Author Topic: Offset knot for climbing  (Read 24298 times)

Mobius

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Re: Offset knot for climbing
« Reply #30 on: May 21, 2016, 03:43:21 AM »
I trialed Dan's offset 9-oh knot again in 10.2mm dynamic kernmantle and it works as far as I am concerned.

The approach I took to search for a better offset than the EDK was simple:
Choose 3kN trials of each proposed knot with the expectation that a knot could be found that would not slip or jam at that force. The knot should be no bigger than 50 diameters in the knub.

(48 diameters swallowed in the knub for a 9-oh).

The knots I trialed were not too big. An offset knot that is flat on one side and looks like a 'tower' on the other side makes little sense to me in terms of not getting caught up on a mountainside somewhere. The tower would defeat the flat side to my mind. Smaller is better the way I see it, as long as it doesn't slip or jam.

Dan has argued that 3kN is probably too high a benchmark for this application, however, that as it may be, I have found 3 knots that can do it. One of them is the 9-oh.

The images below:

1) 9-oh set at 70mm tails

2) At 0.5 kN the knot has settled to 65mm

3) At 1.5 kN the knot has settled to 60mm

4) At 3kN none, or very little further movement observable

10mm movement is not what I am going to be picky with and call slipping, the knot has just settled. One could argue that if I had taken the knot to 6kN and it kept moving then some of that first movement was slippage. The knot did not jam at 3kN and was reasonably easy to undo. I took the 9-oh to 3.5 kN on one other occasion and found it was tighter to undo, however not jammed.

It should be acknowledged that dynamic rope trials are generally a much harder task master than static rope trials. One could expect no problems with the 9-oh used in static kernmantle to 3kN (I have trialed it once in 10.2mm static climbing rope and saw the knot perform well).

Cheers,

Ian.
« Last Edit: May 28, 2016, 07:22:18 AM by mobius »

Mobius

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Re: Offset knot for climbing
« Reply #31 on: May 21, 2016, 03:58:08 AM »
Possibly of interest only to me is how the top overhand looks when it is getting tight in some of these offset knots.

The first image is borrowed as a reminder of the knot in question.

The second image shows some compression of the 9-oh after the choke has been easily slid away after a 3kN load. That top overhand looks easy to undo, however I can attest that once that knot gets a bit more on it a hacksaw has been the only remedy I found to undoing it.

Cheers,

Ian.
« Last Edit: May 21, 2016, 05:36:03 AM by mobius »

Mobius

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Re: Offset knot for climbing
« Reply #32 on: May 21, 2016, 07:23:30 AM »
Here is a knot I spent months finding. It is extremely easy to come up with a knot that looks promising until you stick it on a rig and trial it. A knot will slip, jam, twist, collapse and do all sort of unexpected things.

I know the lohf8 style knot I show below looks simple. I was not happy with the knot I first showed here in this thread because it jammed at 2kN in 11.2mm dynamic kermantle rope (see very first post and following discussion). That first post knot was still way better than an EDK in my opinion.

The knot shown in this post is also a 'linked overhand figure 8', however it does not slip or jam at 3kN in 10-11 dynamic climbing rope. It is small and does not even hint at jamming at 3kN. It settled no more than 5mm, no slippage.

Despite the effort that went into this knot I show here, I have one I like better. The work I did trialing the EDK was beneficial in finding that.

The knot in this post is one I will come back to if needed.

Cheers,

Ian
« Last Edit: May 28, 2016, 07:24:58 AM by mobius »

Mobius

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Re: Offset knot for climbing
« Reply #33 on: May 22, 2016, 06:35:54 AM »
Here is the knot I like most for the offset application. I have tested it the most and I like its compact form. It is small knot, not much bigger than an EDK.

I make no excuses/apologies for my often criticized view of the EDK knot that does get used for this application, in many cases with little problem. My preferred knot doesn't slip or jam in dynamic/static climbing materials up to 3kN, the EDK does (and lower levels), simple as that. If you want to entertain using a small profile knot that does not slip, jam and is easy to tie, then this may be it:

http://bit.ly/1VmOZXy

This knot, rather ironically, is the same knot I started this thread with, except the legs are not twisted. Personally, that finding is rather miffing considering the work I put into finding a better knot than the one I first came up with in this thread ::) Playing with the EDK one day made me try the legs the other way. For the EDK that did not help (see a previous post), however it made a big difference to my originally posted lohf8 knot.

Reversing the legs (parallel instead of the twist I thought was a good idea originally) turned my first knot into one that meets the requirements I set, and quite a lot more. The knot I show below does not slip or jam at 3kN in dynamic and does not jam when I took it to 6kN. I did not see any slippage at 6kN either, though I did not measure for it apart from an eyeball.

I have images showing the knot perform at 3kN in static materials, to show later perhaps. There were no observable performance issues in the 10.2mm static material I tried, a material I believe is generally way easier to test successfully compared to similar size dynamic material.

First image: My knot

Second image: Step one in tying the knot. Step two is not hard to work out and that is it, however look at my first post if in doubt. Keep the legs parallel. I really do not think anyone would have too much trouble tying this knot in the wild.

Third image: Knot at 2kN after being set with 100mm tail markings at nil load. There is no movement/slip as far as I am concerned.

Fourth image: Knot at 3kN; we see a nice flat surface still and there was no movement yet

From here:
1) I am going do a presentation doc that will show this knot in a better to see fashion
2) I will test the knot with different size ropes and post results
3) Hopefully, quick pull tests, properly done by someone with lab facilities, however not by me

Cheers,

Ian.
« Last Edit: May 29, 2016, 09:15:47 AM by mobius »

Mobius

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Re: Offset knot for climbing
« Reply #34 on: May 22, 2016, 12:34:31 PM »
Here are two more tying diagrams, the last one is deliberately loose and needs snugging

Cheers,

Ian

Mobius

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Re: Offset knot for climbing
« Reply #35 on: May 28, 2016, 02:29:16 PM »
Work in progress as a presentation, however some better images to look at here http://bit.ly/1VmOZXy

See the knot at 3kN in both kernmantle static and kernmantle dynamic climbing materials.

Cheers,

Ian

Dan_Lehman

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Re: Offset knot for climbing
« Reply #36 on: May 31, 2016, 09:04:21 PM »
Here are two more tying diagrams, the last one is deliberately loose and needs snugging

Cheers,

Ian
Your knot is a sort of "opposed-directions, offset 8-Oh"
in that you have an overhand & fig.8 resp. in the two
ends but instead of their turning in the same direction
and the latter just making its extra half turn --which
would result in the tails exiting in opposite direcitons,
nb!--, you turn them from the start in opposite
directions and thus that extra half turn of the fig.8
brings its tail to join the overhand's in the exit.

The offset 9-Oh makes a surer *choke* of the
SParts's offset entry into the nub.


--dl*
====

Dan_Lehman

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Re: Offset knot for climbing
« Reply #37 on: May 31, 2016, 09:12:25 PM »
First image: The top knot is Ashley's. If the #1410 is tied like this when climbing... good luck ;) At 30 Kg in this material (mbs ~ 2 kN) the knot had rolled and collapsed with a slippage of 15mm. 15mm when we have a 3mm diameter is hard to ignore, it is a lot.  ...
//
The issue was tying the #1410 in the wrong way initially.
Rest assured, ...

We will rest assured if you would please trial the
"EDK-backed EDK" in this material WITH THE ASHELY TWIST
--a sort of worst case scenario (worse yet would be with
dynamic material, maybe wet to boot! ).

I'm not sure why this requested (several times) knot
(knot-combo) continues to be avoided --are you
worried that it will look (too) good?   ::)   ;)
And only load it to a moderately high load,
not a materials-damaging, like-abseiling-bulldozers
among!

It is MUCH more relevant to the particular task of
abseil-ropes joining than loading things to several
times any reasonable force (i.e., > 200 pounds force,
really, an acceptably exaggerated, 2-B-Sure force).


--dl*
===

Tom_Zal

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Re: Offset knot for climbing
« Reply #38 on: June 01, 2016, 01:24:59 AM »
Mobius, just wanted to let you know I did a few informal tests of your knot against other knots with paracord and light cord in a homemade "apparatus" and your knot performed great. Of course the tails did not get pulled in, but also, even after loading to near breaking point, it was easy to untie and and barely damaged the rope. (Jammed one time out of 4, probably I did something tied or dressed it wrong, because it didn't come close to jamming the other times.)

I only tested the plain overhand bend once, and you may be happy to know that ultimately the 12-diameter tails were sucked completely through. I'm sure I tied this knot correctly and set it well. It's just one trial though. And before extreme load, only about 3 diameters were sucked in.

You might want to make some tying pictures/instructions following what Dan said about how it's tied - I think that makes clear that it's similar to tying the basic overhand bend, but one rope turns in the opposite direction, and therefore has gone an extra half turn when it emerges along with the other. I don't know about others but I can learn a new knot easier if it's presented as "it's like this other knot you know, with this difference".

Seems clear that EDK backed by EDK would be secure, since the backup knot is just functioning as an overhand stopper? (Edit: I'm not saying it shouldn't be tested - and I'm aware there are materials in which it would fail.) I would think that's the most realistic option for someone concerned about EDK safety - I mean, that's what they're most likely to use, rather than learning a new knot.

Hey if you're testing the 9-oh I hope you're clear on how it's tied - I just wondered because you asked in a previous post if you tied it right and I didn't see a response. I'm sorry if I'm butting in but wouldn't it be a shame if you tested it and it turned out it wasn't tied to Dan's specs?
« Last Edit: June 01, 2016, 01:46:18 AM by Tom_Zal »

Mobius

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Re: Offset knot for climbing
« Reply #39 on: June 01, 2016, 07:45:23 AM »
First image: The top knot is Ashley's. If the #1410 is tied like this when climbing... good luck ;) At 30 Kg in this material (mbs ~ 2 kN) the knot had rolled and collapsed with a slippage of 15mm. 15mm when we have a 3mm diameter is hard to ignore, it is a lot.  ...
//
The issue was tying the #1410 in the wrong way initially.
Rest assured, ...

We will rest assured if you would please trial the
"EDK-backed EDK" in this material WITH THE ASHELY TWIST
--a sort of worst case scenario (worse yet would be with
dynamic material, maybe wet to boot! ).

I'm not sure why this requested (several times) knot
(knot-combo) continues to be avoided --are you
worried that it will look (too) good?   ::)   ;)
And only load it to a moderately high load,
not a materials-damaging, like-abseiling-bulldozers
among!

It is MUCH more relevant to the particular task of
abseil-ropes joining than loading things to several
times any reasonable force (i.e., > 200 pounds force,
really, an acceptably exaggerated, 2-B-Sure force).


--dl*
===

Hi Dan,

I honestly thought the poorly tied #1410 was the answer to your concern, though not your request(s).

Two poorly tied (Ashley's twist version) back to back will effectively be a knub size of over 70 diameters and therefore, so what if it works? If you cannot tie a knot tie a lot! A knot that size defeats one of the premises of this knot application, that a small footprint is better. I don't think it will 'work' anyway, however let us see.

So, you win, I'll tie it back to back in dynamic climbing material and take some photos at different loads. I have ordered some new rope, so be a little patient please :D

The #1410 is MUCH more relevant for abseiling? I disagree, people are looking at (already using) alternatives as evidenced right here in this forum. The #1410 is simply a benchmark, and not a very good one. If it was so much more relevant then most would be happy with it and this thread (and others on this topic) would not exist; some here and elsewhere are far from happy with it.

An 'offset style knot' has already had several bad press cases , deserved or (perhaps) not, depending on what offset knot it was exactly. However, the EDK moniker did not come from nowhere.

I suspect that the issue for some climbers is not about using the best offset knot, it is about using an offset knot at all!  So I can see the case of where someone reading this could easily say to themselves that an offset knot is not for them, regardless of what trial results show. I knew that view before I even started looking at a new offset knot.

It would be interesting to me to hear from climbers about their current choices in this application.

I am quite happy to trial alternatives to an offset, if there is some agreement about what to test and why.

Cheers,
 
Ian.
« Last Edit: June 02, 2016, 12:55:13 PM by mobius »

Mobius

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Re: Offset knot for climbing
« Reply #40 on: June 01, 2016, 08:47:11 AM »
Mobius, just wanted to let you know I did a few informal tests of your knot against other knots with paracord and light cord in a homemade "apparatus" and your knot performed great. Of course the tails did not get pulled in, but also, even after loading to near breaking point, it was easy to untie and and barely damaged the rope. (Jammed one time out of 4, probably I did something tied or dressed it wrong, because it didn't come close to jamming the other times.)

Thank you very much for taking the time to do some trials. Regardless of the results you reported I would have been very happy to read about them.

Quote from: Tom
I only tested the plain overhand bend once, and you may be happy to know that ultimately the 12-diameter tails were sucked completely through. I'm sure I tied this knot correctly and set it well. It's just one trial though. And before extreme load, only about 3 diameters were sucked in.

I have never seen the tails sucked through, I normally get a jam somewhere. Really interesting, thanks.

Quote from: Tom
You might want to make some tying pictures/instructions following what Dan said about how it's tied - I think that makes clear that it's similar to tying the basic overhand bend, but one rope turns in the opposite direction, and therefore has gone an extra half turn when it emerges along with the other. I don't know about others but I can learn a new knot easier if it's presented as "it's like this other knot you know, with this difference".

I know one reason Dan's 9-oh is easy to tie is that you can tie an EDK first and undo it a bit before re-wrapping one tail. Unfortunately there are other knots that look like a 9-oh and are tied similarly. Those other alternatives might be ok, or not, however I believe I have a better knot regardless. At the end of the day, an overhand knot linked with a figure 8 knot should not be too hard to learn!? Easier than some of the new bowlines, methinks ;)

I can look at another tying method for my knot, however please feel free to suggest something.

Quote from: Tom
Seems clear that EDK backed by EDK would be secure, since the backup knot is just functioning as an overhand stopper? (Edit: I'm not saying it shouldn't be tested - and I'm aware there are materials in which it would fail.) I would think that's the most realistic option for someone concerned about EDK safety - I mean, that's what they're most likely to use, rather than learning a new knot.

Hey if you're testing the 9-oh I hope you're clear on how it's tied - I just wondered because you asked in a previous post if you tied it right and I didn't see a response. I'm sorry if I'm butting in but wouldn't it be a shame if you tested it and it turned out it wasn't tied to Dan's specs?

I am clear how the 9-oh is tied.... just wanted Dan to be clear on that too :)

Cheers,

Ian
« Last Edit: June 01, 2016, 02:32:12 PM by mobius »

Mobius

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Re: Offset knot for climbing
« Reply #41 on: June 02, 2016, 10:52:54 AM »
Here are two more tying diagrams, the last one is deliberately loose and needs snugging

Cheers,

Ian
Your knot is a sort of "opposed-directions, offset 8-Oh"
in that you have an overhand & fig.8 resp. in the two
ends but instead of their turning in the same direction
and the latter just making its extra half turn --which
would result in the tails exiting in opposite direcitons,
nb!--, you turn them from the start in opposite
directions and thus that extra half turn of the fig.8
brings its tail to join the overhand's in the exit.

The offset 9-Oh makes a surer *choke* of the
SParts's offset entry into the nub.


--dl*
====

Hi Dan,

I agree with you from a theoretical perspective, the 9-Oh does appear to make a surer *choke* than my knot (let's call it lohf8m "linked overhand figure 8 mobius" for the moment). I was surprised to see the 9-Oh move (settle) as much as it did in trials whereas the lohf8m does not apparently move at all at similar loads. Why?

One thing that comes to mind for me is that when I look at the lohf8m it reminds me of a Zeppelin style bend. This is especially true for me after I changed the SParts to a parallel orientation and showed everyone the current knot form. All of a sudden the knot worked really well for me in trials, is that just a coincidence?

I do not think so, however theory should meet practice as much as practice should meet theory. I am quite a fan of the Zeppelin style bends and how well I see them working, I suspect that is less true for many. I am interested in your comments please Dan.

Cheers,

Ian.



« Last Edit: June 02, 2016, 11:58:19 AM by mobius »

agent_smith

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Re: Offset knot for climbing
« Reply #42 on: June 04, 2016, 01:37:44 AM »
I think the concept of interlinking #570 'figure  8' with #46 'overhand knot' has merit and is worthy of further investigation.

The overall 'footprint' is not significantly greater than #1410 - and keeping the volume/size as small as possible is an important design goal.

The important goals of stability and security are (at first instance) being achieved... further followup testing by other interested individuals will confirm.

The are a number of possible variations in how the overhand knot (#46) can be woven into the structure of the figure 8 (#570). I will look into which combination is most effective/efficient.

A desirable goal is to find an easy tying method - that consistently produces the correct structure.

Overall - Mobius has discovered a promising line of thinking.

Mobius

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Re: Offset knot for climbing
« Reply #43 on: June 04, 2016, 04:22:36 AM »
I think the concept of interlinking #570 'figure  8' with #46 'overhand knot' has merit and is worthy of further investigation.

The overall 'footprint' is not significantly greater than #1410 - and keeping the volume/size as small as possible is an important design goal.

The important goals of stability and security are (at first instance) being achieved... further followup testing by other interested individuals will confirm.

The are a number of possible variations in how the overhand knot (#46) can be woven into the structure of the figure 8 (#570). I will look into which combination is most effective/efficient.

A desirable goal is to find an easy tying method - that consistently produces the correct structure.

Overall - Mobius has discovered a promising line of thinking.

Thank you Mark, I appreciate the acknowledgement.

A little background. Several months back I spent a number of weeks playing around with and trialing 'linked overhands' in an offset application. I found nothing I liked enough to show here. I generally found knots that would either collapse or jam at too lower load for my tastes. That is not say there is not a good one, I just could not find it.

The linking of an overhand and a figure 8 showed much more promise right from the start for me. I am quite happy to keep trialing these style of knots, if someone has something they think is good. I made this offer to all earlier in this thread, however it is here again. Just because I found one I like, does not mean I am stopping here.

While I am waiting for some new rope to arrive, I think I will do some pictures of the other lohf8 I found (Reply#32). Some might like the way that lohf8 is tied in preference to what I currently like the best.

Cheers,

Ian.
« Last Edit: June 04, 2016, 08:19:17 AM by mobius »

Mobius

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Re: Offset knot for climbing
« Reply #44 on: June 05, 2016, 04:29:57 AM »
Here is the knot I first showed in Reply#32 (let's call it lohf8m2 for now)

Some quick things to note:

1) It has the figure 8 above the overhand, the lohf8m is the opposite case (better or worse?)

2) The lohf8m2 has not been trialed a lot by me, though I am confident it does meet the standards I set at present

3) It looks slightly bigger than a lohf8m (41 diams), I have not measured it yet

4) Look at the last 6 slides of http://bit.ly/1VmOZXy for a way to tie

5) One possible advantage of this knot is that you could start with an EDK and devolve it a bit before re-wrapping the top into a figure 8 (see 4)

(A bit of a hurried effort overall ... work in progress)

Cheers,

Ian.

« Last Edit: June 05, 2016, 09:16:01 AM by mobius »