Rubber Band Engineer
Transform two handheld battery-powered fans into an automatic paper plane launch pad! By replacing the fan blades with cardboard disks, a paper plane will rapidly launch upward when you feed it between the spinning disks. The launcher can easily fling paper planes a substantial 15' (4.5 m) or more, and you don’t have to wear out your throwing arm while using it!
CIRCULAR Circular container lids, the bottom of CARDBOARD a circular cardboard oatmeal container, COASTERS small paper plates. Any perfectly round, rigid object between 4" and 5" (10 and 12.5 cm) in diameter. If your material is thin, like a plastic container lid, then you may need to glue two layers together for each disk. Cutting circles by hand is not recommended because very small imperfections will cause the plane launcher to vibrate wildly or self-destruct when the fan motor is at full speed.
DUCT TAPE Masking Tape
Remove the fans’ blades if possible. You can skip this step if the blades are fixed onto the motor shaft or if there is no other area for attaching the circular coasters.
To locate the exact center of each coaster, use a ruler to draw three lines across the edge of the circle, each exactly 3" (7.5 cm) long. Mark the center of each line at 1½" (4 cm). The exact position of the lines is not important.
Using the corner of the ruler as a right angle, draw a perpendicular line from the center of each 3" (7.5 cm) line into the middle of the circle. The center of the circle is where the three lines intersect.
Position the coasters exactly in the center of each motor’s axis of rotation and use hot glue to attach them in place. Turn on the fans to make sure the coasters are centered. The goal is to have little to no vibration when they rotate. You may need to remove and replace the coasters if the center of rotation is off by more than ⅛" (3 mm).
Tip: The closer the motor’s center of rotation is to the center of the coaster, the more effective the launcher will be.
Hot glue the cardboard pieces into a triangle with the longest piece on the bottom, as shown. It’s important that the apex (top angle) of the launcher be a right angle. Wrap the launch pad with a long piece of duct tape.
The glue creates a rigid structure, and the tape will prevent the vibrations from the spinning coasters from breaking the glue bonds.
Check the direction of the motors and position the handheld fans on the short side of the launcher.
In this picture, the left disk turns clockwise and the right one turns counterclockwise. Hot glue the handheld fans in place. The spinning disks should have about ⅛" (3 mm) of space between them,
and should have about ½" to ¾" (1.3 to 2 cm) of clearance above the launch pad. Avoid attaching the motors in a way that prevents access to the on-off switch or the battery compartment.
Create the plane guides by cutting two ½" x 5"
(1.3 x 12.5 cm) strips of cardboard. Hot glue them to the center of the launch pad, directly in line with the gap between the discs, with about ¼" (6 mm) of space in between them.
Optional: Wrap a piece of duct tape around both fans. This allows you to tighten the gap between the spinning disks. Loosen the tape if the disks are too close together.
Create your plane of choice and use a small piece of tape to hold the wings together. Usually the valley fold down the center of a paper plane is slightly open, which can cause the plane to slow down when it’s fed into the spinning disks. Make sure the nose of the plane will clear the top of the disks.
Prepare to launch! Turn on both motors, wait until they reach maximum speed, and then set your plane between the guide strips. Although handheld fan motors do not have much torque, the accumulated energy in the spinning disks should have enough force to pull the plane through and launch it into the air.
Lightly tap the back of the plane to give it a push into the spinning disks. The disks should grab the plane and fling it up to 15' (4.5 m) into the air! If you don’t find success right away, try adjusting the gap between the spinning disks to match the width of the center of the plane.
TRIM YOUR PAPER PLANE
Is your plane not cooperating? Try trimming the wings. This means curling the back edge of the wings slightly to correct the amount of lift. Curling the paper upward will increase the amount of lift, while a downward trimming will cause the plane to take a nosedive.