One can see the water of interest here thrown on this topic running off in many directions.
To be effective in getting substantial results of analysis & testing, there needs to be some
channeling of efforts to fewer directions.
As a start, we can try to find sources and compile a list; then, those referenced reports
can be critiqued, from which effort some vision of what improved testing/reporting will
look like can be gained, with the extant testing standing as illustrative example of its
absence.
Another interesting report is ... from the fatherland (Australia) - 'The Bushwalkers Wilderness Rescue Squad'
More recent than this is the updated
Life on a Line e-book ($15 US download fee),
coming from the, ah, "fatherland" Down Under. It makes some surprising, unusual assertions
of testing results, which suggest that traditional testing is far from adequate to practical needs.
(It also contains some obvious nonsense, raising questions itself!)
... whether Dan Lehman and/or IGKT require a certified testing facility ...
I'm not. Good, repeatable methods are important; whether someone has (had the funding ...)
jumped through some hoops required for certification is less important (and conceivably could
even be seen as limiting--binding to methods of questionable relevance to practice).
Like the old joke about a person looking around a street lit sidewalk instead of back
in the alley where he likely lost whatever "because the light is better here", testing using
traditional slow-pull devices might be done because that's what's available (and given
in prescribed procedures) but maybe not all so relevant.
In short, methods need to be analyzed and given a rationale, citing relevance and limitations.
And there might be some clever ways of maximizing the use of materials & equipment.
E.g., suppose one used as a test bridle a future test specimen with loopknots in each
end, and this was wrapped to a bollard and the two eyes attached to a shackle that
connected to another test specimen. The single exercise of the device would then both
pretension this bridle's knots as well as result in the break of whatever else; after some
use qua bridles, the loopknot-ended material itself could come under test.
Determine - with a degree of precision - the location of the failure point of each particular knot
(this could be achieved by video or by a series of still photos)
It's asserted by the spaghetti testers that high-speed cameras can't do this (well enough)
--they might have been specifically focused on monofilament line, though (not sure).
By another tester (Kathrine Milne university/graduate? testing of yacht rope), it was asserted
that there was an upper limit on camera rate beyond which images were too blurred; that
they
helped but weren't so clear as we'd like.
So, I think that one means to do this would be to sew marker threads through rope at every
centimeter (or half-centimeter), and to photograph the knot as it tightens. (Early (lower tension, i.e.)
images won't be needed re break point but might be helpful to assess material movement
under increasing tension. Even with uncertainty about the
exact point of initial rupture,
this sort of information I think will mark a big step towards getting that knowledge (and we
might come to believe that further exactness is overly pedantic rather than edifying).
method of tying each knot must be in accordance with rules established by authoritative (executive?) IGKT members
We should step back and first get a basis for testing--what is it that we want to know & why?
One might point out that pulling new rope, esp. w/o pre-loading cycles, to failure doesn't model
much of practical behavior. Maybe it's more relevant to climbing, where tie-in is manually set
and unloaded until a fall, and less so to other applications where loading is continual and maybe
some abnormal increase might be seen (or one might be concerned about the effects of a history
of loading on ultimate strength).
use braided rope for the testing (ie 'kernmantel' rope)
This goes back to an assessment of purposes. If you want to know how such rope behaves,
then test
that rope. If you're more interested in knot mechanics in general, you'd better broaden
your knotted media. (Btw, Google favors spelling 'kernmantle' almost 3:1, and English's difference
between "mantle" and "mantel" makes sense of the former; I'm trying to learn of German spelling.)
bends should be tested as follows:
#test by forming a 'rope sling' - 2 knots would exist - one on each side & subject to simultaneous loading
#the sling would be subjected to a spreading force in a suitable 'ram'
#the pin/bollard diameter on the ram would need to be determined (eg 10mm to simulate a carabiner)
Well, a critique might show up a need for different testing--AS WELL--, and comparing results.
I suggested the
knots-in-both-sides-of-sling/loop as a way to redress breaks that seemed to come
at the pins and not the knot, allegedly by friction from material fed out from the compressed knot;
one might fear that although knots on both sides allows feed on both sides, that the timing would
not match so well, and there'd be some effect of that imbalance. But one would end up with a surviving knot.
If it's possible to test w/o forming a sling/loop, one might like to have still two knots in the specimen
so as to have a survivor (at presumed near-rupture load) for analysis--but this too raises questions
about effects of knots in proximity.
end line knots ... should be tested with the loop portion of the knot attached to a pin/bollard simulating a carabiner
#the opposite (loose) end of the rope should be wrapped and clamped around a large diameter bollard (ie a 'tensionless hitch')
Here I see less of a reason for not using two knots. And if one is insisting on using a 'biner, it shows an
interest beyond the knot, I'd say.
the rate of increase of force in the static load testing machine (eg ram) should be determined and agreed upon by IGKT
I think that a slow rate tends towards lower break points possibly because fatigue can work,
and fast rates high values. But
LoaL asserts that some knots fare poorly under "shock loads",
because of heat from friction on knot compression!? And some folks assert that "shock load" is a myth!
yes, I know that ABoK has some 3600 knots illustrations
I don't; have you bothered to count? --might be that fewer are of knots, and more of other things.
In any case, somewhere in this forums archives is my rant against the boneheaded assertions
that the book has nearly 4,000 knots--which, btw,
LoaL echoes (the boneheaded...), alas.
If you e.g. go count loopknots, I think you come to around 150, with similar counts for other major
classes. To that I can say that there are many knots not presented by Ashley or anyonElse.
(That so-called "bollard loop" discussed in
Knotting Matters a couple years back is one
seldom seen, though apparently Samson Ropes(?) knew about it enough to photograph it.)
I found an old website where Dan Lehman illustrates a F8 loop in its 'strong form' http://www.iland.net/~jbritton/KnotPhotoContributions.html.
I know that many VR teams and even defence force instructors insist that their trainees tie the F8 loop in the 'strong form'.
Egads! This points to a lack of rigor in forming rationales! FYI, *my* basis for the name comes from
Rob Chisnall (et al.?) and the ca. 1985
Ontario Rock Climbing Assoc. Safety Manual and its
assertion of this being stronger than if its ends were loaded. Testing by Lyon Equipment of seemingly
just such "perfect" forms--my name, as the knot's symmetric--suggests otherwise; but one can question
now the setting of the knot--I'd guess that setting by loading the END is what forms the shape that makes
the best bending of the SPart re strength; and on this
conjecture I devised the "Lehman8", also at
that site, which is hoped to have like strength but w/easier untying.
Meanwhile,
LoaL contends that this form will result in a permanent knot, and they give a particular
and less easily dressed/set symmetric form in which they claim about a "10%" strength difference.
(And as usual there's the ambiguity of what "X%" means--likely a diff. of percentage POINTS, which
is an immediate, easily determined value (e.g., 66% is 10% more than 60%; 70% is 10%-pt.s greater).)
AND, in seeming direct response to the new book, OnRope1's site has Mythbuster #(?) asserting that
it's all bunk, and loading either end gets the same result--but it's clear by their image of the knot,
which is the Fig.8 in idiotic
flat form (simplistic tracing of an 8 by 2nd rope), that they (or just Bruce)
aren't dealing with the same entity, except in name.
And any of these references might be seized by someone as Gospel beyond question.
--truly UNscientific, and quite unwise.
I would envisage that any knot testing would attempt to prove by experiment the merit of the 'strong form'
F8 loop Vs an F8 loop that has no symmetry (ie loosely & sloppily tied with no attempt to 'dress' the knot).
I would challenge you to prove that "sloppily tied" gets one the same entity time after time
such that one can make such assertions! "Correctly tied" stands in need of just such a specification
of what it is, but once agreed it should give like results across different users; but that doesn't hold
for "not correctly tied" and derivatives.
--dl*
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