Tethered Airplane

Everyone has a piece inside of them intrigued with the concept of flight. The feeling of soaring through fluffy clouds in the sky, or watching a drone zipping through the air comes to mind. By following these step-by-step instructions you too can achieve flight on a budget. The tethered airplane is a fun and engaging project for people of all ages to create and enjoy. Keep in mind it may take some elbow grease and a few minutes of your time, but rest assured you'll be in the air in no time.

Machinery

*3D Printer*

A Ditto Pro 3D printer made by Tinkerine was used as the main printer. Any other similar or better printers should be able to get the job done.

*Laser Printer*

Trotec's Speedy 100 laser engraver and cutter was used to print all the required laser-printed pieces. However, you can experiment with new ways to mimic the job of the laser printer if one isn't available.

Materials

• Wooden Dowel (12.3mm Diameter, 56cm Length)
• Foam Board (Pink Insulation Foam)
• D/C Motor (24V, 50 000RPM)
• Packing Tape
• Electrical Wire
• Rigid Wire
• 3mm Plain MDF Board
• 3/16" Corrugated Plastic Sheets
• 2mm Drill Bit
• Vex IQ Bolt
• Vex IQ Nut

Tools

• Hot Foam Knife (Nichrome Wire)
• 32/2 Allen Key
• Vice
• Drill
• Tether Tower (Modified Lathe Chuck)
• Power Supply

Download the .dwg file attached and laser print the Airfoil Guides on a 3mm Plain MDF board.

Cut your foam board into a rectangular shape with the dimensions of 23.5 inches in length and 7.5 inches in width. Make sure the thickness of your foam board is at least 1.5 inches.

Attach the upper set of airfoil guides onto each end of a piece of wood with exactly the same length as your foam and secure the wood in a vice. Your foam board should fit snuggly in between the guides, but you should also use double-sided tape underneath the foam board to be sure that it will not move as you're cutting.

Once set up, grab your hot foam knife or other foam cutter technology, and apply a maximum current and 24 volts to the cutter using a power supply. Wait for the wire to heat up before sliding the cutter slowly and evenly along the airfoil guides to cut through the foam board. Remove the upper set of airfoil guides and attach the lower set. Get set again, and proceed to cut.

After both cuts have finished trim away any unwanted foam on the trailing edge of your wing.

Using 80, 100, 120, and 180 grit sandpaper sand all surfaces of the wing in the order of the values listed. Sanding the wing will help reduce any imperfections which may cause drag when in flight. After the wing has been sanded to your perfection, encase the upper and lower surfaces with strips of packing tape. Since packing tape is very smooth it will reduce the wing's friction with air while flying, reducing drag.

Using the RearWing file attached laser print the horizontal stabilizer on a 3/16" corrugated plastic sheet. There is an option to add a vertical stabilizer, so if you wish to add a vertical stabilizer print said piece.

Print all four 3D parts on a 3D printer. Depending on your printer and filament you may need to scale these models up. Scaling up by 7% seemed to do the trick to compensate for the expansion of the plastics.

You may want to print 3 or more propellers due to the fact you might not succeed in flying on your first attempt and may suffer from some broken propellers.

Loosely fit all the parts together and attach them to the main body of the aircraft. Slide your finger along the body to where the whole craft can balance on your finger. Mark this point on the wooden dowl, it will be purposeful later.

Put the D/C motor into the motor mount casing and tighten using two 8-32 Hex Drive 3/8" bolts and two 8-32 Keps Nuts.

Drill out the center of an 8-32 Hex Drive 1/2" bolt with a 2mm drill bit and screw it into the propeller. Then attach the bolt to the motor by applying super glue inside the bolt and pushing it onto the output shaft of the motor.

Find an old metal coat hanger or some sort of rigid wire, and bend it into a triangular shape big enough to stretch out and beneath your propeller. This vital piece will hopefully protect your propeller from many crash landings.

Using hot glue, set all the pieces into place. First, attach the motor mount and motor, then the wing mount a 1/2" in front of where your center of gravity mark is. Next, attach the horizontal stabilizer to the tail mount, and the tail mount to the body.

Finally, measure the wing and mark a mid-point along its length and place the wing on the wing mount to where the mid-point aligns with the center of the plane. Apply glue along the ridge of the wing mount, and in the designated holes.

Attach the landing gear directly behind the motor mount. Have the landing gear angled outward towards the front of the plane.

Tape down the motor wires to the leading edge of the wing. Have the connecter flush with the edge of the wing.

Let your plane set and dry.

A specially made tether tower made of an old lathe chuck was used in the photo. However, you may source your tower any way you wish.

Setting up the tower consists of raising it off of the ground, and applying a source of power to its positive and negative wires. A power supply works best for being able to control how much current and how many volts are applied.

Connect your plane to the tether and set your power supply to 3 amps and 0 volts. Slowly increase the volts to where the propeller starts to spin. You should feel the air being displaced behind the propeller, if you do not, reverse the polarity of your wires. Once you know the airplane is producing thrust in the right direction, get a friend to man the power supply while you prepare yourself for launch. Be sure to wear your safety glasses because when it does launch, if something goes wrong your eyes will be safe.

Have one person holding the tethered airplane taught and perpendicular horizontally to the tether tower, and the other person slowly increasing the volts. When the power supply reaches around 20 volts the person with the airplane should throw it while trying to stay on the same plane as the tether tower while keeping ample tension on the line.

With the plane in the air, the second person's job starts. By controlling the current you can control how the airplane acts. When the plane starts dipping, subtle adjustments need to be made to counter said movements. At 1.5 amps and 24 volts, the airplane flew on one plane without needing assistance from the power supply operator.

Experiment with your plane and its settings to try to optimize its flight.