ta-yang factory boats in the 80s

[phorvati]

I'm in the process of replacing a rig on a project boat, FD-12 built in Ta-yang factory in 1981. Since so few were built, I am wondering if anyone else took a look at chain plates and so called "stainless steel" on a 1980s ta-yang built boats. Are they all this bad? Form other threads I learned that there was very little quality control, and from surveyor and rigger i learned that stainless was suspect. Is that 304 I asked? And the answer was no, they probably just used whatever was in the furnace. No tractability as to what was in that "stainless steel". I'm taking out all chain plates, plan to have them duplicated with quality stuff. I'm fortunate my decks are sound with no rot. Deck core is closed cell foam, and any water ingress is limited. I'm finding that they glassed in a lot of the metal. What a pain. And I found some undersized bolts for the holes. That must have been post factory.

[HansSolo]

I don't think that the issue is in the quality of the SS as much as it is in the age and the environment they live in. If you have 35 year old glassed in leaky chainplates (even in good quality 316) this is what is to be expected. Scary stuff for sure.

[Matt Johnson]

Man, that's an odd set-up. Just looked at one on Yachtworld, and the chainplate ends at the knee and doesn't extend down with the additional plate like yours. Same year, but maybe yours is a later hull and they were addressing a strength issue with the knee. At least you can use the the old chainplate as a template when your new one is bent!

Just zoomed in on the glass work around the lower mount... do you think this was done after the build? Also, what are the large acorn nuts holding together?

Matt

[phorvati]

There are several plates that are extending, around the knee and down to meet the 8" or so peace that is glassed in. But the bolts are smaller then the holes. That must be post factory. On that he one where chain plate only goes to the knee, I bet there used to be one going all the way, and someone recommended it's not needed.
I don't buy age of stainless suggestion. I lived aboard a1977 c&c for over a decade. that boat is built on Niagara on the lake, and those original chainplates do not show any signs like this. Yes they did leak at some point, but they never behaved like that. Instead of glassing in chainplates, glassing 3/4" marine plywood, and through bolting to that would make a lot more sense. That's how c&c is done.

[Terra Nova]

Poor design. Poor workmanship.

[reed1v]

Extra long chainplates do not add much to distribute the load. Any bends tend to negate load bearing ability for the section after the bend. Ideally you want a straight plate angled to form a continuous line with the shroud attached to it.
If plates are more than 30 years old and are not made of bronze or monel, replace them as a matter of course.
Signs of rust, cracks, or small bumps means replace.This is an area where being very conservative is a wise move if you plan on long distance cruising.

[HansSolo]

Originally Posted by phorvati

I don't buy age of stainless suggestion. I lived aboard a1977 c&c for over a decade. that boat is built on Niagara on the lake, and those original chainplates do not show any signs like this. Yes they did leak at some point, but they never behaved like that.

Ok then, how about these plates from a early 80s Pearson 530? These plates were not glassed in. The major crack occurred in the area where the plate passed through the deck.


Or this one from a mid 80s Irwin? (the rust was cleaned off before this photo was taken) This plate was glassed in.

At one point I had an entire folder of similar photos that I took when I worked as a rigging inspector, but sadly most of them are lost now with the laptop I had them stored on. These are fairly common finds on 30+year old SS chainplates.

[zeehag]

it is not the quality of the stainless..
how many years do you seriously expect chainplate steel to appear pristine?
it aint happening.
chainplates and tangs need changing every 20 years, max.
yes even encapsulated stainless steel becomes mexican loktite in about 5 years.
btdt.
tayanas and others from the same yard seem fairly sound. yours is gorgeous.
as it is over 20 yrs of age, changing all chainplates is a wonderfully safety conscious idea.
our marine environment is kinda hard on metals.

[Cheechako]

Chainplates are a big maintenance issue on many boats. The problem being you don't know where they are bad so just need to replace them. As you said those may be anything 301, 302, 304 etc. There's iron in all of them and poorly maintained will rust some. There is a wide range of constituents in SS specs, so some batches may have a high iron content or carbon and rust more than others.
It's a big job, use good materials.
Stainless in an enclosed damp environment is going to fail eventually. That's the rub with chainplates. 316 is slightly more resistant but not a complete problem solver.

[Pauls]

If you'd like to build chainplates that will have a much longer life then use either duplex stainless (super duplex is the best) or an appropriate bronze. Duplex stainless is not well known, for some reason. It averages double the strength of the austenitiic stainlesses (316, etc) and is much more corrosion resistant. Look up PCRF values for stainless, (Potential Corrosion Resistance Factor) you can get duplex stainlesses with over triple the corrosion resistance of 316.

[bcboomer]

Originally Posted by Pauls

If you'd like to build chainplates that will have a much longer life then use either duplex stainless (super duplex is the best) or an appropriate bronze. Duplex stainless is not well known, for some reason..

How much more expensive is duplex?
Anyone know how much more expensive titanium would be?

[reed1v]

Originally Posted by bcboomer

How much more expensive is duplex?
Anyone know how much more expensive titanium would be?

Bronze is as tough, if not tougher than titanium and less expensive. Will last the life the the boat and then some.

[Djarraluda]

Originally Posted by reed1v

Bronze is as tough, if not tougher than titanium and less expensive. Will last the life the the boat and then some.

Not really, I had bronze chainplates fail after 25 years - where they passed through a teak deck. No flexing, just the stress and mild corrosion caused by the chemical reactions.

[phorvati]

It might be true that 20 years later any stainless is due for replacement, but i will keep the water out and hope to have the new ones fora long time. The rust was not what really concerned me. it was the cracks. Like this one, it was buried in the nav station. No wonder it was not maintained. you have to dismantle considerable amount of stuff to get to it. And on the surface it did not look that bad. but what gave the red flag were the small hairline cracks along the weld. Very small. the rigger swiped the weld with the black magic marker, and wiped it off, leaving cracks clearly visible. Once I opened it, I found that the bulkhead is soft. That hole was from my finger. This is lower aft that shares the chainplate with permanent check stay. On these models, check stay angle is too steep and its putting a lot of force on the chain plate.

[Jim Cate]

Our duplex (2205) stainless chain plates are now 26 years old. Had them out two years ago and they looked like brand new, even in the deck penetration area, which is where most failures begin.

2205 has come down in price, I am told, but is still dearer than 316 by a bit. However, material costs are usually not that big a part of the total costs, and one can use a somewhat smaller cross section due to its greater strength if desired. Seems to me to be a very good material to use for chainplates (and rudder posts, too)

Jim