Building model aeroplanes that really fly is more than fun; it is an adventure. Rubber-band power, built from scratch and minimal cost, add to the attraction. It will take some trial and error and innovation. Do it yourself and then teach others the fine points. What have you learnt? How to do it better and bigger. This article addresses the propeller and rubber-band motor assembly which can be added to any available number of model gliders.
Cut the propeller half sections. Cut blades from a soda bottle at a mild slant. Look carefully at a factory-made prop. The angle twists as it goes from the outside to the centre. This compensates for the outer part going faster than the centre of rotation. You might experiment or see what your friends do in getting a good propeller shape. Another way is to use a commercial nose hook 6-inch propeller from Kelvin.com, order part number # 850654. Get several as you are always breaking props.(See Reference 1)
Make a paper clip shaft. Straighten two pieces of paper clips then hook together forming a "T" shape. Bend a loop in one straightened paper clip and a small hook in the other. Each wire must grab each other and not be flimsy (see pictorial for Step 2 in references) Crimp tightly and hot glue or glue the intersection to lock in place.
Attach the blades to the shaft. Propeller building continues with a couple of techniques recommended, again stressing the option of buying a commercial prop, especially If you run out of patience. However, the pictorials are good, and if you can get though the directions, you will have created your first propeller.
Attach bearings and rubber-band assembly to the plane. Cut open an old ballpoint pen. Use the used ink tube to make supports and bearings. Wrap a wire paper clip around a short piece of the ink tube. Hot-glue a wire to the bearing. The ends of the wire are now hot-glued onto the front of the plane's body. Make sure the alignment of the bearing for the propeller shaft is in line with the body. Place small pieces of the inkwell tube to act as bearings and push the main shaft through to bend over on the prop. Connect the rubber band to the propeller shaft and the rear body. Connect a small piece of paper clip as a hook and glue it in place to pick up the other end of the rubber band.
Add a balsa wood or paper model to the body/prop/rubber band/propeller. Simple kits may be used or do-it-yourself balsa wood and/or paper flying gliders. Add two engines for variety. Fly them in a gymnasium to test without heavy wind gusts. The addition of this motor and prop assembly can easily be accomplished for most gliders and motorless lightweight aeroplane models.
Commercial propellers are 6 inches long. The homemade props are between 6 and 7 inches. Trim the leading edge of the propeller so it tapers slightly toward the tip. Soda bottle propellers are lighter than commercial props. Add weight as necessary to the front or nose of the aeroplane to compensate.
Fly only under low-wind conditions.