Coroplast Political Sign Twin Boom RC Airplane - V1

I have piloted the first successful flight of my experimental RC plane made from easily obtained parts.

Now I will share my creation so others may experiment with the design themselves.

Finished Product

Video of short successful flight into tree.

Control Demo Video

After crashing a balsa R/C airplane and contemplating the repair time, I decided I could make an entirely new airplane which would be much easier to repair in the event of unplanned ground contact.

There are quite a few resources out there for aspiring R/C builders:

The SPAD (Simple Plastic Airplane Design) Forum on rcgroups.com
http://www.rcgroups.com/spad-simple-plastic-airplane-designs-176/

SPAD to the Bone (their websites are a little scattered after they lost "spadtothebone.com")
http://spadtothebone.net/ or http://www.spadtothebone.org/ or http://spadworld.net/forum/

Ed's Experimental Airlines Youtube Channel - Dollar Tree Foamboard Planes
http://www.youtube.com/user/ExperimentalAirlines

A great source for cheap RC supplies
www.hobbyking.com

Design Constraints

1. Wing made from one standard 18"x24" 4mm coroplast campaign sign.
2. Tail attached using a standard 48" dowel, cut in half.
3. Must work with my existing R/C setup (2 servos, ESC and LiPo Battery)

Having these constraints actually made the project a lot more fun for me and kept it from getting too expensive.

Supplies

Body

1. One standard 18"x24" 4mm corrugated plastic campaign sign 
2. Two 48" long,  0.21" diameter wooden dowels. (this is just the common size, for this project you only really need  two 24" and one 36" dowel)
   OPTIONAL - Two 48" long carbon fiber tubes instead (much stronger)
   OPTIONAL - Use arrow shafts, they are between 22 and 30" and you can sometimes find free ones
3. One small plastic Odwalla bottle
4. 4mm thick square piece of wood to fit in bottom of Odwalla bottle
5. A bunch of zip ties
6. Double sided foam tape
   
   Electronics/Control/Prop
   
   
7. ESC (Electronic Speed Controller) (20 Amp)
8. Electric Motor (1400kv Brushless Outrunner)
9. Plastic Prop (10x9)
10. Three metal pushrods w/ threaded ends and clevises (18"x2mm diameter)
11. Three nylon control horns with screws
12. Three linkage stoppers (or you can just bend the pushrods into the holes)
13. Two servo arms
14. Two servos (Futuba)
15. Receiver (Futuba)
16. Transmitter (Futuba)
17. LiPo Battery (Zippy 2200 30C 3S)
18. LiPo Charger/Balancer (Thunder AC6)

You will need to figure out how to hook the LiPo, ESC, Motor, Receiver, and Servos together yourself. I soldered old molex connectors to the LiPo and used a lamp power switch.

Overview

CAD diagram showing the main dimensions, structural components of the airplane, and proper orientation of corrugated fluting.

Here is a link to a PDF of the above diagram: https://www.dropbox.com/s/b6qhd1a3k055w8e/CampaignSignPlane4.pdf

Construction Directions

• Cut wings and tail from campaign sign (you may be able to use just one sign if you are careful)
• Cut two 24" dowels and one 36" dowel
• Cut along top flute approx 1.5" back from leading edge of main wings
• Bend leading edge up and back
• Fasten the main wing together using the 36" dowel and zip ties
• Fasten main wing back along centerline using zip ties, possibly adding a thin balsa rectangle for strength
• Make elevator and ailerons by cutting wedges out from the sides and making hinges as shown below 
• Tuck the 24" dowels under the 36" dowel
• Fasten 24" dowels to wing and tail using zip ties
• Cut a hatch from the Odwalla bottle
• Place wood inside bottom of bottle
• Fasten motor to wood using 4 screws through outside bottom of bottle, making sure it spins easily (you may need a spacer of some sort, depending on your motor)
• Fasten bottle to main wing using zip ties
• Screw control horns on to ailerons and elevator
• Fasten the top wing elevator servo using zip ties
• Fasten the under wing aileron servo using zip ties
• Cut pushrods to appropriate sizes and attach clevises
• Attach pushrods to servos and control horns
• Fasten receiver and ESC using double stick tape/zip ties
• Switch main power off, connect all electronics
• Push LiPo battery into Odwalla bottle so that it will not come out in flight
• Perform prop test in a safe environment so as not to cause damage/injury in event of failure
• Calibrate servos
• Fly!

Detail of a wire I added across top to keep the wing rigid

Detail of aileron and zip tie

Detail of elevator control horn and clevis

Vertical stabilizers added by cutting notches in tail and fins

Detail of motor mount

Odwalla bottle battery housing

Under wing aileron servo with protective bottle

Under wing aileron servo

Detail of under wing aileron control horn and clevis

Cutting Hinges into Corrugated Plastic

Because of the side to side orientation of the fluting I was able to create ailerons and an elevator without any additional hardware by carefully cutting the plastic along alternating flutes.

Use a knife or scissors to slice down the flutes, it is tricky at first, but goes smoothly once you get the hang of it.

CAD diagram of coro hinges