Author Topic: Bowline Cinch  (Read 3426 times)

Dan_Lehman

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Re: Bowline Cinch
« Reply #15 on: March 07, 2011, 01:17:09 AM »
I haven't tried the Quick 8 you mentioned yet.

Which is the "Slippery 8" Roo linked to but with the tail reeved
through the 8 in the opposite direction; it could be used as you
have done with a YoBowl, and I think is better for that (now this
would be with a Fig.8 eyeknot not mere Fig.8, to be reeved into
by the adjustable-length tail).

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I'm kind of pressed for time since every MRA team in CA is getting together tomorrow ... .

Hey, let us know of any developments in thinking on knots
and of cordage in use.  Though, as you say, SAR tends to be
conservative.  --but some things such as Sterling's "HTP" super
static main ropes (polyester w/little stretch), and infiltration of
HMPE (Dyneema/Spectra) into things (also Technora, esp. in
sheaths and firefighter use) such as slings & river rescue rope,
can require innovation to the new materials.

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Is there a better way to dress that figure 8 on a bight?

Fig.8s get dressed in various ways.  I consider what you show
to be the "perfect form" in "weak form", based on some hints of
strength given long ago, which I'm not so sure of, really.  Dressed
the same but loading the other end would be the "strong form",
in my jargon.  Dave Merchant's Life on a Line recommends a
rather awkward symmetric dressing of the Fig.8 and says that
it can be 10% stronger, and easier to untie.

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We use interlocking Bowline with long tails to attach our main and belay lines to the stretcher.
They are much better for ring loading than a figure 8 on a bight.


No:  the bowline will fail on ring-loading --the tail pulls out
(this is the common bowline w/o any securing extension)!
You can't be worse than that.  Maybe a Fig.8 eyeknot (or
offset end-2-end knot) will flype ("roll") on such loading,
but that's not a guarantee and not so sure as with the bowline's
slipping (it can hold in some cases, yes).  Tom Moyer's testing
of offset Fig.8 & water knots did have some Fig.8s going to
rupture, afterall.)

I think that you are referring to some different sort of loading
on the bowline; by "ring-loading", I mean the pulling the eye
apart and essentially treating the knot qua end-2-end joint
--which puts the common bowline as a wrong-formed Lapp
bend
(and the "left-handed bowline" as a (correct) Lapp bend ).


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With rescue we also have to face the challenge of
everyone on every team being able to recognize and check you knots.
This makes it difficult to introduce new knots.
KISS principle definitely applies in the cold night rescue.

Is there any way innovations can be made?  Is there some
governing body (or might there be, or convened collection
of SAR organizations) who might help vet innovations,
including knots?  --for which as you imply there might be
some steep hurtle of first establishing the need for!  (If all
is fine w/current knots set --and how bad can it be?--, why
bother with anything else?  (IIRC, Tom Moyer made some
contact --he, also in an SAR organization-- with a guide group
who then recommended the offset Fig.8 end-2-end joint,
to advise them of what his testing shows about its vulnerability
to flype; they were not receptive, at the time, to his advice.)

It's quite a tricky issue, as you note.  But there should be
some broader recognition & understanding of knots beyond
the KISS set used, for that might be necessary in order to
deal with what is found in the resuce tied by others --the
victims, i.e..  (There was a rumor that someone hooked into
a climber's tie-in bowline and learned --or at least showed--
the dangers of ring-loading with tragedy.)

So, one might stipulate a limited set, but teach a broader
set for knots-knowledge.

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This is very important since the knots never break.
Failure occurs from mistakes or bad edge protection for the rope.

Here I urge circumspection; consider my note above about
conveying any new directions in cordage use.  New cordage
can behave quite differently from traditional cordage in knots.
I try to remind myself et al. of not thinking in terms of *knots*
but of *knotted material* when evaluating knots.  To see
a double bowline just slide down its collapsing eye when knotted
in bare HMPE is an eye opener.  I don't see this rope used in SAR
knotting, but it can slip in in core material, and might have some
unexpected behaviors there.  E.g., some canyoneering main ropes
include it; I'm not sure how much testing has been done to see
its effects on any falls --the very low elongation (4% or so at
rupture force, so maybe 1.5% on possible in-use loadings).
You are probably aware that some cordage makers recommend
a double grapevine (writing "triple fish.") for joining ends
of HMPE-cored cord.  (One of Moyer's old misc. test results was
of a grapevine (non-dbl) breaking its nylon core and seeing the
Technora core pull free like snake from its skin!)

The infamous "cordelette" was introduced into rockclimbing with
celebrity flair and only recently tested by Sterling in help with
John Long's revised Climbing Anchors, 2nd ed., and found to
be wanting in terms of any equalization, esp. tied in HMPE.


--dl*
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« Last Edit: March 13, 2011, 05:28:58 AM by Dan_Lehman »