How to Put a Stringer in a Hull That Is Not Level

Measure the dimensions of the boat hull floor and write down the locations of the stringers in the boat. This way you can install new stringers in the same locations.

Pull out the old stringer and the foam core underneath it with a pry bar. Try to keep the stringers and corresponding core pieces together as you remove them. The core will be at a slant and supports the stringers to make their tops even on the boat floor. Take them out in as close to one piece as you can as you will use them to make your new stringers.

Sand down the "tabbing" where the core of the stringers were attached to the hull with an electric grinder with a 80 grit sanding disc.

Measure the dimensions of the core and transfer it to new pieces of foam.Measure the dimensions of the old stringer. Transfer the dimensions to the wood. Use the same material as the original stringer to ensure that you give your boat hull the proper support. If your hull has foam stringers, measure the thickness of the fiberglass or the skin covering the stringer. It may be thicker on top than on the sides. Write down the thickness of the fiberglass skin to use as a reference later on.

Cut out the new stringers and cores with a saw. Sand down the cut edges of the wood with 80 grit sand paper.

Test the fit of the stringers in the boat hull to ensure they are the correct size. Put the core down first and the stringer over it.

Wipe down all surfaces with a degreaser. Wash the boat hull, stringers and cores with a cleaning solvent.

Sand down the surfaces of the new stingers, foam cores and the areas directly next to the stringers and cores on the boat hull. Sand a 2 inch area around each of the stringers on the boat hull with a 50 grit sanding disc. Use a brush to remove the sanding dust. If the surface has a "heavy" texture, use a wire brush to abrade it. The scratched and sanded rough surface will allow the epoxy to properly adhere to the boat materials.

Apply an even coat of epoxy over all of the sanded surfaces of the hull, including the stringers and core. Mix the epoxy with 404 high density colloidal silica according to the packaging instructions. Run a bead of the mixture along all of the contact edges where the new stringer and core meet the boat hull. Firmly press down on the stringer to make some of the epoxy mixture come out the joint or the contact edges. If the stringer won't stay down without you holding it, use C clamps to hold the stringer in place.

Run the rounded end of a wooden craft stick along the bead of epoxy where it was pressed out of the joint to make it an even angled surface, called a fillet. If the fillet is less than 1/2 inch thick, add more of the epoxy mixture until it reaches that thickness, and then smooth it out with the craft stick.

Cut the fiberglass fabric to the length of the stringer with heavy duty shears. Cut more fiberglass fabric, 1 inch shorter than the first piece. Cut enough to make a stacked layer of fiberglass fabric the same as the original thickness of the fiberglass you measured.

Place the fiberglass fabric onto the stringers, making a thick layer equal to the original thickness of the fiberglass. Mix the fiberglass resin and hardener according to packing instructions. Apply an even layer of the resin mixture to the surface of the stringer. Use the epoxy and colloidal silica mixture to fill in any gaps or holes on the surface stringer and boat hull. Place the biggest piece of fiberglass fabric over the stringer. Apply an even layer of the resin mixture over the fiberglass. Move the resin across the surface of the fiberglass with a squeegee to ensure that it has been covered with it. Add the rest of the fiberglass fabric pieces, applying a coat of the resin and moving it with a squeegee. Wait 24 to 48 hours for the resin to cure or dry.