Converting to and Fabricating Bronze Chainplates/Tangs

[blahman]

Hello all,

I just spent a while searching through past posts concerning this, but have some more specific questions.


I have a 32' Westsail and would like to replace my 30+ year old stainless chainplates with bronze. Initially I planned to have PTF fabricate a set, but it is fairly cost prohibitive. Instead, I believe I can do it myself, but I would like a bit of help deciding on the particular alloy and form.

My current chainplates are 24"Lx2"Wx1/4"T 304 stainless, and boomkin/bowsprit tangs 1 1/4"Wx1/4"T. Talking with PTF, they mentioned wanting to increase the thickness to account for bronze's lower tensile strength and leave room for polishing; how much thicker is necessary? 5/16", 3/8"?

As for the actual fabrication: would I be better off trying to find strip in the correct width, or buying a sheet and having someone chop it with a torch? Most of my strips will need a slight bend - about 15deg; what is a good way to induce this bend? I have not worked with metal this thick before, but feel I should be able to do an acceptable job.

I know to stay away from "bronze" brasses, leaving phosphor, silicon and aluminum bronzes. Which is best and/or most practical for chainplate fabrication, keeping in mind that I don't have a whole machine shop.

Lastly, my current chainplates have square holes for the carriage bolts; I've read in many places to stay away from squares due to cracks forming at the corners. What is the be method for fastening the chainplates/tangs to the hull?


Thank you for your time!
Aaron N.

[Douglas]

Pete Langly at PT Foundry, knows his stuff , but builds in way much "reserve of neglect" !

Don't forget to change your lower bobstay chainplate, too .

You can and should use either Silicon or Aluminum Nickle Brnz for your new chainplates.

I use Alaskan Copper and Brass, in Seattle for a source for this metal, but there are other sources, too.

There doesn't seem to be much tensil stregnth difference between 304 SS and these bronzes, check the numbers, your self.

I used carriage head bolts and made square holes, with out fear of cracks eminating at the corners,,,, but I did orient the square holes to drain moisture, not entrap it.

Bronze is user friendly much more than ss ,,,, and you can bend it much more easily than ss, too .

I use a Bosch variable speed electric jig saw to cut out my chainplates from flat stock, and to square out round holes.

Continue your reasearch until you are confident of your choices before you lay your money down .

Douglas

[blahman]

Douglas and others,

Hello all,

onlinemetals.com offers Aluminum Bronze, alloy C95400, in 3/8"x2" and 1.5". The total cost for all of the bronze I need (12ft of 2", 6ft of 1.5") would be about $300.

I have seen people say that aluminum nickle bronze and silicon bronze are good choices for use as chainplates. However, I'm not sure about "aluminum bronze". It's specifications are thus:

Aluminum Bronze, C954
Minimum Properties Ultimate Tensile Strength, psi 85,000
Yield Strength, psi 32,000
Elongation in 2" 12%
Brinell Hardness 170
Chemistry Copper (Cu) 83.0% min
Iron (Fe) 3.0 - 5.0%
Aluminum (Al) 10.0 - 11.5%


As opposed to silicon bronze:

Silicon Bronze, C655
Minimum Properties Ultimate Tensile Strength, psi 85,000
Yield Strength, psi 55,000
Elongation in 2" 20%
Rockwell Hardness B90
Chemistry Copper (Cu) 97.0% min
Iron (Fe) 0.8% max
Manganese (Mn) 1.5% max
Nickel (Ni) 0.6% max
Lead (Pb) 0.5% max
Silicon (Si) 2.8 - 3.8%
Zinc (Zn) 1.5% max


Does anyone have experience using aluminum bronze; I want to make sure it is a strong enough metal. I'm not sure if "32,000 psi" for yield strength is enough compared to silicon bronze's "55,000 psi". I have found sources for aluminum nickle and silicon bronze sheet, but the total cost is near or above $1000, and I'd still have to cut it, so if this "aluminum bronze" is acceptable, it would be nice!

Thank you for your time!
Aaron

[Jack]

We have a Westsail 32 here in Annapolis that just refit with bronze chainplates. Southbound Rigging
http://www.voyageundersail.com/ Call them and ask for Mike.
They use a waterjet cutter and it sounded pretty reasonable.
I can shoot you pics also. It is bronze chainplate to Collage deadeyes and Dynex Dux rope rigging. We termed it the "Wireless Westsail"
It is Bronze chainplate and Titanium mast tangs, the Dux took 125 lbs. off the rig......:-)

[Jim Fulton]

I saw it at the Boat Show--it's gorgeous. The rigging is impressive. It doesn't hurt that the boat is one of the best-kept Westsails that I've ever seen.

Jim Fulton

[blahman]

Jack,

Thanks for the feedback. I just sent them a rigging.

I've heard about your boat - a BCC owner who just rigged using DD mentioned there was a Westsail that had just gone that route that was "pretty as anything he'd seen". I'd love to see some photos of your boat, especially the rigging!

Our standing rigging is due - would be nice to hear your take on DD for the Westsail.

Thanks!
Aaron

[SV Papillon]

Called Hampijan in seattle yesterday and they said they have no current rep for the PNW as they don't sell direct closest one is San Diego or arizona. Brion want to be there rep???

[Bott]

Originally Posted by SV Papillon

Called Hampijan in seattle yesterday and they said they have no current rep for the PNW as they don't sell direct closest one is San Diego or arizona. Brion want to be there rep???

I ordered mine from Colligo Marine through Fisheries Supply. It just took a little while (~a week) to get it shipped up.

Food for thought.
-eric

[Brion Toss]

Hello all,
I just returned from the Annapolis show, where I had the great pleasure of working with the folks at Southbound Cruising, giving talks for the show, and not incidentally spending a bit of time aboard that Westsail. Southbound is, without a doubt, one of the best outfits I've seen. Great hosts, too. Have I been too effusive yet? No? Then I'll also mention that they have nifty green polo shirts.
Re the chainplates, build to Skene's or L&A specs, and you'll be fine. Not crazy about the square holes, but it is less of a problem with bronze than with stainless, and it is easy to relieve the corners with a chainsaw file.
Fair leads,
Brion Toss

[blahman]

Brion and others,

I know of (but do not own) Norman Skene's book, but do not know of what you're speaking when refering to "L&A's" specs. Could you be a bit more specific?

Thank you for your time!
Aaron N.