How strong a soft shackle to backup anchor shackle

tudorsailor

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Since I always worry about the anchor shackle coming undone, I thought that soft shackle from chain to Rocna would do not harm. (I know I can sieze the shackle)

The question is how strong would the soft shackle have to be or what size dyneema would I use to make the shackle.

The yacht is 14.9m weighs 22ton and is held by a 40Kg Rocna

Thanks

TudorSailor
 
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Elemental

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If the shackle fails and you are left with a ?dyneema / ?nylon link from chain to anchor shank, I wonder about abrasion. The hole in most shanks is a straight drill with hard edges, not chamfered to create a soft curvature.
I have never had any qualms about abrasion on dyneema. I use soft shackles all over the boat - some are under load and in constant contact with a hard-edged chine (eg the one I use to shackle the genoa to the furling gear). After several years, the dyneema has barely shown any degradation and (owing to the huge strength of dyneema) is still massively strong. I will probably replace it this winter - but mainly because it's just so easy and cheap to do.

I would suggest that the odds of

1. Your anchor shackle coming undone followed by

2. There being any damage by abrasion to the dyneema at all

3 Let alone it being sufficient to weaken the dyneema to a breaking point

4. within a single normal anchoring period

are extremely low. If you were leaving the boat at anchor for weeks/months on end and the metal shackle came undone (which I consider to be an extremely remote likelihood anyway) then I suppose there's an increased risk. For myself, I would sleep easy
 

Gwylan

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Regarding abrasion put some NOMEX sleeving over the shackle. Works really well, just have to find a source of odd bits at a reasonable price.
 

tudorsailor

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I have never had any qualms about abrasion on dyneema. I use soft shackles all over the boat - some are under load and in constant contact with a hard-edged chine (eg the one I use to shackle the genoa to the furling gear). After several years, the dyneema has barely shown any degradation and (owing to the huge strength of dyneema) is still massively strong. I will probably replace it this winter - but mainly because it's just so easy and cheap to do.

I would suggest that the odds of

1. Your anchor shackle coming undone followed by

2. There being any damage by abrasion to the dyneema at all

3 Let alone it being sufficient to weaken the dyneema to a breaking point

4. within a single normal anchoring period

are extremely low. If you were leaving the boat at anchor for weeks/months on end and the metal shackle came undone (which I consider to be an extremely remote likelihood anyway) then I suppose there's an increased risk. For myself, I would sleep easy

Thanks

But assuming I make the soft shackle from Excel D12 Dyneema, what size should I use?

TS
 

Old Bumbulum

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Simply a crazy post to start with!
What on earth makes you imagine your anchor shackle might "come undone"? How???
This is fantasy! If you did the pin up tight how could it? Impossible!
And even if you were that paranoid a simple turn of seizing wire would guarantee the impossibility.

So where's the problem?
 

Elemental

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Simply a crazy post to start with!
What on earth makes you imagine your anchor shackle might "come undone"? How???
This is fantasy! If you did the pin up tight how could it? Impossible!
And even if you were that paranoid a simple turn of seizing wire would guarantee the impossibility.

So where's the problem?
Not sure I'd be quite so harsh, but I tend to agree. It's not going to come undone...
 

prv

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I agree with those saying not to worry, but if you’re going to add it anyway then surely the obvious answer is that it should be no weaker than the chain and there’s no point in it being significantly stronger. Same principle used in selecting the metal shackle (you do know what the rating of the main shackle is, right? :p)

Pete
 

Neeves

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Personally I'd forget the soft shackle, invest in a Crosby G209a bow shackle (of the size to fit the anchor and chain - it will then be stronger than the chain). I'd use a red Loctite, liberally, and then mouse the pin (bow though anchor, pin through chain_. You might need a blow torch to free up the Loctite subsequently - but it will not fail (in fact the Loctite will be good by itself).

Given your sensitivity I'm not sure why you would trust a soft shackle off your own production. :)

Few people admit to loosing their anchor as a result of the shackle pin 'falling out' - but possibly reticence is as a result of embarrassment and maybe its more common than reported).

Now - if you use a swivel then you do have cause for worry - but a correctly seized shackle - safe as houses and probably safer than your (or any) anchor.

Jonathan.
 

Stemar

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I've seen figures that claim a soft shackle is more than trice as strong as the line it's made of. As I struggle to work out how this could be, I'd be more inclined to use a figure of 1.5 times.

Jimmy Green's site suggests 22mm chain for your boat, with a breaking strain of around 9 1/2 tonnes. 8mm dynema doesn't quite make it, so you'd be looking at 10mm, with a breaking strain of around 9 tonnes. Make a soft shackle with that and you could almost pick your boat up with it!
 

NormanS

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I've seen figures that claim a soft shackle is more than trice as strong as the line it's made of. As I struggle to work out how this could be, I'd be more inclined to use a figure of 1.5 times.

Jimmy Green's site suggests 22mm chain for your boat, with a breaking strain of around 9 1/2 tonnes. 8mm dynema doesn't quite make it, so you'd be looking at 10mm, with a breaking strain of around 9 tonnes. Make a soft shackle with that and you could almost pick your boat up with it!

22mm chain eh?
 

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scrambledegg

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I've seen figures that claim a soft shackle is more than trice as strong as the line it's made of. As I struggle to work out how this could be, I'd be more inclined to use a figure of 1.5 times.

It can be because each cord of the shackle is made of two dyneema lines (one inserted inside the other), so, as it's also a loop, you have four lines in total. At least it is how I make them.
 
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