'Soft Eye' in climbing anchor construction

[agent_smith]

I gave a background of how this interest arose but should not have, ... [just interested] in the knot expertise on this forum

Some knot experts on this forum may find this remark possibly derogatory.

Roo for example is a fine fellow and extremely knowledgeable about knots. If you stop and think about this for a moment - and look at the response Roo gave - you can see that he needs to understand your context. He gave you the example of a pile hitch - and this is indeed a simple structure. However, it is not relevant to your needs - it is in the wrong context.

You will find most of the knotting experts on this forum will need some context so they can properly analyze the question and then provide a considered response.

I'm not interested in climbing advice

A smart man once told me that the day you die is the day you stop learning.

Being ignorant is not so much a shame, as being unwilling to learn.
             Benjamin Franklin

You question concerning #1080 Bowline on the Bight has already been answered in depth.

What you need is a knot that will isolate each leg of the belay anchor system. The idea being that if any single anchor point fails, it will not trigger a catastrophic failure of the entire anchor system. Knots operate best when the material is rope (not webbing - apart from the 'tape knot'  #1412). Although it is possible to tie common knots using webbing, the performance of such knots will be unpredictable. Very little test data is available on knots that are intended for rope which are instead tied in webbing. Dan Lehman may have something to say about this matter.

The isolating knot must create a 'fixed eye'. This eye will serve as the focal point of the anchor system - and this is where everyone will attach to.
It also permits rescues to be performed (keeping in mind that whenever you rig a belay anchor system - you should always rig for rescue).

With your insistence on using webbing/tape - this is of course being valid in situations where you have no alternative (ie - you have no accessory cord) - reasons might be; you forgot to carry cord, or you dropped it, or you lost it. The ability to improvise is important in recreational lead climbing. But that is a caveat...in that cord should be your first choice - and you only resort to improvising if faced with no other alternative. Given the low cost of accessory cord, its low weight, ability to be carried in compact form, and its ability to absorb energy, makes it hard to ignore as a first choice material for building belay anchor systems.

For me personally, another compelling reason to use cord is that it w i d e n s the scope of possible knots and hitches that can be tied - in other words, you have more choices available. With webbing/tape, it actually narrows your choices.

Dan Lehman may want to weigh in on this discussion - I believe he has climbing experience so he will understand the context very well. Again - context is crucial to providing advice that is relevant.

It is possible that you may dislike many of my comments I have tendered...


Mark G

[roo]

There will be no bollards or posts on the cliff -

There are carabiners.  The OP's picture shows his loop tied into a carbiner.  A Pile Hitch can replace that loop that he shows in his first picture.

I would like to see the picture a little bigger so I don't have to squint.

[roo]

I'm was looking for a 2 stranded loop knot of which the cut/rip/tear of a single loop does not affect the integrity of the knot.

The interest was purely from a theoretical point of view, and I was just interested in knots.

There are some, but I wonder if even in your theoretical search, there are some-real world limitations or application parameters that may narrow the search.

[Jos]

A close-up of the setup as proposed by the german national climbing association (DAV) below. They intend to use it only in situations where there are 2 bomber bolts.

one limitation would be no access to tail ends. a preference would be ease of removing the knot afterwards.

[knotsaver]

Hi all!
(Here comes knotsaver      )

First of all, I agree with agent_smith about the importance of the context,
second, I haven't climbing experience, so I can't provide climbing advice...

(IIRC)
- What about a 2 strands standard bowline ( or better ABoK 1034 1/2 for ring loading?) tied with a bight?
you could use the bight as a third eye, or, if you don't like it, you could "back-flip" the bight (you can choose the side and the position).

- What about ABoK #1085? (but here the back-flipped bight could have the same problem of the collar in the BoaB (ABoK#1080), as noticed above)

I'm only in doubt about the security of the knots if only a single SPart-strand is loaded...

hope this helps,

ciao,
s.

[Jos]

Great suggestion!
Just tried a doubled 1010 and 1034 1/2 in a piece of rope (4 mm kernmantle) and they are definitively improvements on the 1080 with respect to additional strength after removal of 1 loop.
I tried by tying the 1080, doubled 1010 and doubled 1034 1/2 with the bight, or looped tail (what's the proper term for that?) around the ongoing eye leg. In all of them I have an overhand in one of the two loops (for the 1080 I tried both loops). I then put 2 biners through the loops, attach one to the ceiling and stand in the other (using a short sling) and hop a bit (80kg). Then I remove the overhand knot that is in one of the two knots and stand in it again. 1080 fails, doubled 1010 held me the first time but not the two times after that, doubled 1034 1/2 held three times but did slip a bit or quite a bit.

Like you guessed, the 1085 has the same issue as the 1080.

So I 'tested' these without the Spart-strand loaded at all, and I note your worry regarding the security of the knot. So how about the doubled version of the eskimo variant, that should be set up even better for ring loading without loading on the Spart-strand, right?
I'll see what that does.
Thanks!

[agent_smith]

Like you guessed, the 1085 has the same issue as the 1080.

Incorrect. It does not suffer from the 'same issue'.

The double F8 eye knot (#1085) has sufficient internal friction within the core to survive the loss of a SPart limb/leg or a loss a rope segment within the core and not catastrophically fail.

Be that as it may, none of these eye knots were specifically intended for flat webbing/tape. The vast majority of knots were intended to be tied in rope - which has a round cross-section. One can look through the Ashley Book of Knots or any other half decent knot books and you will find the range of knots intended for flat webbing/tape to be quite limited.

The behaviour of knots tied in flat webbing/tape will be unpredictable - and it may be difficult to track down reliable test reports that specifically address knots tied in webbing/tape.

Dan Lehman may weigh in with his opinion on this matter.

...

The other inescapable fact is that all anchor systems - including belay anchors built on multi-pitch lead climbing routes - should be configured so that in the event of a loss of a single limb/leg, there will not be a shock load induced to the other surviving limbs/legs of the anchor system. If for example in a 2 point anchor system - if 1 point fails - you dont want a shock load event to the surviving anchor point. This is particularly important if the anchor points are 'removable protection devices' (such as wired nuts or cams). This same principle applies to bolts - which are not immune to failure (you can never assume that an existing 'in-situ' bolt is 100% secure...because anything installed by humans on a cliff face is subject to failure).
Knots used in anchor systems are applied within a specific context - one has to have a deep understanding of the forces involves and the consequences of single component failure. So when selecting a particular knot - you have to have underpinning knowledge and experience of how it will perform in a dynamic loading event within the context of lead climbing.

MG

[Dan_Lehman]

A close-up of the setup as proposed by the german national climbing association (DAV) below. They intend to use it only in situations where there are 2 bomber bolts.

one limitation would be no access to tail ends. a preference would be ease of removing the knot afterwards.

I'm getting bleary-eyed looking at the various diagrams
and wondering How does this matter, really? --especially
the concerns about one eye of a twin-eye knot failing
(when nOne expresses concerns about one eye of the
usual tie-in knot failing --which would be worse!).

In this particular diagram --which differs from some shown
in above-cited info--, one might ask Why not tie a clove hitch
to the low 'biner, and have the sling-ends similarly
tied to anchor 'biners if not just clipped in? (one would
be fit to length, the other taking up whatever slack).

As for "only both anchors being bomber", the entire exercise
of backing-up suggests that this premise isn't assured:
*bomber* placements don't fail.

As for cord vice webbing, in the given short lengths,
how much could that matter (esp. given that climbing
rope is in the system for most of the tension)?  (There
is some DMM testing of various slings in which they find
some benefits in terms of peak-force amelioration via
knots compressing.  Interestingly, though, they believed
that while their nylon webbing was more elastic it was
sometimes the slippage in the HMPE webbing that gave
a lesser peak force (!).  YMMV.)


--dl*
====

(... whose latest use of knotty/ropey knowledge was
put to the test in making a support for a camera lens
that got broken at its mount --wiggle isn't good. !
Tricky to work in cordage in fine areas and not gum
up focus (AF/manual) ring, et cetera.
used : broad rubberband (for friction purchase/base),
some version of mason line --temporarily.  Longer term
might find:
tighter rubberband,
PP bailing twine fibres piece for tightly set (over rubberband)
harness part, and maybe also for separate(?) bridle connector,
and mason line for tensioning *guy line*/lanyard part (stoppered
at strap mount).)

[knotsaver]

I tried by tying ... doubled 1010 ... with the bight ... around the ongoing eye leg.

Hi Jos,
are you referring to this knot?
http://igkt.net/sm/index.php?topic=5385.msg36532#msg36532

this is a nice knot!

ciao,
s.

[Jos]

Hi Jos,
are you referring to this knot?
http://igkt.net/sm/index.php?topic=5385.msg36532#msg36532

this is a nice knot!

Yes! I like it a lot, and the next even better.

I tried the doubled eskimo bowline with the bight around the leg and it holds perfectly when ring-loaded with either loop 'cut'. The knot shape remains more the same upon loading when compared to the doubled 1010.

[Jos]

I'm getting bleary-eyed looking at the various diagrams
and wondering How does this matter, really? --especially
the concerns about one eye of a twin-eye knot failing
(when nOne expresses concerns about one eye of the
usual tie-in knot failing --which would be worse!).

I'd think that with most anchors there is the potential for continuous rubbing of a single point on the rocks. While the tie-in loop is 'mobile' (or even doubled if you're climbing on twin or double rope). Of course the first should not happen, but that's where redundancy can save the situation.

In this particular diagram --which differs from some shown
in above-cited info--, one might ask Why not tie a clove hitch[/i]
to the low 'biner, and have the sling-ends similarly
tied to anchor 'biners if not just clipped in?[/i] (one would
be fit to length, the other taking up whatever slack).

The eye of the loop knot is used as the central point, not the biner.

Interestingly, though, they believed
that while their nylon webbing was more elastic it was
sometimes the slippage in the HMPE webbing that gave
a lesser peak force (!).  YMMV.)

Definitely interesting, do you happen to have a reference for that?

[Dan_Lehman]

Interestingly, though, they believed
that while their nylon webbing was more elastic it was
sometimes the slippage in the HMPE webbing that gave
a lesser peak force (!).  YMMV.)

Definitely interesting, do you happen to have a reference for that?

It's in Reply#9, http://dmmclimbing.com/knowledge/slings-at-anchors/.

Incidentally, there are ways to reduce some of the
extension seen in some "equalizing" anchor arrangements;
e.g., see https://postimg.org/image/aw7c3eoln/
and
https://postimg.org/image/s1jg2ibin/
(while it lasts : some assoc'd images now get "Error 404", alas).

 

[Jos]

Thanks, should have remembered that point when I watched the movie last time.
It does lead me to a question I find interesting but I'll start a separate thread regarding it.

[Moss]

Agent Smith,

The last link supporting the energy absorbing characteristics of accessory cord vs webbing seems to be broken (the bethandevans.com one).  Do you have any other sources? 

Another advantage of cord over webbing is that the wider surface of the webbing will be acting further from the spine of the carabiner, enabling easier (though not at all easy) tearing of the sling and bending of the carabiner.

What type of knot do you use to create your cord slings?

I admire your Purcell rig.  Here is a three point anchor I have devised, also with energy absorption in mind (though it has come to my attention that I should use thicker cord for this than 7mm and the included angle is too wide).
http://www.mountainproject.com/v/112032742

[KC]

Love the universal language of the cartoons; taking mental art notes!
.
This isn't my game; so been holding back.
But my most immediate answer to self, remains:

.
i think this doesn't so much deform Standing Part tensions(as Bowline/Over Hand/ HH based lacings etc.);
but rather friction hitch type grab S_Part,
in several places, for most 'pure inline' mantra type architecture to S_Part loading.
.
Also, i've always thought it imparts some dynamic round/rope characteristics to the static flat/web device.
In round, i think the amount of extend-ability, compressions on self, slips etc.
and the amount of internal rope work/frictions that it takes rope device to perform ,
consumes/ballasts/neutralizes some of the dynamic loadings.
In this size web and construction (not 4" wide flat web),
i think we can make the flat support device to a round device on end;
imparting some round device qualities w/o deforming it's flatness.
.
i do see later that also wanted 1 leg to hold and this can be slippery,
but the basic construction still has some merit i believe.
Also, if we can make termination strongest part of line thru shared loading,
break at loop logically starts getting ruled out, except as wear point.
Pile Hitch gives more legs to connection than many other.
.
Dynamics more of a concern i'd think if the only flexible device in system;
with anchor extensions to web, carabiner, then dynamic line/link,
rope shock absorption would shave peeks off of dynamic hits to rest of system i'd think.
.
i think because slip design doesn't immediately seat to krab shows :
A> 2 legs of support/1 either side of krab, without bending S_Part(more long splice-ish)
B> this takes work to seat, that uses up some dynamic force to do so.
.
Similarly, in Pile Hitch context, i'd always prefer Dbl. Round Turn around S_Part before final anchor of bight on host krab/post
6 legs to connection, upgrade beyond slip of single Turn on S_Part, and final bight more likely to aid support now,
rather than primarily deform S_Part; can flow more with S_Part.
.
Once again i think this too works from theory of not deforming S_Part from pure_inline
Not using single/simple Turn that deforms S_Part only, doesn't give support;
upgraded to Round Turn or more, can now encompass, compress on line
will join/grip S_Part more than deform
so seems to be able to give extra legs of support for stronger connection
especially when witnessed when hitch doesn't 'scrunch' down to connection/hitch floats.
http://igkt.net/sm/index.php?topic=5630.0
http://igkt.net/sm/index.php?topic=5723.0
Or something like that!