Soft Halyard or Line Shackle

[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

[Anton B]

First off, if I understand correctly, Otto's thing is basically a soft shackle, but instead of using more diamond knots, he using multiple brummel loops to put them in. That would also be a good way to do it, and as I said, I could also do a soft shackle with multiple diamond knots, too. I am still thinking about the best way to do this.

The Yippie slings, or whoopee slings, are cool, and seem like they would have some good applications somewhere, don't know here yet, and taking a piece of line and putting it over the standing shroud would give a moveable attachment point for a block, or ring.

I did finally find a few people that have tried using Amsteel for standing rigging, and the reports are pretty mixed, but I did not find them until after I had bought material. I have been enjoying the splicing, and the line is cheap, so I haven't wasted much money, and if it works, it will be cool to have made it myself. I am also pretty tolerant of a little bit of fussiness, and it might work for me. I will report back when I have assembled it and have sailed it a bit.

Ill be back when I have something interesting to say ;-)

Anton

[Anton B]

Hey, I had not thought of the whoopee sling much, but I think that might be a better way to adjust the shrouds than the way I am thinking of.

Change of plans...

Anton

[allene]

Originally Posted by Brion Toss

Hi again,
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.
Brion Toss

But he should be getting 60-75% of line strength (half of what you get in a full shackle) and they should break at the knot. Therefore, his knots are stronger than one would expect with diamond knots. The multiple knots must be adding strength. Perhaps they make the load sharing better.

Allen

[Brion Toss]

Hi,
Actually, in the shackle, the standing part of the eye is doubled, while in the new configuration it isn't. That makes the single standing part weaker than the doubled-but-stress-risen Diamond knot side.
Fair leads,
Brion

[allene]

Originally Posted by Brion Toss

Hi,
Actually, in the shackle, the standing part of the eye is doubled, while in the new configuration it isn't. That makes the single standing part weaker than the doubled-but-stress-risen Diamond knot side.
Fair leads,
Brion

In the shackle think of two sides. One is just straight doubled amsteel and carries half the load. The other side has the eye and the diamond knot. Each side has half the load of the shackle. If the shackle has 150% of line strength, each side has 75%. His setup is exactly the same as the half with the eye and the knot, except that he has more knots.

Another way to look at is that in the shackle the strength should be 400% but it is 150% and breaks at the knot so the knot is 37% efficient strength wise. In his setup, the knot has two strands so it should be .37 x 200% = 75% and should break before the end with the eye in it.

There is something else interesting going on here.

Allen

[Brion Toss]

His setup is most definitely not exactly the same. In the shackle configuration, the eye side is twice as strong as in his version, because there are two standing parts in the shackle, thus 200% strength there. It would seem that the lanyard knot parts in both versions are stronger than a single part, but I would think not by much. If the knot didn't degrade the strength of the rope so much, the shackle would be much stronger, but as it is, the knot side of the new configuration is -- or should be, properly tied -- stronger than the single standing part of the spliced eye.
This would be easy to test, by making the eye of larger rope than the lanyard knot side, and measuring the break point of the latter.
I would also note that Anton deserves better test equipment to assess his innovation. Regarding this, please see accompanying new thread on the break test extravaganza.
Fair leads,
Brion Toss

[allene]

Agreed that the eye part is not as strong as in the half shackle but it is still as strong as line strength, or at least it should be close. But then again, it has a taper so perhaps it is an especially abrupt taper. I still contend that the knot should be 75% of line strength but if his tapers are abrupt and weaken the line more than to 75% and his calibration is off so that makes us think it is breaking at line strength.

Off to read the new thread... (can't find it, maybe it will show up later).

[Anton B]

I was taking care to make long tapered splices, and got up to line strength on at least one break, and 90% on a lot of them. I was getting 75% when I wasn't taking much care of the tapers.

I bought that scale for $25, how could it be inaccurate? ;-)

I have a new idea; using something like a whoopee sling to make a cascading adjustable shroud with those new fangled friction rings, which would allow the whoppe sling splice part of it to only carry half the load, and use a bungee cord in the same way as the Constrictor jam cleat.

I will mock one up with my tiny line ('cause I'm too cheap to use big line) and break a couple of them and see what happens there.

If you are interested, I could try to do another test of the luggage tag with extra diamond knots using a stronger shackle to see what it takes to break it.

Anton

PS, please link to the new thread...