Anchor Swivel

[craigsmith]

Originally Posted by S/V Alchemy

So am I. I don't know if it's a stupid idea to pursue or not. I'm wondering if this is even feasible in a tidal situation. On Lake Ontario, I will freely admit I miss the bigger picture, even though squalls can give us a lot of veering wind and sudden gusts that inform our technique...

Galvanized swivels are okay, but kind of agricultural - their swivel action tends to bind, and the zinc can/will wear and result in rusting. Stainless is far superior, there's a reason most serious quality swivels are exclusively done in inox. Ensuring quality becomes trickier too with an inherently cheaper product.

Originally Posted by S/V Alchemy

Gord, I am familiar with those, of course. I have several aboard. What I meant is are there galvanized swivels of the Powerball or Quickline type? They all seem to be SS

Ball-and-socket configurations are something of a pointless gimmick - stick to the simple inline designs.

[S/V Alchemy]

Originally Posted by craigsmith

Galvanized swivels are okay, but kind of agricultural - their swivel action tends to bind, and the zinc can/will wear and result in rusting. Stainless is far superior, there's a reason most serious quality swivels are exclusively done in inox. Ensuring quality becomes trickier too with an inherently cheaper product.



Ball-and-socket configurations are something of a pointless gimmick - stick to the simple inline designs.

The rusting of damaged or worn galvanized steel is well-known, but unlike crevice corrosion in SS, you get to see it when it happens. In light of the problem of this and dissimilar metals when an SS swivel is used with a galvanized chain and galvanized anchor, why do you think SS is "far superior"?

Also, why do you consider ball and socket a pointless gimmick? What swivel type would you prefer and why?

[craigsmith]

You will not get crevice corrosion in quality stainless gear. Why does this unfounded belief persist? Do you seriously imagine that this is an inherent property to all stainless steel products?

Ball-and-socket is just a solution looking for a problem. It is supposed to address the issue of articulating loads on swivel joints. However
1) they only articulate to a maximum of 30 degrees, hardly the 90 that is really required, and
2) the issue with articulation is first and foremost the arms on the anchor attachment point, not the swivel joint - and these same designs (Powerball and the Ultra/Quickline copy) are intended to be attached directly to the anchor.

So they don't solve the issue at all and at best are just an expensive and overly complicated way of making a swivel. As I said above the inline designs are the simplest and best, the swivel joint is just a head on a neck securely retained by the other body.

[Cotemar]

Craig,

What is your opinion of this swivel set up.

5/16 chain, swivel, shackel, Rocna 44lb.

Have not used it yet, but my first mate does not like it when the anchor comes up backwards.
I showed her how to grab the chain and give it a bit of a pull and twist, but she does not have the strength.
I was thinking this swivel may help her.

Mark

[Uncle Bob]

Originally Posted by Cotemar

Craig,

What is your opinion of this swivel set up.

5/16 chain, swivel, shackel, Rocna 44lb.

Have not used it yet, but my first mate does not like it when the anchor comes up backwards.
I showed her how to grab the chain and give it a bit of a pull and twist, but she does not have the strength.
I was thinking this swivel may help her.

Mark

Mark, Hi what you have is much the same as my setup, minus the shackel. Why did you include this instead of connecting swivel to rocna direct??
Rob

[Cotemar]

Uncle Bob,

I included the shackel onto the Rocna, so if the anchor gets lodged on a side pull it will not split open the swivel.
That seems to be the mode of failure for most swivels.
5/16 chain, swivel, shackel, Rocna 44lb.

Mark

[Uncle Bob]

Originally Posted by Cotemar

Uncle Bob,

I included the shackel onto the Rocna, so if the anchor gets lodged on a side pull it will not split open the swivel.
That seems to be the mode of failure for most swivels.
5/16 chain, swivel, shackel, Rocna 44lb.

Mark

Mark thanks for the reply, I believe I see your point. Cheers
Rob

[cfarrar]

I included the shackel onto the Rocna, so if the anchor gets lodged on a side pull it will not split open the swivel.

As recommended by Craig Smith. Looks good. I might try this.

[atoll]

would reccomend using a normal u shackle as opposed to a bow shackle,much stronger.
also using a center punch and hammer to lock off the pins on the swivel

[Extemporaneous]

Some of you likely have read this thread, but for those that haven't, it deal with similar stuff. Swivels, stainless steel and galvanized.

http://www.cruisersforum.com/forums/...are-26025.html

Cheers,
Extemp.

[S/V Alchemy]

You will not get crevice corrosion in quality stainless gear. Why does this unfounded belief persist? Do you seriously imagine that this is an inherent property to all stainless steel products?

Why, yes, Craig, I do. Me and you know, metallurgists. 304 and 316 have different pitting and crevice corrosion properties, it's true, but both can be susceptible and it gets worse in warmer water. In the tropics. Where the boats anchor.

From this document: "Which Steels are Susceptible? All stainless steels grades can be considered susceptible, but their resistances vary widely. Their resistance to attack is largely a measure of their content of chromium, molybdenum and nitrogen. Another factor of importance is the presence of certain metallurgical phases (in particular the grades 303, 416 and 430F containing inclusions of manganese sulphide) have very low resistances, and ferrite may be harmful in austenitic grades in severe environments. A clean and smooth surface finish improves the resistance to attack. Contamination by mild steel or other "free iron" greatly accelerates attack initiation. (my italics)."


We also have an interesting, experience-filled thread on the topic on the SailboatOwners.com site here.


So, from this, we can gather that stainless steel, even of good alloys designed to resist corrosion in seawater, can have issues exacerbated by intimate and persistent contact with galvanised steel chain. A bandage solution is to go all stainless, I suppose, but it's only a delaying tactic in warm seawater that gets dosed with air and may, due to the job it's doing, have microscopic stress fractures. Same thing happens with mast fittings, as well...it's the whole basis of the dye inspection.

So, I guess you go all SS from devil's claw to anchor, or you keep an eye on that old galvanised chain and anchor, and replace as needed. Well-used ground tackle becomes more like filters or belts: replace as needed. I am coming to believe, however, that SS bits in the mix are problematic at best. Rust on a galvanised chain shows readily, and you can "dip" once or twice (barring other issues) before you have to replace. Can't do that with SS.


Ball-and-socket is just a solution looking for a problem. It is supposed to address the issue of articulating loads on swivel joints. However
1) they only articulate to a maximum of 30 degrees, hardly the 90 that is really required, and
2) the issue with articulation is first and foremost the arms on the anchor attachment point, not the swivel joint - and these same designs (Powerball and the Ultra/Quickline copy) are intended to be attached directly to the anchor.

So they don't solve the issue at all and at best are just an expensive and overly complicated way of making a swivel. As I said above the inline designs are the simplest and best, the swivel joint is just a head on a neck securely retained by the other body.

Well, I am coming around to your point of view on this; however, I do think that SS isn't the answer...even in the "inline" format.

[S/V Alchemy]

Originally Posted by Cotemar

Uncle Bob,

I included the shackel onto the Rocna, so if the anchor gets lodged on a side pull it will not split open the swivel.
That seems to be the mode of failure for most swivels.
5/16 chain, swivel, shackel, Rocna 44lb.

Mark

If we could get that swivel in galvanized, we'd be onto something. Maybe. It is occuring to me that I could just save my money and get the beefiest bow shackles that would fit..and then just take more care of my rode.

[craigsmith]

Originally Posted by S/V Alchemy

You will not get crevice corrosion in quality stainless gear. Why does this unfounded belief persist? Do you seriously imagine that this is an inherent property to all stainless steel products?

[B]Why, yes, Craig, I do.
We also have an interesting, experience-filled thread on the topic on the SailboatOwners.com site here.

Sorry, you are wrong. Pitting is an issue with 316, it would be nice to see duplex grade swivels, like some high quality shackles, but it's a small issue and can come under the general matter of wear and tear / maintenance - nothing lasts for ever. My point is the whole Chicken Little stainless-is-evil crevice corrosion sky-is-falling lark is bunk.

I don't know what you imagine the point of your italicized statement to be. Keeping stainless clear of steel/iron contamination is stainless fabrication 101. If you get pit rusting on a new product it's likely been so contaminated - that's a quality control problem. So what?

It's easy to find examples of failed stainless gear, including swivels. I have a whole collection. Your linked thread contains no examples but I assume the conjecture in it was supposed to represent some? But these are a testimony to poor quality gear, not some inherent generic problem with stainless steels. Try to find an example of a good quality well-reputed brand swivel failed on account of its metallurgy - no particular endorsement intended, but for example Kong, WASI, et al. You will not find many, if any.

Originally Posted by atoll

would reccomend using a normal u shackle as opposed to a bow shackle,much stronger.

Rubbish. It depends on the design, typically with the type of small body shackles used with anchors and chain there's no difference. It's usually the pin or the pin holes which fail, not the body.

Originally Posted by atoll

also using a center punch and hammer to lock off the pins on the swivel

If you don't want to be able to undo it again...

[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!

Originally Posted by S/V Alchemy

Why, yes, Craig, I do. Me and you know, metallurgists. 304 and 316 have different pitting and crevice corrosion properties, it's true, but both can be susceptible and it gets worse in warmer water. In the tropics. Where the boats anchor.

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).

Originally Posted by S/V Alchemy

stainless steels grades can be considered susceptible, but their resistances vary widely. Their resistance to attack is largely a measure of their content of chromium, molybdenum and nitrogen. Another factor of importance is the presence of certain metallurgical phases (in particular the grades 303, 416 and 430F containing inclusions of manganese sulphide) have very low resistances, and ferrite may be harmful in austenitic grades in severe environments. A clean and smooth surface finish improves the resistance to attack. Contamination by mild steel or other "free iron" greatly accelerates attack initiation

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

Originally Posted by S/V Alchemy

So, from this, we can gather that stainless steel, even of good alloys designed to resist corrosion in seawater, can have issues exacerbated by intimate and persistent contact with galvanised steel chain.

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.

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.

Originally Posted by S/V Alchemy

and may, due to the job it's doing, have microscopic stress fractures

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.

[Wand]

I mentioned in an earlier post in this thread that I had come across some very cheap 13mm stainless by Australian chainmaker PWB, which by all accounts is a maker of quality products. Seems it was a bin end - they haven't made that chain for years.

I had intended to use it for mooring chain (that's what I went shopping for that morning) but there seems to be strongly held views on this and on another current thread that this is not a good idea. PWB do not endorse it for that purpose either. However, no-one has pointed (yet) to any first hand experience of stainless chain failure.

So might as well live dangerously. Since I've now got the chain, and there being no other useful purpose I can see to which it can be put, I'm prepared to settle the arguments with a practical test. I am going to use it for mooring chain, albeit for two light displacement vessels. The test will be super stringent given we have a power station outfall nearby and water temperatures are usually at tropical levels.

But I am not going to entrust the boats to the SS entirely; we have fore 'n' aft moorings here, and the forrard one will be the ever-reliable rod (so the boat won't escape entirely).

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.