Just so you know which swivel to avoid.

Thankyou for your advice and I hope many more sailors out there will read this
Best regards

Here is the reply I have received from Vyv Cox. David’s Photos helped with the diagnosis of the failure.

Reply:
Hi Brian,

Here is my response. Thanks for the opportunity to contribute. Please pass it on to your forum.

Best regards

Vyv

Failed bolt-type swivel ex SV Taipan

I suggest you refer to the page of my website that deals with connectors, http://coxeng.co.uk/anchoring/connectors/ but also other pages, particularly under Metallurgy.

The type of swivel used by Taipan is probably the worst that can be selected. I believe that most of this type are manufactured in Spain for the fishing industry and realistically should never be used for yacht anchoring. Not only does its axial strength depend upon a nut and bolt in tension, mechanically a very poor situation, but also it has very limited articulation in certain attitudes. I suspect that this has been a contributory factor in the failure. It can truly be said that in this case the swivel was the weakest link but others, particularly Kong, can be 1.5 times stronger than the chain.

Bolts almost always fail at the first turn inside the nut, as this is the point of maximum stress. In particular, fatigue failures in bolting are absolutely characterised by this failure mode, examples on the website. The Taipan failure has clearly suffered additional corrosion damage, which might suggest the failure mechanism to be corrosion fatigue. However, I suspect the actual cause to be stress-corrosion cracking (SCC), covered in detail on my website. The rough surface of the fracture face is typical of branched cracking rather than the single crack of fatigue. The temperature requirement for SCC is around 60 degrees C, easily achieved by deck fittings in warm sunny climates. Stress is clearly going to be high and concentrated at thread roots, with the additional effect of bending due to the poor articulation.

Stainless steel is a poor choice for moorings, where a shackle or other component may be immersed permanently in mud. However there are many cases, e.g. propeller shafts, folding and feathering propeller pins, where stainless steel under water is reliable and lasts for many years. My Kong swivel and Wichard shackle, both stainless steel, have been in anchoring service since 2005, anchoring for half of every year in the Mediterranean. Regular inspection is advised.

Some anchoring arrangements work well without swivels, in which case there is absolutely no need to fit one. We find a swivel brings handling benefits and after a trial season without one we made the decision to revert to using it. My website shows the method I developed and found most useful, with three links of chain between the swivel and the anchor. This has been widely adopted and is recommended by many anchoring experts.

Vyv Cox. engineer33@btinternet.com

Hi David,
Vyv has responded and asked for the photos, can you send to my e mail one.23@virgin.net

I am hoping he may be able to offer technical expertise which may be useful to other members on the forum.

I see you are from Australia. We had18 months on the East Coast and a fair bit of land travelling also. We loved the place.

Our time Panama was enjoyable as well.

Cheers

Brian the Pom!

+x

 

bwallace - 7/21/2019

Hi David,
Thanks for the report, And glad all turned out safely for all concerned, and hope Rodolfo eventually is recovered.

My request is can I forward your report to Vyv Cox, a specialists Metalurgy scientist, who writes for Yachting Monthly and is a friend of mine.

I await your reply

Brian and Sue
S/V Darramy in the Peloponnisos

Hi Brian and Sue. That would be fine and I also have photos of the offending swivel.... well what's left of it.  

Hi David,
Thanks for the report, And glad all turned out safely for all concerned, and hope Rodolfo eventually is recovered.

My request is can I forward your report to Vyv Cox, a specialists Metalurgy scientist, who writes for Yachting Monthly and is a friend of mine.

I await your reply

Brian and Sue
S/V Darramy in the Peloponnisos

+x

 

David.Frost - 7/20/2019

We aboard Taipan have just been through a mini anchor drama. Having lived aboard and anchored around the world in over 1000 different anchorages during the past 18 years we were in total shock when our trusty Rodolfo "Other Type" disappeared off the bow as we retrieved it. The cause of this disaster was a 2-year-old S/S  Swivel. The 15mm pin connecting the two rings sheared. Oxygen deprivation corrosion. David had the gear on the ground a month before when we hauled out, inspected it closely and rewired all the shackles after inspection. It was not detectable. We were lucky as this failure could have been very dramatic in the middle of the night in a big blow. Lesson. No more swivel. We had to replace the anchor, at considerable expense here in Panama. We purchased a Rocna 40. This required only a minor bow roller modification. 
We hope to go back to the site off Panama and dive for Rodolfo. That anchor was 55kg. We are 50ft and now we are so overloaded with stuff after 18 years I hate to think what we weigh... but it's over 20 ton. Our chain is 10mm short link galvanised and is now 6 years old. Rodolfo was built (and signed) in Fremantle Australia, by an old fisherman and we purchased it second hand for $60. It doesn't owe us anything, It has never dragged but we did have to upgrade our windlass!!!
No more swivels on Taipan.

Hi David,
It is good to hear field reports such as yours; to often we remain silent about things that do not go well. I have long contended that swivels are not necessary on cruising boats (and are often the weak link) and that stainless steel has no place at all in a ground tackle system.
I am sorry this happened to you but appreciate the report and are glad the discovery was not more painful than a lost anchor.
I very much support your conclusion.
My best, Dick Stevenson, s/v Alchemy

We aboard Taipan have just been through a mini anchor drama. Having lived aboard and anchored around the world in over 1000 different anchorages during the past 18 years we were in total shock when our trusty Rodolfo "Other Type" disappeared off the bow as we retrieved it. The cause of this disaster was a 2-year-old S/S  Swivel. The 15mm pin connecting the two rings sheared. Oxygen deprivation corrosion. David had the gear on the ground a month before when we hauled out, inspected it closely and rewired all the shackles after inspection. It was not detectable. We were lucky as this failure could have been very dramatic in the middle of the night in a big blow. Lesson. No more swivel. We had to replace the anchor, at considerable expense here in Panama. We purchased a Rocna 40. This required only a minor bow roller modification. 
We hope to go back to the site off Panama and dive for Rodolfo. That anchor was 55kg. We are 50ft and now we are so overloaded with stuff after 18 years I hate to think what we weigh... but it's over 20 ton. Our chain is 10mm short link galvanised and is now 6 years old. Rodolfo was built (and signed) in Fremantle Australia, by an old fisherman and we purchased it second hand for $60. It doesn't owe us anything, It has never dragged but we did have to upgrade our windlass!!!
No more swivels on Taipan.

+x

 

bwallace - 7/10/2019

Hi all, not sure where this post should be but I am sure it will eventually end up in the correct (bin)?In last month e bulletin, there was an article entitled “why no one cares about yours travels”. I agree with what has been written, as we find the same.My thought is can someone do a study or has a study been done to understand why when anchored in quiet anchorage, another boat comes in and 90% of the time wants to anchor near you? we can be in a large bay with plenty of room for safe anchoring and peace and quiet. But no we seem to be a magnet. I know we are not alone in this quandary, so maybe someone has looked into the minds of these types of sailorsWe are reasonably sociable folks, but can never stop wondering what are these people thinking about. Amazingly we came across one boat that it turned out were fairly well healed, lived in a large private’s residence, so you would think they would enjoy some space, No, they did not seem to take the hint to move further away.I know we all have examples, and there are some deterrents you may use which again may make interesting reading!Sail SafeBrian and SueS/V Darramy anchored in a quite bay in the Peloponnisos 😎

Hi Brian & Sue, Never underestimate the herding instinct. Dick Stevenson, s/v Alchemy

Hi all, not sure where this post should be but I am sure it will eventually end up in the correct (bin)?

In last month e bulletin, there was an article entitled “why no one cares about yours travels”. I agree with what has been written, as we find the same.

My thought is can someone do a study or has a study been done to understand why when anchored in quiet anchorage, another boat comes in and 90% of the time wants to anchor near you? we can be in a large bay with plenty of room for safe anchoring and peace and quiet. But no we seem to be a magnet.
I know we are not alone in this quandary, so maybe someone has looked into the minds of these types of sailors

We are reasonably sociable folks, but can never stop wondering what are these people thinking about. Amazingly we came across one boat that it turned out were fairly well healed, lived in a large private’s residence, so you would think they would enjoy some space, No, they did not seem to take the hint to move further away.

I know we all have examples, and there are some deterrents you may use which again may make interesting reading!

Sail Safe

Brian and Sue
S/V Darramy anchored in a quite bay in the Peloponnisos 😎