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tugboat
Jul 30, 2011, 5:13 AM
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OK well... I botched this test a bit. So i will do it again in the next day or so.
Long story short... due to rope stretch and knot cinching.... i ended up running out of ram stroke. Pretty wild since i tried to make the test sample quite short,...knowing i would need all my ram length (4 feet). But i still ran out.
I also waffled about what my first test scenario would be. I ended wanting to know if a "short" Yosemite tail finish would be a problem due to knot slip; so i used a short yosemite finish on one end (two inches) and a long Yosemite finish on a figure eight on the other side of the sample.
Result: After running out of ram, i loaded up around 3100lbs. There was no problems in the knots. So i decided to rerig the same sample and bust it anyway. THe rope broke in the knot at the long Yosemite tail finish at 4500 lbs. Remember, though, this sample had already been prestressed to 3100 lbs...and then pulled again to destruction.
While the video footage does lend some info,...it doesn't reveal the answers to the 'requested' info, ie "does the "Yosemite finish" improve break strength?".
Looking back the next (better) test now will be; A regular eight at one end and a Yosemite finish eight at the other. Or does someone have a suggestion for the best setup?
Note: the rope used was 11mm dynamic rope from Rocca. It is all black,...so some might think it is static rope, but its not. I had the rope custom made for the film industry. It was woven to UIAA and EN 892 standards. While unused and well stored,...it is over ten years old.
Anyway,... i'll edit the video and put it up tonight. If anything, it shows the dynamics of the knot, even, with a short tail. And it probably shows how multiple high loading decreases break strength.
But i think a better setup/test is in order.
sorry.....had to edit first load numbers to 3100lbs after watching video...my apologies. Final number is correct though.
(This post was edited by tugboat on Jul 30, 2011, 7:30 AM)
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tugboat
Jul 30, 2011, 5:37 AM
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Post break photos....
(This post was edited by tugboat on Jul 30, 2011, 7:54 AM)
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roy_hinkley_jr
Jul 30, 2011, 3:10 PM
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Just curious, why are you even bothering? It's well known that breaking strength of tie-in knots is totally irrelevant. It's also well known that there is zero reason to use a backup finish or knot of any sort with a figure 8. These matters have been put to rest ages ago.
If you want to be productive, test different finishes and backup knots with a bowline. But that doesn't require your pull tester. Breaking things is fun. But your test above doesn't add anything to our body of knowledge. Useless trivia is still useless.
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ncrockclimber
Jul 30, 2011, 3:36 PM
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Thanks for the pics of your test. I am enjoying your posts!
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majid_sabet
Jul 30, 2011, 3:55 PM
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How come my eyes are saying you got static rope ?
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tugboat
Jul 30, 2011, 4:37 PM
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majid_sabet wrote: How come my eyes are saying you got static rope ?
Becasue its all black. thats how i had it produced. I mentioned that in my first post. The UIAA labelling is CE 0083 EN 892....the required labelling for dynamic rope. It was custom ordered since we needed all black rope with no tracers. Dynamic ropes, as i understand it, must have a tracer color woven in.
(This post was edited by tugboat on Jul 30, 2011, 5:13 PM)
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tugboat
Jul 30, 2011, 4:49 PM
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In reply to: Just curious, why are you even bothering?
I was working on someone's request. Thats all. And i like testing and seeing things for myself.
Have a good day roy_hinkley_jr
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tugboat
Jul 30, 2011, 6:19 PM
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tugboat wrote: In reply to: Just curious, why are you even bothering? I was working on someone's request. Thats all. And i like testing and seeing things for myself. Have a good day roy_hinkley_jr
On the other hand, i do see understand the point you are making. I did consider the value of the test, given the energy and time needed for carrying it out. In the end, i decided i was interested in the "Yosemite tail" finish, as was someone else,...so i took the time to do it.
I have not climbed in quite sometime, so i was not aware of the this finish. Rather than spend hours trying to find a pull test of one online.... i thought i'd spend my time outside, doing it for myself and the fellow who requested it.
While i have busted all the basic knots in the past, it has been quite a long time since then. I felt it would be good see it again for myself,...and if anyone else was interested they could check it out.
As i get more involved in 'climbing testing' again,...and start to get back into the swing of things, im sure there are test requests that i will understand the extent to which they have been 'covered' and are not neccessary. For now i just felt like doing this one.
Testing does take alot of energy and time so i will consider the value of the test requests as you suggest.
peace... thankyou for the feedback roy_hinkley_jr.
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cellige
Jul 30, 2011, 8:41 PM
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Hey Tug,
Thanks for the request ! Sorry I couldn't get back to you earlier, work work you know..
As you found out the tail length isn't an issue since its so hard to tie with the incorrect one anyways.. either way the main reason so many use this is that it gets the tail out of the way on the sharp end.
What is interesting to me is that the first bend that the load strand takes within the knot (which is one of the ones that goes around the tucked tail) doesn't seem to be cinched down nearly as hard as the first bend of both of the loop sides.
From the reading I have done on knot tests they usually say the primary factor is the radius that the first bend of the load strand makes. I would imagine that the first bend of the two ends of the loop receive half the tension of load strand on the other side, so why the dramatic difference in cinching?
Kudos on the testing!
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tugboat
Jul 30, 2011, 9:48 PM
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Hey Cellige. PM sent.
Im not a knot expert by any measure. Im sure there are others who could lend better answers than me,...
I have my thoughts... but will let the "knot" experts explain, critque etc.
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majid_sabet
Jul 31, 2011, 6:51 AM
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something just does not add up right with this test setup cause history shows that 99% of rope breakage during pull test is around the first bend in the fig or almost in near the beginning of the knot and here yours broke off above the knot.
This does not make sense .
see this
http://www.rockclimbing.com/...d;page=unread#unread
(This post was edited by majid_sabet on Jul 31, 2011, 6:54 AM)
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tugboat
Jul 31, 2011, 6:54 AM
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majid_sabet wrote: something just does not add up right with this test setup cause history shows that 99% of rope breakage during pull test is around the first bend in the fig or almost in near the beginning of the knot and here yours broke off above the knot. This does not make sense .
Nope... the rope broke in the knot at the ram end. Not above the knot. Not sure why you would say it broke off above the knot?
In reply to: THe rope broke in the knot at the long Yosemite tail finish at 4500 lbs. Remember, though, this sample had already been prestressed to 3100 lbs...and then pulled again to destruction.
(This post was edited by tugboat on Jul 31, 2011, 6:56 AM)
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majid_sabet
Jul 31, 2011, 6:55 AM
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tugboat wrote: majid_sabet wrote: something just does not add up right with this test setup cause history shows that 99% of rope breakage during pull test is around the first bend in the fig or almost in near the beginning of the knot and here yours broke off above the knot. This does not make sense . Nope... the rope broke in the knot at the ram end. Not above the knot. Not sure why you would say it broke off above the knot?
see this link
http://www.rockclimbing.com/...d;page=unread#unread
record shows it generally brakes off inside the knot or just slightly above the bend where rope comes in . looks like yours broke off 12" above the knot or may be you need to post a better photo of fig8 loop so we could see the breakage point.
(This post was edited by majid_sabet on Jul 31, 2011, 6:59 AM)
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tugboat
Jul 31, 2011, 7:01 AM
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In reply to: see this link http://www.rockclimbing.com/...d;page=unread#unread
yup... same conclusions with my setup...
Still don't know why you are saying it broke above the knot when i clearly said it didn't?...
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tugboat
Jul 31, 2011, 7:23 AM
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Just uploading to youtube the post break anaylsis i did right after the break. As in my written description, you can hear me commenting..."it broke in the knot", in the video.
THe knot that broke went out of frame unfortunately. But it was clear it broke at the knot. The rope was broken but still partially shaped in the form of the knot. As well one can feel the knot bends still in the rope fibers at the break point, and compression of the fibers from the loading in the broken knot.
Ps... your anaylsis was similar to my anaylsis to Cellige. So we are on the same page. I just kept my analysis private in this case.
here's the you tube link of post knot break analysis for your benefit.
http://www.youtube.com/watch?v=hVY8vomYVa8
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tugboat
Jul 31, 2011, 7:49 AM
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 Where the knot started
 Where the knot broke
Ok majid?
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tugboat
Jul 31, 2011, 10:21 PM
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majid_sabet, i think what your not understanding is that i had a double eight with the Yosemite finish at both ends of the sample. One just had a shorter tail than the other. Make sense? If you watch first part of the video and read my original description it should be clear. So one side broke "in the knot".
peace.
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majid_sabet
Aug 1, 2011, 1:32 AM
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tugboat wrote: majid_sabet, i think what your not understanding is that i had a double eight with the Yosemite finish at both ends of the sample. One just had a shorter tail than the other. Make sense? If you watch first part of the video and read my original description it should be clear. So one side broke "in the knot". peace.
here are few safety recommendation:
1- Never touch a loaded rope with your hand
2-place a towel over the biners in case they break
3-keep you fig8 loop short, you got 16" in dia loop and no wonder you ran out of pull
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tugboat
Aug 1, 2011, 2:55 AM
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thanks for your concern, but ive been testing for 15 years.
1) the rope was loaded a small amount, no more than a loaded belay.
2) I wasnt pull testing with "carabiners" in this case. They are extremely high strength rigging links.
3) I pull test by hydraulic remote extension behind a lexan/ply safety barrier ten feet to the side.
I thought your concern was the "knot break issue"....now you want to change the subject? I answered all your initial questions (even though they were visible in the video and in the intial written description and you failed to understand it).
majid_sabet...come on.... a little respect.
(This post was edited by tugboat on Aug 1, 2011, 3:13 AM)
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cellige
Aug 1, 2011, 4:06 PM
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Hey tug,
Hope you don't mind me replying here but I know some others might be interested too, and knot forces are always fascinating.
I attached a simple ms paint from your photo.
It was a bit hard to follow what bend or loop either of us is talking about, as it always is with knots when its just a bunch of loops.. So to make sure we are on the same page:
The red line in the photo is the load strand, enters the knot and goes around the red circle. The red circle gets a radius increase from the final tuck. The two blue lines are coming from the loop of the figure eight and appear to be cinched very tight.
As far as I know there are only two ways to tie a properly dressed figure eight, with the only differences being a swap in places of the two blue lines or the red line with its parallel strand. Neither of which will affect its strength according to the tests I have seen, of course with other knots that might not hold true.
So is my layout what you were saying as well? The first bend of the load strand in my eyes is the red circle however I could see if maybe it was deemed to be the 90 degree turn the red line takes when it crosses the blue lines...
It is interesting that the blue lines are cinched so tight in relation to the cinching of the red line around the red circle. Or perhaps that's just the image appearing that way..
No worries about incorrect analysis, there are few scientists in the world that study knots, comparatively speaking.. so its all laymen conjecture; perhaps through the viewpoint of engineers :)
ps. don't fret about majid, sometimes its a bit hard to figure out the way his mind works. He is a local celebrity though :D
(This post was edited by cellige on Aug 1, 2011, 4:10 PM)
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tugboat
Aug 5, 2011, 2:37 AM
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ok...cellige...let me take in everything you are saying. I had a few "Tugboat days" of care taking so now i can put in a bit of time.
Sorry Majit if i came off harsh,...thanks for your concern; all is good.
(This post was edited by tugboat on Aug 5, 2011, 3:44 AM)
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tugboat
Aug 5, 2011, 4:03 AM
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yup...so looking at your photo lines, cellige, we are on the same page re load strands etc.
In this photo i added the yellow to show the tuck back Yosemite tail.
So, yes, the yosemite tail increses bight radius on the load strands first bend. But it increases it from 3 strands to four. And the bight on the load strand from the loop strands is not changed from what i can tell.
So, as roy Hinkley points out,... it doesn't really matter. Both are crazy and strong and if you near those forces you are dead anyway.
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