Why not bronze chainplates?

[zachduckworth]

Hi all,
I was just thinking about turnbuckles snd reading up on bronze ones. Then I got to wondering why bronze chainplates aren’t a thing? Wouldn’t they resist crevice corrosion better?

[Don C L]

I've got bronze chainplates on my 60 year-old classic, and they seem to be fine!

[hjohnson]

Originally Posted by zachduckworth

Hi all,
I was just thinking about turnbuckles snd reading up on bronze ones. Then I got to wondering why bronze chainplates aren’t a thing? Wouldn’t they resist crevice corrosion better?

It all depends on the rigging design and how much tension the chainplates and similar hardware is going to experience. Stainless steel has higher tensile strength than bronze would.

[S/V Illusion]

Bronze is an alloy or copper and tin, an alloy with far less tensile strength or resistance to sheer than steel.

[Bowdrie]

Originally Posted by zachduckworth

Hi all,
I was just thinking about turnbuckles snd reading up on bronze ones. Then I got to wondering why bronze chainplates aren’t a thing? Wouldn’t they resist crevice corrosion better?

They are a very good "thing", and they resist crevice corrosion much better than stainless steel.
The strength issue compared to SS is easily overcome by simply going-up in the size, (check Skenes Elements of Yacht Design).
The BIG issue is cost, Bronze is much more $$ than SS.
In the old days there was a time when bronze fasteners were cheaper than SS.
That was when SS was considered the new "wonder metal" and there was still a large infrastructure dedicated to the production of bronze/copper based alloys.
Forged bronze turnbuckles, (like the old Merriman products,) are still among the best for yacht use.

[Orion Jim]

Originally Posted by Bowdrie

They are a very good "thing", and they resist crevice corrosion much better than stainless steel.
The strength issue compared to SS is easily overcome by simply going-up in the size, (check Skenes Elements of Yacht Design).
The BIG issue is cost, Bronze is much more $$ than SS.
In the old days there was a time when bronze fasteners were cheaper than SS.
That was when SS was considered the new "wonder metal" and there was still a large infrastructure dedicated to the production of bronze/copper based alloys.
Forged bronze turnbuckles, (like the old Merriman products,) are still among the best for yacht use.

My 39 year old Cape Dory is loaded with Spartan bronze hardware and it is all in the same shape as the day it was installled…much of it is still being produced by Spartan today https://www.spartanmarine.com/.

[Don C L]

And sometimes you can find the good old bronze items in second-hand and consignment shops. Some folks thought they had to replace them, or they came off boats that were being scrapped. Like Orion Jim, my boat came with all bronze fittings and in my case the seacocks are still dry and working fine. I have read that earlier (as in 60s) formulations of bronze are superior to that which came out later but I am not sure how or when the recipes changed. Hopefully someone well versed in metallurgy will chime in.

[dlj]

Originally Posted by Don C L

I have read that earlier (as in 60s) formulations of bronze are superior to that which came out later but I am not sure how or when the recipes changed. Hopefully someone well versed in metallurgy will chime in.

In the early days of brass/bronze manufacture, there was very little standardization. Different foundries would have their own proprietary formulations. But that's before the '60's. That's pre-WWII. WWII saw the need to have greater widespread control on alloys. The CDA ( copper development association) has a nice web site that talks about lots of things related to copper so anyone interested in more should go there and look things up

The main thing that has happened is not so much changes to the alloys, but the use of potentially less ocean resistant alloys being applied. The copper based alloys are very complex. You need to pretty much be an expert in these alloys to know how to specify them. There are still very much the superior alloys you refer to above.

dj

[Benz]

I never use another metal when bronze will do, and I can source it. I cut my chainplates from bronze plate, sized bigger than SS would be, but with no fears of eventual crevice corrosion.

[SailingHarmonie]

Originally Posted by S/V Illusion

Bronze is an alloy or copper and tin, an alloy with far less tensile strength or resistance to sheer than steel.

This is 100% Wrong.

If you ACTUALLY look up an appropriate bronze alloy used for chain plates and compare tensile strengths you will find it very similar to any of the otherwise appropriate stainless steel alloys. Although I will grant you that there are OTHER types of bronze and OTHER types of steel where your general statement would be true.

An example: Bonze alloy 954 has a tensile strength of 85KSI, and 304 Stainless has a tensile strength specification of 75KSI.

Bronze and stainless chainplates can be interchanged size for size, almost exactly. There are only three reasons that bronze is not used by commercial boat builders for chainplates:

#1 Reason: Cost
#2 Reason: Cost
#3 Reason: It doesn't stay shiny without polishing.

[dlj]

Originally Posted by Benz

I never use another metal when bronze will do, and I can source it. I cut my chainplates from bronze plate, sized bigger than SS would be, but with no fears of eventual crevice corrosion.

With all due respect, these kinds of answers are not particularly useful as you are not stating what copper alloy you use. Are you using cast or wrought copper alloys? From the CDA website:

"Broadly speaking, bronzes are copper alloys in which the major alloying element is not zinc or nickel. Originally "bronze" described alloys with tin as the only or principal alloying element. Today, the term is generally used not by itself but with a modifying adjective. For wrought alloys, there are four main families of bronzes: copper-tin-phosphorus alloys (phosphor bronzes); copper-tin- lead-phosphorus alloys (leaded phosphor bronzes); copper-aluminum alloys (aluminum bronzes); and copper-silicon alloys (silicon bronzes)

The cast alloys have four main families of bronzes: copper-tin alloys (tin bronzes); copper-tin-lead alloys (leaded and high leaded tin bronzes); copper-tin-nickel alloys (nickel-tin bronzes); and copper- aluminum alloys (aluminum bronzes).

The family of alloys known as "manganese bronzes," in which zinc is the major alloying element, is included in the brasses, above."

The above are the very broad brush alloy families. Within each of the above mentioned groups, there are many specific alloys.

It would be really useful if folks that are using these alloys actually said what alloy they are using. Simply saying "I use bronze" is barely a step above saying "I use metal"....

This post is meant with the best of intentions....

dj

[dlj]

Originally Posted by SailingHarmonie

This is 100% Wrong.

If you ACTUALLY look up an appropriate bronze alloy used for chain plates and compare tensile strengths you will find it very similar to any of the otherwise appropriate stainless steel alloys. Although I will grant you that there are OTHER types of bronze and OTHER types of steel where your general statement would be true.

An example: Bonze alloy 954 has a tensile strength of 85KSI, and 304 Stainless has a tensile strength specification of 75KSI.

Bronze and stainless chainplates can be interchanged size for size, almost exactly. There are only three reasons that bronze is not used by commercial boat builders for chainplates:

#1 Reason: Cost
#2 Reason: Cost
#3 Reason: It doesn't stay shiny without polishing.

I would probably edit your list a bit. It is not just cost as the top two reasons, I'd say the number 1 reason is ignorance, the second reason is cost. The third reason would be copper based alloys do not have an endurance limit as ferrous alloys typically have. So in your tensile strength numbers you post above, you really should be looking at the fatigue limit stress that is published for these alloys, not the UTS or YS. I'd say your number 3 reason would move to number 4 on my edited list.

dj

[gonesail]

same here. cape dory with bronze thru deck chainplates. good stuff.

[Bowdrie]

Some comments have been made concerning different "recipes" of bronze being used.
In my own boat, which has a large percentage of its fittings/hardware/fasteners that are of bronze, all this stuff is represented by several companies, but still within a fairly short period of time, ('70s>'80s).
Wilcox-Crittenden/Groco/Spartan/Merriman/Barient/Perko, and some stuff by the old ABI company are all represented, (as well as some custom castings and fasteners from the US).
Over the years all of the various items have taken on a slightly different patina/color from their reactions to both salt and fresh water.
This leads me to believe that the various companies were using slightly different alloys.
It's all good and I've seen nothing to indicate that the lifespan of anything has been shortened in any way, whether underwater or on deck.
Good bronze puts your mind at ease.

[Searles]

Good bronze will last many lifetimes ,bronze bolts and nuts are still available in oz as is bronze sheet in many grades , we tend to use bronze and monel fastening in wooden boats,monel and silicon bronze bolts and screws seam to last forever ,we avoid where ever possible using s/s fastenings in wooden boats,some times s/s will even give problems in fibre glass ,more so if composite ,.⚓️⛵️