Yes it is, but I would use Epoxy
instead of Polyester. Fibreglass seperating from the steel
keel is a common problem as Polyester has no real adhesive
properties. Firstly make sure that the damage and delamination
is minimal and not structural. When most keels get a bang either on the trailer or in the water
the resulting damage is usually at it weakest point around the hull
joint and the keelbolts. Look closely at the surrounding gelcoat
for telltale stress fractures if they are evident it may need to be looked at, if not, a diy job of injecting epoxy
mixed with microfibres into the delaminated area should do it. Make sure there is no moisture or water
trapped in the damaged area, flush it with acetone, heat the area to promote curing (a 500w Halogen works well) inject it and brace it under pressure.
Hope this helps.