Stainless Steel Shackles on Anchors?

[UNCIVILIZED]

Shiny sells, so marine vendors capitiize on this. Particularly with the knowledge that not 1 in 100 of these shackles sold will ever be pushed anywhere even close to it's WLL or failure point.

A shackle's strength is rated based on a certain assumed amount of the shackle pin being supported. 80% I believe. And when there's more of a gap than this, then they're generally weaker than their SWL/BS. But again, normally get used so gently that failures are few & far between. Plus there are safety factors of several X which are used on top of the industry standard safety factor for shackles of 5:1.

That said, they do sometimes fail. If you read accounting of boats which have survived hurricanes, it's not uncommon for said case studies to include reports of a number of shackles failing right at the anchor's attachment point. Much of it due to the above reasons.

IIRC SV Jedi penned their accounting of surviving a hurricane at anchor, for both the Dashews at www.setsail.com & for Fortress anchors. And I'm thinking that said accounting is also posted here on CF somewhere. In which they detail the failing of several anchor shackles. It's an easy enough story to find online.

[estarzinger]

mmmm . . . . .we used a wichard HR shackle for about half a decade. I put it on when a prior rated galvanized one started rusting badly and we were in the middle of no-where.

We had previously bent/broke a high end SS swivel, so it was not like we were babying our ground tackle.

This is not to suggest it was the best/perfect material, but it was fine, no problem. I used it simply because I had it on board, it had a nice flush Allen key head which ran smoothly, and it seemed sufficiently speced to do the job. When we got new chain, we swapped it out for a new rated galvanized one - but not because I had any real concern about it.

[UNCIVILIZED]

I'll confess that given the strength of some of those HR shackles in 17-4 PH, the temptation to use them is mighty strong. Assuming that is, that $ doesn't figure into the equation, since they're far from cheap.

Then again, I vividly recall what the stainless Schaeffer downhaul block on my Searunner's centerboard looked like after a couple of years of being half submerged. Cheese graters have fewer holes.

In reality, so long as components are regularly inspected, the odds are with you I'd reckon. But as cheap as Crosby High Load shackles are as compared to 17-4 PH ones, I'll probably stick to the former. Though titanium is tempting
Shackles from Titan are Titanium - Our Shackles will not Corrode And their Ti through hull mushroom barbs, & hose clamps certainly are appealing. In theory at least. Since a Ti barb in a bronze valve would put the valve on the losing end of the argument as to which one would quickly get eaten by seawater.

[SVNeko]

Why would you ever need a Ti through hull?

[thinwater]

I've asked a number of chandleries why they carry higher grade chain, but not the shackles that go with it. Pretty simple question. The answers were quite unsatisfactory.

[Benz]

I've had two SS Wichard carabiners that crevice-corroded startlingly quickly when submerged, but have used Suncor SS bow shackles on my anchor with no ill effects, though I inspected them frequently (I use galvi now that I have good domestic available).

My biggest concern is with dissimilar metals underwater. Do we know what Ti does when paired with Galvi? I had a piece of G-70 chain rust to a thread where it touched a bronze bolt, and it did it in less than an month!

My favorite solution now is to back up each galvi shackle with a dyneema soft shackle or lashing, and to inspect everything frequently.

Ben
zartmancrusing dot com

[Training Wheels]

Originally Posted by UNCIVILIZED

I'll confess that given the strength of some of those HR shackles in 17-4 PH, the temptation to use them is mighty strong. Assuming that is, that $ doesn't figure into the equation, since they're far from cheap.

Then again, I vividly recall what the stainless Schaeffer downhaul block on my Searunner's centerboard looked like after a couple of years of being half submerged. Cheese graters have fewer holes.

In reality, so long as components are regularly inspected, the odds are with you I'd reckon. But as cheap as Crosby High Load shackles are as compared to 17-4 PH ones, I'll probably stick to the former. Though titanium is tempting
Shackles from Titan are Titanium - Our Shackles will not Corrode And their Ti through hull mushroom barbs, & hose clamps certainly are appealing. In theory at least. Since a Ti barb in a bronze valve would put the valve on the losing end of the argument as to which one would quickly get eaten by seawater.

Interesting that it seems the Wichard HR shackles have higher breaking strengths than the titanium shackles, at least in the 5/16" size I would need. But I guess no crevice corrosion concern. Abrasion resistance?

[double u]

Originally Posted by Glenn.Brooks

Iam curious, has anybody ever seen a SS shackle with the remotest hint of crevice corrosion? 45 years commercial fishing in Alaska and sailing, I never have.

Sure, dredge something up off the bottom after 40 or 50 years, it's gonna be corroded. But, really, anchor rode needing a small 1/4" shackle? small craft with such light weight rode is likely never going to be in a position to put such a strain on that size shackle that it will deform. Use either galvanized or SS, it won't matter. You will be safe either way.

had a Wichard shackle that had some slight crevice corrosion on the thread after months at anchor in the Brisbane river, not serious & it had been quite a long time in the mud

[double u]

Originally Posted by thinwater

I've asked a number of chandleries why they carry higher grade chain, but not the shackles that go with it. Pretty simple question. The answers were quite unsatisfactory.

Maggi, the Italian chain guys make special shackles for their Aqua 7 chain:
https://www.jimmygreen.co.uk/image.p...cts/hnw80g.gif

[patprice]

Originally Posted by Benz

I've had two SS Wichard carabiners that crevice-corroded startlingly quickly when submerged, but have used Suncor SS bow shackles on my anchor with no ill effects, though I inspected them frequently (I use galvi now that I have good domestic available).

My biggest concern is with dissimilar metals underwater. Do we know what Ti does when paired with Galvi? I had a piece of G-70 chain rust to a thread where it touched a bronze bolt, and it did it in less than an month!

My favorite solution now is to back up each galvi shackle with a dyneema soft shackle or lashing, and to inspect everything frequently.

Ben
zartmancrusing dot com

And maybe replace the shackle and swivel every 2/3 years. On principle. Ditch the old units in case led into temptation.

I feel like a hypocrite lol

[Cheechako]

Originally Posted by Training Wheels

I've never been one fond of stainless steel hardware for ground tackle use, but is it really a concern? I'm wondering if Wichard High Resistance D shackles, made of forged 17.4 PH stainless steel, would be okay to use on ground tackle. Would there be a real risk of crevice corrosion? As a person ignorant in metallurgy, your expert opinions please!

I have used them extensively on a few boats with no issues. Yes, they are very strong! It's not like corrosion is going to occur overnight.
Not sure if 17-4 suffers from Crevice Corrosion as the 300 series SS do or not.

[leftbrainstuff]

This is a complex topic and others have contributed some good analyses so I wont revisit the propellor hat discussion. I have a BEng Mech, Masters in Materials Welding and Joining, mechanic, toolmaking and airframe / pipe welding trades and extensive, design, failure analysis and reliability engineering experience. I don't have a good answer to the original question but I do understand the failure mechanisms and have skin in the game.

Our ground tackle will experience corrosion and abrasion which tend to align with 10s, 100s or 1000s of hours of immersion. With inspection at appropriate intervals this degradation is manageable.

The bigger issue is one time loads which exceed working load and much less than yield limits which consume useful life. Rate of load is also important. This is where notch sensitivity and impact tests provide usefull information.All materials show reduced toughness and reliability over time.

None of the fancy stainless shackles have overload indicators. (Issue 1) With standard shackles we have indicators, like bent pins and deformed shackles. In load equipment certification applications mandatory replacement is highly effective at avoiding failure due to continued use of a shackle which consumed its usefull life. What constitutes useful life of a shackle? (Issue2)

To simplify this complex topic its helpful to think in terms of usefull life rather than just one material spec or property. (Issue 4)

In the PNW I see lots of fancy stainless shackles. We currently have a galvanised 'vanilla' swivel and shackles. None have load limit markings. (Issue 5)

We also have a Mantus shackle and a Wasi. The Wasi has a Lloyds certification. The Mantus does not. The Mantus also has a deformed when forged stainless shackle and no load markings or certs. (Issues 6)

What should I replace my swivels with? I'm going to trial both swivels. I'm going to replace the deformed Mantus shackle. That issue seems common to this product.

One thing you can do with the polished stainless ground tackle is to measure its weight, and any corrosion, at regular intervals. I will also be monitoring for deformation of individual components. Reliability engineering, and that is the need here, requires monitoring and trend analysis to help us predict and respond before failure. (Issue 7)

Unfortunately all we have is vendor promises amd anecdotal evidence from a few end users. (Issue 8) I tend to put more weight on the anecdotal evidence rather than the vendors.

What is needed is statistical testing by a trusted independent body. (Issue 9)This would require multiple high strain, high load, static and dynamic, and baseline and corrosion tests. Not cheap, not quick and not trivial to do.

For something safety critical we also need redundancy. (Issue 10) Another posted suggested having a dyneema backup. An excellent idea but not without it's challenges.

[leftbrainstuff]

Originally Posted by Benz

I've had two SS Wichard carabiners that crevice-corroded startlingly quickly when submerged, but have used Suncor SS bow shackles on my anchor with no ill effects, though I inspected them frequently (I use galvi now that I have good domestic available).

My biggest concern is with dissimilar metals underwater. Do we know what Ti does when paired with Galvi? I had a piece of G-70 chain rust to a thread where it touched a bronze bolt, and it did it in less than an month!

My favorite solution now is to back up each galvi shackle with a dyneema soft shackle or lashing, and to inspect everything frequently.

Ben
zartmancrusing dot com

+1 to this

[Bluebeard]

Only Benz has really commented on the dissimilar metal corrosion that you will get using SS onto galvanized chain.
Whichever SS you use it will be noble with respect to the chain, and anchor.
But the chain being the thinner component will be the weak link if it is allowed to corrode.
The chain link attached to the shackle will act as an anode and corrode in preference to the shackle.
Why not use a good quality galvanized shackle like a Green Pin?
And you side step concerns about grade of SS and its WL/Breaking strength.

[Training Wheels]

Originally Posted by double u

Maggi, the Italian chain guys make special shackles for their Aqua 7 chain:

https://www.jimmygreen.co.uk/image.p...cts/hnw80g.gif

It seems those are no longer available from Maggi. As I understand, they bought them from another manufacturer and had them galvanized, which the manufacturer recommended against.