Salvaged anchor with free warning about crappy swivels

Yngmar

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Dived our anchor last night here in Preveza (north of the fishing harbour), as there was quite a bit of rattling around transmitting up the chain before it set. Wasn't fouled, but hadn't set deep, very hard ground.

Next to it was a big concrete mooring block (sadly the ring was rusted away or I could've used that) and a severely fouled plough type anchor, which I almost ignored, as they're usually old and rusty, but it looked big and some intact galvanizing peeked out at me.

So this morning we've salvaged it and I spent an hour with a claw hammer knocking the tubeworms off and evicting a few small crabs. Turns out it's a Kobra 25kg in good shape, so I think we might even find a place for that on the boat as backup. It folds down to reduce size a bit.

Now for the interesting bit (to me). From the fouling it must've been down there for maybe 2-3 years I would guess. The stainless was all shiny, no rust, no pitting. Even the bolt that keeps the fold-down shank in place, which was stamped A2-70 had no rust on it. This was in around 5m depth, just laying on the side (not dug in at all).

But the reason it was lost was the swivel. A design with a sex bolt (small bolt screwing into big bolt) on each end and a stainless allen bolt that was welded in for the swiveling part, like the leftmost design Vyv illustrates. The weld has cracked and the swivel bolt is loose, but still swiveling and not coming out. The jaws on both ends were bent open a bit and the barrel bolt on the chain end was gone - someone must've had a bad moment here when they dragged and then pulled up a chain with no anchor. Hope they had a spare!

8ec944dea674ca58.jpeg


More pictures of the failed swivel here.

Makes me glad we have a Kong (with the bolt Loctited in - and the bolt doesn't touch any moving parts).
 
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Dived our anchor last night here in Preveza (north of the fishing harbour), as there was quite a bit of rattling around transmitting up the chain before it set. Wasn't fouled, but hadn't set deep, very hard ground.

Next to it was a big concrete mooring block (sadly the ring was rusted away or I could've used that) and a severely fouled plough type anchor, which I almost ignored, as they're usually old and rusty, but it looked big and some intact galvanizing peeked out at me.

So this morning we've salvaged it and I spent an hour with a claw hammer knocking the tubeworms off and evicting a few small crabs. Turns out it's a Kobra 25kg in good shape, so I think we might even find a place for that on the boat as backup. It folds down to reduce size a bit.

Now for the interesting bit (to me). From the fouling it must've been down there for maybe 2-3 years I would guess. The stainless was all shiny, no rust, no pitting. Even the bolt that keeps the fold-down shank in place, which was stamped A2-70 had no rust on it. This was in around 5m depth, just laying on the side (not dug in at all).

But the reason it was lost was the swivel. A design with a sex bolt (small bolt screwing into big bolt) on each end and a stainless allen bolt that was welded in for the swiveling part, like the leftmost design Vyv illustrates. The weld has cracked and the swivel bolt is loose, but still swiveling and not coming out. The jaws on both ends were bent open a bit and the barrel bolt on the chain end was gone - someone must've had a bad moment here when they dragged and then pulled up a chain with no anchor. Hope they had a spare!

8ec944dea674ca58.jpeg


More pictures of the failed swivel here.

Makes me glad we have a Kong (with the bolt Loctited in - and the bolt doesn't touch any moving parts).

Ist this why Viv Cox recomends a few links of chain between the anchor & swivel
 
Ist this why Viv Cox recomends a few links of chain between the anchor & swivel
Unless you are anchored in a place where you are spinning around, the swivel is pointless and causes problems. We ditched ours many years ago and haven’t looked back.

Thanks for posting as very interesting.
 
Unless you are anchored in a place where you are spinning around, the swivel is pointless and causes problems. We ditched ours many years ago and haven’t looked back.

Agreed- we use a load rated lifting shackle, with no swivel and have never had a problem.
 
The swivel isn't broken, the pin/bolt is missing.
It looks to me like this sex bolt is very reliant on using the right grade of Loctite?

I suspect that when the anchor was on deck, the bolt came undone or loose due to the chain moving on the bolt.

What I would consider a weakness is the lack of articulation between the swivel and the anchor. This would put a lot of leverage on the bolt there, but that's not the one which came undone.

On the whole, a shiny little gadget which should have been left on the chandler's shelf IMHO.
 
So if I had the exact same swivel, would I be doing it wrong?

It's not a brilliant design. The swivel bolt is a threaded bolt that has been tack-welded to fix it and the weld corroded and cracked, but that part was still hanging on, even though it looks like a weak point to me.

The sex bolt attaching it to the chain failed, probably because it worked loose, likely helped by the deformation of the jaws. Attaching it directly to the anchor is not recommended, as that can create sideloads which is probably how the jaws got bent open.

The remaining sex bolt on the anchor side was also loose. I would at the very least put Loctite on both the outer and the inner bolt threads of both of them, and inspect the weld on the swivel bolt. In the long run, probably best to replace it. The Kong is a much better design that has none of the above weak points:

KG-AC08-S-Kong-Swivel-Anchor-Connector-Dia.jpg
 
Thanks for posting this, very interesting. Tack welds in this type of fitting are always suspect as they are so difficult to control.

As ever, I suggest you do not fit a swivel as a matter of course until you know you need one. We went a whole season without one in the interest of research but have now reverted to a Kong plus three links of chain. For us this is a far superior arrangement than a single shackle.
 
When we had our last cruise back in September 2018, my Wife at the bow complained that she couldn't see the chain markers properly but I didn't take any notice until yesterday when I was on the bow and realised that the chain has, somehow, flipped through 90 degrees so that the markers are now vertical rather than horizontal.

The rollers are all deeply grooved and the gypsy is the normal type and the chain has kept it's correct orientation for at least 5 years so I've no idea how, or why, its flipped.

I'll sort it out whilst we are down here.

Richard
 
So if I had the exact same swivel, would I be doing it wrong?

Asking for a friend

Yes if you attached the swivel directly to the anchor as that can impose very heavy side loads on the swivel. I have a fairly similar swivel but the anchor has a 16mm load tested shackle in the eye of the anchor, then three links of 12mm chain to the large end of the swivel with the 10mm chain attached to the small end. That ensures that the swivel never suffers side loads but still allows the anchor to rotate into the proper position for stowage if it comes up the wrong way round. I check the swivel regularly for corrosion, and the screws are loctite fitted. It needed a blowlamp to soften the loctite when I fitted new chain last year. Without the swivel I would have needed chain with a large ring as the final link in order to connect to the shackle.
 
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