Stainless Steel Chainplates (failed 50 miles offshore)

[RECESS]

When we bought the Pearson 6 months ago I checked the chainplates visually. The Pearson has larger 4 bolt chainplates for the upper shrouds and 3 bolt chainplates for the lower shrouds. They looked good, no corrosion visable, they actually looked really good. We sail often and have never had a problem. Fast forward 6 months and we are crossing the Gulf from Carrabelle to Tarpon Springs Florida. We had a great weather window, less than 1 foot and winds 5 to 10 knots. We checked several sources and the weather window looked solid. We start off and it may have been a little more than 1 foot but nothing to get worried about. We are having an awesome sail, doing a solid 6 to 7 knots but the wind is a little to much on our nose, still a good sail. About 25 miles out we hit a dark line of thunderstorms and it is only 10 am. Lowered the main, brought in the genoa and motored through the thunderstorm. It was pretty nasty, white flashes that were so close you could hear the hiss before the boom. The seas kicked up a little and the wind stiffened after we got through the storm. We ended up going through three pretty large thunderstorms and by the time we got 50 miles off shore the seas had built to 8 foot and the wind was howling directly onto our nose. I told my wife that we could sail towards Cedar Key and perhaps the seas would die down a but when we got out of the middle of the Gulf. So I reefed the main and only let out half of the genoa. We were making 6.5 knots and the boat was handling the 8 foot seas with no problem. The swells were constant and close together. As we came over one swell, we go hit with a really solid gust. It pushed the rail into the water but it was not that big of a deal, we had been sailing with the rail close to or in the water most of the day. When we came down the other side of the swell the boat came out of being heeled over as much as it was. My wife said, Dave the baby stay! I looked over and saw that the aft lower shroud on the starboard side was swinging against the boom. My wife took the helm and pulled in the genoa as I went and lowered the main. We motored the boat back and anchored behind Dog Island for the night. The wind howled all night long. The thunderstorms really brought in some weather. It would have been a really rough night crossing to Tarpon Springs had we continued. My wife asked me what we wanted to do now? We had given up our slip in Carrabelle so we could move the boat over to St. Augustine for a change in scenery. I told her that Panama City sounds like a great place to keep our boat. So we motored over and decided to make the city marina our home now.

I pulled the broken chainplate that snapped right at the deck level. I also pulled one from the port side so I could have replacements made. It only cost me $25 for each chainplate to be water jetted using my good one as a template. While researching the best stainless to use, I read several articles about stainless. I read that when stainless is deprived of oxygen, as we do when we bed them and make the area water proof, the stainless will corrode from the inside out. I also read that they have a serviceable life of about 10 to 15 years. I am pretty sure these are the original stainless chainplates from 1982. Well the starboard aft lower shroud plate snapped right where it was bedded. When we remove all the plates we found the forward lower plate on the starboard side was pulling apart too. We were hit with the big gust on the starboard. All the port plates were solid.

Anyway, A word of caution if you have 20+ year old stainless steel chainplates. They could look great and be corroding from the inside out where they are bedded through the deck.

 

[Bob McL]

I had always heard that depriving stainless of oxygen was a no-no, and I was wondering about this quote from another thread on this board:

we laid in layers of heavy fiberglass cloth, a stainless plate and then more layers of fiberglass cloth until the entire area was built up

and also when I read that stainless bolts were used to hold a keel in place. On my boat, the stainless chainplate is open to oxygen on the inside of the cabin, but the nuts are on the outside of the hull and are painted - so I guess I should remove the paint from the stainless nuts (and end of the bolts)?

 

[Ross]

Bronze is a better but more costly choice.

 

[RECESS]

I read that bronze is about three times the cost. Seeing how it cost $25 a chainplate, that means bronze is still affordable. I read that bronze chainplates that were installed in the 1930s were still sound when checked about ten years ago. Some people do not care for the greenish color as bronze ages, but I would be fine with it.

 

[Ross]

Green is good, broken is bad.

 

[Ralph Johnstone]

The Real Question Here is .....................

.......................... what type of SS were the original chain plates made from ?

SS ranges from the cheapest offshore 302, 304, etc. to good quality 316. With corrosion as bad as what you've experienced, I'd say they were considerably less than 316.

What type of SS did you specify for the replacement plates ?

 

[Bob J.]

You guys were very lucky. This could have turned out very badly.
Guess chainplates are just like us, you never know what's on the inside.

 

[RECESS]

The original chainplates were 316 but it is very possible they used 304 as most builders did at that time. In researching I had read that Pearson used high quality stainless, which leads me to believe it was 316. The replacements are 316 and the new bolts are 316. The originals were 30 years old, way past their serviceable life. They were very easy to remove and replace on this boat. I think in the not so distant future I will be switching them to bronze. I wanted to get the boat back to sailing quickly so I had them duplicate the Stainless. I need to do some more research to see if the bronze needs to be thicker?

 

[Anonymous 121765]

R,

These look pretty corroded to me pal.
Am I looking at the backside of the plates? Notice the area of greatest stress & corrosion are in the same spot.

I can tell you from the pictures that they are a cheaper grade of stainless as evident by color & corrosion. I'm surprised you didn't see telltale signs. Had you removed a bolt or two at some time to check, You may have caught this earlier.

Boats built in the 80's did not have too much in the way of quality control. Many builders skimmped where they could as profit margins were thin. My 1980 C30 had alot of subpar stainless. Twice my bowsprit support plates broke almost losing my mast. I only use 316 ss & alot of replacements I have a fab shop do, instead of buying from the manufacturer.

As a side note, I had a new bobstay made from Nitronic 50. A 1/4" dia. solid rod with a 43,000 lb tensil breaking strength. But make sure you only use 316 ss pal.

CR

 

[jibes138]

How about titanium? The amount of metal is pretty minimal and could probably be made from scraps of some aerospace manufacturing process. New planes like the Boeing 787 are using massive amounts of titanium, not to mention golf clubs, I would think it would be a good option for replacement parts if you can get some material.

 

[Delezynski]

Recess,

Go bronze! The correct type will work better than SS. Same strength, much longer life.

You might contact Port Townsand Foundry;
http://www.porttownsendfoundry.com/chain.htm for info.
(I have no connection with them)

I worked for a major aerospace co. They recycle the titanium. And unless you are a dye-hard racing guy, it won't make a difference weight wise.

I am about to start the same project (different boat).

Greg

 

[DJW]

How thick are those. They don't look very thick 1/4 inch? When we replaced all the chainplates on our 42' Cascade in HI we went with 316 SS 2 inch by 3/8" thick. They are very beefy

Dennis

 

[RECESS]

The lower shroud chainplates are 1 1/2" wide by 12" long by 1/4" thick.

 

[rardiH36]

Out yesterday in 30 kt winds gusts in "the slot" from just inside the GG Bridge to just west of Alcatraz Island. Typical day for my location. I do sail mostly with first reef set on the mainsail. And have a 90% jib currently on the furler. But an every day stress test for the chainplates nonetheless.

So what is the inspection solution for most of us with 20-30 year old boats?

Can we slacken a shroud or two and remove just a couple of the chainplates to look for signs of stress cracks forming? Or do the same, but bring them to a testing company for expert evaluation? Or remove every one of the chainplates for inspection? Or after 20-30 years, simply play it safe and have new 316 SS, or titanium, or bronze fabricated?

Don't want to think about how to feel secure about possible crevice corrosion for the keel bolts...

 

[heritage]

I don't think that thicker chainplates would have made much difference. Once the exterior protective coat of ss is breached the corrosion occurs very fast. To breach that coat, there must be no oxygen and salt water. Keep the salt water out and you will have no problem.

My experience with corroded chainplates was a few years ago on a 76 Westerly. Lloyds of London certified boat so what can go wrong. Thank goodness, before a trip to the Bahamas, I decided to check the chainplates. I put a socket wrench on one of the ss interior nuts that holds the plate to the bulkhead, gave it a crank and the nut literally came apart in the socket. The bolt was fairly solid but had a line of corrosion that extended from the chainplate to the nut. There were four other nuts that had no corrosion, but the chainplate was almost in two pieces where it passed through the deck. Of the six chainplates, only two needed replacement.

 

[Ross]

When I rebuilt Bietzpadlin I bought 316L stainless steel. My brother wanted to know why that instead of 304 and I told him about stress corrosion cracking. He looked it up and agreed with me.

 

[Anonymous 121765]

Guys,


Ross nailed it. As I have said earlier, it's not the chainplate design as much as it's the mix & age that counts. The designers did a pretty good job of engineering the boats.

Did you know all life comes from the sea, however anything man made the sea will destroy over time.


Yea, thicker is always better, however the right material & sizing is what is most important.

All hardware will fail over time, it's recognizing the problem before the shit happens. Like all else on boats, stuff needs to be changed out and/or upgraded due to improper design/grade, usage, and/or material.

They have a dye penetrant test you can buy and do youself, however haulouts are a good time to go over your rigging. Until this, you can check a chainplate one at a time for first visual inspection without worrying your standing rigging & spar to fall. Just re-support with rope to a cleat etc.

Twenty years is a long time for longevity on boats. It's all part of the ongoing maintenance/pain we do for our boats. I think shrinks would have a ball with us.

Inferior stainless will show tell-tail corrosion (and you can bet that with production boats, if it's not a mirror finish, it mostly 304 ss). you need but to look before the break rears it's ugly head. That's why it's called "PREVENTIVE MAINTENANCE"............

CR

 

[Chris Patterson]

I just read a very compelling article in Good Old Boat, or Practical Sailor, don't remember, about the virtues of titanium over stainless. IF I had it to do, myself; I would definitively consider this..

 

[Ross]

Very often a good swift kick will reveal any problems with things mechanical.

 

[Anonymous 121765]

Guys,

I forgot to mention that the lower the number of ss grade, the higher the percentage of carbon steel in the mix. All stainless has some carbon steel.

304 stainless is the worst, for if the finished coating, edges, or drilled holes left compromised, just add air, moisture & stress over time and viola, you have corrosion/rust & eventual failure.

And remember, looking at the pics of the failed chainplates this rust, corrosion & failure are very self evident.

CR