We built this model plane last year. It took me about 10 days of laboring. Best of all, it flies!
To start with, order these electric components from HobbyKing in Hong Kong:
- Motor: Turnigy 2204-14T 19g Outrunner. It should be able to generate 250g or 9oz of thrust on a 2S (7v) Lipo battery. Since I used only consumer NiMH, the thrust is about only 70g.
- Propellers: GWS 8×4.3 propeller that is recommended for the motor.
- ESC: Turnigy Plush 6A Speed Control. To generate the max thrust the motor needs 7A current. But I intended only to use 4 AAA batteries, the batter can only output max about 3A, thus a 6A ESC is good enough.
- Servos: 3 of HXT 900 9g servos.
Remote Controller TX/RX
Another important component, the remote control from HobbyPartz:
- Exceed-RC 6 Channel Radio Control System with Receiver. The manufacturer of this model is actually Fly-Sky of China. It should be identical to the cheaper HobbyKing 6A remote control. And also the Turborix 6a. Thus the software for all those models should work. There is also a model called Fly-Sky CT6B on the HobbyPartz web page, I believe it is a later model.
To build the plane, order some balsa wood and aluminum pipes from local hobby stores. Build the plane body and mount the motor and servos to the body. Also attach the tail elevator and rudder. See the picture:
The body is centered around a long aluminum pipe. Glue some small balsa wood pieces in various shapes to form mounting platforms to attach other parts onto the body. Use hot glue to attach fixed parts like servo, elevator and rudder. Use rubber rings to attach removable parts, like the ESC, receiver, battery, and wing.
The wing is two pieces of 12×8-inch cell foam sheets. They are cut off two pieces of Cellfoam 88 by Midwest Products bought from a local hobby store, very much like this one on Amazon.
Soak small pieces of balsa wood in water, bend them at the center and let it dry when keeping it in the bent shape. Then tape the two wings to this center wood piece so the wings go up at the tips to form a so-called dihedral. See the picture to understand how exactly this is done.
Assembly and Details
The plane looked from front:
The tail looks:
Two types of NiMH batteries have been used. One is the consumer Energizer AAA e2 850mAH. The Energizer web site has a technical document showing a discharging curve with up to 4C discharging rate. Let’s interpret it as max 4C discharging rate. Thus 4 * 850 = 3400mA. This should be the max current they are able to supply. At 4C discharging current, the battery output voltage is about 1.1V per cell at 25% capacity. Thus, assume the worst case battery condition is when you fly till 75% discharged, the supply with 4 cell can provide about 4.4V. This is well the minimum for most semiconductor chips. But the Turnigy 6A ESC requires about min 5.5V supply, thus the voltage regulator is removed from the ESC. But test shows the max current with this design supplies only 1.7A current, and provide 70g thrust. This thrust is hard to sustain the flight height (it flies lower and lower till hitting the ground). Thus with Energizer consumer battery, eventually 6 cells are used, as seen in the pictures.
With 6 Energizer AAA cells, the flight time is about 15 minutes. With Kan 1/2 AAA, it is about 6 minutes.
To charge the batteries, a Dynam Supermate DC6 from HobbyPartz is used. Any other charger should work too.
Battery – Lipo
The reason we used NiMH was for safety. The major problem with NiMH is the weight. The minor problem is the capacity, thus the flight time.
Lipo is the new trend, and we are going to switch to Lipo this year. With the original Turnigy ESC, a 2-cell Lipo can be used.
Compare the weights: 6 cells AAA 850mAH weigh 3oz, a 2S 800mAH Lipo weighs only half of that. But if you use Lipo, do be very careful when touching/moving/charging them! Pay even more attention after a crash! Do read the Lipo safety instructions carefully and follow all the instructions.
Where to buy: See a separate post for where to buy the stuffs.
Design: Here is the design of this plane.