I have a model sailing yacht with an ABS hull which has recently developed a hairline crack on the upper hull side, at the location of one of the internal wooden bulkheads. The crack is well above the waterline, but I want to repair it as soon as possible to stop it developing further (the hull is 30+ years old and was broken at the keel when I got it, so the crack may well have been present before I acquired the boat, and opened up by the stresses caused by sailing).
What is the best method to repair a cracked ABS hull? I was thinking of painting expoxy resin (the sort used for GRP) over the inside of the cracked area, then possibly putting some duct tape over the top for extra reinforcement. However, I'm not sure if GRP epoxy will bond to the ABS well enough, or if it will be too inflexible once cured.
I'm reluctant to attempt using a solvent like Plastic Weld to glue the crack together, as I've found solvents can actually worsen fractures in plastic if the parts are still under stress. The presence of the wooden bulkhead on the inside also makes it hard to glue a "patch" over the area.