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Old 21-12-2017, 18:44   #1
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Bronze chainplates silicone bronze or aluminum bronze

Iím going to move my chainplates to the outside of my hull. (Iíve got a Downeaster 32). The chainplates are on the hull but on the inside they go through my cap rail and leak. So I donít think there should be any structural issues and pretty straight foreword job, and later model de32ís chainplates are on the outside. Theyíre pretty straight Iíll heat them up and bend the tops to get them inline with the shrouds and stays. Iím going with bronze over stainless my turnbuckles are bronze, I like the look of bronze,and bronze is better suited for marine use, and the Tensile strength is pretty close. From what Iíve read the aluminum bronze has 0% zinc and silicon bronze has 1.5 max and both are 85000 tensile....etc the silicon bronze has 20% elongation in 2Ē! Wow thatís a lot. So the bronze I want to use is the aluminuim bronze c954 ? Although the silicon has more yield strength so just wanted to check in. I was gonna get plate from on line metals cut it with a wafer wheel drill some small holes then file them square to add carriage bolts. So Iím under the assumption bronze and ss are close on the galvanic scale so Iíll use the old stainless plates as backing plates. Does any one see a problem with this? Also Iím in the preliminary research stages of the grounding of the mast off the top of my head I canít remember if it on the shroud or stay but thereís only one ground wire( which I believe is typical?). And forgive me I havenít gotten deep enough into researching this yet but is grounding all my shrouds and stays together called a faraday cage and thus protecting the boat better then just one? I assume I would run ground from stays and shrouds and connect them to a dynaplate? I. Gonna read up on it more...Iím re doing all my through hulls and was reading up on how to properly bond them got to the tip of the iceberg on grounding .
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Old 21-12-2017, 20:01   #2
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Re: Bronze chainplates silicone bronze or aluminum bronze

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Originally Posted by Eastward ho 24 View Post
Iím going to move my chainplates to the outside of my hull. (Iíve got a Downeaster 32). The chainplates are on the hull but on the inside they go through my cap rail and leak. So I donít think there should be any structural issues and pretty straight foreword job, and later model de32ís chainplates are on the outside. Theyíre pretty straight Iíll heat them up and bend the tops to get them inline with the shrouds and stays. Iím going with bronze over stainless my turnbuckles are bronze, I like the look of bronze,and bronze is better suited for marine use, and the Tensile strength is pretty close. From what Iíve read the aluminum bronze has 0% zinc and silicon bronze has 1.5 max and both are 85000 tensile....etc the silicon bronze has 20% elongation in 2Ē! Wow thatís a lot. So the bronze I want to use is the aluminuim bronze c954 ? Although the silicon has more yield strength so just wanted to check in. I was gonna get plate from on line metals cut it with a wafer wheel drill some small holes then file them square to add carriage bolts. So Iím under the assumption bronze and ss are close on the galvanic scale so Iíll use the old stainless plates as backing plates. Does any one see a problem with this? Also Iím in the preliminary research stages of the grounding of the mast off the top of my head I canít remember if it on the shroud or stay but thereís only one ground wire( which I believe is typical?). And forgive me I havenít gotten deep enough into researching this yet but is grounding all my shrouds and stays together called a faraday cage and thus protecting the boat better then just one? I assume I would run ground from stays and shrouds and connect them to a dynaplate? I. Gonna read up on it more...Iím re doing all my through hulls and was reading up on how to properly bond them got to the tip of the iceberg on grounding .
Get Nigel Calders boat maintenance book. Youíre very close but exactly correct. Too much for me to type out on my phone. To sum it up save the dynaplate for your ssb (or alternatives), bond all thru hulls chain plates, tanks, shaft (via shaft brush) and install a hull zinc or rely on your shaft zinc. Many options and opinions abound as to whether to bond or not but youíre on the right track.
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Old 21-12-2017, 20:02   #3
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Re: Bronze chainplates silicone bronze or aluminum bronze

To make tying it all together easier try and find some lengths of copper flat bar to use as common bud bars rather than having six miles of wire running in your bilge. On the bronze either will do, aluminium, silicone or manganese are all suitable and avaialability will be your deciding factor. PTF uses manganese or silicone, classic marine uses aluminum.
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Old 22-12-2017, 12:57   #4
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Re: Bronze chainplates silicone bronze or aluminum bronze

Just orderd the book you can all breathe a sigh of relief thanks to all
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Old 22-12-2017, 15:32   #5
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Re: Bronze chainplates silicone bronze or aluminum bronze

Itís a good read that can live on board. Another good one if you can find it is the cruising encyclopedia by the Dashews. Little longer and covers (a little too extensively) just about everything but a Ďharderí read.
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Old 22-12-2017, 16:28   #6
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Re: Bronze chainplates silicone bronze or aluminum bronze

Less strength can easily be made-up for with beefier parts. Silicon bronze is stretchier than aluminum bronze so each have their particular uses on a boat (rudder stock parts from silicon bronze means it seats better, for example)


The idea of making a Faraday cage out of your shrouds is a bit speculative, frankly. I would think you'd need quite a few shrouds going all around the boat to create one. Is this to protect against lightning? The truth is all the grounding in the world won't help you if you're struck by lightning. It can jump around, it can weld your engine bearings, it can (and probably will) cook and then blowout the external grounding plate you're supposed to put on your hull etc. in fact the last thing i'd want to do is direct lightning to something stuck to the hull under the waterline, because even if there's no large hole as a result, the heat alone will melt the bolts and cook the resin and make it brittle. Don't bother.

In the old days it was recommended that you attach the end of a chain to the mast and then toss the other end into the water. Heck, might as well, but will it work? No one knows but I guess it makes one *feel* better.

When it comes to lightning, all bets are off. It is that simple.
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Old 22-12-2017, 16:49   #7
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Re: Bronze chainplates silicone bronze or aluminum bronze

Dont heat bronze.
20% elongation is about half of what SS is. Maybe a touch over half. So it's not real easy bend stuff. But you probably only need a gentle bend or two. have someone do it with a brake press or arbor press. You can try a good vise if it's not too thick. Be careful you dont get what's called "1/4 or 1/2 hard"
- if you drill the right size hole, use a coarse square file to make the holes square-ish. The hole doesnt have to be perfect, just enough to hold the bolt. Bronze carriage bolts right?
-Cut the bronze bar with a coarse hacksaw. It cuts very well. much less work than a wheel. The wheel relies on heat, and copper soaks up heat like it's gong out of style.
-Your backing plates should be fine.
-A good source for quality Copper and Bronze is Alaskan Copper and Brass if they are still around.
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Old 22-12-2017, 21:29   #8
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Re: Bronze chainplates silicone bronze or aluminum bronze

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So the bronze I want to use is the aluminuim bronze c954 ?
Use silicon bronze. It's closer to stainless steel on the galvanic scale.

It's not a big deal because silicon and aluminum bronze are close together on the GS. If you want to use aluminum bronze for other reasons, feel free.
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Old 23-12-2017, 10:50   #9
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Re: Bronze chainplates silicone bronze or aluminum bronze

The Dashew book is available on their web site for free via download.
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Old 23-12-2017, 13:29   #10
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Re: Bronze chainplates silicone bronze or aluminum bronze

You are overthinking this. Just contact Port Townsend Foundry and have them cast you a set of chainplates. They do beautiful work, and will use the appropriate alloy. I converted from internal chainplates to their bronze ones more than two decades ago and have had no issues. I have bought other parts there, both from their patterns and my own if needed. They are great to work with.

http://www.porttownsendfoundry.com/

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Old 23-12-2017, 13:41   #11
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Re: Bronze chainplates silicone bronze or aluminum bronze

Another bronze parts and bronze casting source is Bristol Bronze, in RI. They cast a new silicon bronze gudgeon for me.
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Old 23-12-2017, 16:03   #12
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Re: Bronze chainplates silicone bronze or aluminum bronze

Could not find any silicon bronze flat stock, only round, when I was looking for material to replace my chain plates. Only source for silicon bronze was to have then cast but the car was out of the question. 954 aluminum bronze was the only bronze that anyone seemed to have that might work for chainplates. Asked around why Aluminum bronze wouldn't work but got no real answers. Decided to go with 316 SS as the old SS ones had lasted 40 years and had almost no signs of corrosion when I pulled them.

Should be no problem with moving the chainplates to the outside of the hull. Use the old chainplates as backing for the new ones.
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Old 23-12-2017, 23:35   #13
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Re: Bronze chainplates silicone bronze or aluminum bronze

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Originally Posted by Cheechako View Post
-A good source for quality Copper and Bronze is Alaskan Copper and Brass if they are still around.
Alaskan Copper & Brass-Bronze Products
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Old 24-12-2017, 02:30   #14
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Re: Bronze chainplates silicone bronze or aluminum bronze

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Originally Posted by Eastward ho 24 View Post
Iím going to move my chainplates to the outside of my hull. (Iíve got a Downeaster 32). The chainplates are on the hull but on the inside they go through my cap rail and leak. So I donít think there should be any structural issues and pretty straight foreword job, and later model de32ís chainplates are on the outside. Theyíre pretty straight Iíll heat them up and bend the tops to get them inline with the shrouds and stays. Iím going with bronze over stainless my turnbuckles are bronze, I like the look of bronze,and bronze is better suited for marine use, and the Tensile strength is pretty close. From what Iíve read the aluminum bronze has 0% zinc and silicon bronze has 1.5 max and both are 85000 tensile....etc the silicon bronze has 20% elongation in 2Ē! Wow thatís a lot. So the bronze I want to use is the aluminuim bronze c954 ? Although the silicon has more yield strength so just wanted to check in. I was gonna get plate from on line metals cut it with a wafer wheel drill some small holes then file them square to add carriage bolts. So Iím under the assumption bronze and ss are close on the galvanic scale so Iíll use the old stainless plates as backing plates. Does any one see a problem with this? Also Iím in the preliminary research stages of the grounding of the mast off the top of my head I canít remember if it on the shroud or stay but thereís only one ground wire( which I believe is typical?). And forgive me I havenít gotten deep enough into researching this yet but is grounding all my shrouds and stays together called a faraday cage and thus protecting the boat better then just one? I assume I would run ground from stays and shrouds and connect them to a dynaplate? I. Gonna read up on it more...Iím re doing all my through hulls and was reading up on how to properly bond them got to the tip of the iceberg on grounding .
How are the original chainplates attached - to the hull or to a glassed in knee? If they were bolted to a knee and not the hull you need to beef up the hull for the new outside plates. This involves adding glass inside where the plate will be bolted and extending fore, aft, and downwards in multiple layers tapering from a large area to a smaller area. The hull - if the plates were not bolted to it - is not designed to handle the loads of chainplates.
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Old 24-12-2017, 06:00   #15
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Re: Bronze chainplates silicone bronze or aluminum bronze

Yes theyíre bolted to the hull. Just on the inside. I fiberglassed knees right next to them to add some extra strength letís hope I donít get hard spots!
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