Finding the wood for the gunwales may take some time, but the actual work on the gunwales takes less than a day.
Step 1: Materials
You will need a piece of wood 1-3/4 inches wide by 3/4 inches thick by 5 feet long. You will cut this up for risers that go at the ends of the gunwales.
You will need four each 1/4 inch dowels 36 inches long. Exact length doesn't matter as long as you have enough total length since you will be cutting these up. Four dowels is more than enough for working with the gunwales. You will be using the left over dowels for pegging the deckbeams to the gunwales.
You will need about a dozen 1-1/2 inch long finish nails. These are generally referred to as 4 penny nails. You will need more later on so buy at least 4 dozen of them.