Ovation guitars were innovative when they first hit the market with their composite bodies. Their design afforded them a rich tonal quality that made them popular with many entertainers. What made this guitar standout was its use of composite (non-wood) materials for its bowl-like back. Unlike wood, composite materials require a different technique for repairing cracks. The methods are similar to those used for fibreglass. Using fibreglass repair techniques offers an easy and affordable way to fix splits or cracks on composite bodied instruments.
Remove the strings from the guitar. This gives access to the guitar's sound hole. Flip the guitar over to expose the backside. Shine a bright light into the sound hole, which will illuminate the crack. Use painter's masking tape to mark off the crack's beginning and end points. Composite bodies are formed from some form of epoxy resin and cloth, similar to fibreglass. Therefore, epoxy resin should be used to fix the crack.
Sand the edges around the crack. This will allow the resin to adhere to the composite body. Seal the crack with the masking tape from the inside of the guitar. This will keep the resin from dripping into the guitar's body when you apply it. If the crack is in an inaccessible area, purchase some resin thickener (powdered fibreglass) and mix it, in the following step, with the resin until it has a paste like viscosity.
Mix a small amount of pigment into the resin to match the guitar's colour. The pigment is concentrated, so too much pigment can prevent the resin from drying to an even consistency. Do not mix the resin, hardener and pigment together, since resins harden very quickly. Once the colour is matched, mix in the hardener. Mix a small amount, no more than two ounces, which is more than enough to fix most cracks.
Apply a small amount of resin to the crack. Allow the resin to dry for 24 hours. Repeat this process, lightly sanding the resin between coats. The resin will be applied in two or three coats, depending on how large the crack is. On the final coat, lay a small piece of Mylar over the wet resin. Use a playing card to smooth it over the crack. This forces any air bubbles out. Let the resin dry for another 24 hours and peel off the Mylar.
If the crack is accessible through the sound hole, brush a thin coat of resin over the area around the crack on the inside of the guitar. Apply a thin layer of 113gr fibreglass cloth and more resin. Allow it to dry for 24 hours. This will reinforce the resin in the crack and prevent further damage. Remove any remaining tape and the crack is fixed.
Resin dries glossy, so use steel wool to dull the resin, which will match the Ovation guitar's flat finish. If the model has a textured back, take some modelling clay and make an imprint of the texture. Dry the clay in an oven. Apply some paste wax to the clay. When the resin is almost dry, having a slight bit of tackiness to it, imprint the clay on to the resin. This will give you a matched texture.