I have a 14ft Northland that has served my wife and me very well for about 30 years. I have decided to remove the glass which is badly damaged in a few places and re-glass it. I want to remove the keel but after removing the keel screws from the inside and removing the bow and stern wear bands, I can't seem to get the keel off! I would be happy to use greater force but I don't want to cause any structural damage. Any clues?