"at least one person has suggested having a professional do this. This is just not an area for a do-it-yourself experiment
Thanks for the tip. Actually any change to the existing design is an experiment I would say. Don't worry I don't plan on welding these up myself although in my hands on days I was a decent welder certified in oxy acetylene and TIG.
Actually, there has been several bits of conflicting advice. From external chain plates to carbon fiber ones. As an engineer
with 25 years experience it would be dumb of me not to ask questions and get some opinions.
There have been a lot of opinions for which I am very grateful. At the end of the day, I have to take all the inputs and make the decision myself.
The failure point is clearly the ring that is welded to the chain plate
was a significant factor. The deck
and hull are in perfect shape. No signes of stress or cracking. If I have a new chain plate built with a thicker ring and get 30 years out of it, that'll do me ;-)
Delmarrey & Thermal - Regarding the hull strength take another look at the cross section drawing. The rail is solid and is about 1 inch thick. There are 4 through bolts and a backing plate. I could extend the backing plate or improve the connection to the deck but in reality I probably want that fitting to fail before the deck lifts off the boat...
Thanks again for all the great input. I called my mechanic
and he is started on the new plates. I told him to upsize the rings one size and let me see the pieces before welding.