Balsa lumber is very soft and light

Balsa lumber is very soft and light, with a coarse, open grain. The density of dry balsa wood ranges from 40–340 kg/m³ (2.5–21 lb/ft³), with a typical density of about 160 kg/m³ (10 lb/ft³).The light weight of the wood derives from the fact that the tree has large cells that contain water. After the water is driven off in an extended drying process (kiln dried for two weeks), the large surface area of the resulting holes gives strength.
 Unlike dry rotted wood, the surface is made of the usual strong cellulose/lignin mix. As it is low-density but high in strength, balsa is a very popular material to use when making light, stiff structures in model bridge tests, model buildings, and for the construction of model aircraft — especially free flight model aircraft, as well as full-sized light wooden aeroplanes, most famously the World War II de Havilland Mosquito.Balsa is used to make wooden crankbaits for fishing. Sticks of balsa can be used to make crude dip-pens for calligraphy and can be useful when one needs a specific nib-width or structure, when one does not have such metal nibs immediately available.
Balsa wood is often used as a core material in composites; for example, the blades of many wind turbines are made partially of balsa. In table tennis paddles, a balsa layer is typically sandwiched between two pieces of thin plywood. Balsa wood is also used in laminates with glass-reinforced plastic (fiberglass) for making high-quality balsa surfboards and the decks and topsides of many types of boats, especially pleasure craft under 30 m (100 ft) in length.