Adding a safety by tying a second overhand on top of the first is probably a good idea. This likely helps prevent flipping [aka "flyping"]
...Dan Lehman has also proposed some variations of the overhand to me that look very promising. They keep the asymmetry
and are all probably much harder to {flype} than the {Offset} overhand.
It's the last bit of reference to Dan Lehman that got my attention!
Can you elaborate on the 'proposed variations' to the offset ring bend (ORB).
Am very curious...
While I'm not sure of all that I sent to Tom, at least one obvious one is simple
to explain and to effect, and it's likely the surest solution. While I've *designed*
(= *directed discovery* ?!) some
symmetric offset bends, it later occurred
to me that frequently--perhaps most often--the two lines to be joined are not
*symmetric*, i.e., of unequal natures (e.g., often it is a thin, low-elongation haul
line tied to a full-size dynamic climbing line). So, the best solution is probably
an asymmetric knot, with guidance to tie it with the
thinner line HERE,
and the thicker THERE. (And then one can worry whether that distinction
implies a risk where it's ignored.)
Firstly, consider the image here:
www.ukclimbing.com/images/dbpage.html?id=13909For this knot to flype, the darker blue w/red rope must be pried out around
the other (or the other forced through the first). To my thinking, thus, the
thicker rope should be in the "other" position, and be by size alone an
impediment to this particular failure mode of flyping. To Tom's first-indicated
security measure of tying a 2nd/back-up Overhand, I say "... IN THE THINNER
ROPE AROUND THE THICKER TAIL"--this looks pretty good, as it arrests
the early draw of thinner end out of the knot as that line's *choke* of the
SParts is strained.
A better resitance however comes from a simple modification: make a full,
round turn with the thinner line before following the thicker line out through
the loops formed for the Overhand (so, the darker line would wrap again
around the SParts--the image would show two strands--and then be tucked out).
This full circle of material greatly resists being pried open. (It quite possibly
weakens the knot by forcing a sharper bend of the SParts; but the concern
in Abseil-Rope-Joining knots is security, not strength; they are typically
bearing just HALF of the weight of an abseiler.)
The extra/full turn in the should-be-the-thinner line makes a Fig.9 in it
(should you stop to notice that). No, an offset Fig.9 is NOT thus a better
idea (and certainly no thinking of working in some Yosemite finish!! :-) ;
were the full wrap made in BOTH lines, the helix angle of the closing
near-circle(s) spiral would be more open and less effective; the extra
bulk of material if anything would make the knot less secure.
There are some other orientations an extra turn can take, in one case
making a Dbl.Oh / Strangle form in the thinner line.
One can also make just an extra HALF wrap, resulting in a Fig.8 in the
thinner line; the characteristic visual aspect of this, call it "Offset Eight-Oh Bend"
is that the ends point in opposite directions. I think that this knot is more
resistant to flyping than the now infamous Offset Fig.8, because of the
lesser material (given one rope making only an Overhand) and the
exit of the ends in opposite directions (as it is hard to force material
over/around these protuding ends). Note that the opp.-direction-ends
make for a distinctive appearance.
------------------
It is worth reiterating here that
many of these offset bends can be tied
and then given a setting in any position in the range of 180 degrees in
regard to the plane of a surface over which the knot is placed.E.g., in the URLink'd image cited above, the light blue rope enters the knot
and makes backward loop, and the dark blue rope makes a forward arc;
without untying the knot, and even after some setting, perhaps even usage
for abseil, one could grasp the knot and rotate it from this one extreme
to where the two lines equally enter the knot and move to viewer's right
and then curve around ... , or the opposite extreme where the light blue
rope makes a forward arc and the dark one makes the backward loop
--the rotation here would be with the ends going away from the viewer.
There needs to be some exploration as to the effect of these orientations
on vulnerability to flyping.
--dl*
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