Amazing Underwater Photos of an Anchor Swivel Failing

[SVNeko]

Great photos! Talk about once-in-a-lifetime opportunity? I'd rather spend mine on winning the lottery, but this is pretty neat. I don't think the side load had anything to do with it though. The shackle took that out of play and, as others have pointed out, it looks like evident corrosion on a dodgy swivel.

[Prairie Chicken]

Wow indeed! And kudos to your photographer/mermaid.

[noelex 77]

Originally Posted by Sos

As a matter of interest, what were the weather conditions that caused it to fail. Would you consider it high a loading?

The wind was only about 15-20 knots, but there was a bit of wave action. The boat concerned had no snubber. Notice a pattern: unmoused shackles, non-rated swivel, no snubber. Surprisingly, the boat was otherwise immaculate and in beautiful condition.

This wind strength would not normally be enough to lift the chain, even in the gusts, but you can see the chain lifting in one of the photos so the wave action was having a significant effect (fans of the great benefit of catenary take note how quickly much of it disappears ).

One of the surprising things even with a broken swivel is how the forces managed to straighten out the stainless steel loop. I didn't have my callipers down there , but my guess is that the swivel was 18-20 mm SS rod. It takes a lot of force to bend something that thick even when it is an open loop only attached on one side. I sometimes think the theoretical calculations of wind loading on anchoring gear seriously underestimates the forces involved when there are factors such as wave action and sheering forces, which is often present.

I agree with the comments about crevice corrosion (or perhaps a bad weld, crack, and then crevice corrosion inside the crack) being the major factor, but the photo in the second post does show how easy it can be for swivels and shackles to have a load that is well outside the straight pull they are rated for. A bit of overkill with this terminal gear is good insurance.

[HopCar]

That's just weird. It doesn't look like the crappy anchor was even fully set.

[Sos]

Originally Posted by HopCar

That's just weird. It doesn't look like the crappy anchor was even fully set.

That's just what I was thinking! This anchoring malarky is black magic

[S/V Alchemy]

Originally Posted by noelex 77

The swivel gradually parting underwater:

Wow. Reminds me about the folly of dissimilar metals...and in some cases swivels. Good on your mermaid for "capturing the moment!"

[S/V Alchemy]

Originally Posted by noelex 77

(I have obscured the boat name and details)

May I ask why? Personally, even though the odds are low I will ever anchor next to Captain Casual and his quest for lunch, if this is how a "professional" operates, I for one want to know when I'm next to one.

[donradcliffe]

Should have gotten a closeup, so you could see the 'made in China' on the swivel.

[Cheechako]

This is a setup right? In the first photos there appears to be no tension on the chain... and yet the swivel is parting. Finally in the final photo the chain is off the bottom...?
It aint april fools but......?

[SimonV]

Wrong thread

[noelex 77]

Originally Posted by Cheechako

It aint april fools but......?

No this is absolutely genuine. Although I can understand the skepticism the chances of ever seeing this must be about the same as the lottery, but it happened.

There was an onshore wind (but with only a 10 mile fetch to the nearest land) with a bit of wave action. The combination of wave and wind action was periodically lifting the chain ( according to my mermaid and the photos). The swell and wind was also gradually building which made the later photos a bit worse.

As you can see from the final photo of the boat, conditions were still very mild (although the photo as usual does make the wave action look a bit less).

[Cotemar]

Great photos. Just goes to show how some cruisers maintain such important pieces of gear. That swivel crack was very noticeable in those underwater pictures. I cannot imagine how that crack did not stick out like a sore thumb on the deck of the boat.

Great Job

[Jesse]

I didn't want to be the first but since Cheechako lifted the kettle lid I too detect the aroma of fish, and a gentle tug at my leg. Even so, the photo's are top drawer.

[noelex 77]

Originally Posted by S/V Alchemy

May I ask why? Personally, even though the odds are low I will ever anchor next to Captain Casual and his quest for lunch, if this is how a "professional" operates, I for one want to know when I'm next to one.

I think in this sort of situation we are better to try and learn some lessons rather than lay blame. The skipper was very grateful in the end. I suspect our warnings did have some impact, although maybe professional pride prevented acknowledging that the warnings were taken seriously.

After the chain broke my wife tied a rope and buoy of ours on the anchor's shackle so he could pick it up. Even with these simple deeds you need to be careful. He had a capstan on his anchor winch and I would have just picked up the float with a boat hook raised the anchor with the rope and subsequently attached the chain. Shouting across the water we tried to convince him of this plan, but he felt the anchor was too heavy to raise this way !

They dropped the chain on the bottom while holding station and attempted to reconnect the chain. The diver reported the rope was a big help in getting down to the anchor. We thought the rope and float was coming perilously close to prop though! They did succeed in the end.

No one was hurt, nothing was even damaged (apart from a swivel which was better ditched anyway)

[hellosailor]

Aside from the obvious rust on that shackle and elsewhere, are my eyes failing me, or am I the only one who thinks there is seizing wire missing from the other shackle pin?

Sometimes the fault is with the workman, not the tools.