Introduction: Flexcopter

About: I'm a undergraduate student currently at WPI who loves to tinker around and create projects. Some of the things I've created include: drones, 3D printers, robots, and many others.

Hello all, this instructable will show you how to build the flying machine that combines the technology of a tiltable arm quadcopter and a foam plane. I have experiences with all kinds of airplanes and jets. I have also built tricopters, quadcopters, and H-copter. I usually take apart and build a different kind of UAV (Unmanned aerial vehicle) every time I crash it (from training for flips and tricks). However, this was the hardest I have done since there were no tutorial or anything online that explains any of this stuff. Most of the revisions and configurations did not work (some are shown in this instructable), but this version actually worked very well. This was something new. If you have flown an RC airplane or even a real airplane before, the hardest parts are the lift off and landings. Not many people have built things like this, so I had to experiment a lot. I found a lot of cool maneuvers you can do through experimenting like hovering nose up or even nose down (shown in the video). It provides the benefits of more efficient flight through another lift force from the wings instead of just the propellers. It also has the capability to hover which allows for straight lift off and landings. The tiltable arms are used both to switch into airplane mode and to reduce drag flying it as a quadcopter.

Why it's called Flexcopter is explained in the how it works step (step 23).

It uses Naze32 board so you can expand it even more! (adding GPS, First Person View, On Screen Display, barometer, etc.)

I have created three kinds of flight modes for it since it is hard to manually control everything at once.

  1. Gyro stabilized quadcopter with tilting arms
  2. Airplane mode (without stabilization)
  3. Hybrid of first two

The first two modes can be swapped during flight using a switch in the controller, and the third requires some electronics changes. 3D printed parts are also used to make this project possible.

If you like it, give it some support by voting above!

Step 1: Gather the Parts and Materials

The parts were made from my old trainer plane and quadcopter, feel free to use your own parts and this as reference.


- Lexan

- 2x Aluminum Square Tubing 24"

- Zip ties (large and small)

- Screws and nuts

- Heavy Duty Velcro (HomeDepot)

- Propellers CCW & CW

- Foam Safe Glue


- 4x Motor

- 4x ESC

- Battery and charger (3 cell, 5000mah, 30c)

- 6CH transmitter and reciever

- Servo extension cables (or super glue these)

- 5x Relay

- Naze32 (rev6 recommended, but not required)

- Standard Servo

- Connectors for ESC and Battery

- transmitter controlled switch

- servo stretcher (step 25)


- Foam plane (I used the clouds fly floater jet)

- 3D printed Parts

Tools recommended:

- Allen Keys

- Pliers

- Soldering tools

- Drill

- Super Glue

- Hack Saw

- Sand Paper

- Heat Gun

If you are a DIY person, I highly recommend having a drill press (they are awesome).

Step 2: 3D Printed Pieces

I've used Solidworks to model these pieces and printed them with my 3D printer.

The folder contains older versions, but the newest version only requires:

2x RotateHolder

4x Bushings

4x Spinners

4x PushJoint (not shown in picture)

4x Spacers

The RotateHolderAdjuster is optional if things don't come out exactly as the model

Step 3: How It Works (Pretty Cool)

I used Lexan since it is a very flexible and durable. I realized that people like tricopters over quads because they spin much faster (and some other small things). Quadcopters use momentum to spin, and that isn't too efficient for turning quickly. With the flexible body and a specific motor spin direction, you can get the quadcopter to flex the direction of rotation with a much higher spin rate. Hence, I named it flexcopter.

For example: If you turn right, the CW motors spin faster. With the correct motor spin orientation, you can get the front motors to flex right and back to flex left. This significantly improves the spin rate of the quadcopter

The four motors are tilted by a central pivoting rod powered by a single servo.

Step 4: Old Version

This is the older version of the flexcopter. The motor mount and the weight of the frame was improved. 3D printed motor mounts weren't as strong as I thought they would be for some hard landings. Every time I landed I would hear a loud "crack" :P and I fixed this in the version I'm going to show you. This version the plane was hovering at around 85% throttle, and for a nice maneuverable quad, it should hover at 50%. So I cut down on the aluminum and Lexan usage.

Step 5: Sand and Smoothen the 3D Printed Parts

I used a dremel (or sand paper) to smooth the parts so that the bushing spins smoothly inside the spinner because most printers leave seams on the outside. Then I used a 3mm drill bit to make sure that all the holes in the print fit the 3mm screws.

Step 6: Dimension Reference

Use these drawings as the dimensions for creating the parts in the next few steps. The units are in milimeters.

Step 7: Create the Lexan Parts

I used a table saw in this step, but a jigsaw or hacksaw should work fine (more work).

  • Board 101.6mm x 487.7mm
  • 2x additional structural support beams 10mm x 487.7mm
  • 2x pivoting rod 10mm x 391mm
  • 2x servo horn attachment 10mm x 48mm
    • Then glue the two together
  • Lexan servo mount to your servo dimensions
    • the rotating axle of the servo should be 43.5mm high from the board
    • If you have a servo mount already, just use that with spacers, washers, or standoffs

Step 8: Bend Lexan Peices

Skip this step if you have a servo mount already. However, you should still read this since bending Lexan was very useful in my robotics projects. I bent my mount with clamps and a heat gun for the 90-degree angle. Just blow the heat gun at the joint until the Lexan becomes soft, then fold the Lexan to shape. Make sure you don't overheat it as that can cause the Lexan to bubble.

Step 9: Glue the Strengthening Lexan Pieces

Use super glue to combine the Lexan pieces to the edge of the board. Use epoxy or acrylic glue if you have them laying around. I used 2 layers for my older version, but it is not necessary. Let it set.

Step 10: Drill the Board Holes

The dimensions for the 8 holes of the board are shown in the dimension reference. This secures the two layers of Lexan together.

Step 11: Cut and Drill the Aluminum Beams

Cut 2 pieces of 255.6mm aluminum square tubing. Then drill the 3 holes for the motor mount, mine is 19mm apart with a large hole in the center for the axle. I drilled weight reduction holes in each side the beam 1 inch apart from each other. However, in the end, it only removed 40 grams, which is not much for a lot of work. I would recommend not doing this. If you do, use coolant.

Step 12: Assemble the Beam and Board

First, dry fit the parts on the board with everything screwed in. Make sure the clamp piece in the center is on the side where the motor holes are drilled. Then pull out the bushings and apply super glue on the beam where the bushing sits. Then, quickly push it back in, and also making sure it spins nicely. Let the glue set.

Step 13: Prepare the Airplane

I took out the motor on the trainer plane by splitting the motor mount in half and then gluing the foam back together with foam safe glue. I used the blade of a hacksaw to carefully saw off the top of the airplane into a platform. I made sure the platform is parallel to the table.

Step 14: Sand the Platform on the Airplane

The hacksaw made an uneven surface on the airplane. Sand paper works well to make the surface much smoother.

Step 15: Connect the Two Beams

Use the Lexan sticks, 4 spacers, 4 push joint to connect the two aluminum beams so that they rotate parallelly. Some of my screws were out of size because I ran out of some sizes. The box of screws should have enough.

Step 16: Power It With a Servo

Drill a 3mm hole on the top of the servo horn Lexan piece. Then another bigger one so that the top hole is 27.5mm above the rotating axle of the servo (big enough so that the screw fits). Drill two more holes to screw the horn onto the Lexan.

The servo mount is placed around the center so that the battery has space in front of it. Next, drill two holes on the board and screw the mount in. Then assemble everything without the top screw.

Move all the pieces so that they are all vertical (servo and motors). Then drill a hole on the two Lexan strips using the servo horn mount as reference. Assemble and test the peices.

Step 17: Add the Motors

The brushless motors were screwed in through the holes drilled earlier. Don't tighten it too hard since the threads in the motor are made from aluminum, which can strip.

Step 18: On to the Electronics

My motors already have soldered extensions on them, but it would be easier and better to extend the esc to battery wires. Just make sure they are long enough for the four motors. Then solder all of the bullet connectors to the esc.

Step 19: Solder Power Distribution

I used a larger washer to solder all of the power wires of the esc to one wire for the battery. I had two extra power wires in case I needed it. Then solder the battery connector onto these two wires.

Step 20: Set Up the Naze32 Board

I found this very awesome setup video for the Naze32 rev6, much better than what I can explain in text. From there I'll teach you how to configure it to the flexcopter.

Step 21: Battery and FlightController Attachment

The flight controller was attached through screwing onto a foam block, then velcro was used to attach onto the board. The plastic velcros are awesome for strong removable connections. I personally prefer them over battery straps since it saves hardware from crashing where the battery just falls out instead of breaking the battery mount. The second picture shows the two strips of velcro where I used to put my battery.

Step 22: Wiring Testing

I would highly recommend that you test it out as a quadcopter first before any electronic changes are made. Basically, everything is setup like the video and the diagram above. In the cleanflight software, the flexcopter uses a custom mix for the motors since the QuadX doesn't have the motors spinning in the right direction:

#0: 1.000 -1.000 1.000 -1.000#1: 1.000 -1.000 -1.000 1.000#2: 1.000 1.000 1.000 1.000#3: 1.000 1.000 -1.000 -1.000

  1. Go into CLI
  2. Type "mixer Custom"
  3. then "mmix 0 1 -1 1 1"
  4. "mmix 1 1 -1 -1 -1"
  5. "mmix 2 1 1 1 -1"
  6. "mmix 3 1 1 -1 1"
  7. Then type "save"
  8. It should look something like in the picture above

Then every motor propeller should be switched in the opposite direction CW to CCW and CCW to CW

Now it should work like a normal quad, but with much higher spin rate

Step 23: Attach It to the Plane

I approximated where the quad would go on the airplane, leaving room for all for propellers. Then I drilled 4 holes for large zipties to go through, and they secure the quad from the front and back of the wing.

Step 24: Now for the Harder Wiring Part

Here I have shown a wiring diagram for the in flight mode changing between airplane and quad. I'll explain it next if it is hard to understand.

Step 25: Electronics Explained

What the diagram is trying to show is that you use a receiver controlled switch to activate 5 relays which have the 4 ESC and the servo. The esc is changed from Naze32 board input into receiver controlled so that the throttle controls the 4 motors at the same time instead of individually. Then the servo is switched from being controlled by channel 2 to always forward facing. Most of the wires are signal wires as the power wires can just power everything at all times. The servo stretcher is added so that the tilting mechanism can operate by itself. It is added before channel 2 goes into the naze32 board. It is basically used to change all channel 2 signals to the center,1.5ms, by adjusting the screws. this allows the pitch of the quad only be controlled by the servo.

Step 26: Adjusting Naze32 Board

In the configuration tab, enable servo tilt. This changes the output of the board like this:

1 - servo

2 - servo

3 - ESC

4 - ESC

5 - ESC

6 - ESC

This way when the relay is switched into airplane mode, the naze32 board can send a constant signal to the servo

The next picture shows the servo setup for it. I have also reversed my Aux2 channel for convenience.

Step 27: Tips for Wiring

A lot of the connection can be made by taking the female plug for the servo out of its casing and inserting it into other connections. This helps to reduce the amount of soldering needed.

Step 28: Calibration

For the airplane mode to work, the front and back motors should be aligned almost perfectly parallel or the airplane will dive down or do a backflip. My plane crashed many times trying to switch between the modes, and later finally found that it's the motors not spinning parallelly. If you see your plane about to go out of control, just quickly flip the self-level switch back on. It should help save it or make it a softer landing.

Step 29: The Hybrid Mode

The hybrid mode I played around with was plugging the tilting servo into AUX1 Channel to a 3 way switch on my transmitter. And the pitch of the quad was controlled directly. So it can fly forward, hover, and backwards all with the gyro stabilised. I found this mode fun to play with, but not that efficient in terms of battery usage.

Step 30: Done! Video Coming Soon

Thanks for reading my instructable!

3D Printing Contest 2016

Participated in the
3D Printing Contest 2016

Make It Fly Contest 2016

Participated in the
Make It Fly Contest 2016

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