CAS or "Chainplate avoidance syndrome"

[kmacdonald]

Originally Posted by 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.

If they lasted 53 years, them must be good.

[kmacdonald]

Originally Posted by 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.

If it were me, I would remove, inspect, and polish if they are fairly easy to get to and you don't have to tear up the interior. If not, inspect in place often and take your chances. Odds are way on your side.

[ItDepends]

Originally Posted by kmacdonald

If it were me, I would remove, inspect, and polish if they are fairly easy to get to and you don't have to tear up the interior. If not, inspect in place often and take your chances. Odds are way on your side.

See no evil, fear no evil. It's a lot easier to see no evil if you do not look.

This is exactly the kind of rational applied by the guy who posts on here about his forty year old stainless rigging. "Looks good, hasn't failed yet. What are you fussbudgets worried about?"

Kind of like the old George Carlin routine, "I'm planning on living forever. So far... so good!" How'd that work out for him?

Of course on one old boat I pulled interior woodwork apart to inspect chainplates, and had three of the securing bolts fall off in my hand from crevice corrosion. So maybe I am just running scared...

I am also baffled by the perceived need for titanium. Why not just bronze??? It is just as strong as stainless, is very easily machined, and lasts forever without any of the invisible issues. I guess it's not as shiny and that offends some people.

[markxengineerin]

I am also baffled by the perceived need for titanium. Why not just bronze??? It is just as strong as stainless, is very easily machined, and lasts forever without any of the invisible issues. I guess it's not as shiny and that offends some people.

I found it easier to find material properties and fabrication relevant information about Grade 5 titanium vs. the different grades of bronze out there. I suspect this is because it's used in the aircraft industry, which IMO is far ahead of the marine industry with published scientific data vs. black magic. Neither of the two marine rigging companies I contacted for info understood my simple question, let alone had an answer or any reason to back it up. They told me to ask my local rigger. What qualification do riggers have? in my experience, they have on-the-job training based on word of mouth. Contrast this with the way airplanes are designed, made, and maintained. Nothing wrong with bronze if the boat owner can find the necessary information.

[Manateeman]

It depends got it right. Why not bronze. It’s what the turnbuckles are made from.
Yes...it would be a safer world if boat riggers had to pass tests like aircraft guys.
I’m all in favor for that idea. Bronze chainplate specifications can be found in a number of books but for smaller vessels, there are a lot of examples to just copy.
You can look at a well engineered toggle or turnbuckle and you can see the limits.
Going up one size is a good idea and so is extra heavy nuts. The specs on bronze bar stock are reliable. Get a good machine shop if you are going to do button head bolts and or bending the material. Titanium is nice but it has limitations too.
It would be good to have something like the FAA for boats because we see the current system failures all to often. That’s the way the industry wants it. Don’t get us started on the subject of disposable boats.
Mark

[sandy stone]

I bought a 1979 Pearson 32 in 2005. A couple of years later, while replacing the shrouds, I decided to take the extra step and pull the (stainless steel) chainplates. They were perfect, after almost 30 years. The deck core was dry, too.

[fourlyons]

Originally Posted by Manateeman

It depends got it right. Why not bronze. It’s what the turnbuckles are made from.

Yes...it would be a safer world if boat riggers had to pass tests like aircraft guys.

I’m all in favor for that idea. Bronze chainplate specifications can be found in a number of books but for smaller vessels, there are a lot of examples to just copy.

You can look at a well engineered toggle or turnbuckle and you can see the limits.

Going up one size is a good idea and so is extra heavy nuts. The specs on bronze bar stock are reliable. Get a good machine shop if you are going to do button head bolts and or bending the material. Titanium is nice but it has limitations too.

It would be good to have something like the FAA for boats because we see the current system failures all to often. That’s the way the industry wants it. Don’t get us started on the subject of disposable boats.

Mark

Warning; thread drift.

But the problem with a FAA for private boats is that soon owning a boat will be as expensive as owning an airplane. If a private plane falls out of the sky others can be killed. If a private boat sinks, loses a mast, etc. only those aboard face significant risk. Yes, if the primary objective is maximum safety, that might be a good idea, but there are tradeoffs to every solution.

[markxengineerin]

FAA is the extreme of the other direction - but it would be nice if the manufacturer of a rigging toggle at least knew and/or published the tensile strength, or knew exactly what grade of material it was. There are always going to be judgement calls made for every individual boat, but these calls would be a lot easier with a little bit more information than is available today. I don't see this situation changing or really need it to, just explaining why I used Titanium and not Bronze. These forums are actually a huge help- can provide much of the otherwise unavailable information if you spend enough time reading to get a feel for what's what.

[kmacdonald]

I just took my backstay chainplate off. Almost no rust but it's cracked at the bend. Can see crack on all faces. I will probably replace it when I get a chance.

[kmacdonald]

I didn't see the crack on all sides until I polished it. Could only see it on the 3/8" edges.

[ItDepends]

Originally Posted by kmacdonald

I didn't see the crack on all sides until I polished it. Could only see it on the 3/8" edges.

Good on you for looking, and finding, a problem before it was a REAL problem.

Here is an article that describes a similar situation. I'd like the analysis even if I didn't write it....

https://fetchinketch.net/2019/07/26/failure-analysis/

[ItDepends]

Originally Posted by markxengineerin

FAA is the extreme of the other direction - but it would be nice if the manufacturer of a rigging toggle at least knew and/or published the tensile strength, or knew exactly what grade of material it was. There are always going to be judgement calls made for every individual boat, but these calls would be a lot easier with a little bit more information than is available today. I don't see this situation changing or really need it to, just explaining why I used Titanium and not Bronze. These forums are actually a huge help- can provide much of the otherwise unavailable information if you spend enough time reading to get a feel for what's what.

When I switched a boat from stainless to bronze chainplates I bought the bronze bar stock from a standard metal supplier and all of the specifications for the alloy's mechanical properties were readily available, including the testing for the specific heat.

The details of how to do the calculations for the loads are also easily available.

I just don't understand why buying a titanium alloy would have given me any more information.

And for those people who think that an "FAA for boats" is a good idea... please just go away. I can not afford it and neither can you. Take responsibility for your own boat.

[kmacdonald]

Can you size bronze chainplates the same size as 316 stainless steel? What is the best alloy of bronze to use?

[Rumrace]

Not to pick on my favourite brand (for now) but I read an article on how Jeanneau France sent Jeanneau US bad instructions on chain plates. Apparently the mount on one of the side lines is on the wrong angle which cause it to tear away from the hull. It was only one model around 30’ but every single one built. I suppose the French factory discovered the error and prevented the production in Europe but forgot to tell the US. The article went on to show the repair which was a massive undertaking just getting to them.
Moving from power to sail my wife asked what the big ugly turnbuckles are. I said I’m not sure and I’m sure not touching them I’m sure you’d spend 2 days taking the interior apart to inspect the mount. Jeanneau oops is evidence age isn’t everything.
Isn’t there a way a rigger measures your boat to assure chainplates are stable. When if I replace the rigging in 3 years do they replace everything from the chain plates up? The visible turnbuckles look like a couple hundred each !?

[svpatience]

Originally Posted by ItDepends

Good on you for looking, and finding, a problem before it was a REAL problem.

Here is an article that describes a similar situation. I'd like the analysis even if I didn't write it....

https://fetchinketch.net/2019/07/26/failure-analysis/

ItDepends, this was a really helpful article that helped me understand crevice corrosion a bit better - thank you! I have 35 year old stainless chainplates which worry me a bit. I inspect the rig, but struggle to know exactly what I am looking for. The article you linked to states that the corrosion was invisible on the side that could be inspected (green arrows in picture below), but I'm curious what would have been visible on the other side that couldn't be inspected (red arrows). I'm guessing pre-failure the crevice corrosion would have manifested itself as a very thin hairline crack on the hidden side?

Tim