Chain plate replacement confusion

[Jim Cate]

The use of 2205 duplex stainless for chainplates is worth considering. Lots stronger, much less subject to stress or intergranular corrosion, not that much more expensive. Ours are now 26 years and >>100K sea miles old, looked like new when I pulled them recently (well a couple of years ago now that I think about it!). Beats any of the 300 series in my opinion.

Jim

[zeehag]

304 works quite well. i had mine made burlier than needed and watch as my remaining 316 crack more and rust. the 304 has been installed only since 2011 but are showing i did right.
to each his own. i prefer the unbuffed look of 304 to the cheap chromy shiny look of 316.
to each his and her own.

i believe i can find 304 here in mexico.

[Jim Cate]

Originally Posted by zeehag

304 works quite well. i had mine made burlier than needed and watch as my remaining 316 crack more and rust. the 304 has been installed only since 2011 but are showing i did right.
to each his own. i prefer the unbuffed look of 304 to the cheap chromy shiny look of 316.
to each his and her own.

i believe i can find 304 here in mexico.

So, Zee, are the ones that are rusting and cracking original equipment? And if so, why do you think they are 316? The TAiwan yards used whatever was handy, and often it was pretty poor stuff, not conforming to any ANSI grade whatsoever.

Really, I think your prejudice against 316 goes against all common knowledge and practice. It is certainly true that burly 304 chainplates can and do work just fine; I do not believe that 316 would ever be worse in such appliations.

And you can buff 304 up to blinding shiny, and you can use mill finish 316 that will look as rough as you could ever wish.

Jim

[roverhi]

Has anyone tried aluminum bronze??? When I needed to change out the chainplates wanted to go with Bronze but couldn't find silicon bronze in flat stock only round. Aluminum Bronze c954 was readily available and seemed to have all the strength and corrosion of Silicon Bronze but couldn't find anything out about it's long term survivability in a marine environment. Didn't want to be a guinea pig so went with 316 stainless.

Don't know that 304 or 316 survives any better against anaerobic corrosion. 316 definitely stays shiny better than 304 but whether it is more resistant to penetrating corrosion is unknown to me. If I had to do it again, would probably go with titanium. It doesn't have the crevice corrosion problems of the 300 series stainless so doesn't need to be polished which is a savings in fabrication and is pretty much a lifetime material if you believe the hype.

Pulled a couple of chainplates from each side of the boat and measured them. Turned out the lower and upper chainplates were the same so just used one as a pattern. Used halyards to support mast as I changed out the chainplates. Didn't do them all at the same time but staggered the replacement from side to side.

[UNCIVILIZED]

Like Jim said, Duplex Stainless is a good option, & is much better than 304/306 or 316. Titanium is another, probably better, option, especially if you're having them professionally fabricated. The additional cost isn't much, & the material is obviously far superior to any kind of stainless.

Regarding farming out the fabrication. You don't need to take your old chainplates with you to a machine shop, or mail them in, etc. Just find someone who knows drafting or how to do similar drawings. And as long as all of the dimensions & spec's are included, anyone who's competent to operate machine tools will have all of the information that they need, via the drawings.
That said, if you need to pull your chainplates for a week, or a month, simply stay the rig with your halyards. Assuming that you're not somewhere that's subject to big storms. And of course, remove the jib from the furler.


Mention's made in an above post to enlarging the holes in chainplates if their holes are elongated. Which is a tricky call to make (at best), as your rigging likely won't fit the bigger holes. And that could lead to some "interesting", & perhaps unwise solutions, in order to 'make' things fit.
Plus, if the chainplates are that worn...


Also, if you're inspecting chainplates for cracks, after cleaning them well, use a dye penetrant kit, in additon to a pocket magnifier. I have a cigar sized 50x microscope that I picked up via BrionToss, & it's REAL handy for inspecting all of one's critical rigging bits.

And when you pull chainplates, often times, if your deck is cored, there can be issues with water intrusion into the deck that need to be addressed. In addition to what's already been mentioned with regard to bulkhead water damage.


BTW, where does one shop to even find bolts for chainplates that cost $1,800? And what would such bolts be made of? D***! I could almost refit a mid-sized racer's rod rigging for that much coin.

PS: For the DIY guys out there, think cutting oil, when drilling stainless. As it's not been mentioned as yet. And a very slow speed for the bit. Like under 100 RPM.

[UNCIVILIZED]

Originally Posted by roverhi

Has anyone tried aluminum bronze??? When I needed to change out the chainplates wanted to go with Bronze but couldn't find silicon bronze in flat stock only round. Aluminum Bronze c954 was readily available and seemed to have all the strength and corrosion of Silicon Bronze but couldn't find anything out about it's long term survivability in a marine environment. Didn't want to be a guinea pig so went with 316 stainless.

It looks as if you posted while I was typing, & that we had some similar thoughts on materials.

As to Aluminum Bronze. I haven't tried it myself. But ages back, I was doing a refit on a boat, & it was looking like she might need a new shaft bracket, to replace the composite one. With my big concern being that she had a lot of Carbon Fiber in her hull, so I was looking for something that was more noble for the bracket than is the norm.

So since he was virtually my neighbor, I spoke to Pete at the Port Townsend Foundry, in WA. And he recommended Aluminum Bronze for the job. Thus, based on that, I'm guessing it'd be okay to use the stuff elsewhere on boats, with regards to surviving the salt water environment. And it'd be pretty easy to look it up on the galvanic scale too.

[Jim Cate]

FWIW, before Seahawk went to stainless for their feathering props, i had one and it was made of Aluminium Bronze. No material issues in that underwater usage.

Jim

[chris95040]

Originally Posted by Jim Cate

The use of 2205 duplex stainless for chainplates is worth considering. Lots stronger, much less subject to stress or intergranular corrosion, not that much more expensive. Ours are now 26 years and >>100K sea miles old, looked like new when I pulled them recently (well a couple of years ago now that I think about it!). Beats any of the 300 series in my opinion.

Jim

Great point. 2205 is the clear winner over the 300s.

I wanted to go with 2205 for my rudder post last year, but was surprised to learn it wasn't available in my diameter.

[zeehag]

Originally Posted by Jim Cate

So, Zee, are the ones that are rusting and cracking original equipment? And if so, why do you think they are 316? The TAiwan yards used whatever was handy, and often it was pretty poor stuff, not conforming to any ANSI grade whatsoever.

Really, I think your prejudice against 316 goes against all common knowledge and practice. It is certainly true that burly 304 chainplates can and do work just fine; I do not believe that 316 would ever be worse in such appliations.

And you can buff 304 up to blinding shiny, and you can use mill finish 316 that will look as rough as you could ever wish.

Jim

the ones cracking are 40 yrs old. is prolly time to crack. they are cracking in the bends and under the fg that contains em.
i like 304 because it was recommended by my machinist in san diego as a better material to use than 316 and is less expansive and didnt crack under the bending.
so many say how bad the materials are from taiwan. as usa did extensive business with taiwan during the times these boats were constructed and as usa kept them active and trading, i believe the rumors are prolly merely that--rumors.
my masts were supposed to have been rotten-ha ha ha original thai cedar without rot. that is my set of spars., ok.. original chainplates which after over 30 years showed only slight distress..decks were changed out so it isnt a leaker, and all the rest ., what is left of it, was good and original equipment.
there is much about this boat that proves how rampant and without merit much of the dissing was. perhaps my good fortune comes down to my boat being built by the biggest formosa yard in taiwan, the formosa boat builders, which also built all the formosa 51s and where ct originated.
as non production boats, a lot of bad rumors were distributed, but most are exactly that-rumors.
my stainless original equipment water tanks have perfect metal, bad welds. hell after 40 yrs your welds would be questionable as well. yeah prolly they could have done better, but i see better parts used in this boat than were used in my 1960 vw bus.

as for the keel--yes that was also allegedly concrete and wtf was available f or extra weight from yard. toss it into the setting concrete. (another rumor, but...). at least part of the keel has been sealed with fg from water intrusion, unlike the yorktown, built in usa, and some others i have looked at closely.

[Stumble]

I think everyone knows I am a believer in titanium, and if you are going to go thru the trouble of replacing chainplates they are absolutely the way to go.

Besides the corrosion issues stainless has (and yes 316 is more resistant than 304) the other major issue is work hardening. As stainless gets cycle loaded it actually gets stronger, but it looses malleability. This makes is more subject to a specific type of corrosion called stress crack corrosion, as well as increasing the likelyhood of it just snapping.

Titanium by comparison simply will not corrode in the maritime environment (it will at elevated temperatures of around 500C). It doesn't work harden, and can be designed to the same size but far stronger. Frankly once the decision is made to switch chainplates I wouldn't even consider anything else.

Aluminium bronzes can work very well, but good quality bronze can be more expensive than titanium, and is also subject to work hardening eventually, though it can last for decades easily.

[zeehag]

titanio--dang millions of pesos for a repair that will outlast my boat. ok.. i use 304. 304 easily found in mexico. titanio--not so easy to find.
i want to have boat last my life--the next person can salvage it and do own repairs.

[reed1v]

Originally Posted by zeehag

i did mine by 2s, and only 2 needed replacement at that time. i took my 2 in, making sure i made fast the mast using halyards to secure--mine is keel stepped mast, so i can do this--and had them machined in a san diego machine shop across street from downwind marine. he rocks. i then replaced the old ones i kept so i could remake if need be, and went to work bolting on the new ones, which i had picked out in 304 stainless. less than 50 bux each . rousing rahhh.
an alternative is to step mast and redo all of em
another option is singly one by one redo all of em. check tangs and backing plates also. may as well check turnbuckles and cables also so no surprises.

Yup. That is what i did. Two at a time. Most local machine shops can make them up. Suggest monel or silicon bronze. Best to take plates in rather than a drawing. If they have a laser cutter, they can produce an exact copy from the original. Nothing worse than having a plate made with the holes not exactly aligned with the holes where it is suppose to be bolted into. Polishing advisable but not necessary.
BTW, cold chisel, hand held sledge hammer, and vise grips really help to remove embedded chainplates.

[foufou]

Chainplates are easy to make with simple tools. I bought surplus 304 from scrap metal dealer Alco in SF bay area close to dimensions of mine, cut to length with a saber saw, cut end round with same saw, drilled holes with cobalt drill bits and polished with increasingly fine sandpaper up to 600 grit. they looked like factory new and cost like Zeehag said about $25/ per. Bolts likewise sourced locally from Bowlin Fasteners were very affordable. Not in the $100's.

[artisanmach]

Make sure you passivate your chain plates... they will last much longer. mine were all identical. I added 4" to the length and one more bolt per plate. 1 made mine out of 316L then polished and passivated them.

[reed1v]

Before you try to cut stainless, get a piece and try cutting it with any saw you like. Its not easy. But try it on scrap first to get an idea what your getting into. Some of the advice on this topic seem to come from lack of experience.