CAS or "Chainplate avoidance syndrome"

[Cyrus Safdari]

After spending a few years in boatyards and rebuilding/watching others work on their boats I've noticed an interesting phenomenon I've taken to calling "Chainplate avoidance syndrome" or CAS

I gave it this name because it usually becomes apparent in my fellow boaters when the discussion about their boats comes down to inspection of chainplates but it also occurs when discussing cutlass bearings. They'll tell me all about the work then did on their improvements and the new bottom job etc but when it comes to chainplates and cutlass bearings, it's as if they just don't want to know.

"Oh I can tell, the chainplates are fine. The previous owner replaced them (15 years ago)"

But you really can't tell without pulling them and checking on the interior side for crevice corrosion

"Oh no, that's not necessary, see, no rust."

Actually there's rust right there see? But in any case again, you can't tell unless you pull them. No human can see through steel.

"Oh I'm sure they're fine, they're very shiny stainless steel aren't they?"

*sigh* Hey what a lovely anchor...

What explains this of course is that removing and inspecting chainplates is a PITA so easier to just rationalize not doing so. People don't like bad news and don't like the bearers of bad news very much either

[kmacdonald]

If chainplate removal involves removing interior woodwork it might not be worth it if there are no obvious signs of rusting. We all have different levels of risk tolerance and that is what is at play here. Not much risk in a worn cutlass bearing, just a slight vibration.

[Cyrus Safdari]

...if there are no obvious signs of rusting.

Hey, you've got a nice anchor there too...

[kmacdonald]

A rigger might produce a broken chainplate as "evidence" they can break without warning. It happens but is extremely rare. If you wear lightning protection on your head you might consider ripping out the interior to inspect the chainplates. Actually that won't satisfy the fear mongers, they say they cant be inspected adequately and should be replaced. Make your own decisions.

[kmacdonald]

I should also mention the factor of safety of a chainplate is WAY higher than any other component of the standing rigging. They are designed to last the life of the boat. There are some exceptions on known boats that used substandard materials for the chainplates.

[Cyrus Safdari]

Look if it's just too much of a PITA to bother, just say it out loud don't rationalize it because there is no rational reason to not inspect chainplates & it certainly has a higher priority on any boat that wants to keep a mast up.


This isn't some riggers conspiracy, breaking chainplates from unseen corrosion is actually a very regular thing, widely discussed on CF, standard subject of many a boat DIY article emphasizing the need the inpect-replace them & pit corrosion is simply an inevitable fact of life with SS. The machine shop down the road from our boatyard does a good business in replacing corroded chainplates as well as worn/corroded prop shafts. The machine shop owner told me many stories of how he keeps an old corroded shaft & chainplate on hand to show the boat owners who bring in their chainplates and prop shafts for a "quick repair" that the pit or crevice corrosion is not limited to the surface blemishes they want him to "just buff out".

And yes chainplates are indeed often hidden away behind cabinetry in poorly designed boats making them a true PITA to remove & inspect every few years as they should be. Sorry thems the breaks, because no amount of visual inspection will ever see behind the chainplate or the bit where it passes through the deck & pit corrosion isn't something that only happens to other people

Honestly SS is the worst material for chainplates; it corroded when wet but doesn't rust, and does so only where it can't be seen, meanwhile getting weaker and weaker until it suddenly breaks without notice

make your own decisions

Nobody else is making any decisions; nobody cares what others do really & certainly nobody will care about your boat as much as you

[kmacdonald]

I know of one chainplate that broke and the mast was lost. It was the backstay. It broke where it penetrated the hull. There were clear signs of severe corrosion in the form of very heavy rust stains from years of corrosion. Had a simple visual inspection in the stern locker been done it would have been obvious there was a problem. It wasn't hidden by any stretch of the imagination and ample warning of impending failure was present. This case is typical of almost all chainplate failures.

[Manateeman]

Let’s start with the worn cutlass bearing. It’s attached to the transmission. So let’s guess replacing it takes 2-4 hours at $100/hour plus $100 for the part.
So $500? And a new transmission costs what? $1,000 -$2000.
The chain plates that can last the life of the boat. We know exactly the two types.
Solid aluminum bar welded in an aluminum boat...and solid bronze exterior chainplates bolted to a glass hull.
We’ll stop the fear mongering and get back to the pizza.
The manatees.

[Cyrus Safdari]

Originally Posted by Manateeman

Let’s start with the worn cutlass bearing. It’s attached to the transmission. So let’s guess replacing it takes 2-4 hours at $100/hour plus $100 for the part.
So $500? And a new transmission costs what? $1,000 -$2000.

Yup I removed and replaced my own cutlass bearing, following directions of fellow boaters,, Total cost including boatyard time was $500. Yes it can be expensive and a PITA. Whoever said boating was gonna be cheap and easy? A cutlass bearing is a consumable item with a working lifetime that's designed into it. And once it wears there is much more damage than just a funny noise. It needs replacing every once in a while on any properly maintained boat.

The chain plates that can last the life of the boat. We know exactly the two types.
Solid aluminum bar welded in an aluminum boat...and solid bronze exterior chainplates bolted to a glass hull.
We’ll stop the fear mongering and get back to the pizza.

Yes that's ideal! but unfortunately most boats use stainless steel of course
People switch to bronze in fact precisely because of the corrosion issues with ss chainplates so that kinda proves my point
If ypu don't have bronze they probably won't last the lifetime of the boat and will need replacing and more than once (I don't know much about alum)

Bronze doesn't suffer from crevice corrosion nearly as badly as stainless steel and so can even be permanently glassed-in without concern. They're finding thousands year old wrecks with intact bronze bits. (My boat'srudder shoe is bronze encased in glass, I sanded back to check it pristine after 50+ yrs.) However we all know not too many boat came with bronze exterior chainplates from the factory. Lol

[Cyrus Safdari]

Originally Posted by kmacdonald

I know of one chainplate that broke and the mast was lost. It was the backstay. It broke where it penetrated the hull. There were clear signs of severe corrosion in the form of very heavy rust stains from years of corrosion. Had a simple visual inspection in the stern locker been done it would have been obvious there was a problem. It wasn't hidden by any stretch of the imagination and ample warning of impending failure was present. This case is typical of almost all chainplate failures.

It depends on the quality of the stainless used; pit corrosion is called that precisely because on the surface it can appear as just a dimples and blemishes that go deep

[Oeanda]

Post 1 is pretty much a direct transcription of the conversations I’ve had with the first mate. When I showed it to her she accused me of writing it. . Tthough I’d rather believe the second guy. And the third fellow went off to eat pizza. So now what, hmmm.

I look upon those chainplates with suspicion. But with our boat at least it should be relatively easy to disconnect the shrouds and check one at a time. One of these days…

[capt jgw]

I was going to pull the chain plates on my 1969 Columbia 36 but I ended up selling the boat before I got to it. Up to the new owner to do now, he won't.

[capt jgw]

Originally Posted by Oeanda

Post 1 is pretty much a direct transcription of the conversations I’ve had with the first mate. When I showed it to her she accused me of writing it. . Tthough I’d rather believe the second guy. And the third fellow went off to eat pizza. So now what, hmmm.

I look upon those chainplates with suspicion. But with our boat at least it should be relatively easy to disconnect the shrouds and check one at a time. One of these days…

Attachment 265304

At least you can see one side of them, and they don't appear to have a spot where water would be present and free oxygen not present like those that penetrate the deck. Those are the ones that break with little warning, right in the spot where they're buried in the fiberglass.

[markxengineerin]

Titanium chain plates - good for the life of the boat and beyond. Available but $$$ from various sources- Colligo Marine, Allied Titanium, others.
Or, if within your skills, you can DIY with cheap material sourced here:
https://www.sackinmetal.com/titanium selection varies, wait until they have your size
I "saved money" making from scratch but ended up buying a kiln on craigslist to get to 1200 degrees F for bending, a 15 ton press, and already had the milling machine, lathe, etc to make the required tooling then the plates themselves. Major project but very satisfying result to know that I'll never need to touch them again. Titanium bolts were cheapest here: https://www.rsrmoto.com/

Back to the subject of the thread- I think stainless chainplates should be replaced after X years (maybe 10-15) for offshore cruising. I saw how bad mine looked after 10 years in Florida climate. They were good quality 316 stainless and reduced to crumbling when I put a load on them. For coastal cruising, risk tolerance can be higher.

[Oeanda]

I see. Thank you. Yes I’m happy they aren’t buried. The outer surfaces have visible though slight specks of rust. You think the backsides next to the glass aren’t necessarily prone to the issues mentioned? That would be a nice thought.