Author Topic: Modified Water Bowline  (Read 10853 times)

Dan_Lehman

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Re: Modified Water Bowline
« Reply #15 on: January 24, 2014, 04:19:20 PM »
^^ I refer you to this research.  I have a copy of it on my web site here http://l-36.com/read_pdf.php?file=rope/8_strength.pdf&title=Knot+Strength:+The+Study+of+Knot+Performance

It is on the web other places as well.
Yes, alas, so it is.
Calling it "research" greatly distorts its real nature:
conjecture, based on some old utterances that themselves
are often shy of being "research".  It's my hope that we
will advance beyond this primitive state.

And the myth that Xarax copies (for what purpose?!)
is one that finds traction in one's reasoning, but fails
upon focused testing & examination, as I noted.
Breaks in laid rope will come per strand, in slow-loading,
and one can see where the broken strand lay --inner
or outer--, and the myth can be dispensed with in
favor of a theory that explains the observations.
(It was quite some audacity of Dick Chisholm to
advance this essay on knots without having done
or much even sought knot testing!!  His conjecture
about the bowline was ridiculously off: that point
of first contact is so slight, it couldn't be an issue!)

Knot strength is a poorly explored issue.  Even where
one might find test data, there is usually no indication
of what the geometry of the knot was --and the all so
common case of fig.8 eyeknots in which of the
twin ends one is left to guess which one was loaded,
as though that's some sort of irrelevant detail!  (As
I remarked about one of the sets of broken specimens
from EStar that I could see, one such knot, at least,
showed a form that strongly implies how it was loaded
(and this would be that shown by Chisholm's Fig.3;
the S.Parts reach to the far ends, and so when loaded
will compress the "nub" into a blob whose long axis
seems to be at about a 45deg angle to the line;
I'd say that most folks load it the other way, and
the outer turns thus reveal this in being untensioned,
and the nub stays more or less aligned w/the line)
;
I wasn't able to see this in some others, and I think
that there was variety in this.  Naturally, one might
expect variety in results (though they could happen
to be the same, even so, just as between (more)
distinct knots).


--dl*
====
« Last Edit: January 24, 2014, 04:24:18 PM by Dan_Lehman »

xarax

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Re: Modified Water Bowline
« Reply #16 on: January 24, 2014, 04:57:29 PM »
...the myth that Xarax copies (for what purpose?!)

  Allen cited the article, in a reply to me, about something that I had already mentioned, and which was related to this paragraph. However, the main purpose was to show the schematic / simplistic (sic) nature of this explanation / conjecture - but it seems you did nt get this. The physics involved in a breakage are very complex, so, neither this description can be complete, nor the one offered by your not-even-wrong theory... I mumbled something about "heat", which can "flow", like a liquid, through the overloaded fibres from the area it was generated in the first place to another, quite distant one, and melt some less loaded fibres there. Anyway, I believe that ANY too-simple model is condemned to remain detached from the complex reality of the rope-breaking phenomenon.
« Last Edit: January 24, 2014, 04:58:05 PM by xarax »
This is not a knot.