Bronze Brazing/Welding, Unknown Alloy

[bott]

Hello,

Related to my other post about fabrication of a new mast band out of mild steel.

Background again:
I am re-doing the rig on my gaff cutter and came to the conclusion that I need a different arrangement of lugs on the mast band where the shrouds attach. Specifically, I want another lug added to the aft side for the swifter shrouds to attach. The current band is 6" in diameter, 1.25" tall, and ~5/16" thick. The boat is ~20,000 lbs with ~800 sq ft of working sail.

The problem is that I dont know what alloy it is (silicon, phosphor...). I think the easiest thing to do would be to braze/weld new lugs on the existing band. Can this be done with enough strength without knowing the alloy? What kind of fabricator/welder should I look for (I am in Seattle) and how should I propose the job with specific language?

Thanks!
Eric

[PeterSibley]

Eric , this doesn't answer your question , but what are you like at pattern making ? An entire new job would be strongest .I personally wouldn't trust a braze connection between two alloys of possibly differing composition .

In your case I reckon the mild steel job may be the simplest .

[Gold Rock]

Silicon bronze welds pretty well, but other common marine alloys, like manganese and aluminum bronze don't weld well at all. You could take the part to a good welder and have him take a try at it, but if it's a high zinc alloy like manganese brz., the experiment could seriously damage the part. If it's a two piece band, you could possibly have one of the halves prepared by a foundry and used to cast a new part with the tab you want added.

[tomlarkin]

I've had good luck with Broomfields in Ballard. This was some years ago. They identified the composition of some bronze castings and did a good job repairing them. http://www.broomfields.com/