I have a 1972 Oday Mariner that I have been sailing for three seasons now. When I pulled it out in the fall I noticed a little notch cut out of the front edge of the keel. I'm not sure if I hit something under water or maybe my trailer chipped it going in or pulling it out. It's about an inch in diameter and about a quarter of an inch deep. I'm sailing in a lake an usually slide it up on the sandy beach before mooring it for the day. How should I fill this spot in and have I affected the integrity of the hull? Thanks in advance for any help that may be out there.