Author Topic: Dressing a figure-eight loop?  (Read 18250 times)

andy753421

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Dressing a figure-eight loop?
« on: September 14, 2011, 09:56:32 AM »
I recently started rock climbing again and we were all taught how to tie a figure-eight loop (or whatever else you want to call it). We got the standard instructions on how to tie a figure-eight and then were told to follow the running end back through the knot.

It got me wondering though, I've been told how to tie a figure-eight loop many times but I've never been told how to properly dress it, if there is such a way. Just following through and pulling everything tight seems to lead to several rather ugly variants :)

I don't think there wouldn't be too much of an effect on the strength of the knot, but I could see some ways being easier to untie than others. That's just a guess though, has anyone looked into this before?

Hrungnir

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Re: Dressing a figure-eight loop?
« Reply #1 on: September 14, 2011, 01:27:18 PM »
The tying method is correct.

However, make sure  there are two strands beside each other at each part of the knot and that the strands are not crossing each other.

Correctly dressed knot:

xarax

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Re: Dressing a figure-eight loop?
« Reply #2 on: September 14, 2011, 01:56:48 PM »
   See the symmetric variants at :
http://igkt.net/sm/index.php?topic=2198.msg15419#msg15419
   An "ugly" knot is not weaker than a pretty one   :), unless the "ugliness" is due to an asymmetry. In this case, and this case only, one can say that the forces inside the knot s nub are not evenly distributed, and this might lead to the formation of some weaker areas/links.
   In general, it is believed that the most vulnerable areas are situated along points of smaller curvature, and there is a handful of studies that relate curvature at those points with strength. See (1), (2), and references therein.
   I believe that the double eight knot was chosen because of its resistance to slippage, not because of its greater strength. In the climbing world, there was never a systematic, exhaustive strength test of all the different variations of this knot - or of any dressing variation of the few knots used there...Not one of the many rope manufacturer of climbing ropes, did ever a systematic strength study of those different variations of the double eight bend, and all that is taught to the students in climbing schools, is to tie only the standard variation. Who can prove that some other ,"ugly" variation, is not stronger and safer than the most frequently used one ? So much for the claimed "attention to details" in this supposedly technology-oriented field ! It is the progress in the material sciences that saves the ass of the climbers, not their scientific literacy.

1) http://arxiv.org/ftp/physics/papers/0103/0103016.pdf
2) http://www.lmm.jussieu.fr/~audoly/publi/ACNKnots-07.pdf
This is not a knot.

DDK

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Re: Dressing a figure-eight loop?
« Reply #3 on: September 14, 2011, 08:28:52 PM »
(1) The technique I use is to first lay the figure eight flat and have the working end leave the figure eight going away (down) from me.

(2) Then I rethread the working end back through the figure eight having it lay always on TOP of the rope it is following back producing a top and bottom pair.

(3) Once the rethreading is complete, partially tighten by first pulling on the working end (which should be the one on TOP of the pair) AND the leg of the loop which is connected to the BOTTOM of the pair.  (This is the tightening of the inner wraps of the knot, i.e. the inner Thief Knot)

(4) Then pull on the standing part (which was on the BOTTOM of the pair) AND the leg of the loop which was connected to the TOP of the pair. (This is the tightening of the outer wraps of the knot)

This process automatically correctly dresses the loop and produces it in what I believe is termed the "strong" form (standing part connected to outer wrap of the knot).

(personally, I prefer the "weak" form which is produced by transposing the words TOP and BOTTOM above and reversing the two tightening steps)

DDK
« Last Edit: September 14, 2011, 08:48:05 PM by DDK »

Dan_Lehman

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Re: Dressing a figure-eight loop?
« Reply #4 on: September 16, 2011, 05:53:46 AM »
I've been told how to tie a figure-eight loop many times
but I've never been told how to properly dress it, if there is such a way.
Just following through and pulling everything tight seems to lead to several rather ugly variants :)

Yes, isn't that peculiar --that there is much advice to "dress
and set the knot properly," but no specific guidance on what
this might be!?  In a great many presentations of this knot
(or is it just 2-3, repeatedly echoed?), it is not even indicated
which of the ends should be the one loaded, which the tail.

In practice, all sorts of things seem to be tied & tried,
and so far, I'm unaware of any serious shortcomings to any
of them.  Still one might wonder at some vulnerability yet
to be tickled, and further ... .

Of the set of 4 versions of the knot that Xarax points to in
another thread, I call the topmost one "the perfect form",
and the loading of the left white end vs the right side's
orange, "the strong form", with the "weak form" being
the other loading (orange vs. white, left to right).  --this
for the end-2-end knot; for the eye knot ("loop knot"),
one side will have both ends loaded --legs of the eye.

Xarax's knot-C is what Dave Merchant recommends as being
up to 10% strronger, and easier to untie.  I find it an
unseemly and not-so-easily oriented version.  Btw, my
"strong form" arose from a similar assertion of greater
strength (of like magnitude), by someone who could
be believed to be attentive to the knot (and who at least
had presented an unambiguous form, and pointed to the
difference of which end was loaded!).

I recall one fellow who did some informal knot-breaking
in a contest of end-2-end knots, where each test specimen
was configured with two such knots (in a knot-A vs. knot-B
competition), and the ends were terminated with some form
of figure 8 eyeknot --I don't recall him having the details.
In all cases, one of the end-2-end knots broke, never these
eye knots!  And this was with not only the fairly strong knots
such as fisherman's, butterfly bend, & the Zeppelin but
also double fisherman's, blood knot, and even one that
OUGHT to have been equal, twin fig.8 bend !!?

--dl*
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knot4u

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Re: Dressing a figure-eight loop?
« Reply #5 on: September 18, 2011, 03:57:03 AM »
Related issue, do you see any teachers in the climbing world teaching any alternatives to the Figure 8 Follow Through?

For example, is the Zeppelin Loop ever taught?  It's less bulky, easier to dress, quicker to tie, easier to untie, perhaps more secure, and probably stronger.  One disadvantage is the Zeppelin Loop is more difficult to learn for most people, but the benefits outweigh this disadvantage if the student can learn it.
« Last Edit: September 18, 2011, 04:01:51 AM by knot4u »

SS369

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Re: Dressing a figure-eight loop?
« Reply #6 on: September 18, 2011, 02:56:33 PM »
Hello knot4u,

yes, to answer your question, some do teach alternatives to the "standard" re-threaded 8 loop as a tie in loop.
There are threads here that go on about the many variants of the bowline for this purpose.

On the topic: I think that so long as the dressing is neat, paths "railroad tracking" each other in the final tightened knot that the security and strength< for that's worth, is essentially the same.

Quote
In regard to the Figure 8, On Rope (page 45 , col 2) states : According to Montgomery, it is possible to tie this knot incorrectly, resulting in about a 10 % strength loss. Knot destructive tests and Ashley confirm that this is not the case. Whether the standing line travels the inside or the outside path, it really makes no difference. [unquote]

SS

DDK

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Re: Dressing a figure-eight loop?
« Reply #7 on: September 18, 2011, 03:24:09 PM »
@dl & @SS

I would like to be more sure of what you mean by 10% increase (decrease) in strength.  The usual interpretation would be that if the original knot had a strength of 200 pounds, than an increase in the knot strength by 10% would mean that the new knot had a strength of 220 pounds.  Equivalently, if an original knot had a strength of 40% of the ultimate breaking strength of the material in which it was tied, then the new knot would have a strength of 44% of the ultimate breaking strength of that same material.  Just making sure we are talking apples to apples - thanks.

DDK

SS369

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Re: Dressing a figure-eight loop?
« Reply #8 on: September 18, 2011, 04:07:39 PM »
I think that the subject, the 10% Reduction in strength, is a guess at best not proven sufficiently. But, I do think that what is meant (I could be very wrong) is that if the correctly dressed re-threaded figure 8 loop had a so called strength of 40% of the un-knotted line that the incorrectly dressed affair would then be at 30% of the breaking rate.

SS

xarax

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Re: Dressing a figure-eight loop?
« Reply #9 on: September 18, 2011, 05:45:00 PM »
paths "railroad tracking" each other

   Do you mean that this description is an unambiguous one ( is sufficient to help us dress the knot in one, the best, way), or that any dressing where the paths can be described as such, is adequately strong ?
« Last Edit: September 18, 2011, 05:45:37 PM by xarax »
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SS369

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Re: Dressing a figure-eight loop?
« Reply #10 on: September 18, 2011, 08:59:00 PM »
Paths "railroad tracking" is a one-timer. For this topic/knot only. Use at your own risk. lol

It may or may not have relevance to other knots and their proper dressing.

It is a term used by "decorative" knotters, braiders and such to communicate that the path of another line follow alongside, in essence parallel the first line's path.
Although I think a picture notated would be infinitely better, yes, I do think this is an adequate descriptor for the dressing of the re-threaded figure 8 loop.
That is if anyone understands it.
;-)

SS

xarax

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Re: Dressing a figure-eight loop?
« Reply #11 on: September 18, 2011, 11:21:32 PM »
   Railroad tracking, or roller coaster tracking ? That is the question...
   It is amusing that a car that runs on the (parallel) tracks of the "common" figure 8 A, d'Artagnan bend (1) makes 2 inversions ( it turns upside down two times), so it looks more like a roller coaster car, while the car that runs on the (also parallel) tracks of the figure 8 B, Athos bend, tilts but does not turns upside down, so it looks more like a railroad car. ( A car on the tracks of the C, Porthos bend, makes 2 inversions -like at A-, while at the tracks of the D, Aramis bend, makes only 1.)

1) http://igkt.net/sm/index.php?topic=2198.0
« Last Edit: September 18, 2011, 11:27:20 PM by xarax »
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SS369

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Re: Dressing a figure-eight loop?
« Reply #12 on: September 18, 2011, 11:26:58 PM »
Roller-coasting, in the final dressed form, may be more apt, but it makes me dizzy! ;-)

SS

DDK

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Re: Dressing a figure-eight loop?
« Reply #13 on: September 19, 2011, 04:00:31 AM »
There is something to be said for a bend which can be easily identified as having been tied correctly.  This would seem to favor the "perfect" forms of the Figure 8 Bends and Loops.  Along with our love affair with symmetry, this likely explains the popularity of teaching the "perfect" forms.

As far as "strong" vs. "weak" for the Figure 8 Bend, I find the "weak" form more natural when tying from the Thief Knot.  In addition, I do not care for the distortion in the "strong" form where the outer collars try to "overrun" the inner collars.  Admittedly, if the "strong" form is actually stronger, this "distortion" is likely part of the reason.

DDK


xarax

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Re: Dressing a figure-eight loop?
« Reply #14 on: September 19, 2011, 09:47:30 AM »
Along with our love affair with symmetry, this likely explains the popularity of teaching the "perfect" forms.

  There 17 symmetric figure 8 bends, to my latest counting... :) (1) .I doubt that one can prove, with any simple means, that any one of them is more symmetric from the others. The figure 8 bends presented at (2) are symmetric, too ! All those bends can be tied as easily as any one of them, because they are formed by the same number of tucks..I  am afraid symmetry by itself can not help us decide which are the best forms. We need detailed  tests, that are missing. The popularity of teaching the so-called "perfect" forms can only be explained by ignorance from the part of the teachers - and the well known attitude of all ignorant teachers to hide their ignorance under some rug...Are we also going to pretend that we know, when we simply do not, and keep parroting the same old wrong things ? Knotting is not going to be promoted that way, that is for sure.

1) http://igkt.net/sm/index.php?topic=2198.0
2) http://igkt.net/sm/index.php?topic=3148.0
This is not a knot.