Shackles

[Rum_Pirate]

Find it amazing that shackles while they have a pull on them always (if not moused) have a way to unloosen/undo especially those underwater.

They NEVER seem to tighten up.

Never one pull tightens up, then say next pull loosens etc.

It would be reasonable to think that on average it would do so.

Anyone got an explanation as to why?

 

[boomerangben]

I suppose that as you tighten the pin, the threads deform elastically. With the geometry of the thread, there is a tendency for the spring effect to act to undo the pin. However friction is sufficient to stop it happening. But repeated loading cycles is going to cause micro deformations and since there is less work required to undo the pin than tighten it.

It is one of the reasons we only every used bolt type shackles in underwater construction

 

[William_H]

The problem in a mooring is that the boat is constantly tugging possibly every 2 or 3 seconds for 24/7. The variablitly I think of what is probably nearly symetrical tighten and untighten on the pin still gives the chance of total unscrew. All exacerbated by wear of the threads with the movement. In the end they do undo themselves so beware. ol'will

 

[coopec]

That's something I'll have to do - seize the anchor shackle.

I don't like the idea of Loctite nor do I like a plastic electrical tie so I will use ss wire.



Three methods for seizing shackles

 

[jamie N]

Any other type of shackle for 'normal' use underwater is a piece of shit, and could invalidate insurance.

 

[boomerangben]

That's something I'll have to do - seize the anchor shackle.

I don't like the idea of Loctite nor do I like a plastic electrical tie so I will use ss wire.

View attachment 153979

Three methods for seizing shackles

I know that’s not your shackle, but it’s the wrong type of shackle for an anchor

 

[Iliade]

Is how we do it on ultralights etc

eOceanic

Still probably not adequate for permanently immersed arrangements but prettier and less likely to cause injury than most other solutions.

 

[Laser310]

i had a plastic wire tie fail recently when used to seize a shackle

 

[Pye_End]

They NEVER seem to tighten up.

Anyone got an explanation as to why?

Perhaps you only notice when it loosens because of the consequences?

 

[Rum_Pirate]

Perhaps you only notice when it loosens because of the consequences?

I always put a wire mousing on the shackles.

I usually use monel wire, which I also use when fishing.

PS The undoing incident referred to in the OP was relating to a friend's installation. Honest Gov.

 

[simonfraser]

red loctite ? well that is what i use ...
on an oversized anchor shackle with a sunken / flat head

 

[SAMYL]

They say to never use stainless steel shackles underwater, especially salt water, and never use clear/white cable ties as they degrade in sunlight.
Use black ones.

 

[KREW2]

We do not use any shackles in on our moorings, except for the pickup buoy. The riser has two larger egg links on each end of the chain, this is reeved through the ground chain. the same goes for the bridle. These are reeved back through the large egg link on the riser, eliminating the need for moused shackles.

 

[William_H]

They say to never use stainless steel shackles underwater, especially salt water, and never use clear/white cable ties as they degrade in sunlight.
Use black ones.

I have had 10mm stainless steel shackles ( moused with monel wire) in my mooring for quite few years now. However the rest of the mooring gear is SS as well. Starting at the top with a mandatory authority supplied buoy with ss swivel built in, I got some SS chain which does loop through a railway wheel of iron as the mass. All good. The problem with SS is whenb it contacts black iron the dissimilar metals creates wear damage in the iron. ol'will

 

[PabloPicasso]

i had a plastic wire tie fail recently when used to seize a shackle

I use two, usually black, cable ties passing in opposite directions to address the issues of one failing.

Shackle undereater failures are likely often due to corrosion. This may well occur evenly{ish} over the whole shackle, but the threads fail first as there is less material there. Then the pin falls out releasing the shackle and anything dependent on it.

Grease the threads with a water resistant grease to reduce corrosion and make it easier to undo when the time comes.