Anchor Swivel

[Cotemar]

Craig,

You skipped right by my post. Wanted to know what your opinion was on this?

http://www.cruisersforum.com/forums/...tml#post601310

Mark

[craigsmith]

Sorry Mark I did in fact write and post a reply, but it seems to have disappeared.

Your set-up looks okay. It's certainly the correct way to install it.

Does it help with anchor behavior on the roller (self-righting)? Even if not, she can now poke the anchor with a boat hook to orient it correctly.

I don't know about the swivel, I'm not familiar with it.
1) Make sure the chain pin is seized, probably need to use Loctite, what is on the other side (of the pin)?
2) It looks like a neck-and-nut configuration (the swivel joint is made by screwing a nut onto the threaded neck of the chain body) - keep an eye on that weld for corrosion, probably the primary area of risk on account of the possibility of wrong fillers or improper treatment / ferrous contamination / failure to passivate etc.
3) What diameter is the chain pin, relative to the chain.

[Cotemar]

Craig,

We are in the dead of winter here with 30 inchs of snow, so we have not tried it out yet.

1) The swivel pins require loctite per manufacturer
2) Will watch the connections closely
3) The swivel pin is 3/8, which is the largest pin that will fit through a 5/16 chain link. The pin is 7/16 or larger on the shackel, Rocna side of the swivel

Thanks for your feedback,
Mark

[osirissail]

Great discussion of the various shackle systems. But the main problem with any shackle or swivel is simply wear on the parts that move. Over the years, the pins, chain links and bolts grind away at each other until what was 3/8" is not 1/4" or less.
- - Galvanized steel shackles and swivels are commonly available especially in work/fish boat suppliers.
- - Stainless - any grade gets intragranular corrosion and fails when the metal is deprived of access to oxygen.
- - And the most important - real life - issue is you can only buy what the vendors sell unless you own your own smelter and forging shop. So most bolts and fittings are 304 Stainless out of China and a few sources still have 316 (not 316L) bolts and fittings - but they are expensive and rare. Under the current world market system, if they (the manufacturers) cannot sell a million of more of something - they don't make it. So all the discussions of this alloy is better than that alloy are mute if you cannot find or buy the better one.

[S/V Alchemy]

Originally Posted by craigsmith

I'm just going to quickly go through this because it irritates me. The interested reader really needs to have some confidence in reputable manufacturers, and investigate whether their particular products are in the habit of catastrophically failing, before purchasing. Various metallurgical arguments loosely thrown about by non-experts tend to be either completely incorrect, or (harder to argue with) misapplied or out of context. Careful!

I await the production of your degree in metallurgy, Craig, as well as the reduction in your irritation at the ignorance of your potential clientele. As far as I know, you're just an anchor vendor and the son of an anchor inventor. I appreciate that growing up around a fabrication business (until it got outsourced to China, I suppose) gives you certain insights, but I would submit so does the experience of the many sailors who've spent years anchoring with different set-ups in different conditions.

Many of those sailors have a problem with stainless gear in contact with galvanised steel. "Confidence in reputable manufacturers" is of course one factor in deciding what bit of expensive gear is worth getting, but it doesn't trump physics. Gravity isn't a "loose argument" when one is falling out a window, and there are good reasons to at least consider the potential deficiencies of SS with galvanised chain, particularly in a make or break convenience like a swivel.

Originally Posted by craigsmith

See above. Don't use 304 for any important marine application, even 316 is barely appropriate. (But it's okay if handled properly in appropriate designs).

Well, we agree on this. 316 is barely appropriate. It might be OK if handled properly in appropriate designs, but it remains to be seen a) if such designs are currently available and can justify the cost, and b) if the manufacturing is so brilliant that tiny defects don't widen into total failures when subjected to side loads or warm salt water.

Originally Posted by craigsmith

That's great. Now finish the argument by finding the relevance to good quality 316 or duplex marine components.

What do you mean by "duplex marine components"? Differently alloyed stainless steels?

Originally Posted by craigsmith

What? I don't know how you got from pitting to galvanic corrosion, but it's an entirely different matter. The presence of some zinc in proximity or electrical contact won't accelerate pitting, crevice, SCC, or any other form of stainless corrosion, nor fatigue failure.

I mean the presence of zinc-free steel, actually, in contact with the stainless. Shackles and chain, subject to constant chafe of degrees variable to the state of the bottom and the movement of water by tide, current or wind, can physically rub "bright". So I'm not really discussing galvanic corrosion, but corrosion of the rubbed bright steel chain up against the SS shackle or swivel. I will concur that for those that have the money, an oversized completely SS chain, shackle, swivel and anchor set-up makes sense, excepting that SS is more brittle and weaker, pound for pound, than the steels that end up galvanised. Someone has noted that titanium shackles/swivels make perfect sense, but that's a whole different kettle of worms, so to speak.

Originally Posted by craigsmith

In any case, galvanic corrosion with small stainless components is NOT a practical problem, and it (if anything) affects the zinc, not the stainless...
If you're using a stainless anchor (big surface area) with galvanized chain in 30 deg C water anchored 300 days a year, then sure maybe you'll see the zinc near the anchor disappear a bit faster.

I don't have the data to support that. I've only ever seen an SS anchor at the dock, and I sail in fresh water at the moment. You could tie bricks to a pickaxe and use dreadlocks as a rode and expect not to break free in many spots around here. Not all of 'em, mind.

Originally Posted by craigsmith

Why? The fatigue limit of 316 is roughly 35%, well above the 25% WLL:break ratio of most anchoring gear. Quel surprise, don't exceed the stated WLL and you won't have problems. It commonly gets bandied about that the fatigue strength of "stainless" (by which is usually meant 3xx, never mind the far superior duplex grades) is "really really low man, the sky is falling", by implication much lower than - what, steel that stains? Actually the typical fatigue limits of mild carbon and low alloy steels are not much higher, you're doing well if you can get over 45%. Add a bit of extra size in there if you want to compensate, but the manufacturer - who you hope knows a lot more about it than you - has probably already done so.

You hope, but as has been pointed out, some manufacturers either state or stamp their WLLs directly on the product. Even that is not a guarantee against neglect or poor technique, of course, but I imagine if it could be proved (how I don't know) that Rated Swivel X failed under Benign Conditions Y, then a lawsuit would quickly follow.

Is it your contention that SS can be made STRONGER and more ductile than the typically galvanised steels used in shackles and chain?

[S/V Alchemy]

Originally Posted by At sea

So stay tuned for a few months/years/decades and I'll let you know how the SS chain fares. Nothing like a real life observation to inform the theory.

Good on you. There's entirely too much theory in the air. Is there any non-SS in the mooring chain set up? You might want to test for stray current or anything else dodgy in the immediate area that could skew the results.

[S/V Alchemy]

Originally Posted by osirissail

- - Stainless - any grade gets intragranular corrosion and fails when the metal is deprived of access to oxygen.
- - And the most important - real life - issue is you can only buy what the vendors sell unless you own your own smelter and forging shop. So most bolts and fittings are 304 Stainless out of China and a few sources still have 316 (not 316L) bolts and fittings - but they are expensive and rare. Under the current world market system, if they (the manufacturers) cannot sell a million of more of something - they don't make it. So all the discussions of this alloy is better than that alloy are mute if you cannot find or buy the better one.

The last two points are very good. A SS swivel buried in the perhaps anoxic silt of an anchorage will, or so I am persuaded, be subject to corrosion if there are even slight defects. Design may disguise or hide these defects until the item inconveniently fails. Galvanised steel shackles seem to have grosser defects more readily noticed...and fixed.

I have had some experience having steel fabrications made (I am fitting out a steel boat) and understand how the quality of a weld, in concert with the grade of the steel and its mode of forming (forging or casting, for instance, along with quenching/cooling) can affect both the longevity and strength of the finished piece. I agree that Wonder Alloy held together with Two Threads and a Nylok isn't going to be a good advertisement for Wonder Alloy, nor is Wonder Alloy on an inherently duff design likely to survive. That is why I am leaning toward the "big link on the end, followed by oversized jaw-jaw" method. It has the benefit of transparency in that the parts most afflicted by the physics of the thing are, like a tire losing tread depth, very easy to spot. And, should problems be found, such a shackle is much cheaper to replace than SS, which may be a case of a Tiffany solution for a WalMart need.


PS: I've read through that thread cited earlier on. It's quite a good read and ties in nicely with this one: http://www.cruisersforum.com/forums/...e-26025-7.html

[rocksculpter]

In response to Craigsmith's comment on alloy, from my engineering background, yes alloy makes a difference when it comes to corrosion resistance. Generally the higher the better but all "stainless" is prone to crevice corrosion especially in areas that have less oxygen in contact and in the areas that have been 'formed' in the manufacturing process. Typically like eye end of a turnbuckle or a bolt head. Even the slight bending on a chain plate can set you up to a failure.
A fully machined fitting is less likely to be problematic but beware of any design that puts threads in bearing. Prudent periodic inspection looking for discoloration or minute cracks could save the day.
My person thanks to those who participate in strings like this that keep us knowledgeable and safe.

[Jim Cate]

G'Day all,

Lots of passion here!

But I have a specific query for Craig Smith: Do you have a source for shackles and/or swivels made from 2205 or other duplex grades of s/s?

Our boat has chainplates made of 2205 bar stock and I'm quite happy with it in this service, but have not seen fabricated items like the above offered for sale.

Cheers,

Jim

[Extemporaneous]

I'd have to do some looking for the article, but I'm sure that I've read that once crevice corrosion in Stainless Steel starts, galvanic corrosion can begin within the crevice. The reaction being from one side of the crevice to the other.

Has anyone else read this?

Extemp.

[Therapy]

Originally Posted by Cotemar

Craig,

We are in the dead of winter here with 30 inchs of snow, so we have not tried it out yet.

1) The swivel pins require loctite per manufacturer
2) Will watch the connections closely
3) The swivel pin is 3/8, which is the largest pin that will fit through a 5/16 chain link. The pin is 7/16 or larger on the shackel, Rocna side of the swivel

Thanks for your feedback,
Mark

Thanks for the pic that is what I am going to do. I thought I needed two shackels.

[Cotemar]

Therapy,

Pictures really tell it all, don’t they.
I alway try and take a pictures to share with others.

Mark

[Extemporaneous]

Originally Posted by Cotemar

Craig,

We are in the dead of winter here with 30 inchs of snow, so we have not tried it out yet.

1) The swivel pins require loctite per manufacturer
2) Will watch the connections closely
3) The swivel pin is 3/8, which is the largest pin that will fit through a 5/16 chain link. The pin is 7/16 or larger on the shackel, Rocna side of the swivel

Thanks for your feedback,
Mark

Hi Cotemar,
I think you've already been told that your setup is okay. I do have one observation though, based only on my version of logic, and that is.... if you had a couple of chain links attached to the anchor side of your swivel then you would end up with much much more bearing on the swivel bolt and shackle pin due to them being round and fitting up against the inside round of chain links.
This could only be a good thing (I think??).
Right now, with the two round pins/bolts crossing each other (swivel to shackle) the forces are trying so very hard to bend them right from the get go.

Do you see what I'm saying? (not sure if I'm explaining clearly)

Extemp.

[Cotemar]

Extemporaneous,

Yes, that would work also, but due to the size of pin and chain link you always end up with one point contact. Match fit is the only way to get a larger contact area and that would entail fabricating exact parts.

I will keep a close eye on it and see that it meets my first mates expectation of bringing up the anchor the right way.

Mark

[Extemporaneous]

Originally Posted by Extemporaneous

I'd have to do some looking for the article, but I'm sure that I've read that once crevice corrosion in Stainless Steel starts, galvanic corrosion can begin within the crevice. The reaction being from one side of the crevice to the other.

Has anyone else read this?

Extemp.

Didn't find the article where I'd read this but came across this which is not the same but similar.
Corrosion Type Concentration Cell Corrosion.

Regards,
Extemp.