I would like to convert a very cheap foam toy plane into a radio control plane
- The foam plane (2 euros)
- 2 Micro servos
- Very small motor
- 2 Amp motor controller
- A RC receiver and a transmitter (of course)
- Some wood
- And thin carbon tubes
The most important here is to ensure:
- It can fly
- The final weight of the plane cannot be too much
- Respect the current mass center
The first concept is to understand that the most important in a plane is how many grams per cm2 of wing. This is crucial because if you have to support more grams you’ll need more speed.
For instance the plane weight is 45 grams. The both wings surface is 342 cm2. Then each cm2 has to support 5.3 grams per cm2
So, as consequence of that is very important to choose the correct motor. The motor has to have the enough power to impulse the plane with the require speed to create a pressure in the wings to maintain the weight. If we choose a small motor, it is not going to achieve the required speed. If we choose a better motor is going to be bigger and the weight of entire plane is going to increase. But also related is the battery. A bigger motor requires a bigger battery to ensure enough flying time and also the enough discharge capacity to supply the intensity that this motor is going to require.
- Motor with controller: 30.5 grams
- Battery 45 grams
- Servos: 2 of 8.8 grams and other of 5.7 grams
Then the selection means extra 98.8 grams. But the plane has to plumbs to stabilize that we can remove (18.8 grams). then the final result is extra 80 grams
The second concept is where to put the things, because we have to respect the mass center should be at 1/3 of the beginning of the wing. To ensure that before doing nothing to the plane, I measured it using a home-made balance. Of course the motor should be placed on the front. But we can remove one or two centimeters of the nose of the plane to move the weight to the wing. After that the position of the battery should be the last step because is the heaviest element and is going to determine the mass center.
This is the final result.
I also included a big aileron to increase some wing surface