Next up was the reinstatement of the pivot tang. Simply bonding it back in place seemed unwise, as this was clearly the weak point of the rudder in the first place (though, to be fair, it did last for 40 years). I decided to through-bolt it with a stainless steel backing plate either side (kindly fabricated by Robin in his Broomhouse Workshop [garden shed]).
This was done with plenty of resin in place and everything left clamped and tight for a day to set up.
Three layers of glass cloth were then bonded right around the base of the rudder, to eliminate the weakness along the seam where the two halves were stuck together back in '67 (or thereabouts). After fairing and smoothing, I applied a couple of coats of unthickened epoxy resin for a nice smooth finish.
Finally, I filled the hollow interior of the rudder with 2-part polyurethane buoyancy foam (see this site for a hilarious cautionary tale about the use of this stuff). Said cavity was completely full of water when we took the rudder off (about 6 or 7 litres). I bored two rows of holes (8 in total) across the cavity and then poured small batches of foam into them in sequence. 50 ml at a time, with an expansion ratio of 20:1!