Balsa wood is a common building material for model aeroplanes. Strong, steady and lightweight while remaining easy to work, the wood is used to build models of any size covering aircraft from the dawn of flight to modern prop driven and jet propelled aircraft. Building with balsa has its limitations, though. The wood is fragile and easily tears, so there are a few construction tips to keep in mind when using the material to build a model aeroplane that will last, and can even be converted for flight.
Choosing the Wood
Choose carefully when picking the balsa wood to use for your model. Examine the wooden pieces to find the strongest wood available to build the structural support pieces for your aeroplane. You want to use a dense piece of balsa. Check for denseness of the wood by squeezing a piece of the wood tightly between your fingers. Denser sheets will be crush resistant, requiring strong pressure to deform between your fingers. Squeezing the balsa will destroy the wood, however, so purchase samples of balsa lots to test before buying the pieces for your model. Visually, dense pieces tend to be darker in hue.
Decide early how much work you wish to put into building your model. You can buy a set of model plans and go from there, choosing the wood and cutting the pieces before joining and covering them to complete the model, or you can purchase a kit with the parts already precut and ready for gluing. The more complete the kit, the less control you have in the overall quality of the model, but you'll have less difficulty in completing the model and it will take less time.
If you're building a kit, inspect the balsa sheets before beginning. Check that all parts are there and in good shape. If a sheet is broken, it may be repairable with wood glue, but the part will be weaker. Replacing the sheet or kit will give you the best results. Remove the pieces from the sheets and lay them out according to the sequence that you require them during building to make them easier to find.
Build the largest parts of the model first, beginning with the fuselage and then moving onto the wings and tail. When gluing the pieces use a very thin layer of glue and allow each section to dry for an hour before attempting to move it.
Thin the glue slightly at the joined areas if using wood glue to prevent the surface of the balsa from tearing at the joined areas. The thinned glue soaks into the balsa wood, creating a stronger join, as the piece at the joined area is a bit more solid. Sand the pieces of balsa wood to be joined so that they create a flat, even join. Any gaps at the joined areas will weaken the connection.
Skin all the wooden pieces after they've dried completely as a final step. If using plastic film as a skin, apply the heat evenly, using a light pressure where the skin meets the structural pieces. If the model iron is held against the film too long the film will shrink at the edges of the structural pieces creating a skeletal look. Moisten tissue skins with a spray mist before gluing to the plane's surface. This helps create a tighter skin on the aeroplane as the paper shrinks while drying.