Balsa wood is very lightweight, stiff, and easy to cut, carve, and shape. It is perfect for making experimental wind turbine blades. In fact, some real wind turbine blades use balsa wood skeletons inside fiberglass.
While we also like chipboard for wind turbine blade designs, balsa wood is lighter and thinner, allowing for some very efficient blades. Check out the KidWind Airfoil Balsa Blade Sheets (10 Pack) for even more advanced blades. These sheets are 12 in long, 3 in wide, and 2.5 mm thick.