I am thinking that the English word 'slip' or 'slippage' is being used in a way that belies what is actually taking place.
...
I am unclear whether Mobius and Dan have actually taken notice of the test results I had posted?
I measured a 20% reduction in the overall tail length at a load milestone of 2.0kN.
It is important to note that this 20% reduction did not occur suddenly or within a very short time interval.
The shrinkage of the tails occurred progressively (ie gradually) in direct proportion to increasing load.
The English word 'slip' or 'slippage' is not an appropriate descriptor in my opinion.
I would also comment that in all the testing I have done, I have never seen tails increase in length as load is applied.
I have however, always seen tails decrease in length as load is increased.
I have also observed that as load increases, the knot core compresses.
But this is going silly : we know what "slippage" means,
but there can be the discrimination between you & Mobius
of slippage forced by transformation of the knot to some
more stretched or compressed form
and what might come at certain forces continuously,
the knot failing to hold, then --as is shown impressively
in the French, Beal video of "pure Dyneema" braided rope
just pulling through even a
double grapevine/trip.fish.(until it did break)!!
IMO, what Mobius sees is, yes, some "silppage", but it's
what comes in the knot opening wider (the particular one
pulling in some tail from choking strand to accommodate)
on increased load --upon which it holds, but then the load
is raised and ... <repeat>.
There is also the sort of "ratcheting" slippage that was
reported by both Tom Moyer and some other testers of
solid nylon & solid HMPE webbing in the
water knotwhich came
at light, cyclical loading, where on the
relaxing of load there was this peculiar absorption of some
SPart but not the
"exterior" [my term] tail, and so by
cyclic increments, it got pulled through --and slowly (to the
puzzlement of those who recall needing tools to untie such
knots after usage!).
"I have never seen tails get longer" :: well DUH!! But you
have seen --or sh/could have done-- SParts lengthen.
.:. So I take A_S's point in resisting "slippage" as not seeing
the sort of it-just-keeps-flowing-out sort of thing one would
worry much about, but technically it is some bit of slippage
at a point (nipping the tail) in the knot in accommodating
forces that does happen. (And one might wonder if it could
happen in the going-one-direction-only way that was seen
for webbing in that "ratcheting" --something to be worried
about for repeated loadings, e.g. !)
AND we can note that Mobius is seeing things at relative
forces WAY WAY beyond expected usage --costing him
materials, and me gasps of exasperation (air pollution!).
AND TO THIS POINT --of EDK tail slipping, and choking tail i.p.--,
I tried amending this knot by tucking the choking tail around
back under its SPart's initial turn into the knot. This tucking
works okay with thin+thick, but is problematic (in being
rightly oriented and not botching dressing) in like-diameter
ends (meaning "do NOT do it"!). Done rightly, the lock
looks good --that tail can't **slip** but only stretch a bit,
the nip coming w/high load and all.
SOOOO, that particular detail might be something to see
about incorporating into a *new knot*, avoiding the issues
of dubious dressing/positioning/stability.
(A stopper knot in the choking tail works similarly,
at the cost of this added knot-bulk.)
And please stop grousing about "EDK" :: we have enough
confusion in this world --growing in leaps & Trumps, now,
courtesy of shoot quickly and broadly Net communications--
w/o furthering that :: best info is that the name arose from
dubious Yankee observers of Euro practice (a practice that
yes we hope was safe); with the knot's broad acceptance,
though still not wholly bereft of doubters, it becomes kind
of an inside joke. --less funny when avoiding the safer
variety (overhand) a worse one (fig.8 ) is employed;
though that one, too, has been used safely much,
just sadly not as much. "EDK-8" is something generally
understood when uttered; "offset fig.8" is the prettier term,
which we'll hope finds traction, as "offset" then gains legs
to go where needed.
Positive tests in this setting are less helpful than ones
that reveal problems. And my urging Mobius's testing
of the material AND dressing that got such amazingly
quick failure w/the commonly used & working
EDKis wanted to see if the backed-up version can stand up
to that --yeah, a mere single positive, but one that
should impress us (if it works) into seeing how badly
tied things can be and yet be saved.
We won't so much do this all 'round,
and can recommend something *cleaner* and so on,
but for an ace-up-the-sleeve (or wildcard!), knowing
a clumsy but stupid-tired-proof solution is a lot.
(And SAR team might be working in deliberate ways
amenable to doing some careful things; climbers in
threat of weather after overreaching their abilities
can make mistakes.)
--dl*
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