With Justine’s backbone completed, it’s time to start covering the frames with planks and make a watertight hull.
A lot goes into getting the hull planked. First, you must determine how many planks will go on each side of the hull, and how wide each plank will be. This is called lining off the planks. Once you know where each plank will begin and end, you have to determine the shape of each plank by a process called spiling. Small adjustments to the shape are made with a hand plane to get a close fit with adjacent planks.
Each plank’s shape must conform to the curvature of the frames on which it lies. So each plank needs to be planed on its inside surface accordingly: mostly, this means that the planks need to be concave on their inside surfaces. The process of making the inside surfaces concave is called backing out the planks.
Justine’s planks are as long as 21′. The planks in my pile of planking stock ranged from about 11’–14′. So most of Justine’s planks consist of two pieces of planking stock, joined end-to-end with pieces called butt blocks.
All but the uppermost plank that is closest to the deck, called the sheerstrake, are made from northern white cedar (Thuja occidentals), also known as arborvitae. These planks are 5/8″ thick. Justine’s sheerstrake is made of mahogony, and it is effectively a molding with a cross sectional profile that has a maximum thickness of 1″.
While the inside surface of the planks is generally curved, I left the outside surfaces flat until after the planks were fastened. The immediate result is a faceted exterior hull surface. The entire outside of the hull needs to be made smooth and fair. I did this by starting with a hand plane, then finishing with sandpaper.
Once the entire hull is smooth and fair, the seams between the planks get caulked with cotton to impart watertightness to the hull. Then the hull gets painted.
I’ll cover all these topics in more detail with subsequent posts. In the meantime, here’s a photo showing Justine’s planked hull shortly before turning her over and starting to build out her interior.
