Chainplate materials

[Kinsa]

I am delighted that this thread has generated some interest, and thanks for the replies. I haven´t looked at Titanium because of the difficulty I had trying to source Nitronic 50. I feel that in the US it is much easier to source "exotic" materials, whereas in Europe it is either difficult or expensive - or both.
I was surprised to find NiAlBr, forged not cast, at such a reasonable price. Replacement chainplates in 316L would have cost approx $40 each, and I shall be paying approx double for NiAlBr. The only quote I could find for Nitronic 50 was approx $300 each - although to be fair about 1/3 of the price was for machining the available bar stock down to size.
I think that overall strength in chainplates is not an issue. The breaking strength of chainplates is generally 3 to 4 times that of the wire rigging attached - on my boat about 19 tons/7 tons. But corrosion really is an issue, and I am surprised that it doesn´t receive more attention on forums. The real problem with stainless is that SCC results in catastrophic failure (although tell when a chainplate failure isn´t catastrophic). ;-)
But I shall certainly go back to my supplier and ask what Titanium would have cost. Too late to change this time, but useful experience.
Thanks again for the replies.
Yours aye,
Bill Attwood

[Kinsa]

Hi Douglas.
My source for forged NiAlBr in 3/8" bar is:
Chrome Nickel Alloys Limited
The Barn, Manor Farm Barns
Baines Lane
Seaton, Rutland
LE15 9HP
www.cnalloys.co.uk
Andrew Clark is the MD and is very helpful. Mention my name when/if you contact him - I might get a discount next time!.
Yours aye,
Bill

[Stumble]

Kinsa,

You are correct that strength in chainplates is rarely the biggest concern. They are typically the strongest part of the system when new. The problem is that there is no good way to attach them to a hull that doesn't result in corrosion problems. Either you go with external plates that leaves an entire side in an anaerobic situation, or thru-deck ones that almost guarantee a ring (where they pass thru the deck) where corrosion will occur. This requires relatively large corrosion allowances be used in order to have a long enough expected lifespan.

This is where titanium is really a great OEM material. The strength and size can be reduced because the corrosion allowance can be reduced to nothing, and they just need to be strong enough to handle the loads, not the lost material.

In fully engineered chainplates I have actually quoted some that were less expensive than the stainless original parts because we needed so much less volume.

[Kinsa]

I have a quote from my supplier for chainplates in Grade 5 titanium alloy, about 5 times as expensive as NiAlBr. Not a fair comparison, as the quote is based on the same chainplate dimensions as for NiAlBr. If the dimensions were reduced to take advantage of the superior strength of titanium, I´m sure that the price comparison would be more favourable. However, for a crusing sailor (with a budget) I am happy that NiAlBr is a better solution than 316L for strength, corrosion resistance and price. Bur thank you for your comments, which have widened my knowledge!

[Stumble]

Would you mind sharing the supplier and the cost? Five times sounds a bit high to me compard to nialbr.

[Brion Toss]

Originally Posted by Stumble

Would you mind sharing the supplier and the cost? Five times sounds a bit high to me compard to nialbr.

Yeah, that is very high; I'm getting it for about the same as good 316, sometimes less.
Fair leads,
Brion Toss

[Kinsa]

Hi.
I was about ready to post my reply when I hit a wrong key on my very small laptop and the reply disappeared. However, if this appears as double reply, please forgive! I have been working all week in an unheated hall (temp below freezing) and the fingers are about as flexible as sausages.
Here goes again:
NiAlBr: "price will be £57.95 / PC"
Titanium: "A ball park figure for titanium plates would be £225 / PC"
Supplier: Chrome Nickel Alloys Limited
Figures in quotes are from supplier´s email.
My mental arithmetic wasn´t too good either, but there is a significant difference in price.
Bear in mind that the US seems to be a totally different envíronment to europe when it comes to anything a bit exotic. I am a keen woodworker and so have experienced exactly the same problems with regard to sourcing fittings for furniture. The adverts in the back of Wooden Boat, Fine Woodworking, and Good Old Boat leave me with tears of frustration! We´ll be sailing up from the Marquesas to Alaska via Hawaii in 2014, and Port Townsend is on our itinerary on the way back south. Whether the boat will still float after being loaded with bronze goodies is an open question.
Yours aye,
Bill