This project shows you how to build a small, rubber band -powered ornithopter.
Step 1: Gather Materials
1. 7 inches balsa rod 1/8"x1/4"-Cut into lengths of: 5" motor stick, 1 1/2" front vertical connector
2. 6 inches balsa rod 1/16"x1/4"-Cut into lengths of: Two 2 3/4" connecting rods
3. 24 inches balsa rod 1/8" square -Cut into lengths of: two 8" wing spars, 5" top wing attachment member, 1 1/2" back vertical connector, 1/2" crank standoff
4. 14 inches balsa rod 3/32" square -Cut into lengths of: two 7" tail members
5. 10 inches music wire .032" diameter-Cut into lengths of: 3" tail/rear motor attachment wire, 2 1/2" crank/front motor attachment wire, two 2" wing spar wires
6. Sheet of tissue paper, 18"x18"-Made specifically for modeling, approx. .04 oz/100 sq.
7. Square of 16 lb. paper, 1 1/2"x1 1/2"
8. Heat-shrinkable tubing, 1/16" diameter-three pieces 1/8" long
9. Small beads-Three w/inside diameter just large enough to allow music wire
10. Medium thickness rubber band 12" in circumference
11. Cyanoacrylate (CA) glue
12. Cyanoacrylate drying accelerator
13. Glue stick
14. Needle-nose plyers
15. Utility knife-To cut balsa wood
18. Vegetable Oil (optional)
Step 2: Make the Fuselage
Make a hook in the rear tail motor attachment wire. Push the wire carefully through the center of motor stick at a point 3/8" from tail end. Next, make two 90 degree bends in wire and glue into place using CA adhesive. Reinforce the wire-to-balsa joint by putting a tissue paper cover over it. Dab the joint w/thin layer of CA. Spray CA drying accelerator on joint to speed process. Next, glue the fuselage together (see diagram).
Step 3: Paper Roll
Roll the 1 1/2"x1 1/2" paper into a narrow tube using music wire for a mandrel. Pull music wire out and carefull daub w/CA (make sure to maintain openings at each end). Spray w/CA accelerator. Cut into three 1/2" long tubes. Attach the tubes to the fuselage as shown (use the CA & CA Accelerator).
Use needlenose pliers to bend the wire for the crank. Insert the crank wire through the paper tube glued to the crank standoff. Make a 60 degree bend in the center of the 3/4" side. Place 3 beads on the wire (as shown). Make a bend in the back part of the wire for a motor hook.
Step 5: Make Wing Spars
Bend music wire as shown. Carefully push wire through wing spar at a point 3/4" from one end. Glue into place using CA and reinforce the joint by wrapping layer of tissue paper around the joint and coating with CA. Repeat process for 2nd wing spar.
Step 6: Make the Tail
Use CA to glue the balsa rods into a T shape. Reinforce the joint by covering it with tissue paper soaked w/thin layer of CA. Poke the end of the fuselage tail attachment wire into the balsa tail member. Then glue the assembly w/CA and finally reinforce by wrapping w/tissue and CA.
Step 7: Make the Connecting Rods
Harden the rods by coating the last 1/2" of each end of both with CA. Make 2 holes for the music wire in each in each connecting rod, 1/4" from each end.
Step 8: Cut Out Wings
Cut out tissue paper wings as shown.
Step 9: Final Assembly
Glue tissue paper wing to wing spars and the top wing attachment member. Next, glue tissue paper tail to the balsa T frame w/glue stick. Connect connecting rods to the wing spar attachment wires and crank. Adjust spacing of connecting rods so the crank turns smoothly.
Place heat shrinkable tubing over the crank and wing spar wires to maintain alignment, and carefully heat w/match to shrink tubing. NOTE: Materials are very flammable, so use great care! Finally, bend the tail up so that it is at about 15 degrees from the plane of the motor stick.
Step 10: First Flight!
Place rubber band over the front and rear motor attachment hooks. Wind up the rubber band motor by turning the crank 30-35 times. Angle the ornithopter's nose up slightly and release gently. *Optional: Rub the rubber band with a little vegetable oil for lubrication; this can help it go smoother.