Author Topic: Flemish bend with different diameter ropes  (Read 3870 times)

tobyharper

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Flemish bend with different diameter ropes
« on: September 07, 2005, 08:45:31 AM »
What is the maximum difference in the diameter of ropes appropriate for the use of a Flemish (figure-8) bend.  For example, would it be appropriate to tie a 10mm rope to a 7mm rope?

Dan_Lehman

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Re: Flemish bend with different diameter ropes
« Reply #1 on: September 07, 2005, 11:18:56 PM »
Your question's particulars suggest that the situation you're interested in is one
of joining a rockclimbing (dynamic) rope to a haul line (low-elongation)?
And the point of doing this is most commonly to abseil the full length of the
climbing rope (but to not bear the load of two such ropes).   --one argument
for using twin (8mm) climbing ropes!  (-;
--and the knot preferred for the above-guessed situation is the Offset Overhand Bend
(aka "European Death Knot (EDK)", "(dbl) Overhand Bend", "Thumb Bend").
For the case of the offset knots (even for the Flemish, aka Fig.8), the difference you
state should be no problem; but those asymmetric offset knots should then
have the thinner rope first wrapping the SParts (so that it would have to be
pushed up arouund the thicker rope to flype/capsize,  which is harder than
pushing the elastic thicker rope around the thinner).

As for the intended-to-be (but scrutinize presented images and see how often
it is NOT) symmetric Fig.8 bend, that gets problematic as ropes differ.

MOREOVER, please note that a definite orientation of this knot is ALMOST
NEVER PRESENTED:  in a symmetric form, which two ends are you loading?
(Test data is inconsistent re how much this matters.)
Cf. www.iland.net/~jbritton/KnotPhotoContributions.html
Updated Link > www.pssurvival.com/PS/Knots/Knot_Knowledge_Photo_Illustrations_2004.pdf
and about the 4th
knot down the page for a perfect form of the Fig.8 trace knot; the bends
corresponding to this loopknot would be those loading either the two dashed
parts ("A-B" vs. "H-I", or "S-Q" vs. "G-FE").  Usually, the exact form or the knot
is not known/reported in discussions about it.  E.g., in some testing done by
Tom Moyer, in which such loopknots in 7mm nylon kernmantle broke quite
consistently around 92% (!!!--of his tested tensile!), he had a couple of slightly
asymmetric forms (and his images are a bit ambiguous).  YMMV.

In the case of mis-matched sizes, the former version indicated above seems
to work better (more secure/tight).  But here's an argument for using the
Grapevine, where the component Strangle knots are somewhat independent
of each other, abutting to jam tight.

--dl*
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« Last Edit: December 09, 2012, 08:29:57 PM by SS369 »

 

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