Mooring shackles

[Refueler]

I’m intrigued by your findings. We always used bolt type anchor shackles for lifting offshore, usually for single wire strops as they are safer than screw pins and easier for divers to use. I think they were also better at being righting themselves when loaded away from the axis, which is why anchor shackles tend to be bow type. But to have one fail as you describe sounds interesting. Do you have anymore detail on how the shackle failed and it’s arrangement in the mooring system?

Sadly I don't have the shackle anymore to show. It got left in my Land Rover when I sold it many years ago.

Best I can say ... when I walked out to the boat at low tide ... Farlington Moorings at Havant end are on relatively stony bottom. Its a real work-up to 'dig in' sinkers.... the chain was laying out relatively straight indicating the path boat took. At the end of the chain was the bow shackle with pin snapped and the bow opened out about 25% more than its designed throat.

The sinker - a 1m diameter solid concrete disc of about 15 - 20cms depth had an iron hoop set into centre.

Putting the two items together - the only explanation for the shackle to be in such condition is if it had rotated and all load was now carried by the sides of the bow instead of the pin and crown .....

A suitable sized D shackle would have stayed in its correct load design orientation.

As a Ships Deck Officer for many years previously - Bow Shackles as I observed and was instructed were more designed for having multiple lift chains, so that in lifting - the chains aligned. The throat of the shackle should be suited to the point it is attached and not oversized allowing it to 'turn'.

As to use of bolt / nut / pin etc. - I do like the use of suitable nut and bolt with pin. But I must be honest and say that I am not in agreement with use of Threadlock .. Red or whatever.

 

[boomerangben]

Sadly I don't have the shackle anymore to show. It got left in my Land Rover when I sold it many years ago.

Best I can say ... when I walked out to the boat at low tide ... Farlington Moorings at Havant end are on relatively stony bottom. Its a real work-up to 'dig in' sinkers.... the chain was laying out relatively straight indicating the path boat took. At the end of the chain was the bow shackle with pin snapped and the bow opened out about 25% more than its designed throat.

The sinker - a 1m diameter solid concrete disc of about 15 - 20cms depth had an iron hoop set into centre.

Putting the two items together - the only explanation for the shackle to be in such condition is if it had rotated and all load was now carried by the sides of the bow instead of the pin and crown .....

A suitable sized D shackle would have stayed in its correct load design orientation.

As a Ships Deck Officer for many years previously - Bow Shackles as I observed and was instructed were more designed for having multiple lift chains, so that in lifting - the chains aligned. The throat of the shackle should be suited to the point it is attached and not oversized allowing it to 'turn'.

As to use of bolt / nut / pin etc. - I do like the use of suitable nut and bolt with pin. But I must be honest and say that I am not in agreement with use of Threadlock .. Red or whatever.

Thanks for explaining. I can see why you prefer D shackles. Most of the time we put the shackles onto padeyes which prevent the sort of loading you witnessed, as would a bow shackle on an anchor.