I have come across some great discussions of building issues for longevity of plywood boats.
The first source is from John C. Harris at Chesapeake Light Craft. John has done an interesting investigation of wear and tear on his fleet of demonstration and prototype boats. The fleet probably has an accelerated wear rate based on its heavy use and transport to boat shows. John goes through many case studies of various types of damage, probable causes and required fixes. The blog posts can be found here.
A 15 year old CLC Eastport Pram, perhaps oversanded during the build.
The second paper is from Jim Brown and is titled Building for Longevity from the Searunner Construction Manual. I found this over at Small Trimarans. Jim shares his long experience on essential building techniques using epoxy and plywood.
Thirdly, there is a post by Dudley Dix discussing painting and coating requirements on plywood boats.
These three texts overlap and reinforce each other. My takeaways are:
- Pay extra attention to make sure all plywood is triple coated with epoxy. Jim Brown says that this includes the edges of plywood that will be bonded (eg. bulkheads). I had mistakenly thought that the bonded edges would be OK with a primer swipe and the glue layer.
- Carefully avoid any over sanding. Of course you don't want to hit the glass, but beyond that you must maintain the full thickness of the epoxy envelope over the glass.
- Consider extra protection in high wear areas.
- Immediately take action to repair and seal any dings or scrapes.
- Maintain UV protection inside and out.