What do you do if the Bill of Materials for your boat calls out a 1/4"x4'x16' sheet of plywood?

You have two choices: find it, or make it. In the past, long sheets were more readily available than now.

If we were to build the boat in our shop, we would use 4'x8' sheets and join them with a butt block. An alternate method would be to use a scarf joint to join the panels; but in this particular instance, a second joint would be required to make up for the loss in length that occurs when you make a scarf joint.

Both of these methods are described on the back of the "How to Use Patterns" sheet that comes with each plans and pattern package.

The "sheer" on our theoretical boat is called out at 1" x 1 1/2"x 18' mahogany, and your local lumber yard stocks mahogany only to 12' long. What do you do... find it or make it.

Commonly a scarf joint would be made using the same method as used for scarfing plywood.

Another option would be to look for alternate types of wood. The following are commonly used boatbuilding lumbers: cypress, Douglas-fir, long-leaf yellow pine, mahogany (Phillippine-dark red, Honduras, African), white oak, Sitka spruce, and sasafras.

In all cases the material should be select material, properly dried.

PLYWOOD FACTS

The two types of plywood acceptable for boat building are exterior and marine grade. The exterior veneer surfaces are graded alphabetically, "A" being best, etc.

Douglas-fir is commonly available in the U.S. and imports with various types of veneers usually can be found. Exterior and marine plywood generally use the same adhesives. However, a marine grade has solidly joined inner cores while an exterior panel will have voids (the "football-shaped" voids which are often visible).

Can you use an "AC" exterior panel?

If you're building a 30' craft that's going to cost thousands of bucks, then go for the best. In contrast, if you're working on a tight budget (aren't most of us?), then a lower grade plywood can be considered.

When we build a prototype of a small boat, we generally use an "AB" exterior grade. Not to save money, but to see if the panels with interior voids will make the bends without fracturing. We've had few problems with an exterior grade but, if an invisible void was at a point of stress, the panel could fracture.