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Old 18-11-2015, 21:31   #76
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re: Unveiling the BB Soft Shackle

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Originally Posted by estarzinger View Post
Theoretically I think it is optimal to pre-tension it in the 'actual use' condition (eg closed shackle). So that the two strands are evenly pulled at the angle they will actually be used. If you pre-tension it in the open orientation, then in the closed orientation in-use one strand may take all the load rather than sharing it evenly. Again, in theory, if you want to pre-tension it in the open orientation, it might make sense to not tension it up too high, so there is a little self-adjustment movement left in the actual use orientation. BUT I doubt it makes much difference in real world practice - its going to break at the first tight compression/bend in the knot in either case So, if you prefer the complete symmetry, go for it
I love tossing ideas back and forth . I have enjoyed this exercise tremendously. Thanks for all your posts.

The reason I would prefer symmetry is because the Button will not be pushed into the loop the same way each time.

This is one of our old shackles (don't look too closely at the construction, it was one of the very first I made ). The Diamond has not been shoved onto one spot, its has been looped randomly. If pretensioning is important, it makes me think this should not be done for just one configuration of the loop:

http://i1377.photobucket.com/albums/...ps797upipt.jpg
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Old 19-11-2015, 05:41   #77
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re: Unveiling the BB Soft Shackle

^^ my understanding is that pre-tension is important for two reasons. (1) most critically so that a cut short tail does not get sucked back into the stopper. You obviously can also accomplish this by just leaving the tail longer - which your BB design does in an elegant way. and (2) so there is not significant slipping/melting/heat damage in a surge load.

Those two can be accomplished either open or close - does not matter.

So we then come to the question of symmetry. I have some opinion here and some test results.

The test data suggests that it does not matter at a gross level, say +- 10%. I believe the explanation for this is - the weak point for the stronger design is the noose and the weak point for the weaker designs (allen's better and you BB) is the first bend/compression in the knot and those are weaker than one (doubled) strand - so even if all the load is on one strand (rather than split between the two) it is still stronger there than at the weak point.

Now if we want to min/max the design within my -+10% test tolerance we end up at opinions. My feeling is that you have a net better design if it is tensioned closed. I think that because you then have a better than 50% chance that two strands will be taking some of the load and thus somewhat reducing the loading at that first bend/compression point. If you have a 'symmetrical' pre-tension, I believe 'in use' you have a near 100% chance that only one strand will be taking the load. You will only get two strands taking the load if it is placed in absolutely perfect 'sideways' orientation.

anyway . . . we are getting to details which are beyond my understanding and testing of this application. I would say if you like symmetry . . . go for it
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Old 05-12-2015, 02:49   #78
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re: Unveiling the BB Soft Shackle

This latest BB soft shackle (final design for now) has been in action for 18 days now in the Cyclades. Variable conditions, 3 anchorages.

I snapped a shot of it yesterday when the wind was only about 20 knots, but gusting to around 30.

Seas always look calm in photos, particularly when there is little fetch. The angle of the snubber gives some indication of the forces involved. Even roughly knowing its strength, it is quite amazing that this tiny scrap of a soft shackle is holding our boat:

http://i1377.photobucket.com/albums/...psefb3p2hy.jpg

This is a fuzzy enlargement to show the shackle itself being lifted out of the water. I was hanging on to stop myself being blown over, so there is a fair bit of camera shake:

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

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Old 08-12-2015, 10:48   #79
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re: Unveiling the BB Soft Shackle

This is how the BB soft shackle looks after 3 weeks acting to join chain to snubber. Conditions haven't been severe, but we have had several patches of 1-3 days of 20+ knot winds with gusts to 30+, so it is has been enough to give the shackle a bit of a workout:

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


I sewed a "marker" at the base of the BB (after tightening the Button stopper by hand with a marlin spike, then threading it through a big washer and pulling it by hand while gripped under the jaws of a vice) to see how much it would shift with pretensioning on a winch and then later with use.

Negligible movement has occurred (the marlin spike technique seems to be very effective). Check out the after and before shots showing this marker.

After pretensioning on the winch and 3 weeks use underwater. The "thinning" at the base is where the loop grips the Button:

http://i1377.photobucket.com/albums/...psdshk6snu.jpg


How it looked when the marker was initially tied on after the marlin spike and vice tighten:

http://i1377.photobucket.com/albums/...psekxav58n.jpg
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Old 18-06-2016, 07:05   #80
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re: Unveiling the BB Soft Shackle

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Originally Posted by Seaworthy Lass View Post
In future I would really like to pretension the BB open, not closed (that uneven tension on the Button bothers me, even though that is how load is eventually applied) and I will do this next year when I get hold of more Amsteel and can make up a couple of lengths with eye splices on each end. I can pop on 2-3 washers (I think just one will bend) to ensure the load is even and this will have the added benefit of a nice flat base resulting on the Button.
Given the slight shift of the Button that will occur as load is applied, I wonder if I should wait to bury the tails after the winching, allowing them to be fed into the core as close as possible to the base of the Button. It will also mean the bury will not interfere with the pretensioning.
I am finally back on board and I have more dyneema and the first shackle for the year is being produced.

I have made a BB, as in post #49, but with a finished length of 400 mm from tip of noose to base, allowing 30 x line diameter bury (tapered), which should probably give 230% of line strength (equivalent to the High Strength soft shackle). It used 1.7 m of dyneema.

As in post #49, I buried the central portion with no locking stiches at either end (unlike the Better Soft shackle) as I like the freedom of movement this gives.

It is being pretentioned open on a winch at the moment, sitting for the 20 minutes Evans suggested was needed.

At first I tried secure it with a length of dyneema with eyes at each end, but it skewed quite a bit, so I made a loop via two long tapered bury using 72 x line diameter with no lock or stitching (just to check out if a bury on its own really works ) and threaded the soft shackle through so that the loop sat snuggly against the button (idea courtesy of Evans in an old thread I was reading this morning).

It is still a bit skewed, so I will be more careful next time how it is positioned before I start winching.

I used a few washers to give the button a nice flat bottom. I will try the next one au naturale.

This is how it looks on the winch. The tails will be buried after the pretention and then the shackle pretensioned again:

http://i1377.photobucket.com/albums/...sse12cadj.jpeg

PS The unsecured buries in the big loop held beautifully. It is as hard as steel under tension. Just amazing!
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Old 18-06-2016, 07:29   #81
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re: Unveiling the BB Soft Shackle

You may have answered this elsewhere...

What is the estimated life of the shackle?
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Old 18-06-2016, 07:32   #82
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re: Unveiling the BB Soft Shackle

Quote:
Originally Posted by Seaworthy Lass View Post
I am finally back on board and I have more dyneema and the first shackle for the year is being produced.

I have made a BB, as in post #49, but with a finished length of 400 mm from tip of noose to base, allowing 30 x line diameter bury (tapered), which should probably give 230% of line strength (equivalent to the High Strength soft shackle). It used 1.7 m of dyneema.

As in post #49, I buried the central portion with no locking stiches at either end (unlike the Better Soft shackle) as I like the freedom of movement this gives.

It is being pretentioned open on a winch at the moment, sitting for the 20 minutes Evans suggested was needed.

At first I tried secure it with a length of dyneema with eyes at each end, but it skewed quite a bit, so I made a loop via two long tapered bury using 72 x line diameter with no lock or stitching (just to check out if a bury on its own really works ) and threaded the soft shackle through so that the loop sat snuggly against the button (idea courtesy of Evans in an old thread I was reading this morning).

It is still a bit skewed, so I will be more careful next time how it is positioned before I start winching.

I used a few washers to give the button a nice flat bottom. I will try the next one au naturale.

This is how it looks on the winch. The tails will be buried after the pretention and then the shackle pretensioned again:



PS The unsecured buries in the big loop held beautifully. It is as hard as steel under tension. Just amazing!
I think I would be tempted to use bar steel or block of wood to hold the shackle instead of the rope.. just drill hole of right diameter to pass the cord through...
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Old 18-06-2016, 08:39   #83
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re: Unveiling the BB Soft Shackle

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Originally Posted by weavis View Post
You may have answered this elsewhere...

What is the estimated life of the shackle?
I think it delends on the usage - amount of UV exposure, whether or not the shackle was subject to shock loading, compression, chafe .....
In vital systems if they still look good I would replace them yearly, but that is being super conservative. Top figure may be a decade with light use.

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I think I would be tempted to use bar steel or block of wood to hold the shackle instead of the rope.. just drill hole of right diameter to pass the cord through...
JCapo suggested this. Yes, it is an alternative .
The dyneema loop did work very well.
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Old 18-06-2016, 08:44   #84
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re: Unveiling the BB Soft Shackle

This is how the finished product looked.

It is essentially a High Strength shackle design with a central unsecured bury to make handling nicer. I also think when used between snubber and chain the single central portion is less likely to get pinched between the links of the chain than the two thin legs in a standard HS shackle are.

http://i1377.photobucket.com/albums/...sehoczmos.jpeg
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Old 19-06-2016, 18:50   #85
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re: Unveiling the BB Soft Shackle

nice - what size dyneema and what size chain - I presume it fits nicely thru link
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Old 19-06-2016, 21:46   #86
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re: Unveiling the BB Soft Shackle

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nice - what size dyneema and what size chain - I presume it fits nicely thru link
6 mm dyneema, 10 mm chain.

We have been using this combination for few years now (roughly 14,000 hours at anchor). The first year and a half it was just the old Colligomarine design. Then last year the BB with varying amounts of tail bury and initially with the central bury locked (as with the Colligomarine and Better versions).

The final version last year was with a tapered tail bury of 15 x line diameter and no locks around the central bury (see post #49) and pretensioned closed on a winch.

This one has a tapered 30 x line diameter bury and has been pretensioned open. I thought I should really go for maximum strength in this application, although the snubber is the weak point in our system.

No problems with any of the designs regarding strength (the original version withstood storm conditions), but as it aged the original became very hard to open and milk shut, and also it thickened up substantially making it hard to insert in the chain.

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Old 19-06-2016, 23:50   #87
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re: Unveiling the BB Soft Shackle

Four "standard" BBs (15 x line diameter tail bury, as in post #49) have just been finished off.
Several soft shackles were used up last year to lead 12 m of our snubber on the side deck in a gentle curve, so we had run out. New uses just keep cropping up .

This proportion is sweet to handle and would have at least 175% of line strength and possibly around 200% (needs testing). One of these is destined to head over to friends anchored nearby on Norna Biron tonight:


http://i1377.photobucket.com/albums/...sna9ewraq.jpeg
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Old 20-06-2016, 08:09   #88
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re: Unveiling the BB Soft Shackle

Quote:
Originally Posted by Seaworthy Lass View Post
This is how the finished product looked.

It is essentially a High Strength shackle design with a central unsecured bury to make handling nicer. I also think when used between snubber and chain the single central portion is less likely to get pinched between the links of the chain than the two thin legs in a standard HS shackle are.

And this is how it looks in action after arriving in a new anchorage this afternoon.
Fins have been donned for the first time this year and I am on cloud nine .

Unfortunately, I misjudged the proportions by about half a cm and the twin legs are captured by the chain. Just the thing I wanted to avoid .

Still, it looks good .
The chain is limp, the sea is like a millpond currently, so a high strength shackle is nothing short of satisfyingly overkill :

http://i1377.photobucket.com/albums/...suvzblf0n.jpeg


http://i1377.photobucket.com/albums/...stsowcejr.jpeg


SWL (sipping on an early sundowner of homemade tonic with a dash of gin and feeling very content .
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Old 20-06-2016, 08:34   #89
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re: Unveiling the BB Soft Shackle

^^ if you push the button thru the thimble, so it is on the other side - would not that allow you to rotate the shackle enough that the chain is no longer on the twin legs?
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Old 20-06-2016, 08:42   #90
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re: Unveiling the BB Soft Shackle

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^^ if you push the button thru the thimble, so it is on the other side - would not that allow you to rotate the shackle enough that the chain is no longer on the twin legs?
Yes, but I am at the helm not the bow, so I need to allow that it will go on randomly . WIth those dimensions I had a 50-50 chance that would be right. The wrong 50% occurred. I will make another one.

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