Part of building your own model aircraft is developing not only your knowledge of flight principles but an intuitive "feeling" for what will work and what won't. Constructing the wing, or airfoil, of your aircraft is probably the trickiest task for an amateur flier because little changes in the airfoil shape can greatly affect flight performance. You can start learning about aircraft design by building a basic airfoil from balsa wood and tissue paper.
Draw an elongated, symmetrical teardrop shape on a sheet of drawing paper. Make its length from fat end to thin point four times as long as the teardrop is wide at its widest point.
Trim the bottom of the airfoil. Turn the paper so the teardrop is on its side and redraw the bottom half of the shape so it is not as thick or curvy as the top half.
Add six 1/8-inch thick notches around the edge of the airfoil shape. Put one notch at the leading edge -- the thick end -- with two notches positioned evenly across the top, two across the bottom and one at the trailing edge -- the tapered end.
Cut out the paper airfoil shape and use it as a template to cut out three 1/8-inch thick pieces of balsa wood.
Cut out six 4-by-1/8-inch strips, or spars, of balsa wood.
Fit and glue the balsa spars into the notches of your balsa airfoil shapes. Space the airfoil shapes evenly. Place one at either end of the balsa strips and one at the halfway point. Let the glue on your airfoil frame dry.
Sand the airfoil frame so all the edges are smooth.
Cut two pieces of craft paper about 1 inch larger than your airfoil frame.
Apply glue to the bottom side of your airfoil frame and set one sheet of craft tissue on it, making sure the paper is evenly and smoothly applied over the frame. Apply white glue on the top edges of the airfoil frame and wrap the overhanging craft tissue around the edges. Let dry, then repeat the process for the top of the airfoil frame. Trim any extra paper with the utility knife.
Fill the spray bottle with half alcohol and half water. Set it to fine mist, then carefully spray the airfoil. Don't overspray; just mist it so the tissue shrinks. Do the top and bottom of the airfoil at the same time. Let dry.
Cover the airfoil with clear spray paint to seal the tissue and keep moisture out. Spray one light coat at a time. Apply two or three coats, allowing the airfoil to dry between coats.
This basic airfoil can be expanded for use in flying models by adding more airfoil cutouts and making the supporting spars longer. There are actually many types of airfoil designs, each with different flight characteristics, so feel free to experiment. This particular design should work well with gliders or other model aircraft where "hang time" is more important than speed. A sharper leading edge will create a faster airplane, but the tradeoff will be stability and a higher stall speed.