General FAQs
Spiling is an old boatbuilding term meaning: to fit a plank. It has been 'stolen' or perhaps borrowed from the days of plank over frame construction.
Fitting planks is required in cold-mold boatbuilding for two reasons:
  1. To ensure tight joints
  2. Adjust the angle of the planks on the boat

To Ensure Tight Joints

As you bend flat pieces of plywood around a surface that forms a compound curve, the edges of those piece are also forced into subtle curves. When it is time to apply the next piece, it won't fit tight along the entire length.  Scribing and then cutting along the scribed line will ensure a tight fit.

Adjusting the Angle

If you were to measure around the boat at the chine, and then do so at the sheer, you would find that the 'circumference' at the sheer is, of course, much longer.  Therefore, if you are going to keep the plank angle constant, relative to the frames, you have to create wedge shaped planks.  This isn't necessary on every plank, although you could if you would like.  Just, every so often, create an adjustment plank.
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