Converting to and Fabricating Bronze Chainplates/Tangs
 

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.

Aluminum Nickle Brnz is Better
 

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

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

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......:-)

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

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

Dynex Dux PNW
 

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

Amen
 

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

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.

Blahman

Here are a few links to most recent stuff. (as in just this past week)

http://www.madmariner.com/node/37560/print

http://www.duckworksmagazine.com/09/...opes/index.htm

Give me a few minutes and I will have photos of the Westsail on my photobucket URL below.....along with a few candid shots of Brion maybe....:-)

Question about rig tension with Dynex Dux
 

In the Rigger's Apprentice and on this forum we are repeatedly cautioned to size (wire) rigging to the loads that the boat will exert on the rig. However, much of the publicity on Dynex Dux emphasizes how much stronger it is than wire in addition to being lighter. People seem to be using Dynex Dux that is much stronger than the wire it replaces. In some applications this might be a good thing. But, according to what I have read, Dynex Dux rigging should be tensioned to something in the neighborhood of 15% of breaking strength. This being the case, a fully-tensioned Dynex rig might exert excessive loads on the hull or deck. Shouldn't the Dynex be sized for strength in the same way that wire is?

Jim Fulton

There is a number of things to consider. Dynex does not need to be tensioned to 15%. In fact you do not size Dynex Dux that way. You size it to eliminate creep and stretch. It is so strong you do not use the same set up.....sorta

Here is an example: Westsail 32 Formerly had 1/4" and 5/16" SS wire. Brion says to never load a shroud more than 10% of it's breaking strength and a headstay/backstay more than 15%. If I recall 20% is the ultimate maximum on any wire.

1/4" wire is 6,900 lbs
5/16" wire is 10,600 Lbs.

The maximum tension on your stays should never exceed 1590 lbs. (15% of 10,600)

This would be the same tension you put on a Dynex Dux rig....those numbers.

This is the number we use to determine what size Dux rope to replace the wire. Our rule is keep the static load or tension under 15% of the breaking load of the rope, and you will eliminate creep and stretch. In fact it stretches less than wire, when sized properly.

We used 9mm Dux on the Westsail. Breaking strength 26,500 lbs. If the Westsail is tensioned to 1k or so (in reality) We have a huge margin before we ever reach the 15% point.

15% of 9mm Dynex Dux is 3,975!

By replacing the rig with rope that is more than two times as strong, we have gained a huge leap in overall strength, and have no stretch or creep. The rig uses the same tension numbers as with wire.

You are right, if we were to tension it to the 15% of the ropes strength, we would pull the mast right trough the bottom, or some other nasty thing.

I uploaded a bunch of photos of the boat on the URL below. Enjoy!:D

All,

I spoke with Pete out at PTF today and he assisted me in understanding the alloys. Basically, the cast alloys with high corrosion resistance are fine choices for chainplates, so aluminum bronze, aluminum nickle bronze; things in the C95XXX range. The trouble with these bronzes is that they are very hard, inelastic, strong metals, so working with them is trouble. Fabricating using silicon or manganese (wrought) bronze is much easier for its elasticity and bendability; it can be cold worked.


Most of PTFs castings are C955 or C954, aluminum nickle bronze or aluminum bronze. If they are going to be working a piece, they cast it of silicon bronze to enable easier working.


So the 3/8" aluminum bronze stock will work great, the trouble will be bending it. It can't just be put in a hydraulic press as it'll crack or shear; it has to be heated. I didn't ask him about the procedure for heating and working with the metal as that's his trade! I'm going to dig on the internet to see what I can learn and then decide whether or not I'll by the stock and make the chainplates.


Chainplates from PTF would be $180/ea, plus $100 for bending, plus $150 or drilling. Boomkin and bowsprit whisker tangs would be $90/ea. So I'm going to check into working the metal myself and doing it for $300 total as my pockets just can't support that now and I don't want to keep sailing on cracked chainplates!

Anyone have knowledge of working with the cast alloys?

Thank you all for your time!
Aaron N.

Bronze Chainplates / Dynex Dux
 

Hi all,

I'm specifically interested in bronze chainplates as well. I have a '66 Allied Seabreeze yawl with inboard chainplates mounted on the bulkheads, which I plan on replacing with bronze, on the outside of the hull. Incidentally, I'm already in the process of re-rigging with Dynex Dux as well, having installed twin backstays to replace the original split stay. The stuff is awesome, incredibly easy to splice, and the deadeyes / lashings look rather dandy on my old yawl, as they did on the Westsail in Annapolis. I actually spliced both backstays in the cockpit while we motored down the ICW just last week, installing the stays dockside.

Anyway, I found another source for DIY bronze. Atlas Metals, based in CO, supplies all sorts of metals, including silicon bronze, that comes in convenient 2" wide x 1/4" thick strapping, sold by the 6' length. Saw their ad in Wooden Boat magazine, and talked with them on the phone, just out of curiosity. Not sure yet what my solution will be, but they seem like a good lead. Google them. Also, anyone considering the Dynex Dux with questions can feel free to contact me for personal details of how the re-rig is going on 'Arcturus.'

Cheers,
Andy
www.fathersonsailing.com

Andy, I have to smile at how stoked you are. I swear, I feel like street corner preacher sometimes.....I mean it is hard to get your arms around how cool/fun/great/amazing...well you get the idea...:-)

Glad to hear you have become a user and believer in Dynex Dux. It will certainly mess with your head

To update you all,

I went ahead and purchased the aluminum bronze stock to fabricate my own chainplates. Total cost for the material was $280, so we'll see how it goes. The metal will be here this Monday, and I'll give feedback and photos on how it goes.

Any last minute advice on drilling or working with it? C954.

Cheers!
Aaron N.

Hey all,

Just wanted to let you know that I wound up using the 3/8" Aluminum Bronze to fabricate my chainplates and it was a breeze. Took maybe four or five hours to do all ten, including polishing. The material is very strong and makes the boat look much better, I think!

You can see all the photos of our ongoing renovation at:

Deck Renovation/Rerigging



Thanks for your help!
Aaron N.