I wonder if you could take a moment to educate me about what incorrect conclusions about knots MBS testing could (or has) lead to.
I contend that knot choice in all cordage (not limited to 11mm kernmantle) if done without considering knot efficiency, and based solely on security, stability, jam-resistance, and verifiability, could lead to incorrect conclusions about knots! Take for example, a theoretical knot that has a low efficiency, but very good S,S,Jr&V. By your criteria, this knot would be excellent, but without further analysis of design factor (which requires knowledge of MBS efficiency) a failure may occur under load, despite the knot passing your S,S,Jr&V criteria.
A fair question (which I might try to address),
but turnabout is fair play, as they say, and to
you then comes the return,
What actual case
can you cite where knot efficiency (aka "strength")
has made a difference?To your question, a weak answer is that one can see
debates about which knot --for various purposes--
is "better" and answers seeming to point simply to
some indication of differences in break strength
(as measured in a particular --perhaps though not
well known-- way on a test device in some kind of
rope (though not necessarily that of user's interest)).
And the general case Agent_Smith has argued against
has been that of Abseil-Ropes-Joining knots used by
rockclimbers (and perhaps SAR folks, and some others
of similar applications, but with different rope --canyoneers?);
in such normal uses with usual cordage of the application
there is no approach to forces that will test strength
(arguably in some knot cases because instability will
cheat such a test --give sooner failure!).
However, this statement is predicated on the fact that the 'canon' of climbing knots all have adequate, known efficiencies, and it's somewhat disingenuous to state that MBS is meaningless. I'll give you an example of a non-climbing-canonical knot that has excellent security, stability, jam-resistance, and verifiability: the Zeppelin Bend. Would you climb with it? Do you know it's MBS efficiency in Kernmantle? (or any other line? I'm curious)
Actually, I'll challenge the bit about "known efficiencies"
on two grounds:
1) it's arguable what is actually known, in that testing
is done somewhere and in some materials (usually new)
and knots are tied in a dressing & setting (& orientation)
that is typically NOT known (a simple case : the *traced*
fig.8 eye & end-2-end knots offer either of two twin
ends that might be the S.Part, yet seldom is the one used
explicitly indicated (one can sometimes infer which ... by
the shape of the loaded knot, if one knows how))
and
2) the loading done by a slow-pull test device is not the
sort of loading that will come by actual usage --more sudden
loading.
Now, there has been lots of testing and lots more usage
--i.e., knots loaded dynamically in practice-- and we can
say that the safety margin sure looks real by such experience.
(I think I lost a train of thought re above two points ...)
But I also will say that in general, it's hard to conceive of
ANY knot being weak enough to cause concern in the
above application, really. But perhaps a tie-in (eye) knot
can be weak over time : i.e., repeated falls on some inferior
knot in the region of tying in (that end of the line) will see
degradation of rope strength at that region sooner than if
another knot had been used. (There have been strength
tests done of cut-off ends of climbing ropes that show a
weakening there that exceeds weakened states mid-rope.)
And re the
zeppelin bend, I don't think that one should
question its strength (there are some tests here and there
of a casual sort), though one might question its security
when slack and rubbed along rock. (Rockclimbers only see
end-2-end knots in abseiling and in forming round slings,
yes?)
--dl*
====