I understand that the diameter of the object (a post, carabiner, rope [a bend made from two interlocking loops]) does not affect the strength of a Fixed Loop (e.g., bowline loop). It will always break at the knot, not the loop. Is this also true of a Slip Loop (e.g., scaffold noose)?
Be careful about what you understand (and how you came to
do so).
I recall an old test report done in nylon hawsers in which
bowlineswere interlocked simply and then united as with a
square knot (but
all ends --the legs of
bowline eyes-- loaded : and the point of the
testing was that the latter structure was stronger --which seems to
imply that the break came not at the bowlines but at their joining,
or did so in the weaker case. But it could be that (a) the joining
structure influenced bowline strength, or (b) the variation was
not statistically significant and the testers not clever re this.
(Break points are seldom reported, alas.)
Then, currently, there's a YouTube video of the rupture of HMPE
1/8" ? line with eyes of splices run through loops of cordage,
not all so much thicker (doubled, in one case, I think). Well,
although HMPE suffers much strength loss in knotting, and so
you'd think would/could be affected by a hard bend such as
being reeved through a small soft eye, the breaks didn't occur
there. Hmmmm!?
AND if the diameter spreads the eye widely, it increased the load
on the eye-legs and what the deliver into the knot, as well as
the exact geometry/angles of such parts; that could affect the
behavior.
In a test of the
Scaffold knot (well, actually a
Strangle noose,one turn fewer) tied in 8mm Bluewater II low-elongation kernmantle
rope around a 'biner, the rope broke --at a high load-- in the NOOSE's
S.Part (not the knot's) at the point of entry, where the
strangle was,
er, strangling it. --so the turn around the object didn't make the
strength determination here; in thicker ropes, I'm not sure that
the same thing occurs (and have a vague tingling that some
testing of arborist cordage around a half-inch pin (about 1:1
nominal ratio (rope will compress)) there was evidence that the
knot broke --I'm not certain re this, though).
Anglers work with slippery fine material and so often employ knots
with many turns; you'll see notes about some of these knots to
use fewer turns for thicker angling material, too.
--dl*
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