Sources for the right Bronze

[Woodonwater]

I have been looking thru the threads but have not yet seen a discussion of which bronze alloys are better for wooden boats in marine environments. I understand silicon bronze is best, but I was on McMaster-Carr's website at mcmaster.com and they don't offer flat bar stock in SB (for chainplate material).

They offer Alloy 954 which appears to be suitable, but is it? I will need 3/8" x 1 1/2" (or possibly 2") x 30" straps of bronze to replace the badly rusted iron chainplates. It looks like that will run me at least $800. for 12 chainplates. Ouch.

Any other sources where I will do better?

There is aluminum and I think a small amount of iron in 954, but no zinc or tin, which is good right?

[dredbob]

Try Atlas Metals. They advertise in WoodenBoat. I bought a 2" x 1/4" bar about a year ago. Don't know about the prices, I've heard that the cost of copper based alloys are going up because of the war (all that ammo being used).

Atlas Metal Sales (http://www.atlasmetal.com)

Bob

[Woodonwater]

Thanks. They don't seem to have the right size, exactly. I did find the right size on onlinemetals.com and the price was $40. each for 26" lengths. Not sure 26" is enough, nor am I sure 954 is ok to use.

[George Ray]

http://www.classicmarine.co.uk/articles/metals.htm#Copper
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http://www.clementsmarine.co.uk/PDF/TD014/TD014.PDF
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STAINLESS STEEL IS NOT A MAGIC CURE

The McGeorge's wrote in about making new chainplates for their boat out of Manganese Bronze. This would be all right as long as they used #70 Manganese Bronze. This has a minimum tensile strength of 65,000 pounds per square inch as cast. That is a low end, as it can go as high as 70,000 pounds as cast.

There are two other grades, 90 and 110. These should not be used for chainplates for they are much harder and subject to work hardening in many situations.

Many people seem to think that Stainless Steel is a magic cure all for metal problems. It's not so. I've seen some chainplates made of low 300 series stainless such as 302-304. This is the lowest grade, and you can see why, because it rusts when used for deck fittings. It's also low strength. Type 316 or 316L is the best of the 300 series.

The best bronze alloy for chainplates would be Nibral, which is Nickel Aluminum Bronze. It contains no zinc, and therefore, unlike Manganese Bronze is not so subject to electrolysis. Nibral is the metal of choice for high performance boat propellers. They will take a great load, are flexible, and don't work harden.

The top of the line for stainless steel would be Nitronic 50 or Aqualoyt 22. At 135,000-145,000 pounds per square inch, it's high strength. It will not crevice erode as will the 300 series Stainless. The main source for this material is Western Branch Metals in Portmouth, Virginia.

I have been in the marine trade since 1946 at Pitchometer Propeller in Alameda. We had our own foundry and worked in all the above mentioned materials. I have also sailed the Bay since 1938. I am now retired and only consult as asked.

Robert Kilian
Pitchometer Propeller Co, Kilian Propeller & Bay Propeller
Alameda

http://www.latitude38.com/letters/200409.htm