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Re: Mammut dyneema sling breaks at girth hitch.:
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knudenoggin
Oct 28, 2006, 4:47 AM
Views: 41689
Registered: May 6, 2004
Posts: 596
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In reply to: I own Misty Mountain Threadworks, the maker of the sling that the broken dyneema was girth hitched to. I just tested a bunch of 11/16" nylon and 5/8" spectra slings and found that when girth hitched together they broke at about 50% of their normal breaking strength, and always at the girth.
NB: your results are a whopping 20 %-points LOWER than those from Chris
Harmston's testing linked to by Catbirdseat & also at another site, http://www.climerware.com/knot5.htm
Your consistency in results is the point of rupture--in the sling making the Girth
Hitch.
Now, about "Girth Hitch": note that this name is ambiguous re knot form, as for the
hitch to something solid (like a 'biner or tree) brings the hitching material back around
itself (to make a sort of collar), whereas when made in webbing, it usually
goes around the hitched-to sling. BUT, in the case at hand, the collar makes
a compromise--it's neither here nor there but pretty inbetween!? So the testing
done is not entirely relevant to that structure (no more than it is to the case of
a hard object).
Frankly, that's a might sharp/neat break!? It's also right at or a little even
past the point of contact? --at least, the knot stayed tied, there was enough of
the broken side jammed by the collar to hold (as opposed to one part coming
out the front, and the other spilling around the opposite way, unwrapping the
collar. !?!?
Elsewhere it has been reported by the owner that the broken sling had been stored
near an acide source; but HMPE is supposedly pretty resistant to acid (and most
chemicals). Mammut is to examine/test it.
In doing further testing of slings, how about giving some further testing to the
sling-2-sling joint(s) proposed at the climberware site (actually, to the one given
there, and to the not-quite-the-same one shown in a link from Franz Bachmann
in the other RC.com thread on thin HMPE slings (see it). --rather than toss out
the idea of ever putting slings together, let's see about maybe a better way to
do so.
Oh, and on the slings you (Grimbo) did test, did the breaks look the same?
(like a cut) And did the Girth hitch stay intact? (break at similar point)
*kN*
(This post was edited by knudenoggin on Dec 5, 2006, 6:56 PM)
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Edit Log:
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Post edited by knudenoggin
() on Dec 5, 2006, 6:56 PM
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