Author Topic: FYI test results for misc. Fig.8 EyeKnots (4x2)  (Read 78 times)

Dan_Lehman

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FYI test results for misc. Fig.8 EyeKnots (4x2)
« on: August 01, 2020, 04:36:15 PM »
www.blackdiamondequipment.com/en_US/experience-story?cid=qc-lab-can-i-use-a-sharpie-to-mark-the-middle-of-my-rope

Just a blip in the radar in testing.  It's not possible for me
to surely discern what state of dressing/setting the various
Fig.8 EKs were in, though the survivors do (or 3/4 do) show
a telltale untensioned eye collar that suggests *interior*
loading (but, then, of what sort of imperfectly dressed knot?).

Of the pre-test layout, L & R I see:

Interior dive of exterior approach   vs. same
 [ "  meaning that the twin that WOULD've taken the
   exterior path judged by its entry has tucked down
   into interior position at the U-turn ]

perfect form exterior loaded   vs   <ditto of above>

<again>   vs  similar re loaded strand, but the eye bight swings out of perfect form

<same but eye bight ... IMperfect finish>  vs. <like above, exterior at critical point>

Now, I hesitate to match pre- & post-tested knots --i.e., that the
layout is intended to match (though noting that it does seem deliberately done).

!?

Ah, in all cases the rope "broke at the bottom knot",
and in another posting by the Black Diamond site I see
that the (same, presumably, by looks) test device
MOVES THE UPPER UPWARDS,
so the breaks reported came at the stationary end.

And in a test of 20yr-old UNUSED climbing rope,
which performed "as though made yesterday" in
tensile (Fig.8 EK) & drop testing (impact forces),
one has a good look at the two Fig.8 eye knots:
the broken one (again at bottom) is in my "perfect
form", *exterior* loaded,
and the upper, surviving knot is imperfectly formed
with the loaded strand swinging out wide around
its twin --which gives it the larger diameter at the
critical u-turn bend.  IMO, consistent with one
theory of knots weakening.
This imagery is a couple scrolls down, on this page:
www.blackdiamondequipment.com/en_US/experience-story?cid=qc-lab-old-vs-new-gear-testing

TO EMPHASIZE, IMO were the lower knot in the
"perfect form, exterior loaded" FIRST SET BY
hauling hard ON THE TAIL,
then the loaded strand would not so readily crush
inwards to its hard, 2-diameter (and really more
like ONE dia. with other just *behind* this) bend.
Note the difference as seen in the center image with
loaded knots with the upper knot where the loaded
strand in swinging wide encompasses another diameter.


--dl*
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« Last Edit: August 01, 2020, 04:54:16 PM by Dan_Lehman »