I tied the butterfly bend ...
Here is the first problem, which most people gloss over
(such as the ensueing discussion here) :: there is no "the"
knot, but some commonly formed ones and others of a
similar construction but with different dressing.
To begin : since the
butterfly --unlike a quite lookalike
Ashley #1408-- is
asymmetric, there are
two *knots*
(structures with a loading profile) to consider re loading
--i.e., which end will bear tension while the other dangles?
Before this, there is the matter of how the knot is oriented
via dressing --e.g., do the eye legs (or in this common
eye-from-end2end relation, and eye leg & the tail) cross?
(Most presentations of the
butterfly do not cross them
(but maybe it's best if the parts are crossed).)
Making an eye knot from a given end-2-end knot as you have
done is the common way of relating these types of knots; but
it is not the only one --another, which I'm currently exploring,
entails tying a bight's twin legs to a single strand in the way
of making the end-2-end knot, and then seeing how the tail
from the single strand can be *fused* with one of the bight's
tails to result in a corresponding eye knot for that bend.
This latter correspondence better preserves the workings
of the end-2-end knot, in some cases (though in being
roughly end-2-DBL_end it of course has that difference).
> Is this eye knot an already known and named knot?
One might say simply that the relation --the way of deriving
the eye knot-- is understood and so exists for any end-2-end
knot (though some won't result in good eye knots (e.g., the
square knot)!).
So despite Mr Delaney's assertions - the Butterfly does jam!
I recall his assertions about
Ashley's #1452 jamming, and how
it took some persistent pressure from me to discover that he
was tying the knot in a version different from others in which
jamming was prevented; I suspect that there might be a like
issue with your
butterflies, which as aforementioned begin
with a dressing choice upon which then comes the loading one.
Meanwhile, someone reported a jammed
zeppelin knot,
so never say 'never" on that.
(Dynamic rope probably has the greatest potential for jamming,
as with such great stretch comes diminished diameter and
great knot compression (potentially) to fill the voids of
disappearing bulk; then, if material swells outside of the
knot (recovering towards original diameter & length) but
cannot gain entry past the tight constriction at entry,
... jam!)
As for "SPart loading", by definition one typically loads
a (if not more than "a") SPart. "End-2-end" or "through"
loading is what's meant, here in the mid-line eye-knot case.
And the issue re asymmetry points to the duality of
potential SParts for the eye.
And what is seldom (ever?) tested is the behavior of
whatever loading AFTER the knot has been otherwise
loaded (not merely "dressed & set"), which might be
how a practical circumstance delivers force. (Watching
some arborist fellow's loading the
butterfly qua eye knot
and seeing how the collar around the unloaded end collapsed
was pretty eye-catching; how the knot would then perform
on through loading is a question, with that so-tightened
collar. (Although forces were probably well higher than
some practical likelihood.)
--dl*
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