Unveiling the BB Soft Shackle

[Seaworthy Lass]

The Better soft shackle is currently considered the favoured, although the High Strength one is about 30% stronger.

See these recent threads:
http://www.cruisersforum.com/forums/...st-155318.html
http://www.cruisersforum.com/forums/...ot-155591.html

Anyone playing with making these will have considered the option of combining the two to incorporate the optimal features of each.

Stumble commented on this here:

Originally Posted by Stumble

.... I don't like the double legs coming down from a usage point. Though obviously these are stronger, to me they just look messy.
I am considering trying a button on a 'better' construction however. Do you know if any testing has been done with this configuration?

Evans Starzinger replied:

Originally Posted by estarzinger

Yes, I tested that . . . if you do not bury the tails then it is the same strength as the regular 'better' diamond construction.

My thought is to actually bury the two tails, but not for the full length required for the High Strength version (28x line diameter), but perhaps 5-10x EDIT: 15x

The shackle is likely to have a slightly higher strength than the Better. Maybe in the region of 20% higher with a 10x bury (the High Strength is 30% higher). It would be useful to test this out with a few different lengths of bury.
5x would still be enough to bury the ends and would produce a super neat looking shackle with only a small double line portion.

If the shackle was made slightly longer than normal, you could then still have a very neat central buried portion (no "messy legs"). Longer shackles are more useful anyway.
If it is made a little longer again, the full 30x bury can be incorporated, making it "high strength".

Using a Button rather than a Diamond knot removes the tatty tail sticking out of the Diamond stopper (my only objection to the Better).

Evans, do you still have your test bed set up? It would be good to test a few different amounts of bury of the working ends.

Unveiling the BB soft shackle (the Better Button)

This is a combination of 3 designs (primarily the high strength Button soft shackle plus the central bury of the original Colligo Marine style one, but without any locks, plus the easy opening noose of the Better one).

Edited to add: This is the most current one using 6mm Amsteel with a 15x bury, finished length 360mm from tip of loop to base of the Button. See post # 49 for instructions. Unlike the Better, it uses a Button knot as a stopper, not a Diamond. Also, there is no lock either side of the buried central portion:

[Seaworthy Lass]

The first one made was with a 15x line diameter tail bury, but I milked the centre too enthusiastically so the opening below the noose ended up shorter than it should be. I was in a hurry to have breakfast . I made the second one more carefully, trialling a shorter bury of the tails.

Instructions for the BB soft shackle:

Edited to add: After making several of these, instructions are in post #49 of this thread. In this latest version I have not added the lock before or after the central bury and the tails are buried 15x line diameter.

Details of the one below (second one made):
5mm Dyneema was cut 1400 with about 300 wasted, but about 150mm extra is really needed on each tail to easily tie the button unless you are very familiar with it and can make it snug while tying.
Loop was made to fit 4x line diameter.
Next insertion after the loop made 80mm from the loop end.
Long central bury made 200mm long
40 mm left for the bury of the tails. Edited to add: I made subsequent ones 15x line diam.
Button then tied.
A few mm had to be left below the Button base before the bury could be started.
Full thickness bury was 25 mm (5x line diameter)
Tapered bury was about 15 mm.
Total bury 40mm (8x line diameter)

Tip - don't trim the bury until you have pulled it through.

The completed shackle ended up nearly 320mm from the tip of the loop to the base of the Button:

[Seaworthy Lass]

This is how the Second BB soft shackle looked closed.

Its strength should be at least equal to the Better soft shackle and I think it would be greater. The exact amount would depend on the amount of bury of the working ends (ie tails). If the shackle was made long and 28x the line diameter could be buried it would probably have the same strength as the High Strength shackle.

[Seaworthy Lass]

In case anyone is unfamiliar with them, here are photos of the opposition :

The Better Soft shackle:

http://i1377.photobucket.com/albums/...psxkt7oshi.jpg


The High Strength soft shackle with Brion Toss's Button stopper:

http://i1377.photobucket.com/albums/...pslzqexj6h.jpg


I am smitten with the BB, as it combines the best of both of the above. It has the head of the High Strength (Button knot and buried working ends and noose) and the body and the central bury of the Better, but without the locks at ench end of this bury. (EDIT) Once you have conquered the Button knot and tied a few, the BB is no harder than the Better to make. The only extra step is burying the working ends at the end, which takes barely a minute.

I have 2 pieces of 6mm Amsteel Blue left, so I am planning to make a BB soft shackle to use between our snubber and chain. Our boat is about to serve as a guinea pig .

I will report back.

SWL

[estarzinger]

I took my test rig apart - wife wanted the spare bedroom back

But I did enough testing to know that:

#1 Yes, it will certainly be no weaker than the diamond regular better shackle, and yes probably stronger

#2 sewing would be easy and would definitely make it better/stronger

#3 I would not get precise enough test results with that design. I just simply don't have the precision to say test 10x bury vs 12x bury, nor the precision to distinguish between 10% stronger and 15% stronger. And it will depend a lot on the exact implementation (taper and pre-tension) and the exact type of load (slow pull or sudden shock load).

So, it is a fine design . . . somewhere in strength between the full out 'stronger' design and the weaker 'better' design - that's about all we can say.

I should note that there is a concern with the better design - that the two tails are possibly not allowed to equalize tension (because one is squeezed/buried inside the other for some length). Sometimes this causes a problem (eg weaker shackle) and sometimes it does not seem to. My feeling is that it has to do with how the pre-tension is done, as the pre-tension can equalize the two strands while tightening up the stopper knot. I think the pre-tension key is two fold - #1 don't allow heat to build up and then cool off inside the knot while putting the tension on (as that can prematurely 'freeze' the knot in place), and #2 then allow the tension to sit on the knot for20 minutes or so to allow it to all equalize.

I personally think the designs with the simplest interaction between the two strands are functionally the best. The 'better' design has reasonably complex interaction. But if you like the esthetics better. . . . so be it The fact is that all these designs are very strong - strong enough for most of our applications. There are only a very few applications where I would push for the extra strength over the extra esthetics - chain snubber is one, and places with significant shock loading (like spin pole guys).

[Seaworthy Lass]

Fantastic to have some feedback. Many thanks.

Originally Posted by estarzinger

I took my test rig apart - wife wanted the spare bedroom back

But I did enough testing to know that:

#1 Yes, it will certainly be no weaker than the diamond regular better shackle, and yes probably stronger

#2 sewing would be easy and would definitely make it better/stronger

Would you lock stitch it just below the base of the Button? I am not sure I want the fuss, but it is good to know. Allen indicates on his website that this is what he does with the Better (he does not use a 28x bury).

Originally Posted by estarzinger

#3 I would not get precise enough test results with that design. I just simply don't have the precision to say test 10x bury vs 12x bury, nor the precision to distinguish between 10% stronger and 15% stronger. And it will depend a lot on the exact implementation (taper and pre-tension) and the exact type of load (slow pull or sudden shock load).

It would be useful to know how the bury length affected the strength. Did it go up linearly with the length until suddenly it started breaking at the loop? I think the results would transfer reasonably and help with the decision of how much working end to bury.

As I understand, the Diamond and Button have similar strengths, so the added strength of the High Strength shackle is due to reinforcing the lines at the base of the stopper by burying the tails. You found the max strength increase of 30% with the Button was with about 28x line diameter buried. Was there a 15% increase with 14x? My gut feeling is that it was higher than this.

I have this impression that a 10x bury may be a good amount to aim for - significantly higher strength than the Better, without the long bury of the HS.

Originally Posted by estarzinger

So, it is a fine design . . . somewhere in strength between the full out 'stronger' design and the weaker 'better' design - that's about all we can say.

I should note that there is a concern with the better design - that the two tails are possibly not allowed to equalize tension (because one is squeezed/buried inside the other for some length). Sometimes this causes a problem (eg weaker shackle) and sometimes it does not seem to.

My feeling is that it has to do with how the pre-tension is done, as the pre-tension can equalize the two strands while tightening up the stopper knot. I think the pre-tension key is two fold - #1 don't allow heat to build up and then cool off inside the knot while putting the tension on (as that can prematurely 'freeze' the knot in place), and #2 then allow the tension to sit on the knot for20 minutes or so to allow it to all equalize.

I agree. I have played a bit with knots and one major thing that has stood out is the importance of dressing a knot, which is the first step in pre-tensioning. It is not just the sudden slippage that must occur when force is suddenly applied (and heat generated with it), but knots can slip and fail entirely.

The long bury in the Classic/ColligoMarine style did my head in regarding equalising the tension between the inner and outer layers of the buried portion when I was making them. The only comforting thing was that the weak spot was the base of the Diamond .

One thing that I have thought about the Classic, but never tested out (and the same applies to the Better and now the BB), is that the design would be better without the final lock near the stopper. This would leave the core and outer layer free to equalise. The loop at the end would alter in size slightly as this occurred, but this is no big deal.
What do you think about that? Unless you can see a reason not to omit this, I will leave it out on the next one I make for the snubber.

Originally Posted by estarzinger

I personally think the designs with the simplest interaction between the two strands are functionally the best. The 'better' design has reasonably complex interaction.
But if you like the esthetics better. . . . so be it The fact is that all these designs are very strong - strong enough for most of our applications. There are only a very few applications where I would push for the extra strength over the extra esthetics - chain snubber is one, and places with significant shock loading (like spin pole guys).

I do like the aesthetics better , but it is not just that. The shackle is easier to handle without the bit sticking out of the stopper, particularly when fumbling with cold hands. Unlike the Diamond, the Button just slides through the loop like butter. As with the Better, the loop tightens up beautifully with zero fuss. For shackles that need to be undone and done up again I think it will be easier to use. I will see what happens as the Dyneema ages with use.

The BB is really no harder to make than the Better, nor does it take any longer, in fact may be quicker, as I always whip the end poking out of the Better (or use a double Constrictor).

SWL

[Stumble]

My issue with the stronger isn't just aesthetics. The double leg also adds aero drag, and placed at the top of the mast as shroud shackles or jib hanks this is important. The single leg also seems to make it easier to use one handed.

Of course the twin legs also provide some benefits. I suspect that the extra load area will reduce chaff when used on toe rails, and the smaller line allows a relatively higher bending radius around things like wire rigging.

[Seaworthy Lass]

Originally Posted by Stumble

My issue with the stronger isn't just aesthetics. The double leg also adds aero drag, and placed at the top of the mast as shroud shackles or jib hanks this is important. The single leg also seems to make it easier to use one handed.

Of course the twin legs also provide some benefits. I suspect that the extra load area will reduce chaff when used on toe rails, and the smaller line allows a relatively higher bending radius around things like wire rigging.

Hi Greg
The Button is considerably easier to handle single handed, as there is no end sticking out, as with the Diamond. I am just sitting here having a go.

Regarding twin legs being occasionally beneficial. You are right. There is no need to have just type of one soft shackle in your armoury though .

This is another shot of the second BB with a 5x 'line diameter bury' of the working end (8x tapered). I am very happy with how it has turned out. I am going to make this my standard soft shackle design:

[estarzinger]

Originally Posted by Seaworthy Lass

Would you lock stitch it just below the base of the Button?

I tend to stitch it down the length of the bury, because that is area you are trying to increase the 'grip' in. The stitching adds 'cover' compression friction strength, in addition to just the stitch strength.

It would be useful to know how the bury length affected the strength. Did it go up linearly with the length until suddenly it started breaking at the loop?

I know it would be useful to answer that . . . . but I really try to not overstate or push the statistical validity of my results . . . .and I unfortunately just can't say. There is simply too much noise in the results. At low bury lengths there are just a whole bunch of variables determining if/when the cover grips the core - down to how fuzzy that particular line is and what sort of coloring/coating/impregnation it got. Different batches of line can vary in strength as much as 15%. If I test really really carefully, with lots of samples made from the same batch of line, I am lucky to be able to distinguish 5% differences.

I have this impression that a 10x bury may be a good amount to aim for - significantly higher strength than the Better, without the long bury of the HS.

I believe I told you that I thought my testing showed that 17x was not enough (without stitching). There is not enough compression grip on the core, so the cover just slips on the core and breaks on its own without much support from the core. You know that the recommended bury for a bury splice is in the range of 62-72x . . . that has a lot of safety margin in it . . . but we are talking about REALLY short buries here. There is a minimal amount of friction required to 'bond' the core and cover together so they strengthen each other (and don't just slip). IMHO 10x is just not long enough - probably not even with stitching (the stitching itself will take the load and break rather than providing enough compression friction).

the design would be better without the final lock near the stopper. This would leave the core and outer layer free to equalise.

I tested that, but did for some reason did not record the results and can't remember what they were now. They much not have been all that noteworthy or I would have written something about it

................

[Stumble]

Lol,

Talking about needing multiple types of shackles in your inventory... On my A-Cat I am really not happy with the stainless shackle I have been using to attach the shrouds and was planning on making a couple of the BB shackles to replace it. But it just hit be I am going to try the Stronger and splice the shrouds onto the legs of the shackle. So the port/starboard shrouds will attach at the p/s leg of the shackle.

Of course it won't disassemble without a knife, but I don't need it too. Just detachable from the mast is enough. Now the only question is 7/64 or 1/8... And guesses on strength per leg?

[Seaworthy Lass]

Evans, I guess the safest thing it to treat the BB as being no stronger than the Better, with the improvement simply being in easier handling and better aesthetics by virtue of eliminating the tail sticking out of the stopper (although I tighten the Diamond well and could cut the tail shorter, I always leave the recommended inch for safety).

This gives around 1.75 x line strength regardless of the bury length. There are so few applications where anywhere near the strength of this is required.

I have just looked up again the minimum breaking strength of Amsteel Blue from Sampson Rope's tables:
3/16 inch (5mm) = 4900 lbs 1.75x = 8575 lbs
1/4 inch (6 mm) = 7700 lbs. 1.75x = 13475 lbs

Sampson Ropes comment regarding Amsteel Blue: "Size-for-size, is the same strength as steel".
Phenomenal stuff isn't it .

Soft shackles made with 6 mm Amsteel Blue just fit through 10 mm chain (this is what we have been using for the last 18 months for our snubber to chain connection).

Nylon strength (snubber):
9/16 inch (14 mm) = 7200 lbs
5/8 inch (16 mm) = 8910 lbs
This is reduced roughly 15% when wet and more with the action of salt crystals and loads more with chafe.

A Better or BB design of soft shackle seems more than adequate even for a chain to snubber application.

If someone's choice of chain or nylon size means more strength is required, I think the best thing would be to simply use a High Strength soft shackle design with a 27x line diameter tail bury rather than fussing to improve anything else.

I will put a BB soft shackle into use on our chain and I will report back how it performs long term. We anchor out in all weather all year around and on average we encounter one storm each winter.

SWL

[estarzinger]

Originally Posted by Seaworthy Lass

A Better or BB design of soft shackle seems more than adequate even for a chain to snubber application.

I generally agreed with your conclusion.

But just be careful - as the safety factor is not as big as those figures make it look. Those values you quote (for amsteel and nylon breaking strength) are for static loads. As Thinwater will tell you, and my knot testing showed, dyneema will do rather worse than nylon with dynamic loads - which you get on a snubber.

Thinwater helped build me a dynamic loading spreadsheet/calculator (I believe its linked on our load testing page). But just for a graphic example under a knotted drop test I conducted 1/4" nylon actually was 'stronger' than 1/4" dyneema (eg the nylon held the dropped weight while the dyneema broke at the knot)!

. . . but how exactly to use it will depend on how long (the nylon portion of) your snubber is. You will remember that my 'better snubber' used dyneema from cleat over the bow, to eliminate chafe, which is the most common cause of failure . . . but that does reduce the nylon length of the snubber, so I anticipate higher dynamic loads than those who use extra long all nylon ones (but who will be more vulnerable to chafe).

It has always been fascinating to me that the climbing world and climbing rope suppliers (mostly) simply don't even list static breaking strengths, because they are misleading and irrelevant. They quote a dynamic measure 'UIAA Fall Rating' (which interesting is built around the 'breaking strength' of the human body!)

[Seaworthy Lass]

Originally Posted by estarzinger

I generally agreed with your conclusion.

But just be careful - as the safety factor is not as big as those figures make it look. Those values you quote (for amsteel and nylon breaking strength) are for static loads. As Thinwater will tell you, and my knot testing showed, dyneema will do rather worse than nylon with dynamic loads - which you get on a snubber.

Thinwater helped build me a dynamic loading spreadsheet/calculator (I believe its linked on our load testing page). But just for a graphic example under a knotted drop test I conducted 1/4" nylon actually was 'stronger' than 1/4" dyneema (eg the nylon held the dropped weight while the dyneema broke at the knot)!

. . . but how exactly to use it will depend on how long (the nylon portion of) your snubber is. You will remember that my 'better snubber' used dyneema from cleat over the bow, to eliminate chafe, which is the most common cause of failure . . . but that does reduce the nylon length of the snubber, so I anticipate higher dynamic loads than those who use extra long all nylon ones (but who will be more vulnerable to chafe).

It has always been fascinating to me that the climbing world and climbing rope suppliers (mostly) simply don't even list static breaking strengths, because they are misleading and irrelevant. They quote a dynamic measure 'UIAA Fall Rating' (which interesting is built around the 'breaking strength' of the human body!)

So many variables to consider, aren't there!

Nylon is fabulous with shock loads. In the snubber connection application, the nylon will, I think provide quite a bit of protection for the soft shackle in this regard. We use 14m of nylon with stronger wind.

SWL

[estarzinger]

^^

You have made me rethink here a bit . . . I know I firmly came to the conclusion that the 'regular better' design was just marginally strong enough and that the stronger design was much more appropriate for the snubber. But I cannot for the life of me now recreate exactly how I came to that conclusion.

It is one of the few applications where you are limited in the diameter of line you can use (by the chain hole size). And it is possible I reached that conclusion back when allen and brion toss were insisting that soft shackles were/could only be trusted to 100% of the amsteel strength (they both insisted on that for a while until I showed them both by logic and by test results it just was not true - brion even said he had NER test results that only went to 100% but NER had a history of not doing these sort of 'small stuff' tests very well).

In any case, at the moment, I agree with you that pretty much any of these designs would seem to be strong enough for the application.

And I also agree with you that the dynamic loading 'problem' is more of an issue for the sort of application Stumble was talking about (in low stretch rigging applications) and much less of a problem when there is nylon in the system.

And I do also agree the button is better from a functional perspective because the tails are out of the way. I really should go back and try to further develop my 'easier' solutions to make them more user foolproof - because they give the advantages of the stronger and button without the tieing difficulty - but I got discouraged because allen did not like the asymmetry

On bury lengths, I did manage to dig up an old spreadsheet where I was noodling around with them a bit. I see two things that might interest you.

First, I came up with the 12" shackle length because I wanted the bury to be (only) half the length - to make it easy to slip thru the chain hole. That seemed to work well for me.

Second, looking at my test data - the strength/bury length curve is "probably" not linear. It is "probably" more of a binary tipping point situation, where either the bury is long enough to clamp the core or it is not. I am not going to say that with much statistical certainty but if I had to guess looking at the data, that's what I would guess.

[Seaworthy Lass]

Originally Posted by estarzinger

^^

You have made me rethink here a bit . . . I know I firmly came to the conclusion that the 'regular better' design was just marginally strong enough and that the stronger design was much more appropriate for the snubber. But I cannot for the life of me now recreate exactly how I came to that conclusion.

It is one of the few applications where you are limited in the diameter of line you can use (by the chain hole size). And it is possible I reached that conclusion back when allen and brion toss were insisting that soft shackles were/could only be trusted to 100% of the amsteel strength (they both insisted on that for a while until I showed them both by logic and by test results it just was not true - brion even said he had NER test results that only went to 100% but NER had a history of not doing these sort of 'small stuff' tests very well).

In any case, at the moment, I agree with you that pretty much any of these designs would seem to be strong enough for the application.

We have had a fair amount of experience now with using a soft shackle as a connection between snubber and chain - I estimate more than 12,000 hours, in all sort of conditions.

We have used the old original Classic/ColligoMarine style soft shackle with 6mm Amsteel for this purpose, as I made a few early last year and we are only just using the last one. None have failed, a couple have simply been lost overboard.

Regarding ageing, the soft shackles have chafed a little and I guess there would be some degradation from UV exposure, but this is less of an issue underwater due to the penetrative ability of UV, particularly at oblique angles. They are so easy and inexpensive to make that doing the safe thing and replacing them yearly or even six monthly (off the cuff estimates) is sensible.

I have no doubt that 6mm Amsteel in any current soft shackle design is adequate in any conditions for our 48' vessel.

One unusual feature I have noticed that I have not found commented on before, is that the exposed portion of Amsteel thickens up with use underwater in this application. Looking at a 6 month old shackle in 6mm Amsteel, the line in the loop has a diameter of approx 8-9mm, while milking down the casing and exposing the still faintly blue core, shows the diameter here is 5.5mm). If I feel enthusiastic, I may monitor how this diameter alters with time.

This thickening with age means the loop of the shackle is harder to insert in the 10 mm chain, so the ability to use 5mm Amsteel would be good. In this thickness, a boost in strength is appealing.

Originally Posted by estarzinger

And I also agree with you that the dynamic loading 'problem' is more of an issue for the sort of application Stumble was talking about (in low stretch rigging applications) and much less of a problem when there is nylon in the system.

And I do also agree the button is better from a functional perspective because the tails are out of the way. I really should go back and try to further develop my 'easier' solutions to make them more user foolproof - because they give the advantages of the stronger and button without the tieing difficulty - but I got discouraged because allen did not like the asymmetry

Evans, try my instructions for the Button. I think they show a foolproof way of tying this knot. Nothing else I have found written online truly explains how to ensure you insert the ends correctly in the final step. Now that I am familiar with the Button, I would say it is possibly even quicker than the Diamond to tie. There is little need I think for much improvement in this area.

Improving the strength of the loop is another matter .

Originally Posted by estarzinger

On bury lengths, I did manage to dig up an old spreadsheet where I was noodling around with them a bit. I see two things that might interest you.

First, I came up with the 12" shackle length because I wanted the bury to be (only) half the length - to make it easy to slip thru the chain hole. That seemed to work well for me.

Second, looking at my test data - the strength/bury length curve is "probably" not linear. It is "probably" more of a binary tipping point situation, where either the bury is long enough to clamp the core or it is not. I am not going to say that with much statistical certainty but if I had to guess looking at the data, that's what I would guess.

Thanks, that makes it clearer

I will be able to access Amsteel again in the New Year and I am planning to make a 5mm BB soft shackle with a working end bury of 30x (round figure) in around a 400mm length, which should make its strength around 230% of line strength, similar to what you tested with the High Strength soft shackle. The twin legs of the High Strength bother me for use with chain, as there is more potential for jamming between the links.

SWL