Introduction: Card Stock Trainer Airplane [STEM Plane]
This easy-to-build airplane includes two wing shapes in the plans. Additional wings can be created and subjected to testing. The fuselage design allows wings to be replaced effortlessly.
A 1/2" diameter vinyl thread protector (or thread cap) is used to mimic a cowling and protect the nose. It's an inexpensive item that is available at hardware stores. A substitute piece could be fashioned from chipboard rolled into a cylinder.
Other than the nose cap, only card stock and chipboard are needed to make this plane. I used chipboard from food packaging (such as cracker boxes). You can buy 12" x 12" sheets of chipboard at your local arts and crafts store, and that works well. Due to variations of weight, you may need to adjust the center of gravity by sliding the nose cap back or by adding a bit of clay, or even a small metal washer, in the nose cap to increase the weight.
The CG should be behind the leading edge of the wing, about 30% of the chord length.
-Card stock (65 lb.)
-Chipboard (such as a cracker box)
-1/2" diameter vinyl thread protector
-Utility knife or hobby knife
Step 1: Download and Print
Print or photocopy onto card stock.
Step 2: Cut Out the Pieces
Scissors will be your main tool. The blade can be handy for tight corners.
The fuselage pieces need to be traced onto chipboard and then cut out.
Step 3: Glue Together Main Pieces
The central fuselage piece has the tail fin. Two side pieces are glued to it and must line up precisely.
Step 4: Rudder, Elevator, and Wing
The edge of a ruler is handy for making creases. Use one hand to clamp the card stock (horizontal stabilizers) or chipboard (vertical stabilizer) to the ruler, such that the edge of the ruler is where you want the crease to be. Use your other hand to gently bend the material that overhangs the ruler. The elevator should be raised by about 5 degrees, and can be adjusted after test flights. The rudder should be straight until adjustments to flight are needed.
As explained in the directions, there is a fold at the leading edge of the wing. Fold down and under, and use glue (preferably a glue stick) to bond it to the bottom side of the wing, creating a double layer of card stock.
Step 5: Attach the Tailplane
Use a fair amount of glue. Scrape away the excess and allow this to dry for a few minutes before working with it.
Step 6: Establish Camber and Dihedral
This is another step that is shown in the video.
You can use the edge of a table, desk, or book to camber the wing. Place the wing flat, allowing it to overhang the edge by a couple of millimeters. Apply some pressure with thumb or fingers, pushing the leading edge downward a bit. Use very light pressure so it bends rather than creases. Slide the wing so it overhangs by another millimeter or two. Apply pressure again. Repeat this a few times along the leading edge, and several times along the trailing edge.
Establish a crease for the dihedral angle. Start with a slight angle. Over time, the crease will lose stiffness and the wingtips will want to rise when the plane flies. This can be countered by adding a strip of paper or clear tape, 4 or 5 cm long, across the bottom of the wing.
Step 7: Attach the Wing Pull Tabs
These tabs extend forward, past the leading edge of the wing. They help stabilize the dihedral angle and add nose weight.
Use glue and attach the tabs to the centers of the wings. They should taper outward toward the nose. Again, this step is shown in the video.
Two wing shapes are in the plans. If you're going to come up with your own wing designs, try to make them so the median chord is in the same position (relative to the nose of the airplane) as the other wings.
Step 8: Place Wing and Nose Cap
Once everything has dried for 15 minutes, you can try sliding one of the wings into the fuselage. Hopefully it will be held by friction. If the slot is too narrow, use some sand paper to widen it. If it is too wide, add a layer of card stock to the pull tab to make it thicker.
If desired, use a marker to shade in a ring on the nose cap, giving the visual cue for an old radial-engine.
Slide the cap over the nose. This is the primary source of nose weight, so its position will affect the flights of the plane. With the versions I have made, the CG is correct when the cap is on just far enough to grip the nose securely.
Step 9: Flights and Adjustments
Sight down the nose and tail of the plane to check for straightness of the fuselage and symmetry of the wings. Make corrections with a light touch.
Conduct some test flights indoors. Throw the plane straight and level, using just a little force. Try to throw it as consistently as possible. Use the elevator to influence the pitch (nose up or nose down), or try sliding the nose cap a little forward or back to change the CG.
Keep in mind that the nose cap will get pushed back by collisions. Make a little pencil mark on the side of the fuselage, once you've found a good position for it, so you can quickly adjust it after a crash.
Use the rudder to influence the plane's yaw. A tad to the left, and it will tend to go left. A tad the the right, and it will go right.
If the plane is wheeling over to the right or left, and crashing nose first into the ground, it is probably tail heavy. If so, the nose cap needs to be further forward, or you may need to just add some nose weight.
CAUTION! Plane may cause eye injury. Be careful when throwing it. If other people are around, allow a safe distance.