Break Testing

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Moray, how did you test the Grapevine bend (Dbl.Fish.)?
I.p., how did you anchor the ends of the test specimen?

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As I was testing attachment knots, it was the double fisherman's loop, not the bend. One at each end of the rope, each held by a 3/4-inch steel pin.

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And, Moray, are you still taking the measure of various
knots etc. in ropes?

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I am. At the moment I have some splice experiments at the top of my list but I will be doing some more knots before long. Do you have something you want tested?
 
Hello again,
I went looking for the twice-around-the-standing-part video. Apparently I had deleted it, but I found this one: http://www.youtube.com/watch?v=Fy6Y2Xoo4Ak. It shows the same knot as the second video, but tied looser. You can see how the knot closes up immediately, then holds until break.
On other fronts, I'm waiting to hear back from some ropemakers on arranging for tests of knots in HM fibers; if any of you have any suggestions, be sure to be in touch.
Fair leads,
Brion Toss
 
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http://www.youtube.com/watch?v=Fy6Y2Xoo4Ak
Any Better?
Brion

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MUCH better -- beautiful! (But will it go "viral"? :o)
The knot is clearly shown; the lower but not additional Half-hitch
/loop part rotates, the eye legs are constant, and then at 28 sec.s
comes the (partial) rupture. Now, one could've traced those few
broken strands back to approximate the rupture point, which
looks to be as expected in the hard turn of the first loop/HH.
Good to see that in some cases at least the testing can stop
w/o severing the rope.

*kN*
 
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Moray, how did you test the Grapevine bend (Dbl.Fish.)?
I.p., how did you anchor the ends of the test specimen?

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As I was testing attachment knots, it was the double fisherman's loop, not the bend. One at each end of the rope, each held by a 3/4-inch steel pin.

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Ah, I see: the Strangle noose.
I have a thought about this (though you got high results, so ...):
in 8mm BW II around a 'biner a tester got breaks in the mainline
where it entered, which is a point of high contriction. I think that
to avoid this, and also to have a structure that can be untied (with
some work), it would make sense to tie an Anchor Hitch noose,
or what is similar, a reduced Blake's Hitch noose: i.e., tie to the
mainline with Blake's modified to have (1) one fewer wrap and
(2) tuck the end out under just one turn vs. 2. (If you tuck it
out two and have only two, that is the Anchor hitch, fyi.)
The thought is that by bringing the tail around to wrap away
from the pin (vs. back towards it, as done with the Strangle),
you offload more force, and the tucked end helps cushion
pressure of the tail wraps constricting the mainline -- also,
this harder constriction occurs not at the entry but exit point
of the knot. All in all, it might also be possible to work this
knot loose, after heavy loading even, though it is still a secure
knot.

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And, Moray, are you still taking the measure of various
knots etc. in ropes?

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I am. ... Do you have something you want tested?

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Sure.
In addition to one or two of the noose-hitches suggested above,
from this thread's posts the #190898 "Semi-Symmetric Fig.9",
#191260 "Quick Fig.8", & #191935 "False Bowline 8 HAH" eye
knots (in this order of preference, if I must choose, I guess).
If you tie the knot in both ends, you're sure to have a surviver
along with the one that broke. (I have seen such a case where
the "survivor" showed signs of initial rupture, though, in a test
in 9/16" tubular nylon!)

*knudeNoggin*
 
Hello all,
New England Ropes has stepped forward to conduct break tests in uncovered Spectra. This is something they have done for our shop in the past, with results I've alluded to in this thread: tremendous weakening, and amazing slippage. But kN will be getting some materials to tie and send in soon. Stand by.
Fair leads,
Brion Toss
 
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