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chainplate followup

16K views 43 replies 18 participants last post by  transmitterdan 
#1 ·
Last spring I replaced the chainplates on our 1982 Crealock 37.Upon removal we thoroughly inspected the old plates including a dye test.The old plates looked and tested fine,no cracks and no corrosion.Since I had no further use for them I gave the old plates to my friend who is a metal shop instructor at a vocational high school
Yesterday my friend called me to tell me that he had attempted to cut one of the old chainplates with a hydraulic shear for a project. The metal crumbled like an old cookie rather that shear.He tried again with another plate and that too crumbled.
We can only think that 20 plus years of weathering and stress has led to some molecular or crystalline changes in the metal.
The lesson being that even though the plates may appear sound and strong the prudent thing to do is replace over time.Lesson learned.

Dianne and Chuck Burke S/V NiftyNickers C37 #139
 
#3 ·
Yikes!!
 
#4 ·
That is a sobering observation. However, does your friend have experience using his hydraulic shear on stainless steel of that gauge? I'm wondering if this may be a property of the massive stainless.

Flip side of this is whether we have examples of apparently flawless PSC chainplates failing as a result of suspected change in metallergy?

Bob Steneck
PSC 34' Alaria
Christmas Cove, Maine
 
#6 ·
chainplates

The date is purely incidental I would not joke about something this serious.The facts are just as I wrote them.Secondly my friend has been in the business of metal working and welding for over 30 years he has worked with plenty of SS i varying grades and hardnesses.He felt so strongly about this metal failure that he called me immediately to warn me about my headstay and backstay which were not replaced.They will be replaced within the month.You can take this info for what it is worth,I simply felt that I had to inform others with similar boats about what I felt was important info.

Dianne and Chuck Burke S/V NiftyNickers C37 #139
 
#8 ·
A shear is a shear, that wouldn't have anything to do with the SS crumbling. Might be a good idea to pass this experience on to the C37 owners group if there is one. I would want to know if I had one.
 
#9 ·
Implied in your posts in this thread is that there is something unique about the material or fabrication method Pacific Seacraft used for their chainplates.

According to a PSC 34 brochure (I believe this also applies to the 37) . . .

Chain plates are ¼" thick and 2" wide type 304
stainless steel thru-fastened to the hull with ½"
stainless steel bolts and full hacking plates.

Perhaps anyone with similar chainplates of that age should be concerned? Why aren't we seeing much more widespread problems in actual use if this is a real issue?
 
#10 ·
Hi Chuck,

Thanks for the heads up on this. I'm glad you got those chainplates replaced!!

Just to clarify a few details, for posterity:

1) Had your boat's chainplates previously been replaced? (You mentioned the chainplates were 20+ years old, and your boat is an '82.)

2) Just to confirm, but I recall that your boat is a PSC C37, not a Cruising Consultants C37, correct?

3) If your boat is a PSC, do you know whether your boat was factory finished, or sold as a hull/deck kit for owner finish?

4) Are the chainplates/bolts on your boat tied into a grounding system, i.e. wired to a ground that is interconnected with through-hulls, engine, etc?


Again, thanks for the heads up and any additional info/details you think might be relevant.
 
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#11 ·
chainplates

John et al.
I,ll try to answer your questions in order:
The chainplates are indeed 1/4" SS 306,they were the original factory installed in 1982.The boat is a Pacific Seacraft not a Cruising Consultants boat and was factory finished and commissioned at Washington NC in 1983 as Salem.The chainplates are all common ground to a grounding plate.I will try to upload some pix of the chainplates shortly.

Dianne and Chuck Burke S/V NiftyNickers C37 #139
 
#13 ·
Chuck,

Thanks very much for the follow-up info, and the excellent high quality photos. Yikes!

...The chainplates are all common ground to a grounding plate....
I suspect this is the culprit, in your case. I would humbly suggest that you disconnect that ground. I have heard of similar chainplate issues (on non-PSC boats) and in every case they were grounded. The chainplates on our 31 are not grounded and I would not want it any other way.
 
#12 ·
chainplate fotos

This is an attempt to send some pix of the chainplate.Note the hairline cracks near the break and the rusty brown color of the metal at the break.I repeat when this was removed we did a dye test on the plate and it showed NO problems or cracks.If this saves someones rig I,ll be a happy sailor.

Dianne and Chuck Burke S/V NiftyNickers
 

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#15 ·
Thank you for the cautionary information Chuck, and I appreciate you are sharing to be helpful to the rest of us. So I can get the maximum information out of this though, I'm confused about what I am seeing with the condition of the chainplate around the hole for example. My untrained eye sees that as significant corrosion that wouldn't require a dye test to observe. I must be missing the point. Was this not so apparent while on the boat, or is the message that we shouldn't just write that off as surface corrosion if we see something similar?

John - After three boats were struck by lightning in our marina last year, I thought it was a good thing my chainplates were grounded. Some argue this might just be asking to be struck though. Sounds like you'd take the extra risk with lightning to avoid this insidious long term corrosion risk. Why hasn't someone come up with the perfect solution to all these issues yet? :)
 
#17 ·
Guys,

I was reluctant to comment about the grounding issue, but I felt it's worth pointing out that this is a variable not common to all boats.

Chuck has posted a very helpful cautionary note here, replete with photos. If we want to talk grounding and/or lightning protection, it's definitely a good topic of discussion, but maybe we could start another thread? Or revive one of the many old ones already running here on Sailnet.
 
#18 ·
Dear Friends,

Stainless steel, particularly 302/304, is fickle stuff. It crevice corrodes and work hardens, both invisible time bombs on a boat. IMHO, we don't really need to look at factors other than these to find cause here. Personally, I begin to look at any stainless steel rigging component with distrust after 10 years, even less in the tropics. This includes wire, turnbuckles, toggle straps, tangs, etc. Stainless steel chainplates with bends in them that work every time tension comes on the rig are even more suspect.

As Annie Van De Wiele reminds us, "The art of the sailor is to leave nothing to chance."
Better to swap it out early.

Dave Mancini
s/v Swan PSC34 #305
 
#20 ·
From the photos it looks like an intergranular corrosion to me. If the plates are truly 304 SS (as opposed to the low carbon 304L or one of the stabilized 18-8 stainless steels) and if the chainplate was heated to place the bend below the eye then not annealed or if it was mis-annealed at the mill (unlikely), it could have been sensitized in the heated area. While hot, the carbon in the alloy would be precipitated out the near the grain boundaries as chromium carbide leaving the outsides of the grains depleted of chromium and subject to corrosion. This sort of corrosion eats away the metal between the grains leaving them unattached to each other. Until the part began to fail mechanically, there would not be enough of a crack to detect at the surface with dye. If this was the cause of the crumbling of the metal when it was sheared, it might be common among similar chainplates.

Chloride induced stress corrosion cracking could also be present. When under tensile stress and in the presence of chlorides, any of the 300 stainless steels can develop cracks that go deeply into the metal. I used to see this in bolts which appeared to have been purposefully cut in half. Dye testing might have caught this before mechanical failure began.

There are three ways to handle chainplate maintenance: wait until it fails then replace it, wait until testing shows it has started to break then replace it, or replace it when it nears its known service life regardless of its apparent condition.

Bill Murdoch
1988 PSC 34
Irish Eyes
 
#22 ·
Well sure Bill, everybody knows all that! :) (just kidding - appreciate the information.) As we're deciding where to purchase new chainplates from, what questions should we be asking concerning how they're fabricated? Any particular known-good sources? Or, should we by from a reputable source (like PSC) and just plan to replace them every N years regardless?
 
#21 ·
It sounds as though Bill has detailed knowledge of the subject and I certainly wouldn't argue with his conclusion.I can tell you that this piece was being cut from the lower end of the chainplate,the part nearest to the water and possibly submerged when heeled.The bend was at the other end which has not yet been cut (but will be).
I sort of comfort myself by thinking that there were four bolts above this part of the metal and it probably wasn't stressed too badly.
But I sure am glad that I did replace these chainplates before that failure that Bill speaks of.

Dianne and Chuck Burke S/V NiftyNickers C37 #139
 
#24 ·
I can tell you that this piece was being cut from the lower end of the chainplate,the part nearest to the water and possibly submerged when heeled.The bend was at the other end which has not yet been cut (but will be).
I notice the hole is round. PSC must not have been using the carriage bolt holes at that time, or am I missing something?

Dave Mancini
 
#25 ·
Dave,
As you noted the holes are round but the bolts were carriage bolts.The corners of the square part of the bolts fit into the holes which are 5/8".I thought that that was a rather strange way to mount them but on the other hand it worked for over 25 yrs.
I seem to remember a post some time ago from someone else noting the square shouldered carriage bolt in a round hole and theorizing that perhaps the square shoulders caused stress and corrosion where they cut into the hole.I did not see evidence of that having happened.
When I replaced my chainplates I oted to use standard hex head bolts in 316 SS and 316 SS chainplate material.
Dianne and Chuck Burke S/V NiftyNickers
 
#27 ·
Seems like I have read discussions over the years (probably here on SN) about some SS supplied on boats built in Asia (70's-80's?) that was suspect. I don't remember the specifics or which boats/models were involved. Has anyone else heard anything similar?
 
#28 ·
I have followed this chainplate discussion with interest because we too have an older Crealock 37 (1983). My one big question to those who have actually done this replacement on PS boats is: how do you remove the old chainplate from behind the teak rub rail that runs down the side of the hull?
Dave
Crealock 37 #151
"Eowyn"
 
#30 ·
As Dave said a whack with a heavy hammer and some wiggling and some prying worked for me.Make sure that you clean out the groove that the chainplate is in with a putty knife and then drive the chainplate upward with a drift pin and hammer. More difficult was getting to the nuts inside the salon.Trying to remove the teak battens without destroying them is very difficult.
I'm now looking forward to replacing the stem piece for the headstay.The more I think about that job the more dubious I get.The stem fitting is integral with the bow rollers and must be removed as one piece and of course the nuts must be accessed thru the anchor locker.I'm trying to convince my tiny wife that the anchor locker is really a nice place for her to work.
Good luck with that, right.

Dianne and Chuck Burke S/V NiftyNickers C37 #139 1982
 
#31 ·
Chuck,

I gotta wonder whether that stem fitting will need replacing. I suppose some would argue with me, but if you look at the scantlings for that thing, they're twice what Skene's recommends for chainplates of that wire size. Also, it fixed between the bow roller plates so it can't flex like the chainplates do. I've opted for frequent inspection instead of replacing. It may be a rationalization for my basically lazy personality, but I'm going to stick with it.

Dave
 
#32 ·
Dave,

I initially felt the same way about the stem head fitting but I think that the older boats like mine may be constructed differently from yours.I don't have a bowsprit like the newer boats and the build may not be as robust.
Mine has a SS strap that bolts thru into the anchor locker and is welded to the 2 anchor rollers at the bend around the deck.The strap is 1/4 SS the same as the port and strbd chainplates.After seeing the degradation of the plates that were rpld ,I'm no longer confident in the stem or stern plates.The thought of what could happen if the stem breaks would keep me awake nights if I didnt replace it.Ditto for the stern.

Dianne and Chuck Burke S/V NiftyNickers C37 #139
 
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