Fiberglass for Wooden Hulls

Radio Control Boat Modeler, Aug 2004 by Tritle, Pat

Pro finishes made easy!

There are several ways to seal wooden boat hulls; my favorite is fiberglass. The fiberglass base not only seals the hull tightly against water, but it also adds great strength and a solid base for paint and finish. The technique I use to fiberglass the hull is not difficult, and it ultimately builds up the finished surface quickly and easily. The materials I recommend are of automotive or full-scale aircraft quality, as I've learned over the years that if you use highquality materials, your finish will look much better with far less effort.

To start, fill in and sand your hull to remove any gaps or bumps. Model Magic putty or a spackling paste will do nicely for filling the gaps and will not adversely react to the resin. If you have a planked workboat, don't try to get all the planks to disappear completely, as this will detract from the boat's overall charm.

This is the hull, filled and sanded-ready for fiberglass. Before yoy apply the fiberglass cloth, clean the hull with window cleaner to remove the sanding dust.

Lay the dry cloth on the hull, and with stationary clamps (or clothespins), hold it in place for wetting.

Thin the resin about 30 percent with denatured alcohol and brush it into the cloth on the first side. The finished layup should be "wet" and even. Work out the resin to remove any puddles that might build up along the way.

When the resin has cured, sand the excess cloth from the edges with 320-grit paper. Before you proceed, wipe the fiberglass surface with a damp cloth to remove the wax residue that comes to the surface of the resin during the curing process.

Apply and wet the cloth on the second half of the hull, as you did in steps 2 through. 4.

When the resin has fully cured, trim the excess cloth, clean the surface with water, and sand the surface with 220-grit sandpaper. be careful not to sand through the cloth. Clean the fiberglass with window cleaner to remove the sanding residue from the surface.

Using the spot-glazing putty, squeegee a thin coat over the entire surface. This application will fill the cloth weave and arsy deep depressions in the surface. Allow the putty to cure completely before you sand.

Carefully inspect the surface for any remaining flaws, and putty them as neces- sary. Sand and prime again as needed to remove any remaining flaws in the surface.

Sand the entire surface with 320-grit sandpaper. As you sand, the putty will remain in the weave and all the low spots. The idea is to get a good smooth surface-not to remove all the putty. Don't worry about the slight irregularities between the planks, as you'll need those for a good scale appearance.

Once you're satisfied with the overall surface, resanii the whole hull with 320-grit sandpaper, and shoot a final coat of primer. Last, wet-sand with 600-grit paper, and you'll be ready for color coats.

Clean the surface with window cleaner to remove the sanding residue. Spray on a good, heavy coat of primer to build up the surface and fill any remaining weave. Allow the primer to cure, and wet-sand with 320-grit sandpaper.

And that's really all there is to it! Fiberglassing wooden hulls is not difficult but does require a bit of practice to perfect. Fiberglass is also the best choice to simulate steel-hull workboats to which surface detail will be added because it provides a solid base for those details and a smooth uniform surface when a high-gloss finish is desired. And if your boat is ever damaged, fiberglass is infinitely repairable using the same techniques described.

Using high-quality materials will net excellent results almost immediately and will yield a finish that lasts many years.

West System; distributed by Gougeon Brothers Inc. (517) 684-7286.