Soft Halyard or Line Shackle

[allene]

I looked at the flicker pictures again and my guess is that you are pulling on line that goes around one of your pins and then breaks after the pin. My thought is that you are getting friction at that pin so not all the force on the line goes to the DUT. But I can't really know for sure because the setup is not clear from the pictures.

Allen

[Anton B]

I attached the one end in several different ways, only in order to get the length right, not having taken any care in the length of the connecting line. None of which affected how they broke.

They broke at the end of the bury in the spliced line for the most part. The eye and the knot breaking were anomalies.

I will re-do the test with more care, and better pictures and I hope I will confirm that the breaking point will consistently be the bury and not the knot, and not the eye, but we shall see.

I am pretty sure I have already proved that it will break at close to line strength, in the application the tension is probably less than 20% of breaking strength even at peak loads, I just wanted to make sure that there wouldn't be some freak situation at the diamond knot that would give me less than 50% strength.

What I am doing is exactly like Allen's Soft Halyard, only with more diamond knots. In 9 test pulls, it never broke at the diamond knot closest to the loop, only at the last knot, the one the eye was pulling on, and seemed to break at about 80% of line strength.

I'm pretty happy with that.

[Anton B]

Brion,

how does Otto's sling work? Do you hook the different openings onto something? Is he using the diamond knot like I am, like the Soft Halyard?

Also, I do not seem to be allowed to post attachments, thus the Flickr {ics. Is there a way to do it that I am missing?

Thanks,

Anton

[allene]

First, to insert an image, you click on the insert image icon and give a web address where the picture is. It has to be a web address ending in jpg so I don't think you can use a flicker image. Google plus images work if you open them in a new tab and then use that url.

The issue Brion and I have with your reported results is that they are so far from our experience. Roughly a soft shackle is about line strength. Well, it may be higher than that and probably is but not double. Since the load is shared with two sides of the loop, that means that the strength of each end is somewhat above 1/2 of line strength. But you are seeing something close to line strength and breaking the line to prove it. That would mean that the string of diamond knots that are beyond the knot under load are increasing the strength considerably. Possible and if true something we want to understand as it may have implications for making soft shackles stronger. So we want to see pictures of your setup to see if anything pops out. You may have discovered something significant.

[Anton B]

O.K., here it is!
Here is the Soft Halyard with extra Diamond Knots. It might not be clear, but the tails on the loop with stop knots end just out of the picture, and the other end of the line with the eye splice/shackle ("connector line") is about a foot long and has another eye splice on the other end. One end of the connector line gets put over a stop knot, the other goes to the hook on the scale, so as to pull it with the come-along.



Here is the test rig. Note that the "connector line" has been hooked to the s-hook on the scale, and the eye/shackle has been put on the last stop knot on the luggage tag which is attached to a bolt on the table.



Here are the results



Here's what they look like



Basically, out of 7 tests, 6 of them broke at the end of the bury in the splice and one of them reached almost 100%. After doing 20 splices in a row, they get much quicker, and I was making more of an effort on the taper, so they got better. Because I am lazy, and I was doing a lot of splices in order to just break them, I did not do any sewing or whipping on any of the splices. They would have to be sewed to stay in place under light loads.

On the first pull, the first diamond knot broke, at about 375Lbs, not sure why, but the rest of them lasted, all the way up to 500Lbs, and it was the first knot, rather than any of the ones closer to the loop. It may be that that particular diamond knot was not well made, or that it had suffered wear and tear from the last 10 test pulls wherein other parts of the assembly broke

I am convinced that the diamond knots farther from the loop are as strong as the ones closer to the loop, which is what I hoped to prove.

It occurs to me that I could build a soft shackle with multiple diamond knots to make it of adjustable size.

[Anton B]

Yahooo! I did some more (oh, lord how much time do I have in it now?) looking around and found someone doing very much what I am about to do: use Amsteel for shrouds and forestay. A couple of people recommend against it because of constructional stretch and rebound, making it hard to rig and de-rig, but another says that he had minimal trouble, and said the same thing that I am imagining, which is that the boat is flexible (Prindle 19 catamaran) and that after using it for a while, I will be familiar with which diamond knot it needs to be set up to, I'll just rig it up at one setting and let is sit while I get on the wetsuit, put away the truck, etc., at which point, I put it into its final position. I figure I will have a large number of extra diamond knots to be able to account for a large variation in length. So I am now fully confident that it will at least work and be safe, though it might be more trouble than the SS rigging. Should not have problems with creep, it will not be rigged up too tight, and I got SK-78, which is the low creep Amsteel. Also, if I leave it rigged up, I can back it off one or two knots.

"The one thing I would say is that all woven dyneema products will have an initial mechanical creep associated with the construction and splices. Don't be suprised to take 100mm out of a 6m stay over the first couple of sails. once this is done it will be rock solid. The amount of time that a racing dinghy is tensioned up is negligible in the context of visco-elastic creep.
If you take the mast down and put it up again, the stay will recover some of that mechanical creep again, so will appear shorter on rerigging, but that beds back in quickly."

See here if interested:

http://www.yachtsandyachting.com/for...=11036&TPN=999

And here:

http://www.catsailor.com/forums/ubbt...t&Number=32225

On another note, this picture here shows a cascading deadeye adjustment/tightening system, and I had a brilliant thought!



I could use the idea that Essington posted a picture of to use as the anchor for the top part of the cascade system! One could use the deadeyes with a top pulley with a jam cleat to allow easy on the fly adjustment!

The thing that Essington posted is like the adjustable part of a whoopee sling, and according to another 18 hours on internet research (!) the likely strength reduction would be only 20%,and that is only where and if the tail end exits; it breaks like a badly done taper. If you just sleeve the line over the other one to have tail hanging off, it should not affect the strength of the main line, just the add-on, which, if it's only holding the low tension part of your cascade, should be way more than adequate.

Will have to test. Might use that system to make adjustable trapeze lines too....

Anton

[Brion Toss]

Hi again,
Lots going on here. I think I finally have an idea of the configuration you have been testing, and it explains things I was confused about. What you have done is to put all the load onto the spliced eye, whereas in the shackle configuration it shares it. That's why the shackle breaks at 120 to 150%, and you can only get, by definition, 100%, assuming that you make all the diamonds correctly, with no slack between them on either leg. I think it will work fine for some applications.
Otto's is a kind of inside-out version of this, with one Diamond and a series of eyes, the latter formed by Brummels. The spacing between the Brummels is a snug fit for the Diamond. I haven't seen destruction test numbers for it, but it should be about as strong as yours, with the Diamond being the break point in his case.
As for taking up on deadeyes, welcome to traditional rigging. All you need is a scored fid to jam in the bottom deadeye so you can release the purchase without losing the tension. Note also that this method has twice the pull as hanging the tackle on a halyard or separate pendant, though you might have a challenge making a hitch that won't slip down the standing part.
Finally, I think Amsteel is the wrong material for standing rigging; too elastic, too weak, and too much constructional come and go.
By the way, have you found Yippee slings yet? Also known as Loopies.
Fair leads,
Brion Toss