I would do an outside repair, with
Posted by: g2d on Sep-30-12 4:04 PM (EST)
a plate strong enough to carry the rudder. I would attach the plate over the hole with both thickened G-flex and with pop rivets. The boat and plate surfaces should be flamed with a propane torch so the G-flex adheres well. The pop rivets are mainly to keep the plate down on the hull and the G-flex while the latter hardens.
As for the material for the plate, poly, metal, ABS, or composite (maybe 6 layers of alternating Kevlar and glass) could work. It just needs to be stiff.
I'd probably just ditch the rudder, but they don't contribute much to my kayaking experience.....