estarzinger
Well-Known Member
I have just included some more measurement information for the length of line, bury's and loops, in that instruction article I linked to in the OP.
Improved soft shackle
- Thread starter estarzinger
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alahol2
Well-Known Member
I feel really thick because I cannot for the life of me see how you get from photo 3 to photo 4 in the instructions.
tudorsailor
Well-Known Member
I am upset. First I made a schoolboy error in going from pounds to kilograms.
Next I am told that the soft shackles that I made by following diligently the Colligo video are out of date
Lastly, I too cannot see how to follow the photos. If one follows OP's links, the crown knot looks the same as the crown knot on my soft shackles. He is saying that the crown knot is the weakest part of the shackle. Am I right in understanding that although he has made the shackle simpler, the knot remains a crown knot?
TS
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estarzinger
Well-Known Member
Real easy . . .
step one: tighten up the whole mess on the right of photo 3. That all tightens up into the stopper knot on the right of photo 4. Just push it all hard to the right and tighten it up all around until it is really firm. Do you follow that?
Step two: take the 'noose' that is on the left side of photo three and open it up and slip it over the stopper knot you just formed and tightened up, and then slip the noose back closed around the doubled line. Do you follow that?
You are at photo four.
I am honestly interested if you follow, as I will obviously have to fix up the instructions a bit.
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estarzinger
Well-Known Member
The traditional soft shackle uses a diamond stopper knot (see http://www.animatedknots.com/lanyard/index.php?LogoImage=LogoG).
This knot tests at about 45% of line strength in dyneema. and one of the strands always breaks just where it enters the knot.
The stopper in my instructions is not at all diamond. Its very different in many ways. But the key difference, which causes the strength increase, is that I have buried the tails back into themselves, so they are each doubled where they exit the the stopper knot, exactly where they break in the diamond. This eliminates that weak point. You can in fact also do this (bury the tails) with the diamond but it makes the knot too big, because you have double size line in the knot. A soft shackle with the normal diamond will break at about 160% of line tensile, while a soft shackle with one of these buried tail stoppers will break at about 230-250% of line tensile (and it will break at the noose rather than at the stopper)
Do you follow, or is that confusing?
At the slight risk of making this more complex
there is an alternative to the stopper knot that I show in my instructions, which uses the same 'loop bury' approach and is the same strength, but is smaller and easier to tighten up. Some people like the one in my instructions and others like this one better. The bigger one is more secure, but a bit more difficult to tighten up and perhaps more 'obtrusive'. Here is a sequence of photos for the smaller alternative:1. Make the 'loop bury's in each tail', and then bring the noose end thru both loops (note - in these pics I did not actually form the noose but it is the folded end at the right in this photo)
View attachment 40892
2. Then bring the noose end thru the loop you formed in step 1
View attachment 40893
3. tighten up
View attachment 40894
Finally, take a look at http://l-36.com/soft_shackles.php if you are interested in the evolution of soft shackles and how the designs have changed and improved since the Colligo design. These are all 'conventional diamond' shackles - roughtly 160% strength.
If you really like line and knots, take a look at http://www.bethandevans.com/load.htm and at the discussion at http://forums.sailinganarchy.com/index.php?showtopic=154025&page=1. You will see how all this evolved.
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rustybarge
Well-Known Member
The traditional soft shackle uses a diamond stopper knot (see http://www.animatedknots.com/lanyard/index.php?LogoImage=LogoG).
This knot tests at about 45% of line strength in dyneema. and one of the strands always breaks just where it enters the knot.
The stopper in my instructions is not at all diamond. Its very different in many ways. But the key difference, which causes the strength increase, is that I have buried the tails back into themselves, so they are each doubled where they exit the the stopper knot, exactly where they break in the diamond. This eliminates that weak point. You can in fact also do this (bury the tails) with the diamond but it makes the knot too big, because you have double size line in the knot. A soft shackle with the normal diamond will break at about 160% of line tensile, while a soft shackle with one of these buried tail stoppers will break at about 230-250% of line tensile (and it will break at the noose rather than at the stopper)
Do you follow, or is that confusing?
At the slight risk of making this more complex
1. Make the 'loop bury's in each tail', and then bring the noose end thru both loops (note - in these pics I did not actually form the noose but it is the folded end at the right in this photo)
ATTACH=CONFIG]40892[/ATTACH]
2. Then bring the noose end thru the loop you formed in step 1
ATTACH=CONFIG]40893[/ATTACH]
3. tighten up
ATTACH=CONFIG]40894[/ATTACH]
Finally, take a look at http://l-36.com/soft_shackles.php if you are interested in the evolution of soft shackles and how the designs have changed and improved since the Colligo design. These are all 'conventional diamond' shackles - roughtly 160% strength.
If you really like line and knots, take a look at http://www.bethandevans.com/load.htm and at the discussion at http://forums.sailinganarchy.com/index.php?showtopic=154025&page=1. You will see how all this evolved.
Thanks very much for posting these interesting solutions, I've learnt something new!
tudorsailor
Well-Known Member
How about a video from start to finish?
TudorSailor
TudorSailor
vyv_cox
Well-Known Member
I'm very intrigued about your tensile figures. How can you achieve values of 250% of the line tensile without breaking the line first? Can you advise what tensile tester you are using, please.
Very interesting stuff though, I have downloaded your descriptions and will try a few when my Dyneema arrives. Thanks.
Very interesting stuff though, I have downloaded your descriptions and will try a few when my Dyneema arrives. Thanks.
estarzinger
Well-Known Member
This is a cut and paste from my post #18. I believe it explains the tensile results - let me know if it leaves unanswered questions . . . . The 'engineering' of this is: a loop will have twice the tensile of the line used (because there are two pieces holding the load in a loop), and a soft shackle is a doubled loop (there are two strands around a soft shackle). So in theory, a 'perfect' soft shackle will be 400% of line tensile. However, knots in dyneema cut the strength. The diamond knot is about 45% of line strength. That gets you to 180% (400% x .45). There are then typically small imperfections in the shackle construction (typically the two strands are not exactly the same length so one takes more load than the other). And that imperfection gets you down another 20%, on average down to 160% (although if you are very very careful you can/I have made one with near 180%). My 'improved design' replaces the diamond with a stronger stopper (where the exit to the stopper is 4 strands rather than the traditional 2) which moves the weak point to the small bend radius at the noose. This is about a 2:1 bend radius, which 'should be' 65% strength, so in theory 400% x .65 = 260% strength, but again there are imperfections in the construction and my samples have tested at 230-250%.
I have a 5000kg calibrated Dillion load cell and two 5000kg hydraulic rams. I bought the bits for last Christmas and built a 3m test bench to mount them on and have been breaking stuff since. Top line summary of results so far at http://www.bethandevans.com/load.htm
By the way, one application where these soft shackles is brilliant is to replace the chain hook on the snubber. The soft shackle will never fall off, will roll in and out over the bow roller (so you can attach it right on deck without any fiddling over the pulpit) it will not accidentally ding your gel coat, and is strong. . . And is inexpensive (if you make your own) to boot
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rustybarge
Well-Known Member
Just wondering if you could test the shake hands knot in post 17, if you have a few spare moments, obviously it's only a single line loop.
Thanks.
alahol2
Well-Known Member
I think maybe I do. Difficult to visualise if you don't have a bit of rope to try it out with. Just to check, the two loops on the ends of the rope are buried in the middle of that stopper knot?
Thanks for the extra info, it helped a lot.
estarzinger
Well-Known Member
Just wondering if you could test the shake hands knot in post 17, if you have a few spare moments, obviously it's only a single line loop.
Thanks.
I made three tests on it - two of the results I expected, one I was surprised by.
1. for a soft shackle, it is not really right, because it is a bend rather than a stopper. You really want a stopper where the two working strands come out at the same point, where as with this knot the loaded strands come out at opposite ends. I did give it a test, and it was not secure. The noose popped off the knot (at about 1000kgs - about half the load that a 'proper' stopper would hold).
View attachment 40910
2. I tested it as a bend in dyneema single braid. Because dyneema is very slippery, simple bends are very very hard to construct that will hold. None of the conventional ones will hold. Even the triple fisherman slips. So, it was no surprise that this one slipped at 200kgs (16% of line tensile). One of the very few 'bends' that will not slip in this material is back to back estar knots. Or you can use one of the very simple tuck splices, like the brummel.
View attachment 40907
3.I then tested it as a bend in new dacron double braid. The construction looks similar to a number of other good bends (like the zeppelin) and I expected it to hold similarly. But it also slipped here, at 1000kgs (50% of line tensile) - the 'good' bends would hold and break at about 60-70%
Here it is before load
View attachment 40908
and here it is after slipping
View attachment 40909
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estarzinger
Well-Known Member
Actually they end up outside the knot, pressed on the bottom of the overhand knot. Does this close-up picture help:
View attachment 40911
alahol2
Well-Known Member
Yes, that now makes it abundantly clear. Thank you.
rustybarge
Well-Known Member
Thanks very much, I was taken in by an article written by the inventor of this knot that it was the 'answer to everything'.
I did try it on two big 1.5 inch ropes to lift the back of a big steel barge, and the knot held well, and came undone afterwards.....
...just shows how naive i was!!!!
Very disappointing result, thanks again for saving me from making a maybe disastrous decision to use it in a critical situation.
back then to the old reliables, and your knot which is tried and tested!!
I did try it on two big 1.5 inch ropes to lift the back of a big steel barge, and the knot held well, and came undone afterwards.....
...just shows how naive i was!!!!
Very disappointing result, thanks again for saving me from making a maybe disastrous decision to use it in a critical situation.
back then to the old reliables, and your knot which is tried and tested!!
vyv_cox
Well-Known Member
Thanks for the other info. I had picked up your soft shackle idea and incorporated it in an upcoming article, so thanks for that, too.
My tensile testing is on a rather bigger machine, on the website under 'Anchoring'.
estarzinger
Well-Known Member
yes, I like your work . . . I quote it a lot when people ask about thru hull metals.
My tensile machine is a 'good hobby bench'. . . . quite accurate, and it feeds 10hz data to excel on my laptop so I can make pretty graphs (I plan to take a look at real world anchoring loads later), but it is not all that high load nor that long a throw (testing nylon can give me fits because of how much it elongates), and the hz is a bit too slow for true/fast dynamic shock load testing ( I did some 'drop tests' on tethers and jacklines, and had to find another way to measure the peak shock loads)
I thought I knew quite a bit about rope work, but I have been astonished by how much I have learned doing this testing.
estarzinger
Well-Known Member
One note: on both alternatives of the 'bury loop' stopper, it is important that the loops be made as small as possible while still just allowing the noose to fit thru them. They must be smaller that the stopper knot and not allow it to pass thru them. If they are too big, the stopper will be pushed thru them and it will collapse. This is easier to accomplish with the bigger style shown in my instruction document, but is easily possible with the smaller style I show a couple posts above, but you need to be careful that the loop is as small as possible.
the way to get the noose the right size is put a fid one size bigger than the diam of the line thru the loop and then tighten the bury up against this fid. Another even easier way is to leave the very end of the tail of the bury sticking out and pull it tight once you push the noose thru.
the way to get the noose the right size is put a fid one size bigger than the diam of the line thru the loop and then tighten the bury up against this fid. Another even easier way is to leave the very end of the tail of the bury sticking out and pull it tight once you push the noose thru.
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GHA
Well-Known Member
Something like this...?
Look about right, Evans?
My pet bit of string is a bit short....
(Footnote, this came about after noticing that a remote control on its way to the bin last night had an infrared LED in it, a few taps with a hammer rescued the LED and connected to an arduino microprocessor with a little downloaded code it now works as a programmable remote control for a nikon d50, either for timelapse or to trigger the camera by hitting return on the laptop keyboard
)estarzinger
Well-Known Member
^^ perfect . . . excellent
the shackle will get bigger when you put some load on it - quite a bit of line will pull out of the stopper knot. You want to make sure that at least a bit (say an inch) of the bury has pulled out of the knot and is extending into the actual shackle area just below the knot where the noose will pull. This is what gives the extra strength.
the shackle will get bigger when you put some load on it - quite a bit of line will pull out of the stopper knot. You want to make sure that at least a bit (say an inch) of the bury has pulled out of the knot and is extending into the actual shackle area just below the knot where the noose will pull. This is what gives the extra strength.