Chainplate We'll
Hello,
And ouch, a series of nasty problems. I am, first, amazed that a shop that allegedly works primarily on marine projects can't bend bronze without destroying it, and further shocked that they didn't pay you for the damage. But what is done is done.
The P.T. Foundry plates might be made to factory spec, but are definitely thicker than they need to be for this boat; 1/2" is the thickness you might see for 7/16" or 1/2" wire. So they can definitely be milled down some.
What wire size is specified for your boat? If 1/4" is the biggest, then 1/4" thick is fine. I realize you are using Dux, but the loads will be the same. If larger diameter is called for, re-check the clearance inside those deadeyes; I have some here in the shop with a gap of about 5/16". It might make for a tight fit on a similarly-sized chainplate, but occasional treatment with Tef-Gel should prevent any corrosion.
The short form is to thin the chainplates as little as possible, to preserve maximum strength. Also, be sure that the transition to the thinner dimension is gradual, so you don't create a stress riser.
Bronze specs are indeed the same as for stainless, according to most sources. Some bronzes, like aluminum bronze, are a good deal stronger than 316 stainless. But note that manganese bronze isn't a bronze at all, but a brass, and therefore vulnerable to de-zycifying. Avoid it, along with the similarly misnamed naval bronze.
Fair leads,
Brion Toss
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