Author Topic: In search of the goldilocks bend! (joining abseil ropes)  (Read 20835 times)

alpineer

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #15 on: July 06, 2011, 01:21:03 AM »
Please, give a slow typist a chance.  

 :) And you should also take into account the fact that I was, simultaneously, responding to the other thread, too !
    Do you consider the one-sided double overhand knot a "fancier" solution ?  I would say that it is "simpler" than the two overhand+the stopper knots mentioned above. What about the Salty Crackers -ABoK#1031 alternative to the fisherman s knot?

By "fancier" I mean more complex (though t'is a pretty thing to behold) than compounded Overhands. Considering ABoK #1031 and the Fisherman's, I use ABoK #1031 Bend for tying my abseil backup hitch loops (I like it).
« Last Edit: July 06, 2011, 02:09:17 AM by alpineer »

agent_smith

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #16 on: July 06, 2011, 06:03:27 AM »
Here's another variation of the Offset Overhand Bend (aka Offset Ring bend)... Could this the Goldilocks Bend?!

I like this one because:
[ ] Relative ease of tying - only adds one 'binding loop' to the existing structure (an idea borrowed from Dan Lehman's 'End Bound Double Bowline')
[ ] Secure and stable up to 3kN (tested by load cell today - as a double strand to duplicate double rope abseil descent - since force would be split between 2 rope strands)
[ ] Translates around a 90 degree edge due to its small profile - unlikely to become stuck at a 90 degree edge from low set anchors (similar profile to Offset Overhand Bend #1410)
[ ] Easy to untie (bounced my 100kg body mass for 30 seconds - no problem untying after loading)
[ ] Works well with different rope diameters (I played with 8mm and 11mm cords - seemed to bind well)




Comments please...

By the way, I'm not convinced of the criteria "relative ease of tying"...a climber by definition is already competent in tying a range of knots (eg Prusik hitch, Double Fishermans, Clove hitch, Tape knot / Ring bend, Figure 8 loop and rethreaded method of tying, Bowline variant (eg my EBSB variant), French Prusik, Double figure 8 loop (AB0K #1085), etc etc. Some of these knots are arguably 'difficult' to tie. It comes down to practice, practice and practice. Anything is hard at first (eg learning to drive a manual car) - but over time and with practice, it becomes 'easy'.

Statistically, more climbing is done on nice sunny crags with easy access in comparison to high altitude mountaineering in gales force winds, subzero temp and with oxygen starved brains...in any case, the high altitude mountaineer still had to tie and use some knots just to reach the summit. I don't accept that one knot from a repertoire is going to be more or less trickier than another. One could argue that a double F8 loop (ABoK #1085) is 'tricky' to tie. One could also argue that tying a figure 8 (ABoK #1047) into ones harness is also 'tricky' (its a 2 step process).

Be that as it may, my current 'Goldilocks Bend' is the image shown below.. aka 'End Bound Offset Overhand Bend' (mouthful of words).

Mark
« Last Edit: July 06, 2011, 06:05:31 AM by agent_smith »

xarax

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #17 on: July 06, 2011, 07:11:06 AM »
The Offset Double Overhand Bend uses more rope than is necessary

   More rope, relatively to which knot ? Is the supposed economy of rope length a virtue for climbers ? Who continue to tie the double eight bend...
 
and is unnecessarily bulkier (and is therefore more likely to get caught On or In some natural terrain feature) than the Offset Water Bend (a.k.a. EDK).

True. It is bulkier, although not very bulky, because, when tightened, it takes a cylindrical, elognated form.

So why would you use it? Because it's prettier? Not a good enough reason. It also takes more hand gymnastics to tie.
alpineer

Is it prettier ? I would not go as far as to use the word "pretty" for it, no...but, of course, it is less ugly than the two knots mentioned above !  :)
   I think that it is a "simpler", easier and quicker to tie knot -  actually, it can be tied with less hand gymnastics in one move, although it is more difficult to dress correctly.
   Again, I repeat that have not made any suggestions bearing any knowledge and expertise of climbing, like your suggestions.
« Last Edit: July 06, 2011, 07:22:48 AM by xarax »
This is not a knot.

xarax

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #18 on: July 06, 2011, 07:21:48 AM »
Here's another variation of the Offset Overhand Bend (aka Offset Ring bend)...

  I see it as halfway solution between the simple one sided Overhand bend and the double one sided Overhand bend. It is less bulky than the later, but more asymmetric, too. As it is a one piece knot, I like it more than the compound knots proposed by Dan Lehman...
This is not a knot.

agent_smith

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #19 on: July 06, 2011, 07:46:02 AM »
Thanks xarax, I like it too :)

I haven't seen it published before..or anywhere on the net (have you?).

I want to be up front and admit that the binding loop idea is borrowed from Dan Lehman (who in my opinion is a great thinker and contributor to world knotting knowledge).

I'm not sure what the proper naming convention ought to be for this particular knot (bend).

Dan appears to favour the term 'offset' to indicate any knot/bend that is what you call "one-sided".

My view is that the 'off-set' structure is a crucial form for any knot/bend that must translate around a 90 degree edge from low set anchors.

I haven't done enough rigorous testing of ABoK #1410 (offset overhand bend) particularly with wet/icy ropes and with climbing ropes that have a slippery, tightly woven sheath (all climbing ropes differ in their sheath texture and structure from one manufacturer to another). It is possible that one day I may encounter a particular combination of factors that causes ABoK #1410 to become unstable at relatively low force. The crucial force threshold will be on or about 3kN (approx 300kg) - this assumes worst case scenario of 2 person accompanied descent (ie assisted abseil) with some bouncing/cyclic loading en route. Therefore, any joining knot (bend) must remain secure and stable up to at least 3kN under all conditions...
Math note: The 3kN downward force is applied on double ropes - that is, 2 ropes share the force of 3kN (1.5kN per individual rope strand). The Bound Offset Overhand bend would only be subjected to half the load.

I think that the 'binding loop' that I have added to ABoK #1410 increases its security and stability (I'm not sure what term Dan Lehman will want to give to this structure).

Perhaps a better name should be 'Bound Offset Overhand bend'... need advice here.

Mark
« Last Edit: July 06, 2011, 08:26:39 AM by agent_smith »

xarax

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #20 on: July 06, 2011, 08:10:33 AM »
I think that the 'binding loop' that I have added to ABoK #1410 increases its security and stability

   No doubt about it ! It increases its security and stability greatly, and also it increases its resistance to dynamic loads, due to internal cushioning (1).

1) http://igkt.net/sm/index.php?topic=3148.msg18846#msg18846
« Last Edit: July 06, 2011, 11:04:21 AM by xarax »
This is not a knot.

agent_smith

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #21 on: July 06, 2011, 08:27:29 AM »
Edited my post...see above.

Mark

alpineer

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #22 on: July 06, 2011, 08:29:32 AM »
Hey Agent Smith,
It's good to see you back on the forum. You must have been busy what with all the flooding going on in your part of the world. I hope things are going well for you.

 
Here's another variation of the Offset Overhand Bend (aka Offset Ring bend)... Could this the Goldilocks Bend?!

 By the way, I'm not convinced of the criteria "relative ease of tying"...a climber by definition is already competent in tying a range of knots (eg Prusik hitch, Double Fishermans, Clove hitch, Tape knot / Ring bend, Figure 8 loop and rethreaded method of tying, Bowline variant (eg my EBSB variant), French Prusik, Double figure 8 loop (AB0K #1085), etc etc. Some of these knots are arguably 'difficult' to tie. It comes down to practice, practice and practice. Anything is hard at first (eg learning to drive a manual car) - but over time and with practice, it becomes 'easy'.

Statistically, more climbing is done on nice sunny crags with easy access in comparison to high altitude mountaineering in gales force winds, subzero temp and with oxygen starved brains...in any case, the high altitude mountaineer still had to tie and use some knots just to reach the summit. I don't accept that one knot from a repertoire is going to be more or less trickier than another. One could argue that a double F8 loop (ABoK #1085) is 'tricky' to tie. One could also argue that tying a figure 8 (ABoK #1047) into ones harness is also 'tricky' (its a 2 step process).

Be that as it may, my current 'Goldilocks Bend' is the image shown below.. aka 'End Bound Offset Overhand Bend' (mouthful of words).

Mark

But your OOB Variation offers us nothing that we don't already have in the OOB +Stopper. In fact less. It's more bulky, at least from the more important footprint perspective. It's not that it can't work. But why add unnecessary bulk? What do you get for it when considering the bigger picture? Your quoted arguments are understood, but if accepted in their fullness, still leave us no better off than before IMO.  Show me something else.

agent_smith

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #23 on: July 06, 2011, 08:58:54 AM »
Thanks alpineer...

No major flooding in my town - be we had a glancing blow from cyclone Yasi (only 130kph wind force)... many trees down and we lost power for 3 days.

Anyhow, here is some trivia for you (and tongue-in-cheek):

ABoK #1410 Offset Overhand bend was found on the 'iceman'  - he was dated at 3300 years old.

I like to think that I (your humble agent smith), have evolved a bit further than the iceman :)

My little addition of the binding loop is a nice innovation (even if I do say so myself :) ).

I already did a quick field test up at my local crag and deliberately rigged the retrievable abseil (rap for Yanks) over a rough 90 degree edge. I deliberately set the anchors low. During the abseil descent, I threw in some cyclic loading (by bouncing on the way down) for good measure. I am 100kg mass.

I survived the experience :) No problems untying the knot and tail lengths had not drawn in by any significant amount.

As xarax pointed out, the binding loop does add some internal cushioning and it also adds another rope diameter to the structure (which I thought any self-respecting IGKT forum member would approve of :)  ).

I like this derivative of ABoK #1410 - but maybe the iceman was right all along? Maybe I am wrong!


Mark

xarax

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #24 on: July 06, 2011, 11:11:53 AM »
ABoK #1410 Offset Overhand bend was found on the 'iceman' 
   
  Ice man was tyng knots 5300 years ago ! (he was living at 3300 BC) :)
This is not a knot.

Morgoroth

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #25 on: July 06, 2011, 12:28:47 PM »
You'll have to forgive me here as I am relatively new to this high level of knotting, but if the climbers are already familiar with a figure-8 with a follow through, couldn't you use that as a more secure bend?

You could still tie it in an offset manner, and while it is still larger than the Double-Offset-Overhand the edge that would encounter the cliff in those 90degree corners is relatively small.

alpineer

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #26 on: July 06, 2011, 03:24:19 PM »
You'll have to forgive me here as I am relatively new to this high level of knotting, but if the climbers are already familiar with a figure-8 with a follow through, couldn't you use that as a more secure bend?

You could still tie it in an offset manner, and while it is still larger than the Double-Offset-Overhand the edge that would encounter the cliff in those 90degree corners is relatively small.

Welcome Morgoroth,
The Offset Figure 8 (a.k.a. Flemish) Bend has been used for Abseiling/Rappelling. However, it cannot be recommended for life critical situations due to it's propensity to invert, or roll, at very low static loads (much lower than the Offset Overhand Bend). It has been implicated in several deaths .

alpineer

Morgoroth

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #27 on: July 06, 2011, 03:40:59 PM »
Well that is good to know.

So it is not good for a bend, but does well as a loop?

alpineer

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #28 on: July 06, 2011, 04:31:24 PM »

So it is not good for a bend, but does well as a loop?

No, it's fine as a Bend used in the traditional manner, but not as an Offset Bend.

Morgoroth

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #29 on: July 06, 2011, 04:50:06 PM »
OOOoooooo.  Ok.

Thanks.