I believe that in a wooden boat that the part you mean would be called a "strongback." In a FRP boat, we usually refer to the individual members of any part of the entire structural grid as a "stringer."
So now, after reading tommays thread (thanx, as I had not seen it), it seems that CAL designed the boat around a galvanized steel (
) strongback, which was covered with an FRP liner, and then had the compression post mounted on top. Then, CAL designed the icebox, the head compartment, and the limber hole for the bilge to pass through this structural component!
It appears that tommays replaced the galvanized steel with stainless, of a heavier gauge.
- credit SailNet user tommays
I very much like what tommays did to repair the job, but I would also look at doing the job with G10 instead of stainless. Even stainless steel will rust (it's called "stain-less," not "stain-proof" for a reason).
What is it worth? How much do you want to pay, realizing that you will have to do this job...