "self")
(This post was edited by spikeddem on May 30, 2008, 4:09 PM)
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morse8000
Jul 7, 2008, 1:41 AM
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Trenchdigger,
I have been fooling around with something sort of like what you are talking about. Basically, I take a 10-12 foot section of 7mm or 8mm. On one side, I tie a FROST KNOT. On the other side I tie an OVERHAND KNOT. So the main difference from your diagram is that both tails of the cord are on the side where the FROST KNOT is.
The origin of this idea was trying to make a super-clean, pre-rigged, 2-point anchor for wall climbing. It can be used in 3 different modes.
Mode 1 Frost Knot only at the powerpoint non-extending, but imperfect equalization. In this mode you are eliminating the double fishermans knot that you see in most cordalettes. But to achieve okay equalization you have to take up excess slack by making extra turns in the cord around one of the biners in the anchor.
Mode 2 Frost Knot on one anchor loops on the other anchor to make a redundant sliding x with limited extension on one side only.
Mode 3 Frost Knot on one anchor overhand knot on the other anchor. good equalization, limited extension on each anchor.
I don't really use the set-up that much, though. Mostly, I use the rope with clove hitches whenever possible and 60/120 cm slings or cordalette/webolette when more equalization is required.
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ja1484
Jul 9, 2008, 10:54 PM
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Hell of a chunk o bait you got there kN.
I basically agree with John Long's assertion in the second anchors volume that trying to determine absolutes (even in the form of definitions) in climbing safety systems is a fool's errand.
I'll simplify things even more, and feel free to analyze this however you'd like:
Build it so it won't fail.
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LamontagnedeGatineau
Nov 20, 2008, 6:14 PM
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OK, I have been trying to remain awake while reading through all this "equalette" stuff. Quite frankly, all this is WAY to complex for my simple mind. However, I do see three major flaws in all the complex cordelette systems being discussed:
1. If you use this system, BRING A KNIFE! All these knots will have to be untied once climbers leave a hanging belay. Anybody who's had to untie a double fisheman's knot after hanging and bouncing around on it for an hour or so knows that this can be time consuming to do at best, and downright impossible at most other times. This is not an option on multipitch climbs where efficiency and speed are important, nor is it much fun for climbers who mainly want to ENJOY their climb, while remaining reasonably safe.
2. I think the Equalization/extension idea is bunk on set-ups which go down by 2 feet long or so. I would say that Equalization beats Extension worries hands down and here is why: I expect a good jump on a belay will provoke about the same shock load as a 2 foot slide on a slider X setup (someone else can calculate that for me). If one of the anchors can't handle even that kind of load, the redundancy principle is compromised from the start anyway. Furthermore, at a 20 degree angle on an equalized anchor, the load si basically split 50%/50% BUT, in all cases where the load is not PERFECTLY lined up between the anchor, the knot and the shock-load, the initial shock of a non sliding X set-up will go 100% on one of the anchors: BAD KARMA THERE MAN.
3. Knots on cordelettes will reduce their strength by up to 50%. Why weaken the system in the first place?
In conclusion: I remain convinced that the good ol' sliding X solution, particularly with sown webbing is, by far, the simplest, quickest, cleanest and safest approach to setting-up multi-point belays.
(This post was edited by LamontagnedeGatineau on Nov 20, 2008, 7:20 PM)
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rgold
Nov 21, 2008, 8:02 AM
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In reply to: ...the climbing community needs to get over extension. The tests by Jim Ewing at Sterling have basically shown it to be a non-issue in terms of load multiplication as long as the climbing rope is in the system.
It seems to be my fate to periodically reissue the same remarks that the conclusion about extension being a non-issue is premature. (Oh well, it took several years before folks started to believe that tied cordalettes might not equalize...)
Jim's tests were done in such a way that the minimal effect of extension was (at least in retrospect) a foregone conclusion---there was too much rope in the system relative to the extension allowed for their to be much effect; the change in fall factor due to extension was small.
I'm going to go out on a limb, if for no other reason than to at least mitigate the complacency that these tests seem to be inspiring, and suggest that if extensions are tested in realistic scenarios, in which the rope connecting the weight to the anchor is not very long compared to the extension, then the result will be that extension can be a serious condition leading to very high anchor loads.
In the meantime, people tying in to potentially extending systems should, first, absolutely insist that their load-absorbing connection to the anchor be the climbing rope and not some low-stretch tether, and second, should endeavor to make their rope tie-in as long as is feasible given the constraints of their stance.
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