Introducing the "Crown Jewels Soft Shackle"

[Seaworthy Lass]

Originally Posted by Cu Mor Glas

I will try this in 4mm when I get out of work and back to the boat. I never really mastered the diamond knot. Using your instructions for the button turned out so much easier and I just quit trying as there seemed no advantage to the diamond. I'll try the short bury at the loop end.

I am just making a Button version.
Using 5mm I cut two 850mm lengths to make another one 200mm long. I worked out earlier that about 65x line diam is needed to make the Button (more for those inexperienced with the Button), plus have enough for 30x line diameter bury for the tails.

Although the bury can only short on the opening side, it still needs the extra length for tying unless you place the opening bit next to the first Button, then form the second Button low and once tied inch it up. That way you can get by with a minimum amount of dyneema. I didn't do this, but will next time.

I am making it with about a cm of central bury as I really like the handling when opening (it creates a "stop" so it is easy to equalize the leg length properly), plus it keeps the legs together (it is taking all my willpower to resist commenting on the importance of keeping your legs together with this design ).

SWL

[Seaworthy Lass]

By the way, looking at how the Jewel tightens up, I am not sure that the Buttons will provide additional strength as they do for other soft shackles with buried tails. The load seems to be taken on the sides of the stopper. Having thicker legs below the stopper base may not be needed and may actually hinder things.

Load testing results will be very interesting.

SWL

[Seaworthy Lass]

Good news for all of you who prefer Diamonds to Buttons.

My first attempt at making a Jewel soft shackle with my favourite stoppers (Brion Toss's Button stopper) was not a great success. I think my initial thoughts are correct - the thicker legs only hinder the design.

With only a short bury of the tails possible on one of the Buttons, this will need stitching in place, as the bury is bound to come out in time with lots of manipulation of the shackle.

One thing it did teach me though is that it is better forming the opening next to the first stopper, rather than the second. As long as you still keep the legs an equal length, you don't need to fuss about the exact final length of the soft shackle. It is easier. I will add an edit to the original instructions.

Cu Mor Glas, if you are interested, I can put together some easy instructions for the Diamond for you.

SWL

This one turned out a tad short, as I forgot the allow for the bury of the tails . These can be made any length you desire:

[Cu Mor Glas]

Originally Posted by Seaworthy Lass

One thing it did teach me though is that it is better forming the opening next to the first stopper, rather than the second. As long as you still keep the legs an equal length, you don't need to fuss about the exact final length of the soft shackle. It is easier. I will add an edit to the original instructions.

Cu Mor Glas, if you are interested, I can put together some easy instructions for the Diamond for you.

SWL

This one turned out a tad short, as I forgot the allow for the bury of the tails . These can be made any length you desire:

I see the issue. I still think i will try when i get home.

for 4mm i need about 270 mm to make a button comfortably. that's about a cm longer than 65x. i have also noticed the grave importance of keeping your legs together for both the bb and high strength. i've made a couple bb style key chains in 2.2 mm with very short tails that don't really need the strength. the short one worked out pretty quickly. i wound up stitching them in place with one of the strands from what i cut off. that way the whole keychain retained it's color.

YES! instructions for the diamond knot similar to your button knot instructions would be wonderful! i had tried sever other instructions and even some youtube videos for the button knot and none of them got me there. yours did. and after doing 50 or so of them, now i also can do them with my eyes closed.

ive also made a bunch of longer bb style ones in VERY cheap polypropylene rope and use them for sail ties and assorted other bundling of stuff. overkilli am sure but also darn convenient.

[Seaworthy Lass]

Originally Posted by Cu Mor Glas

I see the issue. I still think i will try when i get home.

for 4mm i need about 270 mm to make a button comfortably. that's about a cm longer than 65x. i have also noticed the grave importance of keeping your legs together for both the bb and high strength. i've made a couple bb style key chains in 2.2 mm with very short tails that don't really need the strength. the short one worked out pretty quickly. i wound up stitching them in place with one of the strands from what i cut off. that way the whole keychain retained it's color.

YES! instructions for the diamond knot similar to your button knot instructions would be wonderful! i had tried sever other instructions and even some youtube videos for the button knot and none of them got me there. yours did. and after doing 50 or so of them, now i also can do them with my eyes closed.

ive also made a bunch of longer bb style ones in VERY cheap polypropylene rope and use them for sail ties and assorted other bundling of stuff. overkilli am sure but also darn convenient.

Many thanks for the feedback. It makes it all worth while if someone has found my posts useful. I will put together some simple instructions for the Diamond in the next week or so.

I just love the Button stopper. I use that almost exclusively now. Exceptions are only if I have a very short length of dyneema leftover. The Button can still be tied with no tail bury (just whip the tail at the base of the stopper), but it uses a bit more line than the Diamond. Doing this gives roughly the same strength as the Diamond apparently, but with a stopper that is just beautiful to handle. I have an 8mm one I made a while back and the handling is lovely.

In this application I do not think the Button works as well though. Too much room is taken up at the base if the tails come down. The load is placed on an entirely different part of the Jewel compared to conventional designs and thicker legs just seem to interfere with this.

SWL

[mickeyelam]

Wotname,

As for determining the total load exerted by your press, you should be able to roughly calculate it if you have a hydraulic pressure gage plumbed into the jack portion of your press; if you take the hydraulic fluid pressure in pounds per square inch (psi) and multiply that value by the area (in inches) of the internal hydraulic piston, you should get a tension value in pounds. Obviously, the hard part of this exercise is determining the piston area. It might be listed on the jack but you'll probably either need to contact the manufacturer or measure the piston area when changing seals. If you already know you internal diameter of the hydraulic cylinder body you can measure the ram diameter and subtract the smaller area from the larger area to get the piston area.

This won't be as accurate as you'd get with a load cell or other more advanced instrumentation, as there are friction loads unaccounted for, but it should be within a reasonable margin of error.

You could also "calibrate" your calculation if you have access to a line (or other material) with a known breaking strength. Just test to breaking and see what your pressure gage measured at the maximum, then reverse your calculations. It probably goes without being said, but obtaining a pressure gage with the ability to retain the maximum hydraulic pressure via a tell-tale needle would simplify this exercise a great deal.

[ingrid75]

Or.....you could just use a regular shackle such as seamen have been using for centuries. Nah......we all wanna be 'space-age', foiling-type sailors.

[StuM]

Originally Posted by ingrid75

Or.....you could just use a regular shackle such as seamen have been using for centuries. Nah......we all wanna be 'space-age', foiling-type sailors.

Soft shackles have so many advantages over regular shackles that I don't know why people still use them

[Perna]

Originally Posted by Seaworthy Lass

I have been playing with soft shackle design and have come up with a new concept.
Currently the strength of well made soft shackles is limited from around 170-230% of line strength, depending on design. Either the base of the stopper or the noose is the weak spot. This new design tries to minimise this.

I'm missing something here. How can the strength of a soft shackle be 170-230% of the tensile strength of the line?

Firstly what would be the point? and secondly how do you prove it? By definition the rope has long since broken.

Thanks in advance for an explanation.

[Seaworthy Lass]

Originally Posted by Perna

I'm missing something here. How can the strength of a soft shackle be 170-230% of the tensile strength of the line?

Firstly what would be the point? and secondly how do you prove it? By definition the rope has long since broken.

Thanks in advance for an explanation.

Second explanation first. The first one is a long essay .

If the load is distributed equally between the 4 legs in a soft shackle, theoretically the very best strength possible would be 4 times line strength (each bit of the line is only receiving a quarter of the load applied.

So achieving 170% is less than half of the ultimate possible.

To measure this is "easy". Attach a load cell and measure what load it takes to break the shackle. Don't take the manufacturer's specifications as gospel. Repeat using a single line so that you have a benchmark.

The strength of these have been measured in numerous load tests worldwide and although results vary, well made shackles that allow for good load distribution between the legs (and have the stopper pretightened so it doesn't move suddenly under high load) have on average a strength of around 170% of line strengh if using the Diamond Stopper and around 230% of line strength if using a stopper with buried tails (eg Button stopper, Overhand stopper or toggles).

SWL

[StuM]

Originally Posted by Perna

I'm missing something here. How can the strength of a soft shackle be 170-230% of the tensile strength of the line?

A simple loop, if there is no strength loss where it bends around the anchor point and there is no strength loss in the splice, will have 200% of the breaking strain of a single line since the load is distributed over two legs.
(In practice, you always lose a bit due to the turning radius and the splice - so a simple loop will have less than 200% of the line's breaking strain. That's why many soft shackles are only about 170% - the weakest point may be where the eye bends tightly as the two legs come off the "point" of the eye.)

The same with a splice where one hollow braid runs inside another - the load is taken by both lines so the theoretical strength would be 200%.

Combine these two concepts into a button knot for example where you have a total of four lines coming out of the knot (spliced into two legs) and you have a theoretical 400% strength in that area of the shackle.

Of course, different parts of the soft shackle will have different make-ups so the strength will vary at different points.

Firstly what would be the point?

The point is that you can use smaller diameter Dyneema to get the same safe working load - which means a smaller shackle, easier to handle, can be used in more places, and cheaper.

and secondly how do you prove it? By definition the rope has long since broken.

Thanks in advance for an explanation.

Prove it by putting the shackle between two strong points that can take a much higher load such as thick steel bars and pulling until the shackle breaks somewhere.

The "rope" will not be broken at 100%.

No single piece of rope takes 100% of the load on the shackle. If the shackle breaks at 200% of the breaking strength of the rope itself, that means than at its weakest point, one single strand within the composition of the shackle is finally taking the breaking load and one or more other strands are taking the same amount of load between them.

[Seaworthy Lass]

Originally Posted by Perna

Firstly what would be the point?

They are invaluable .
Let me count the ways :

- These shackles are super strong for the weight. The one I make in 5mm dyneema using Brion Toss's Button stopper has a breaking strain of around 8000kg. Safe working load should only be taken as around 1/5 of this, but that is still 1600 kg. Weight particularly at the top of the mast can be critical, so these replace stainless steel in lots of applications.

- They are soft, so help avoid damage to the deck of the boat, other equipment, (or the crew).

- They replace bulky knots where metal shackles are totally unsuitable, eg for attaching headsail sheets to the sails or snubber to chain.

- They are easy to open and close, don't require additional equipment to do so and never seize.

I have run out of breath

SWL

[weavis]

Its hard to fathom how 5mm Dyneema can handle these loads. Wow.
How does UV affect the material?

[Seaworthy Lass]

A few comments about soft shackle design:

The reason strength generally needs to be increased at the base of the stopper in designs with a noose is because at that point load is applied not lengthwise on the dyneema, but obliquely (not far off 45°). The strength is not as high when load is applied at this angle.
Edited to add: Thinking about it, scrap that. The reason is probably more complex, as load is taken on the noose perpendicularly and it doesn't suffer the same melt the base of the stoppers do with prolonged high load.
Anyway, thickening up the base strengths this zone, to the point the noose becomes the weak point. So over 200% line strength is possible relying on a conventional noose alone.

If the radius of bend is increased for the noose, the strength of the shackle will increase (for example a 6:1 bend radius could give 80% of 400%).

I am tackling increasing strength in a totally different way though. My thought was simply to get rid of the noose if this is the current limitation . With the twin stoppers, the base of one acts as the apex of a "noose". Also, as a lot of the load otherwise seems to be taken on the side of the stopper, there should be less stress on the legs below the base, hopefully improving strength above the current 170% limitation.

Anyway, that is my thinking behind coming up with this design. Load testing is invaluable with design improvement, as the weaknesses can then be tackled.

This particular design may not work as expected, but it is only through making mistakes (and learning from the mistakes of others) that rapid improvement is possible. Fear of making errors or ridicule doesn't get us far .

SWL

[Seaworthy Lass]

Originally Posted by weavis

Its hard to fathom how 5mm Dyneema can handle these loads. Wow.
How does UV affect the material?

From memory there is about a 50% loss in strength over 10 years, with most of the loss occuring in the first few years. Although highly chafe resistant, this can be more of an issue in some situations.

These soft shackles are still very seductive .