While going through some rapids, we slid across a jagged rock and it put a huge gouge in the bow of my fiberglass canoe. What method and process is best for repairing it, so that next time I hit some rocks they don't immediately break through and swamp the canoe?
They sell fiberglass repair kits at most boating stores which are made for this exact sort of repair. It includes a fiber glass cloth which you put over the damaged area, as well as a resin / hardening agent to hold the patch in place. Any kit you buy should have instructions for applying the patch in it.
During the trip: duct tape. It's strong and flexible and it's easy to carry 3 or 4 feet with you. I've used it to repair a yoke in the middle of nowhere.
Once you're home: a little fiberglass cloth and some epoxy resin. Or if it's more a deep scratch than a gouge, just the resin.