Xarax's comment.
Which is in part
At the secure bowline, the segment of the rope just after it leaves from the nipping loop for the last time and just before it enters into the collar for the last time, is never tensioned ! In other words, after the very first stages of the pulling, it does not participate in the function of the nub any more - or, even if it does participate is some degree ( by altering the geometry of the nub, and by enlarging the diameter of the nipping loop ), its role is only secondary. The nub tries to withstand the tensile forces with the segments it has before that part, which are about what a standard bowline has - no wonder that, statistically, in some cases, this secure bowline will be not much stronger, or even that it will be slightly weaker, than a standard bowline.
Firstly, any secure bowline will be infinitely stronger than
an untied #1010, which is the main concern of climbers
--not the upper reaches of a test device! NB!
I'm inclined to see an issue with the amount of *slippage*
--or call it, perhaps better, "SPart feed" (i.e., feeding its
material out of the knot)-- shown in the breaking knot;
near the critical point, look at the check marks that come
out of each knot : on the left, one slowly emerged; whereas
on the right, movement is greater --again, at high load/friction
= heat. Note that one part that the SPart crossed got quite
damaged.
.:. So, it bring to question those knots that might seem
"strong" and kind to the rope for their gradual --which
necessarily implies relatively
long-- initial curve
having a cost of such heat-generating movement!?
<sigh> Back to the drawing board?
Note that the
mirrored bowline has this built-in
looseness to it, and "security by proximity" (i.e., though
not set snug-tight, the loosening is arrested quickly by
parts bumping into other parts); it also turns the SPart
around 3 diameters.
But will testing show this to have a top-strength cost?
(And might some repeated drop tests well shy of break
forces reveal some accumulating damage?!) Or is the
rapidity/quickness & shorter duration of the heat going
to offset its potential damage, at least somewhat (making
long falls worse than short at the same Fall Factor --IIRC,
peak impacts are the same, but
duration grows with
fall length.
--dl*
====
ps : I saw this sans any audio so know only ... visuals,
but I think some boater dude is promoting . . . a knot
more familiar to this forum! --to wit:
www.youtube.com/watch?v=-rGROTyDv88
