Bronze vs Stainless Chainplates

[juanacruz]

Originally Posted by cal40john

I'm guessing that price is the reason you see stainless steel used most of the time. My old boat has everything bronze except for the forward lower chainplates. I have no idea what the history of my chainplates are and so I priced new ones. I was told that if I wanted bronze replacements for the bronze main chainplates they were going to be 25% over the cost of SS.

John

Just wondering if anyone knows if I can install fresh cut 304 SS chainplates for my cal 34 ( onto brand new bulkheads) or do I need to polish them up first I'd love to clean them up a little , but visual perfection is not super important ( I had them made at a local metal shop and will work great, I hope) money for polishing is my hurdle but I could do myself if nesesary. Upsized from 3/16 x 1 1/4" to 1/4" x 1 1/2" thanks

[osirissail]

Originally Posted by roverhi

. . . Most productrion boats have 304 stainless chain plates, not 316. . . .

I would be interested in where that information came from . . . It does not seem logical - although maybe from a monetary standpoint for cheaper boats it might be true.

Here is a link to the differences in common marine utilized stainless steel - 18-8; 304; 316
Stainless Steel Information Knowledge alloys 316 304

- - I would be amazed if "production" boat companies would risk using 304 for chainplates. 316 is commonly available in most all the marine metal and rigging suppliers in Florida. They can cut and polish you new chain plates at reasonable prices since they do it for so many other boats.

- - As to the question about "bronze turnbuckles" - the most commonly used turnbuckles are chrome plated bronze - but the eyes (terminals) are 316 stainless as are the clevis pins. It is very important to use "Tuf-gel" or "Lanacote" on all fasteners and threaded fittins if you are in the salt water environment.
- - Although stainless turnbuckles are available they are not preferred as stainless to stainless threaded fittings have a high propensity to "gall" - which is when the actually threads fracture under load and sort of weld themselves to each other. Which translates to you cannot remove or turn the fitting to adjust it anymore. The two parts are now trash and you have to install new fittings.

[GordMay]

Bronze or Stainless Chainplate Scantlings:
➥ http://www.cruisersforum.com/gallery...r&imageuser=79

[ShipShape]

This is an informative page: Metals in a Marine Environment Also, if you have access to Richard Henderson's "Understanding Rigs and Rigging" he goes over the pros and cons of stainless and bronze in his chapter about standing rigging.

[jim767]

Thanks to all who replied.
I found the scientific evidence surprising. Who would have thought that an ancient metal like bronze would stand up to and even surpass modern concoctions.
As to which metal I would choose for my weapon in a sword fight,most likely stainless steel based on hardness. However, if I were to be faced with 50,000 fights over 20 years in a marine environment my sword would be bronze.

Thanks again,

[wolfenzee]

Originally Posted by Pblais

What boat?

When you get into replacing the chain plates it's the removal of the old ones that cost blood, sweat, and tears. The new super stainless alloys are unbeatable compared to anything. The cost of the material is not much compared to the cost of the machining and removal of the old ones. You can install poor plates as easy as really good ones too. I have a bronze stem fitting but it connects to a stainless plate.

The funny thing is if you could remove the plates and x-ray them you would know for sure if they needed replacing but the cost of doing the testing it isn't worth the effort once removed from the boat,

I can't see why there would be any problem removing the old chain plates, the chain plates are on the outside of the hull and the builder made all of the bolts easily accessible inside and the ones on there now have only been there for 30 years, before things like 5200 were used.

[osirissail]

Originally Posted by wolfenzee

I can't see why there would be any problem removing the old chain plates, the chain plates are on the outside of the hull and the builder made all of the bolts easily accessible inside and the ones on there now have only been there for 30 years, before things like 5200 were used.

Only some boats have externally installed chainplates. The modern boats usually have chainplates that pass through the cabin top/deck and are bolted to the inside of the hull or a transverse member inside the cabin of the boat.
- - Removing these chainplates is a job and a half as sometimes cabin walls and furniture have to be removed to access the chainplates and bolts.
- - An additional consideration when choosing stainless or bronze for internally mounted chainplates is the flexing of the chainplates. If the metal flexes too much then the seal between the chainplate and the cabin top/deck can open up and let water leak into the area. Sealing the hole where the chainplate passes to the inside is a major pain in the butt.

[Shanaly]

hello i have a relevant query, my stays' chainplates do straight thru the deck and bolt to the hull frames. i recommend this fofr you if it is possible. in fact the outer and inner horizontal plates only meet via 4 large short ss bolts.

now to my query: i would like to strengthen the foot od th deck stepped mast, by passing a metal fitting round it 3' above deck and then taking a metal brace directly down through the deck at an acute angle, on each side. this could be chain, bar, or tube. how to fix to mast? how to waterproof thru deck? reason is that i have seen too many deck stepped masts swept off their tabernacles in capsize, needs some reinforcement to stop mast flexure making a mockery of a few inches of tabernacle and a couple bolts!

[cruisingdog]

[QUOTE An additional consideration when choosing stainless or bronze for internally mounted chainplates is the flexing of the chainplates. If the metal flexes too much then the seal between the chainplate and the cabin top/deck can open up and let water leak into the area. Sealing the hole where the chainplate passes to the inside is a major pain in the butt.[/QUOTE]

We've just done that on out boat. Took all the chainplates out one by one, cleaned the components, caulked with Silicon Sealant and refitted and re-tensioned all the stays. Hopefully that'll keep all the water out for another 20+ years!

It really is a 2 person job. Makes it easier to have on guy on the outside and one on the inside. Basically you need to seal everything!

[cruisingdog]

Originally Posted by seacap

316 stainless steel:
Ultimate tensile strength, psi 85,000
.2% yield strength, psi 35,000

Aluminum bronze:
Ultimate tensile strength, psi 85,000
.2% yield strength, psi 32,000

Every rigging shop I have ever been to has a display of failed rigging parts. All the parts displayed are always SS. I have never seen any failed bronze parts on display.

A local rigger here told me that Lloyd's will not insure any SS rigging parts over 10 years old. I have not confirmed that. Also I do not know what Lloyd's limit on bronze is.

In 40 years of sailing I have seen many SS failures. I have yet to see a bronze failure.

Why isn't bronze used more? it's not shiny (marketing) and it runs the cost of an already pricey endeavor up.

My .2c

Careful with advertising!! The fact is that 99.9% of boats made use SS chainplates. As a result you are 99.9% more likely to find a failed SS chainplate!! It doesn't mean that SS is better or worse than Bronze. There's jut more failed SS chainplates to find and show people!!

I would like someone to do an experiment with 2 identical boats , one with SS and one with Bronze chainplates and then do an xray/ultrasound on them after the same number of hours of sailing. I'd bet that there's hardly any difference.

[Stumble]

No stainless is actually a pretty poor material for the marine environment.

The better option isn't to go to bronze, but switch to titanium. A bit more, but won't corrode.

[cruisingdog]

I stand corrected! Thanks for the info.