My Experience
My understanding is that some of the O'Day 25's had a solid fiberglass rudder, and some had a clamshell around a foam core. Mine was the latter. I didn't learn all this until after the rudder broke. My rudder gave me PLENTY of "notice" that it was going to fail, had I known what to look for. When I bought the boat, the rudder had a small split along the seam. Basically new to sailing (the college sailing 25 years earlier hardly counts), and totally new to the boat, I didn't perceive it as a major problem. About 6 months later when I was sailing way overpowered in 20-25 knot winds, I noticed that the boat was becoming less and less responsive. I finally looked at the rudder, and noticed the split that was originally 3-4 inches was now well over 18 inches. The rudder was twisting against the force of the water when I turned the tiller. My adivice would be to inspect it in place before each trip. Take it off once a month or so (assuming it's a stern mount like my '76 model). If you see a split at all, assume it's going to go soon, and start looking for a replacement. I've heard that there really is no "preventative measures" that will help. I refiberglassed mine, and it lasted another year, but the real "fix" was a new rudder.
