Chainplate Inspection

[Stumble]

Exile,

30 year old stainless needs to be replaced even if it is not corroded. Stainless work hardens and becomes brittle as it ages.

Allied opened a US fab shop in Washington a year or so after I left the company. I am not sure where the mill stock is coming from however. For a long time US titanium mills were the worst in the world, they may have gotten better however.

[Exile]

Originally Posted by Stumble

Exile,

30 year old stainless needs to be replaced even if it is not corroded. Stainless work hardens and becomes brittle as it ages.

Allied opened a US fab shop in Washington a year or so after I left the company. I am not sure where the mill stock is coming from however. For a long time US titanium mills were the worst in the world, they may have gotten better however.

Yes, it generally sounds sensical to simply replace any SS plate that is that old, regardless of outward appearance. I must say, however, that one of the plates I've pulled for inspection thus far is 9/16" thick, and while showing some surface corrosion & minor pitting on the exposed surface, it was completely clean & showed no crevice corrosion (w/a magnifying glass) on the inside where it was bedded with butyl tape. If work hardening and becoming brittle with age are two additional factors, then I would think deck hardware that is not otherwise subject to crevice corrosion would also be suspect. I thought instead that SS would otherwise last almost indefinitely if always exposed to air/oxygen?

Your comment about the source of the Ti mill stock Allied is using is kinda why I'm gravitating back to going with SS again. It eliminates the vagaries & uncertainties a layman is presented with when it comes to sourcing & sizing both Ti & bronze, and I'm more likely to be able to deal with it locally. What I do like about both alternatives, however, is the idea of being able to forget about ever having to deal with it again (assuming I can get it right, that is).

[Jim Cate]

As I have pointed out before, another alternative to 300 series s/s for chain plates is duplex or super duplex s/s. Our 25 year old chainplates, made of 2205 duplex are still as shiny and uncorroded as the day they were installed. 2205 is essentially immune to crevice corrosion, is much stronger than 300 series and only a bit more expensive than 316. Becoming easier to source too,, as I understand it... but have not actually purchased any recently. I'd pick it over bronze any day... don't know enough about the practicalities of Ti to comment intelligently.

Jim

[Exile]

Originally Posted by Jim Cate

As I have pointed out before, another alternative to 300 series s/s for chain plates is duplex or super duplex s/s. Our 25 year old chainplates, made of 2205 duplex are still as shiny and uncorroded as the day they were installed. 2205 is essentially immune to crevice corrosion, is much stronger than 300 series and only a bit more expensive than 316. Becoming easier to source too,, as I understand it... but have not actually purchased any recently. I'd pick it over bronze any day... don't know enough about the practicalities of Ti to comment intelligently.

Jim

Thanks for the reminder about 2205, Jim. It also struck me that if yours is 25 yrs. old, then perhaps my boat was also built with it & maybe why my plates seem to be holding up so well. I'll look into it. Do you (or anyone) know if there are any obvious ways to determine the difference b'twn 2205 & 300 series?

[billknny]

Originally Posted by Stumble

Bill,

The major issue with bronze isn't an alloy issue it is a foundry problem. To start with naval bronze and magnesium bronze with are the common marine alloys are actually brass and have too much zinc. So to use bronze you need to use siliconized bronze. Which is fine, except that it is primarily cast, and cast parts used in tension structures like rigging MUST be load tested and X-rayed to ensure there are no casting defects. This is a pretty expensive proposition for a set of chainplates, though it is certainly possible.

Secondly bronze turns green if you don't polish it regularly.

Third, titanium last time I priced it was running about 15% than si-bronze for bar stock. So the price advantage isn't really that much.

Yes, just like with Ti or stainless, or anything else, you have to chose the right alloy. That is NOT even remotely an argument against using bronze. Just an argument against using the wrong material. While on the subject of the "right" alloy, you do not need to use silicon bronze (although you can). C954, which is actually an Al-Bronze, makes good chainplates

Lots of boats use continuous cast C954 chainplates and I have never ever heard of anyone xraying the material before use. By this logic, shouldn't stainless plate be xrayed and load tested before installation as well? After all it CAN have flaws... but maybe we are all just living on the edge...

Bronze turns green...well...duh...yeah.... Actually, Al-bronze doesn't usually get very green. Rather, it does turn a dull yellow-brown. For some of us traditionally minded sailors a good patina on bronze hardware is actually attractive, so that is a plus If you want to argue aesthetics of that sort, heck properly electropolished SS is way shinier than Ti!

I am wondering about the cost you quote. I can buy a 2 inch wide, 3/8 inch thick, 36 inch long piece of C954 for less than $100. Round the top corners on a grinder, drill 6 holes, Presto--chainplate that will last the life of the hull.

But, having said that... Your argument is missing the point of what I am saying about cost. Buying the Ti is just a fraction of the cost, you still have to pay to machine it. I can cut, drill, bend and finish C954 in my woodshop, or even with handtools. Try that with Ti.

Again, again... for the boat owner contracting out all the fabrication, the cost of Ti is not that much higher when all is said and done. Go for it!

For the one doing his own fabrication, Ti is not even remotely an option, and bronze can be way cheaper, and much easier to machine for the average boat owner than even stainless, and give you fine, permanent chainplates.

[01kiwijohn]

Well, thank you all for the information. Looks like I'll have to spend a greater part of this NW Winter grinding out the old ones anyway, then I'll shop around to get materials; I can make those simple parts myself.

[Stumble]

Bill,

Working titanium is actually pretty easy. Its reputation for machining difficulty comes from 50 years ago when shop tools were primarily HSS. Modern carbide drill bits will cut through titanium pretty well, just use plenty of refined olive oil as a cutting liquid. Any reasonably experienced home mech with a drill press should be certainly capable of drilling it, and a fab shop will have no problems.

Bending ti is a pain in the #$$ however. It's high yield strength and high spring back means it is tricky to bend to a defined radius. It can be done, but unless you have a lot of experience bending metals I wouldn't bother trying.


A .375 X 2" X 36" G2 titanium bar will run about $120-130if you use a retailer. Buying enough bars for a boat will likely allow you access to a whole saler where the price would Likely drop to $110-120. I haven't working in the industry in a few years so I don't keep up with specific prices any more.

But I just replaced some life line stantions with G9 titanium, Schafer's price per is $120, our titanium ones cost $85 per. Not including shipping.

[Jim Cate]

Originally Posted by Exile

Thanks for the reminder about 2205, Jim. It also struck me that if yours is 25 yrs. old, then perhaps my boat was also built with it & maybe why my plates seem to be holding up so well. I'll look into it. Do you (or anyone) know if there are any obvious ways to determine the difference b'twn 2205 & 300 series?

There is an easy means of distinguishing between 2205 and any 300 series s/s: 2205 is highly magnetic!

Our boat was launched in 1990, but she was built by a very knowledgeable shipwright who was willing to spend the extra bucks for the 2205 (a considerable difference back then). I don't know of any production boats that have used this material. FWIW, in his newest boat, this chap has used 2205 or similar alloys for the rudder stock, keel bolts, shaft and other high stress items. The chain plates, however, are all carbon fibre... times change!

Jim

[Lokiyawl]

Originally Posted by Exile

According to Stumble, you can buy Ti chainplates from a co. called Allied Titanium. I looked into it, along with bronze, but am now leaning back towards SS. I am in the process of pulling all of mine now and having them professionally inspected. AFAIK (and therefore have to assume), they are original and almost 30 yrs. old. Thus far, they have all checked out fine. I think if good quality to begin with & properly bedded (butyl tape in my case), SS can survive a very long time.

Bronze can be difficult to source & have properly machined, and identifying the proper type can also be challenging as we just witnessed above! Ti can also be difficult to source, and machine shops who can deal with it aren't exactly commonplace. Allied sources & machines all of their Ti from China -- not necc. a bad thing & they seem to have a good rep, but I think I prefer the idea of walking into a local machine shop and having them make exact duplicates of what has already done fine in my boat for the past 30 yrs.

Just buy 655 bronze from a reputable supplier like Atlas Metals and no issues with the quality. As to machining, bronze can be cut on a band saw even with wood blades..super easy to machine, especially compared to 316 SS! The best bronzes are the nickel bronzes actually..monel 400 is fantastic but probably more expensive than the Titanium.

James