Marine plywood grades are only half the story
When buying any plywood, it is important to think about what you are building and what functionality is most important. This is especially the case with marine construction as marine grade plywood is a term that gets used a bit too loosely and not all of it is created equal.
The things to consider with marine plywood are:
- Bending ease
Certainly there can be more factors to look at but the above will guide you to determine if a particular product is right for you and your specific needs. In general marine grade plywood will have no voids in the core and minimal repairs (football patches) to the faces of the veneers. A water and boil proof (WBP) glue must be used and this is usually either a Melamine or Phenolic resin glue. Right away if the particular panel you are looking at uses a different face veneer from the core, it won't be a good quality marine panel for boat building. But again this is where your particular needs will dictate what to buy. Are you building for exterior construction or actually building a boat where the plywood will be submerged and stay in contact with water for long periods of time? The answer to this will immediately change the products and manufacturers you should be looking at for plywood.
For boat building, plywood selection should be a paramount concern. It will be expensive, no doubt. For the hobbyist and small boat builder it can be a sticking point. But good quality material will make that boat last a lifetime and only the finest materials can be counted on to perform in such harsh conditions.