All materials used in this tutorial can be found at boatbuildercentral.com
Boat Plans are available at bateau.com
Boat Building Plywood
Currently (2007), the situation is as follows:
If you did spend some time reading boat building magazines or rec.boats.building
on the Usenet, you probably witnessed some discussions or arguments
about the type of plywood that should be used to build a good boat.
We plan to expand on this subject soon and present a much larger file about this but in a nutshell, you do not need marine plywood to build a good boat if you use epoxy.
Epoxy resin will completely encapsulate your plywood and protect it from the water. No need for special glues or rare species of wood: the water will never get to the plywood.
The most important components in our stitch and glue boats are the epoxy resin and fiberglass, not the plywood.
You can built most of our small boats with cheap plywood and end up with a good boat if you use the proper resins and glass but this is not true the other way around. If you use expensive marine plywood and bad resin, you may end up with a weak structure that will not last very long. While we specify marine plywood in some of our larger boats mostly for its mechanical properties, the most important components are still the resin and fiberglass.
The controversy about plywood is based on confusion and lack of understanding of new boat building techniques and materials. Stitch and Glue, as we specify it, is not wooden boat building. It is a composite boat building technique that uses plywood panels. In some of our boats, the plywood is used as a core sandwiched between layers of fiberglass. The structure of our boats and the way we protect them from the elements is much closer to fiberglass boat building than to wooden boat building. The structural engineering of our designs is similar to composite boat building (fiberglass etc.) and has very little to do with traditional wooden boat building. For most of our small boats, we recommend the use of inexpensive Lauan plywood. Larger ones use good exterior plywood with no voids or boat building plywood (an APA specification) or in some cases, marine plywood.
Yes, there have been problems with plywood parts encapsulated in polyester resin but not with epoxy. 20 years ago, boat builders did not understand that polyester is not 100% waterproof and this resulted in rotten plywood transoms and floors and also in hull blisters. This problem has been solved with epoxy resins: we exclusively specify epoxy resins, never use polyester.
Trust our 25 years of design and engineering experience: we specify inexpensive plywood for some of our commercial designs since 10 years and out of thousands of boats built, there was never a failure.
Use the plywoods that we specify with the proper resins and fiberglass: epoxy resins that are formulated for boat building and directional glass that participates in the structure. These materials are always available from us as mail order kits, at a discounted price, if you can not find them locally.
Learn more about plywood: See our page about plywood classifications as per the APA. See our resin-fiberglass basic tutorial for more information about these materials.