Balsa wood is light, cheap and easy to manipulate. For these reasons, balsa wood is a perfect material for building small, workable model aeroplanes. While numerous commercial kits are available, they are not needed, provided you have a working understanding of simple aerodynamics. All you will need are a few sheets of balsa wood, sand paper, an X-acto knife and wood glue.
Form the Body
Form the body of the aeroplane by selecting a "thick" piece of balsa wood. The word "thick" is slightly misleading; you want the plane's body to be thicker than the wing and it should have more weight. However, the body should still be relatively thin, perhaps less than a few centimetres wide. You want as little drag as possible. Therefore, the plane's front should be rounded and it should taper toward the back. It should look like a stretched tear drop from the side. Use sand paper to smooth the surface, but be careful not to sand so much that the body becomes brittle and fragile.
Form the Wing
The simplest way to make a balsa wood air plane is to use one wing. Two wings can be moulded, but there is the problem of making sure both wings are exactly the same shape. Before shaping the wing, use an X-acto knife and cut a slot out of the aeroplane's body. The slot should be wide enough to slide the wing into once it is finished.
Once the slot is formed in the aeroplane's body, sand a thin piece of balsa wood much in the same way that you formed the body. You are looking for a rounded front edge that tapers off to the back. This allows air to travel over the plane's wing and create lift without causing too much draft that allows your plane to fly. Once the wing is shaped, slide it into the slot on the body. Use a very small amount of wood glue to secure the wing in place.
Glue on Tail
Create a tail to help stabilise your plane as it flies by cutting three triangular pieces of balsa wood and gluing them onto the plane's back end. The triangular pieces should be relatively small. They are only there to help keep your plane balanced as it flies. Attach the two pieces on each side of the tail and one piece sticking straight up. Use wood glue. Once the glue dries, test your aeroplane.