I have no explanation for the difference in strengths of the line/twine
(sorry for the naming inconsistency, I should have caught that).
The twine was from several different but identical rolls.
I kept the average twine strength from each set of tests local to that set of tests.
The cumulative average for both sets of tests which would have been 37.38kg.
For the bend tests, the maximum load at failure was 38.0 kg.
The maximum load at failure for the loop tests was 42.9 kg.
Okay, this is interesting, and a little troubling --one could
as much wonder at the
scale's consistency, perhaps?!
Btw, following up on kd8eeh's question (p.2 above?), could you
describe in detail how the specimens are configured, to what
on the scale end (and is this a spring scale of some sort?),
and to what anchorage & how --those ends aren't breaking,
are they?
FYI, when I got a chance for some rope-maker testing of
eye knots, I had each specimen terminated by the same
knot, so I'd have one broken and the other presumably
quite near to rupture --loaded geometry to scrutinize for
gaining some understanding as to what.../why... . And
I sewed (tucked might be better term!) into the rope
in a couple places some bright thread as markers,
so to assess what changes came during testing --how
much rope was pulled out of eye legs, SPart, in knot
compression (and any slippage); where the break point
was (lotta guesswork here, but markers help).
NO, I don't expect that in such small material this would
be possible --maybe not all so revealing. In 5mm and larger,
it has more viability.
If indeed there were the stated (but see above) continuity,
we should remark at the variation seen for the end-2-end
knots contrasted with the greater similarity (and the
higher values) of the eye knots!?
I agree. This is one of the things that struck me as well. Given these results,
it would seem that the strongest means of bending two lines together
should be with two end-of-line loops.
side note re underscored phrase :
this is how "to bend"
was used historically (pre-Ashley's influence), as noted by Day;
given Ashley's urged sense, "together" would be redundant.
But one spoke also of, e.g., "bending the sheet to the clew"
or "... to the anchor". And in light of this, why I've abandoned
Ashley's cause of (re-)defining "a bend" as an end-2-end knot,
and my use of this latter term, for now.
(Am I
bent out of shape over this?)
Now, to the point about what should be the strongest
means of joining lines : well, tying eye-2-eye is viable,
and more assuredly workable over differently sized/natured
lines. But an interesting point to recall on this is one
fellow's informal, break-by-pulling-with-truck testing
of small lines (PP & nylon solid braid? --don't have that
info in hand) was that in all cases
fig.8 eyeknotsterminated each specimen for anchorage of his tests
of two *competing* (A vs. B) end-2-end knots, and
one of the knots tested was the
"twin fig.8s"--i.e., essentially opposed eyeknots sharing an eye
(knot-A's initial leg reaches to finish knot-B, and
vice versa (could be different knots, but then one
needs a different name than "twin <knot-type>s"))--,
and yet this wasn't the strongest knot tested! ??
(One might expect at least that it would better other
end-2-end knots, even if the *pure* like-formed
eyeknots kept an edge over it.)
Then, again, I don't know that the actual geometries
matched --the end terminations could've been tied
in the bight vs.
traced which is necessarily how
the end-2-end joint would be tied.
(I.e., it is a valid research topic to observe how rope users
tie
fig.8 eyeknots in the different circumstances when
going in-the-bight and traced. (A local indoor climbing place
--viz., SportRock-- had a FULL HOUSE last week when I went
in to observe knots, and apparently requires tying in with
a
fig.8 eyeknot + strangle back-up ; the general form
was (a) imperfectly dressed with an
interior ("weak form")
loading --this tends to make the loaded knot draw up more
parallel with the axis of tension; loading the
exterior strand
will compress the knot into roughly a 45deg angle to the axis.)
Now, were these same people asked to "TIB" the knot,
would we see the same orientation? Would we maybe
get more well-dressed knots, or some common departure
from this, say, where the eye bight/legs made their U-turn?!
)
The fig.8 end-2-end
knot stood out starkly in strength over others; but in
the eye knots, many are of like strength. Interesting
(I can understand how the fig.8 & overhand eye knots
would be stronger than end-2-end knots (as one need
only treat one part (the single "SPart") just so, not
having to be able to reciprocate for another; and yet
these results don't show that --both are strong!
What I'm thinking of here is that to the
eye knot's SPart
the twin eye legs bear around it both (a) in half the force
--or less, per force mitigation on knot entry-- and (b) in their
twin/adjacent spread of force over the SPart, vs. a single
strand's double load and sharper *bite* should result in
some better reception of the fully loaded strand into the
knot. Whereas, in the end-2-end knot, one must replicate
such a kind, gradual-increase-of-nipping pressures for the
opposite end as well --which can imply very clever knotting
or more material in which to work this magic!
But in these quick tests, we don't see such a difference;
indeed, by the thinking above, we should be amazed at
the end-2-end version's performance. (And might this
be a result only available in such small sizes of material
--but why?)
[ I've altered labels ("LAF" gets in the way of recognition,
and can be understood as what all values are for --failure--);
average strength is given in two ways, which I put together. ]
I do think your way is clearer. I'll have to use that format in the future. Thanks.
Another pet peeve : why do some folks think that it
is at all sensible to present "strength lost" figures?!
--having e.g. "34%" as a datum is less useful, even,
isn't it? I.e., in figuring a system's ability, one would
want the corresponding "66%" to use in multiplication,
and it is this figure that quantifies
"efficiency" !?
(The latter is also what is immediately resulting of
the test device's read-out.)
AVG...34.98 kg (100.00%) MIN: 33.00 SD: 1.52[/u]
I should remark here that one thing I wanted to do
for a published table was to point out the discrepancy
of the base, "tensile" value, but comparing it to the
material's
rated strength --so, one would see e.g. "95%"
here --indicating that actual testing found that the rope
wasn't as strong as promised (or, maybe it was more so,
if rating assumes a minimum value, as has been
recommended I think by the Cordage Institute).
One thing I have discovered during the course of testing these knots
is that there is a hope that the results will conform to the tester's expectations.
And when they do not, there is a temptation (resistible but real) to make them conform.
Good point! And when things are as expected, we accept
them; when not, we question --which is natural, but we
should be more vigilant overall, of the expected results.
You may have noticed that the standard deviation for the bowline
was much greater than for any other knot. This is a result of one test.
In that one test, the bowline tested at higher than at any time before or after.
Without that one test included, the standard deviation for the bowline was 1.51
and the average was 34.15, both nicely within the expected range.So the dilemma was whether to just skip that result and have numbers that conformed to my expectations and the rest of the test results. I chose to leave the test in question in the data.
One can speculate that somehow in the one test case
there was some slippage that gave more/less? force
to the collar!? One can see the wisdom of Roo's seeking
SD values.
I have included photos of the overhand loop.
Ah, this would be the "weak form" --loaded strand being
interior, and for strength this has been found, in some
testing, inferior/lesser.
Thanks,
--dl*
====
postscript :
comprised of[/s] => comprising
I should give a note --pet peeve thing--: "comprise" denotes
the
entirety of constituent parts (or whatever's listed),
in contrast to "include"; it should
never appear in the form
crossed out --with "-ed of ...". My guess is that newspeak morons
like the
sound of it, and as they seem chosen more for looks
& sound vs. smarts, lacking regard for the instrument of their
business --i.e.,
language-- (and as imagery & hype push
substance to the side), so the population of this solecism grows;
and then there's Merriam-Webster's adopted
descriptive vs.
prescriptive follow-the-leader stance, losing another guard
of the language.