The chips are the diameter of a BB, giving these areas the appearance of the surface of a golf ball. Some have been painted over, indicating that this problem existed before the hull was last painted. New chips started popping off as I stripped the bottom paint.
I expect this condition will only worsen, and therefore I am planning to strip the gelcoat and seal the fiberglass with an epoxy sealer to eliminate the concern.
Here is a cluster of dimples at the waterline, at the juncture of bottom paint and bootstripe.
The fiberglass covering has split at the top of the rudder, around the rudder post. I'm not sure what caused this, but I'm worried that the rudder post has corroded, which caused it to swell and split the fiberglass. It may be that previous sanding in preparation for painting made the fiberglass skin too thin, and stress caused the cracking. Or, maybe it was a result of abuse, like an improper placement of lifting straps.
Whatever the cause, it's going to require investigation and correction. Unfortunately, the construction of the trailer she is sitting on makes removal of the rudder difficult, if not impossible. This is going to take some thought... Suggestions are welcome.