Moderator: Tim White
Chads93GT wrote: is the inline 8 not a 3 way directional knot?
Chads93GT wrote:I never thought of that. Thanks for pointing that out. is the inline 8 not a 3 way directional knot?
knudeNoggin wrote:As for the Butterfly / Lineman's Loop doubts, this is going into academic
realms: we have a lone person rapping, not the lowering of a Hummer.
knudeNoggin wrote:Seldom will you see a clear image of exactly what knot geometry
was tested -- and tying guidance & practice lead to different geometries:
with the Butterfly, do the eye legs cross on exiting the knot (as one pair
of originators --Wright&Magowan-- stipulated) ? Do you know which end
of the knot was loaded? (It is asymmetric, so this makes a geometric difference.)
... and so on. Moreover, in practice, one will see the knot loaded in some
variety of ways --on all four parts, or maybe on ends only-- before some
exceptional event might occur: that's a lot of variability to toss into some
testing regimen!
Secondly, one should consider that slow-pull testing doesn't so accurately
model in-practice loading: when rope partially breaks under slow-pull
testing, there is often a momentary reduction of tension by some release
of material, until the steady-rate-of-movement hydraulic pulling catches
up -- not so in practical circumstances, where e.g. a falling mass will
keep on keeping on (albeit with some reduction in force).
Thirdly, in the given example here, there's little chance of any significant
"shock loading" -- the knot will begin under tension on all parts, which I don't
know of any test showing.
AlanfromOz wrote:Many people have love the ABK, but there is some debate about its' usefulness.
Some (generally older) sources claim it is "one of the strongest knots", but testing shows as little as 60% residual strength, with very variable results. The problem is that it is used in any different ways (eg end loop, mid rope loop, 3-way loading) and different test results have used different modes and not always said how they tested it!
I found some test results where it failed before the bowline in the other end of a 11mm rope (~900kg at breaking from memory?) Shock loading performance is also not great according to some tests. This might be because the first loop of rope in each tail has a quite small bend radius?
It is far from ideal for a rebelay, because you're using it for an end loop knot (something is wasn't meant for) and if your rebelay anchor fails, you're shock loading it end to end!
Whilst it looks like the best knot for a 3 way load, there is usually a better / as good knot. Many people use the ABK in the centre of a cowstail lanyard, but a fig 8 or overhand is better (when do you load both lanyards in different directions?).
Even for a 3way load, a figure 9 knot will perform as well or better, even with the tails pulled apart (yes, it looks wrong!)
AlanfromOz wrote:There is some information on knot strenght in Vertical. I know from speaking to Al that he performed drop tests on a lot of knots before the first version of vertical. Some people have disputed his results, but never presented the claimed test results to back it up!
NZcaver wrote:Knots declared as "non recommended" by Warild were and are regularly used by cavers and rescuers, and there's no trails of dead bodies in their wake. Knots like the clove hitch, the bowline and the butterfly.
NZcaver wrote:Surely somebody has?
AlanfromOz wrote:Many people have love the ABK, but there is some debate about its' usefulness.
It is far from ideal for a rebelay, because you're using it for an end loop knot (something is wasn't meant for) and if your rebelay anchor fails, you're shock loading it end to end!
Even for a 3way load, a figure 9 knot will perform as well or better, even with the tails pulled apart (yes, it looks wrong!)
NZcaver wrote:Interesting point about inconsistencies caused by quoting older sources of information (perhaps older ropes used for testing?).
Knots declared as "non recommended" by Warild were and are regularly used by cavers and rescuers, and there's no trails of dead bodies in their wake. Knots like the clove hitch, the bowline and the butterfly.
I had a brief look for more recent testing results for the butterfly, and all I found was this <Dave Richards's testing> which doesn't indicate anything too upsetting ...
I'm wondering if Life on a Line or Lyon or anybody else has done recent testing with the butterfly. Surely somebody has?
I like the butterfly in certain applications and I think it can safely be relied upon, but I'll keep an open mind.
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