Early catapults first appeared on the battlefield back in 300 A.D. The basic catapult design has stayed the same over the centuries, and is still used today in aircraft carrier launchers. Handheld catapults are fairly simple to make and can easily fit in the palm of your hand.
Prepare the Popsicle sticks. Cut three Popsicle sticks into 2-inch lengths. Cut six Popsicle sticks into 4-inch lengths. Cut one Popsicle stick into a 4-inch length with one rounded end, Cut one Popsicle stick into a 3-inch length with one rounded end.
Build the base. Tape two 4-inch sticks and two 2-inch pieces together end to end--short, long, short, long. Fold the Popsicle stick line into a rectangle and tape the open ends together. Tape a 2-inch Popsicle stick to the inside of one of the 2-inch sticks in the rectangle for reinforcement. Use plenty of tape on either end but none on the centre of the stick.
Tape two 4-inch Popsicle stick together side by side. Tape another pair of 4-inch Popsicle sticks side by side. Tape one pair of taped 4-inch sticks to the top of your rectangle, covering the rectangle at one side. Tape another pair of 4-inch sticks to the top of the rectangle on the other side, leaving a gap in the middle. Reinforce the corners of your base with tape.
Build the hinge of the catapult and the arm. Tape one end of the rubber band to the rounded end of one 3-inch Popsicle stick. Reinforce with tape. Inset the stick with the rubber band into the base of your catapult. It should slide neatly in the side of the rectangle with two Popsicle sticks. Use a small screwdriver to open up the gap to make the stick fit in there. The stick should be able to stand up on its own with the end of the rubber band dangling down.
Cut four pieces of tape about 2 inches long and stick them together so you have a thick layer of tape. Cut the tape lengthwise. Use the side of a Popsicle stick as a guide to mark two lines in the centre of the twp pieces of tape. Tape one piece of marked tape to the flat end of a 4-inch Popsicle stick. Position the Popsicle stick so that the flat end meets the first of the two lines. Stick the other pieces of marked tape to the other side of the stick. Pinch the free ends of tape together and secure the marked tape to the stick with more tape.
Assemble the catapult. Tape the catapult arm in the centre with the hinge facing the catapult. Do not place tape between the two lines in the middle. Tape the end of the rubber band to the catapult arm. Without any tension the rubber band should sit at a 45 degree angle.
Make the catapult cup. Cut a piece of paper into a 2-by-2 inch square. Fold the sides in about 1/2 inch on each side, then tape up the corners to form a square cup. Tape the cup to the catapult arm. It should be close to the end, with enough room for your finger to press the catapult.