Plywood is considered the skin of your boat in boat building. It is what connects the skeleton of the boat and provides the strength and the outside surface of your boat. Choosing the correct plywood for building your boat is determined by the type of usage as well as how much use and the type of storage of the boat you decide to build.

All basic boat construction starts with a skeleton. The skeleton is placed and built on your jig and consists of the keel, the transom (or stern) the chins, ribs and finally the rails. This is the framework that the plywood will be attached to.

Plywood is compressed sheets of Douglas fir. There is also mahogany veneer which is beautiful for aesthetics but I strongly recommend against this unless you are in love with labor. Mahogany is extremely high maintenance and is not recommended for anyone who is actually going to put the boat in water.

For all practical purposes Douglas fir plywood is what boat builders use and 3/8″ is the thickness recommended for its flexibility and ease of working with. Plywood sheets come in 3/8, 1/2 and 3/4 inch thickness.

Seasonal or weekend boats can get away with using construction grade exterior plywood or CDX. Construction grade plywood for boat building will cut costs considerably and is sufficient for boats that will be used in either salt or fresh water that are dry stored. This is for and kind of boat you choose such as a duck boat, bay skiff, small run-a-bouts, fishing boats for light bay or coastal use.

For boats that will have heavier usage and stored in the water the only plywood for your boat building should be marine grade. Marine grade plywood is high quality sheets of Douglas fir without knots that are laminated together with waterproof glue. Again the thickness recommended is 3/8 inch.

When building a plywood boat that will experience heavy usage such as rough water crossing, circumnavigating the globe or commercial fishing crosshatch construction or lap streaking is used. This involves layering your marine grade plywood at 45 degree angles and gluing together with weldwood glue. Ninety percent of these boats use 2 layers although there are plywood boat builders that use more. Weight is also an important factor.

Weight and horsepower ratio is imperative to get correct to prevent your boat from sinking. For instance a light boat with a high horsepower engine may not fare well in an emergency stop and be sunk by its own wake when it catches up with you. Basically just remember to properly ballast your boat with a high horsepower engine. Depending on where your stern is pointing a properly ballast boat will not swamp as easily by a passing wake anchored or en-route.

When considering which fasteners to buy that will hold your plywood to the skeleton of your boat they should be stainless steel screws as your number one choice. The number two and three choices for fasteners would be silicon bronze screws and copper marine nails (serrated edge nails) respectively. Note there is a huge difference between silicon bronze and brass. Brass should not be used.

Regarding the coast guard and your boat this is the general rule. Private boats do not have to be certified by the coast guard but a boat that will be carrying paying passengers must be certified each year.

Now that you have taken in all of the considerations of the grade of plywood involved in your boat building and a few other tips enjoy the process. There is nothing in the world like christening and the celebration of your new boat that you built on its first launch.

The tremendous satisfaction of knowing you built a boat from scratch is very rewarding. The thousands of dollars that you saved is also a good feeling. Oh, and the best part is having a beer with friends and automatically having bragging rights about your first plywood boat building adventures.