Shackle from chain to anchor

[tudorsailor]

I have galvanised 12mm anchor chain. I have a galvanised anchor. Am I right that I ought to use a galvanised steel shackle and not a stainless steel shackle.

As I do not have a large terminal link, I can only get a 14mm pin through the chain. Does this mean that the shackle is now the weakest link?

Thanks

TS

 

[vyv_cox]

The results of my destructive testing of swivels, connectors and shackles are shown on my website, under Anchoring>Connectors. The shackles tested were all 10 mm, which fit 8 mm chain. Most modern anchors have a slotted hole at the shank, allowing a shackle to be passed through it, the pin then passing through the chain. As you can read on the website, stainless steel shackles were almost all stronger than galvanised ones. A further factor was that the galvanised ones varied in strength, by some margin in a few cases.

Galvanic corrosion between the galvanised steel and stainless steel is not an issue for anchoring equipment. After three or four seasons you will find that most of the visible zinc has been lost from the chain but corrosion is minimal (assuming the original galvanising to be good).

I use Wichard 17/4PH shackles for my anchor to chain connections. Expensive, but the best.

 

[lw395]

A 14mm pin is 'quite strong'
How strong do you need it to be?
You might consider replacing the pin with a high(er) tensile bolt?

 

[vyv_cox]

A 14mm pin is 'quite strong'
How strong do you need it to be?
You might consider replacing the pin with a high(er) tensile bolt?

That's the beauty of the 17/4 PH, it is relatively high tensile.

 

[tudorsailor]

How strong is strong enough

Good question! I have a 12mm chain and according to the manufacturers the strength is as follows:

12 x 36mm grade 30 chain : Proof load is 31.kn Min break 77.4kn and the maximum service load in tonnes 1.50t.

I guess that I want a shackle that is at least as strong as the chain.

Sounds like a SS shackle is the way to go. I have contemplated a soft shackle made of dyneema max. It has a safe working load of 6500Kg! Maybe a bit radical however

TS

 

[lw395]

I don't think I'd use a soft shackle where it is likely to be dragged through gravel etc.
An M12 grade 8 bolt is supposed to be good for 50kN or more in single shear, so M14 in double shear ought to be OK?
The most likely form of failure may be the shackle coming undone, as soon as the chain has worn the pin ever so slightly, a 1 ton load on it will equate to quite a torque.
That's why, for moorings where I couldn't weld shackles, I put bolts through with pinned locknuts.
They are easier to torque up properly too, sometimes.

 

[tudorsailor]

I use Wichard 17/4PH shackles for my anchor to chain connections. Expensive, but the best.

The Wichard site is hard to negotiate

I have found that Wichard refers to 17/4 steel as High Resistance Stainless Steel. Once you know this you can Google high resistance shackles and get several companies who sell the HR Wichard shackle such as this one

I hope that this helps someone else who had difficulty finding the 17/4 shackles

TS