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Mainly I had big dings all along leading and trailing edges - there was lots of exposed core along those edges under the fiberglass shell. Remarkable how well it stayed bonded actually but only a matter of time before something was going to happen. PO's had just kept bottom-painting over the damage, which had the side effect of seeping into some of the cracks to visually help show where significant issues were.
From working with it, I have two observations: First that the original construction is surprisingly tolerant of damage - mine barely had any spots along the waterline where the two glass halves still met. Second is that despite this, I think it is massively advisable to do preventative repairs, which if done decently will make the part far more robust that original -i.e. not just 2 clamshells gooped together but a true joint along the edges which are highly likely to receive traumatic impacts.
Generally I found two types of damage - either the shell pulling away from the filler, which is evident in a real hollow plastic sound when 'percussion testing' (i.e. tapping the surface), OR in a crack developing up the middle of the filler core from stresses pulling on either side.
First thing I did was to sand/grind/carve out any spots where I had damage. Pretty much like being a Rudder-Dentist, digging back until you get to solid material. This included grinding a taper into the glass shell on either side of the seam in the conventional glass-repair fashion. Then I filled the uneven surfaces to a minimal smooth level, followed with glass tape running along the length of the seam and joining the two halves.
There was one spot where I could tell that the delam extended significantly into the surface (most was isolated along the edges). Water and stress had apparently eroded a small cavity inside the shell at that point. This would have required grinding back a large expanse of the rudder face and using significant amounts of mat to fix 'right'. In this case I injected a lot of filler mixture, taped up the hole, then inverted the piece so that any remaining airspace/bubble would be as far towards the interior as possible and the resin-filler would flow to the edges of the gap and surface of the rudder.
Remaining work will be to use a fairing filler to smooth over. Won't be cosmetically perfect but will be much stronger and watertight than before, and much more tolerant of leading edge traumas.
My intent has been to make this rudder decent without doing so much work that it would be smarter to buy a new blade.
Regarding the pivot, clearly mine had a previous repair where a new metal bushing was driven into the pivot hole along with more resin filler because the hole had been wearing into an oval shape. Seems to be working well, so have not touched that.
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Rudder repair -- Tim Walsh, 6.7 #151 "Anna," Madison WI -- 5/14/03 10:39a.m.
Re: Rudder repair -- Bob Pr., S2 6.7 #81 "The TARDIS" Topeka, KS -- 5/14/03 10:45a.m.
I'm at the end of repairs on mine right now (long) -- John Cunningham 6.7 #84 Boston -- 5/15/03 6:18a.m.