If you enjoy building scale models of aeroplanes, rockets or other vehicles, you may be familiar with balsa wood. Balsa wood is lightweight and easy to work with. Unfortunately, many balsa-wood models develop cracks or gaps during or after building. Balsa wood can break easily and it can be difficult to perfectly align all the components of a model on the first try. The good news is that you can fix balsa wood gaps or cracks yourself, using basic model-building supplies.
Lay a sheet of newspaper down on your working surface, to protect your table from any dripped glue.
Measure the crack or gap in your balsa wood model with a ruler.
Cut a thin repair strip from an extra balsa wood sheet with a craft knife, sized to fit the length and width of the crack or gap.
Test-fit the balsa strip in the crack or gap. If it does not slide easily into place, sand the repair strip lightly with fine-grit sandpaper until it fits. Wipe all sanding dust away from the repair strip with a clean cloth.
Apply a thin bead of yellow wood glue to the repair strip and slide it into place. Wipe any excess glue from the model and hold the repair tight with masking tape while it dries. Allow the repair to dry for one hour.
Remove the masking tape and sand any ridges of dried glue away with medium-grit sandpaper. Examine the repair for any remaining dents or imperfections, holding the repair up to the light.
Fill in any remaining imperfections with lightweight spackle, spreading the spackle smooth with a small putty knife. Allow the spackle to dry for a half hour and sand the entire repair area with fine-grit sandpaper.