How to Fix a Lapstrake Boat

Like a modern automobile, where the body is an integral structural element, a lapstrake boat's hull is formed by the overlapping planks of its sides. All the planks are the same width even though they vary in length. Each has a recess called a "rabbet" cut along one edge. Lapstrake construction, like the ship-lap planking on a house, begins at the lowest point on the hull, the keel. It then rises to the top of the side of the hull, with each plank overlapping the one below. The planks are held in place by copper nails that are bent double.

Things You'll Need

  • Measuring tape
  • Needle-nose pliers
  • Nail puller
  • Razor knife
  • Rabbeting bit
  • Bench jointer
  • Chop saw
  • Marine paint
  • Adhesive marine caulk
  • Marine brass or copper nails
  • Hammer
  • Steel nail
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Instructions

    • 1

      Measure the width and the widest thickness of an undamaged plank with a measuring tape to determine what size replacement planks to obtain.

    • 2

      Straighten the bent copper nails at the end of each plank with a pair of needle-nose pliers. Remove the straightened copper nails with a nail puller.

    • 3

      Push a razor knife up between the damaged planks and the undamaged planks on the outside of the boat hull. Cut the caulking away from the side of the rabbet. Push the knife down between the damaged and undamaged planks on the inside of the hull to cut the caulking away from the top of the rabbet.

    • 4

      Measure the length of each of the damaged planks. Record the individual measurements. Measure the width of of the rabbet on the edge of the planks. Install the correct size rabbeting bit in a bench jointer. Adjust the jointer's depth of cut to one-third of the thickness of the plank.

    • 5

      Push replacement planks through the jointer, to cut the rabbet needed in each. Cut the replacement planks to length, using a chop saw. Paint all surfaces of each plank with a marine paint.

    • 6

      Replace the damaged planks from bottom to top, installing the lowest first. Apply adhesive marine caulking to the inside of the rabbeted edge of the lowest -- usually the shortest -- of the replacement planks. Position the replacement plank so its rabbeted edge sits on top of the undamaged plank below it. Nail the plank in place using the hammer and marine brass or copper nails.

    • 7

      Place a steel nail next to the copper nail after you drive it in. Bend the copper nail double, over the steel nail. Apply caulk to the rabbet of each of the replacement planks in turn, and nail them into place.