Author Topic: a new way to tie the alpine butterfly knot?  (Read 13629 times)

agent_smith

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Re: a new way to tie the alpine butterfly knot?
« Reply #30 on: April 22, 2015, 11:06:58 AM »
Quote
The CMC rescue guide states that the alpine butterfly has a efficiency of 75% when the loop is loaded, and 57% when pulled end to end

Hmmmmmmmmmm.

Strength is irrelevant.

For rope rescue and general climbing applications, knot strength matters least. What matters most is:
[ ] security
[ ] stability
[ ] jam resistant
[ ] and a 'new' concept (from mobius) that has long been understood but rarely documented - verifiability.

Note that I have not arranged these in any particular order of importance.

I also wish the knot could be referred to simply as a 'Butterfly knot' as it was previously known per Wright and Magowan (Note: Originally known as the 'Lineman's rider' per AA Burger 1914).

Mark


xarax

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Re: a new way to tie the alpine butterfly knot?
« Reply #31 on: April 22, 2015, 11:32:17 AM »
... the knot could be referred to simply as a 'Butterfly knot' as it was previously known per Wright and Magowan
 ( Note: Originally known as the 'Lineman's rider' per AA Burger 1914).

   Where did this "Alpine" come from ?
   
   Strength is irrelevant.

  OK. When they will come to rescue us, I will let you go first ( provided you grasp the loop with the weaker knot, of course, because knot strength is irrelevant to you ), and then I will try my chances with the other one... :) 
This is not a knot.

agent_smith

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Re: a new way to tie the alpine butterfly knot?
« Reply #32 on: April 22, 2015, 12:46:10 PM »
No problem xarax.

I have always wanted to travel to Greece and climb there (eg Kalymnos) - I have read a lot about climbing in the Greek islands and it looks absolutely spectacular. If I visit - i would like to meet you and take you on a climbing adventure :)  See also: http://climbgreece.com

By the way, Sterling 11mm diameter abseil rope has a typical MBS of 31.1kN (thats over 3 metric tons) - even with a worst case scenario of 50% loss of strength due to a poor knot - you still have over 1.5 metric ton remaining. As an example, I weigh 100kg.
Sterling dynamic rope example ('Evolution Velocity'): http://www.sterlingrope.com/c/climbing_dynamic-ropes_9-8mm-evolution-velocity?action_type=switch_product&selected_cat_keys=1114670.46335.1114274.0.0&selected_product=1d60eff37814c55515ec6ef2334af5c8&redirected_post=1   NOTE the absence of any MBS / Ultimate tensile strength data!
[ ] Another popular climbing rope: 'Beal Joker' http://bealplanet.com/sport/anglais/corde-joker.php      Note again lack of ultimate tensile strength data!

Tie-in knots dont cause rope failure - the main culprit is falling over a sharp edge - thats a very bad thing for a rope. Another issue is cyclical loading over a rough/abrasive/sharp edge as can happen when a fixed rope rubs repeatedly over the said rough/abrasive edge (caused by the cyclic bounce of ascending or descending).

When I take falls in lead climbing, the thought that runs through my head is whether my gear placements will hold or whether my rope will run over a sharp edge. I'm never concerned about % strength remaining due to the tie-in knot on my harness.

Mark



xarax

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Re: a new way to tie the alpine butterfly knot?
« Reply #33 on: April 22, 2015, 01:20:29 PM »
   You know much better than me that nowadays very few people climb with an 11 mm rope...
   Also, knots can also be tied on the much thinner personal escape ropes ( I have read that many people use 5mm ! ) - and there is always the possibility a single rope will be used by a rescuer and a rescued, that is, a load of two persons. You should also take into account the dynamic aspects of the loading, because the load and/or the vehicle on which it is attached by the rope moves, and the speed and direction of this motion may change abruptly.
   However, I was not talking only about climbing and rescue ropes... Knots on ropes are used by riggers in transportation, lifting and construction work, in mooring lines, in fishing lines, etc. You should not suppose that the safety factors on all outdoors activities are as high as in climbing. You can never know how strong a gust of wind or a wave will be - so, if you can chose from more than one "similar" - regarding every other safety characteristic and factor - knots, it is reasonable to select the strongest of them, just in case. A strong knot does no harm...
   Ask a fisherman if he believes that the strength of the knots he ties on ins lines are irrelevant or not ! Of course, if you are not hungry, and you also wish to offer one more chance to the poor hungry fish, you tie the weakest knot you know...  :) 
« Last Edit: April 22, 2015, 01:42:53 PM by xarax »
This is not a knot.

xarax

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Re: a new way to tie the alpine butterfly knot?
« Reply #34 on: April 22, 2015, 01:46:34 PM »
   Do nt take me wrong... I am not saying that the strength of a knot is the first thing that will make me chose the one knot or the other !  It is most probably the very last thing - but it is not irrelevant !
This is not a knot.

agent_smith

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Re: a new way to tie the alpine butterfly knot?
« Reply #35 on: April 22, 2015, 01:53:05 PM »
Xarax,

11mm (7/16 inch) diameter low stretch rope is very popular and is the gold standard for vertical rescue and industrial rope access work. Fire rescue teams use 13mm (1/2 inch) diameter rope which has an even higher MBS.

Dynamic climbing ropes are getting thinner - I like to use a Beal Joker but Sterling USA also make great dynamic ropes.

In the context of the original poster, it appears to me that he works at height (maybe rope access and some rigging with cranes) and might also do a bit of climbing??? The Butterfly knot he posts about is mostly used in rope access work and also climbing applications (including rope rescue). I dont think he was referring to fishing line or fishing applications.

I standby my assertion that strength is not a critically important factor in modern kernmantel ropes (either EN1891 low stretch or En892 dynamic).

What matters most is what I alluded to in my previous posts - ie security, stability, verifiability and resistance to jamming.

...

Do you live anywhere near Kalymnos?

Mark

xarax

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Re: a new way to tie the alpine butterfly knot?
« Reply #36 on: April 22, 2015, 02:52:45 PM »
  13mm is NOT 1/2 inch !  :)
  I had pointed out that your calculations were based on an 11mm rope, while now, as you say, even ordinary climbing ropes are getting thinner. A 7.8 mm rope has half the <area> of an 11mm rope ( so, presumably, half the strength, too ) - and you had also ignored the factor of dynamic loading. And a 5.5mm personal escape rope the one fourth of that... So your 1.5 metric tons of strength become much less, and your 100 kilograms of weight become much more.
  Personally, I am not interested where a knot may be used, and/or by whom - even whether it will be used, by anybody, or knot !  :) :)  I am interested in each and every possible simple knot per se - as a structure, a mechanism, a physical object.
   Have you ever measured the area of a triangle ? I suppose you did, but you had not used the formula which derives the area of the triangle from the lengths of its sides - and I am sure you do not consider the existence of this formula "irrelevant" to geometry. Recently, a generalization of this formula was offered for the volume of a polyhedron, where all the faces are triangles - and this proved the theorem that every such polyhedron has a constant volume, even if it is flexible ! You can squeeze it and transform its shape, but its volume remains the same.
   No, we do not need to know which knot is stronger of which, only to use this knowledge, in general, and to use this knowledge to do a particular job, in particular. We want to do our job as correctly and accurately as we can, and our job is to learn about knots as much as we can. If everybody, everywhere, does the same, then there will be much less accidents ( and possibly no murders at all !  :))
   ( There are thousands of rocky islands in my neck of the woods  :) - I am sure we will find one to test the strengths of our knots !  :) You will climb, I will watch and rescue... )
« Last Edit: April 23, 2015, 08:05:47 PM by xarax »
This is not a knot.

agent_smith

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Re: a new way to tie the alpine butterfly knot?
« Reply #37 on: April 22, 2015, 04:25:57 PM »
Sorry Xarax, I was 0.3mm out. In Australia, we are fairly easy going in nature and it is normal to round up to 13mm.

It is common to say that a half inch is 13mm (rule-of-thumb).

To be exact; Half inch = 12.7 mm

I'm not going to continue any further debate about about this matter as it is getting further off topic.

I do hope that future knot reviewers spend less time discussing pure % strength and focusing more on security | stability | resistance to jamming | verifiability | .... :)

I came across a board gaming group called HAMTAG the other day. Acronym for 'Half As Much, Twice As Good'.  I am transposing this concept toward keeping things as simple as possible - that is; less convolution, less bulk, simplicity, it just works.

having said that, examining raw strength data can give us insights into the relationship of knot structure and trying to pinpoint the localised region of rupture when rope is pulled to failure. But I maintain that raw knot % strength reduction in relation to the same unknotted rope is really not a crucial factor in human life support applications (like climbing, abseiling, caving, vertical rescue, etc).

For example, I use #1410 for retrievable abseils (rappel systems where you need to retrieve your ropes from below). In a raw pull test - this knot would yield low % strength figures. And yet, it is 'fit-for-purpose' - it is the best choice to ensure ropes will retrieve around a 90 degree edge. Strength is not important - what is important is being able to retrieve your ropes. I have already alluded to the dangers involved with stuck ropes. It is a nightmare scenario - I remember wanting to climb Great Trango tower in the mid 1980's (Karakorum Himalaya) - only to learn of the Norwegian tragedy during their epic descent. This spooked me and my team mates and we switched to a satellite pinnacle of the Ogre group. My point is that #1410 is a 'weak' knot - but it works well (it wont cause the ropes to suddenly and catastrophically fail). I have often descended in a tandem configuration on this end-to-end joining knot - meaning 200+ kg. The knot works.

Mark




xarax

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Re: a new way to tie the alpine butterfly knot?
« Reply #38 on: April 22, 2015, 05:46:04 PM »
   To be exact; Half inch = 12.7 mm

   Therefore, if you want to round it up, 1/2 inch is 12.5 mm, not 13mm.
   Therefore, your rounding was 0.5mm out - 4%  :)

...a crucial factor in human life support applications ( like climbing, abseiling, caving, vertical rescue, etc ).

   Please, read my previous post more carefully, again.
   Knots are utilized by humans ( like numbers do...), but knot tyers can also study them for their properties as knots, independently of their applications ( like mathematicians study numbers, independently of their usefulness in counting apples... :)) . You can design, built and use wheels to go to the next village and steal the other chief s wife, but you can also study the properties of the circle per se. And pi, you know, should not be rounded to 3...  :)
   Anyway, knots are NOT used only in "human life support applications", by "climbers", etc ! To learn who needed most, and contributed most in the evolution of practical knots, read the very first sentence of ABoK !  :)  The absolute strength of a knot is not "nonsense" or "irrelevant", because there is always the possibility of an unexpected, uncontrollable, excessive loading, which will test the properties of this-knot-assisted structures beyond the "safety factors" ( those structures may be just scaffolds made of ropes, knots and bamboo poles, used now, as we speak, at construction sites in China and NorthEast Asia...).
   You are a climber, and it comes natural for you to "see" the knots merely as means to your beloved end, so you are interested mainly in knots utilized for climbing, and mainly in the properties of those knots which are useful in climbing  - the hammer and the nails ontological relation, you know... :)

  Strength is not important - what is important is being able to retrieve your ropes.

  In THIS particular application ! In other applications, the priority relation may differ, or even be the exact opposite.

   The knot works.

   So what :)  Almost ALL knots, even the most dumb ones ( like three-four overhand knots or half hitches, the one after the other, for example ) will "work", in most cases... Do not limit your view in what a knot can do, "see" what a knot is independently of the particular application - and even independently of any application ! Knowledge has a "value", which may be transformed into a "price" hundreds of years after it is acquired - or never ! 
   Every even integer number can be expressed as the sum of two prime numbers. NOBODY will "use" this conjecture ( still unproved ), ever ! However, thousands of people, for the last 250 years, who study numbers, are "wasting" their lives trying to "see" the truth of this most simple fact, beyond any "practical" reason.
« Last Edit: April 22, 2015, 05:56:32 PM by xarax »
This is not a knot.

knot rigger

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Re: a new way to tie the alpine butterfly knot?
« Reply #39 on: April 22, 2015, 08:06:38 PM »
Hi guys, 

Quite a debate :)

agent_smith, I work as a rigger in the entertainment industry, mainly acrobatic rigging currently, but my experience includes arena, theatre, circus, hemp-house, fall arrest, and ropes access rigging.  I have some limited hands on knowledge of sailing and arborist rigging as well, as theatre rigging borrows from many other fields.

I agree with you that strength is not the only consideration in a good knot.  But perhaps not the least important.  I would use the term inspection, or inspectability, instead of verifiability, but I understand what you mean.

As far as #1410 goes, I personally wouldn't allow it in a ropes access environment, or for lifting heavy loads overhead (regardless of design factor).  It doesn't meet my criteria for stability.  I do know that it is widely used, and I understand why you haven't used it's common (usa common) name :)

I consider myself fairly well read on the topic of knots, but haven't come across  "Wright and Magowan"  Could you tell me the name of their work, so that I could find a copy?  Thanks.

Lastly,  what do you think of my method of tying the butterfly?  Is it original, and does it have merit? 

as for you Xarax:

I am seeing, more and more, that we have different points of view on knots.  I wonder if you've ever used a knot for a practical application, or if they are just objects for you to admire and dissect?  Knots came into existence to do a job, to serve a purpose.  I judge a knot by how well it serves a purpose, even "decorative" knots serve a purpose, and most were invented by sailors to do a job, the fact that they are pretty is an added bonus.

You've said a lot in this thread, but you haven't told me if you think my new method of tying the ABK has merit, of if it is original.

Thank you both for your input, I've greatly enjoyed reading your posts

andy

alpineer

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Re: a new way to tie the alpine butterfly knot?
« Reply #40 on: April 23, 2015, 03:48:08 AM »
Alpineer:
The two methods you mention of tying the ABK: would those be the hand wrapping, and twisting methods?

Well, yes and no. They are ergonomic adaptations, or re-interpretations, of how the traditional methods are typically depicted. The hand-wrap version is closely related to the "Hybrid" method as it uses one less wrap than the trad.
« Last Edit: April 23, 2015, 04:51:00 AM by alpineer »

Dan_Lehman

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Re: a new way to tie the alpine butterfly knot?
« Reply #41 on: April 23, 2015, 07:25:13 PM »
  13mm is NOT 1/2 inch !  :)
  I had pointed out that your calculations were based on an 11mm rope, while now,as you say, even ordinary climbing ropes are getting thinner.
A 7.8 mm rope has half the diameter of an 11mm rope ( so, presumably, half the strength, too ) ...
Evidently, you outnumbered yourself!   :o   ::)
(11/2 < 7.8, well less.)
You must've intended "... the material/volume",
which presumably implies strength.

In common rope parlance, I think that much of rope
sizing is based on "nominal" sizes, with specifics coming
from weight-per-100' or whatever.  Oddly, in rockclimbing,
ropes now are specified by fractions of a millimeter!!!
This must seem ludicrous to other rope users!  (IMO, yes!)
For one thing, just making such an exacting measure
(fraction of mm) seems dubious.  (In the good ol' days,
it was 9 & 11mm, 3/8 & 7/16th inches.)


--dl*
====
« Last Edit: April 23, 2015, 07:34:37 PM by Dan_Lehman »

alpineer

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Re: a new way to tie the butterfly loop?
« Reply #42 on: April 23, 2015, 07:55:12 PM »


I notice that if you accidentally reverse the loop twist of the very first step, you end up with an evil imposter knot for the butterfly loop, namely the half-hitch loop

xarax

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Re: a new way to tie the alpine butterfly knot?
« Reply #43 on: April 23, 2015, 08:09:41 PM »
  Evidently, you outnumbered yourself!   :o   ::)

  Lost in the copy and paste... Obviously, I intended to write, and meant, "area", not "diameter". THAT is the meaning of the "too", too !  :) Strength depends on the cross-section s area, not the diameter, of course.
This is not a knot.

knot rigger

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Re: a new way to tie the alpine butterfly knot?
« Reply #44 on: April 23, 2015, 10:33:09 PM »
So I've found out this method is (as I suspected) not new, and is know to some folk out there.  I have by no means exhausted the possible forums to post this method, but I did find some arborists in the uk to whom this method is know.  One guy described learning it back in 98! At an arborist convention.

If I find out more, I'll post it here

Andy