I've been playing with this stuff all week, thought I'd give my final thoughts, for what they're worth.
Pretty much all of the suggested permanent inline loops (lineman's loop, span loop, bellringers with half hitch, #1074, #1057, #1058) have the same attributes: easy to tie, with a tendency to jam under a heavy load. None of them stand out from the others too well. If I want one of these loops, I think the alpine butterfly loop (ABOK #1053) is probably the easiest to untie. I like Andy's method to tie his Bellringer knot with the half hitch, but I still favour what I always used, which was the slipped stevedore knot. It's fast to tie, fast to undo and isn't a permanent loop, yet is more stable than just a slipped overhand. I think these are the most important attributes for a trucker's hitch.
"Playing" is good; but please give details of materials & loading,
so we can try to understand exactly what you're doing.
There should be an easy selection of non-jamming knots here,
esp. those with
bowline-like bases. As noted, I tried a sort of
version of what I think Knot4U calls a
"Stevedore" structure,
stabilizing it with counter-wraps, and loading it pretty substantially
after hauled tight. (Though we should note that the
haulingputs more challenge to the mid-line eye-knot than the holding,
as it will be somewhat imbalanced vis-a-vis the part leading
away down to the anchor hook/ring, given friction --i.e., it
will be more an end-eye than a mid-line eye, in loading.)
I've brought ropes to near breaking, but the Span Loop still unties easily for me.
How did you bring
ropes to near breaking (and how can you tell)?!
--that's some few thousand pounds force! Even with my (crummy) 5:1 pulley,
I figure that I'm only reaching around 800# or so if I bounce on it some.
(I have accidentally broken some cords, and Fishline, Beware!)
a Butterfly tight and difficult to untie, I'll use it in a Trucker Hitch.
Noting that the
butterfly is asymmetric, and has various ways to
orient the eye-legs (or tails) --crossing or not (not is usually depicted).
Above, Roo noted that a slip knot can subject a Trucker Hitch to a Poldo Tackle problem if there is a strong vibration or tampering:
http://igkt.net/sm/index.php?topic=1870.msg12642#msg12642
No, Roo only mused that maybe something like that could happen
(and, frankly, it's unlikely in the (dubious)
Poldo tackle, for that matter)
--to wit:
"wondering if it might be subject to a poldo-tackle-type effect" .
NONE of the slip knots pass.
...
I didn't take his word for it. I verified this when I put various slip knots through a tamper test.
And I don't take your word for it, and ...
I call BS --and let's see some details of your test set-up.
I've just tried to see this in sub-1/4" soft solid-braid nylon,
and 4mm? slick soft-laid (firm strands) PP. Only with some
deliberate lifting of the haul-down side of the bight to the
anchor hook could I force some shift in the nipped sheave
bight, and only before hauling the structure tighter.
That any such de-tensioning can happen with a tied-off
structure in normal cordage is beyond belief : the slippage
will have to go through the tying-off hitch around haul legs,
around the hook, and through the strongly nipping S.Part-eye!!
That is some kind of tampering. (My lifting, to be clear, removes
any load from the "slipped" eye-sheave; normal use sees this with
tension.)
--dl*
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