to make an inexpensive solar RC plane that can fly by using only energy from the sun to run motors.
Making and flying this plane requires experience in flying and building of RC planes. So this is not best plane for first timers. If you are making RC plane for the first time and chose this plane for it than it is recommended to take help of some person having good experience with RC planes.
[60$ cost do not include cost of transmitter – receiver and tools]
It is highly recommended to view these videos for better understanding.
Step 1: Collect Required Material:
Solar cells: 8 no’s of SunPower C60 cells (160₹ *8=1280₹) [buy some extra cells]
battery: 500mah 3.7V LiPo (300₹)
Servo motor: 3.9g servo (3 no’s) (250*3=750₹)
Coreless dc geared motor: 2 no’s (with counter rotating prop) (400*2=800₹)
dapron sheet: 1 sheet of 5mm (200₹)
carbon rod: 2 no’s 5mm thickness (2*150=300₹)
wire for electric connection (50₹)
note: 1$=~ 65₹
soldering kit (wire, flux)
adhesive for dapron
here, It is possible to cut even more cost if you have old quadcopter from which you can extract battery and motors.
Step 2: Overall Plan of Plane:
During making of this plane, we would always follow this plan. So keep a copy of it during the making.
Step 3: Preparing Wing:
Here we have used a ishii airfoil type wing section. It has some flat top and curved bottom surface. The main reason for using this airfoil is ease to attach solar cells to the top of the wing. Follow the dimensions given in plan or you can even modify it for improvement. Use carbon rod for reinforcement of wing. This is very important because if the wing is not stiff enough it tend to bend which will crack cells.
Same way makes tail section using plan. This section is directly copied from tiny trainer by flight test. Follow same procedure that we use for making a typical plane.
so the procedure is:
- Stick two layers of foam board
- Sand it to five it shape of the airfoil
- Give it proper reinforcement
way make tail section using plan. This section is directly copied from tiny trainer by flight test. Follow same procedure that we use for making a typical plane.
Step 4: Preparing Solar Cells:
Each solar cell can provide 0.55Volts and 6amp current max. so that’s way it can provide maximum 3 watts of energy. The motors we are using 3.7 to 4 volts of supply. To generate 4 volts of supply we need 8 solar cells in series that way we can have 4 volts of supply.
We can see a point in both sides of cells. This is a place where we need to apply some solder flux and also some solder. And that connect all of these in series (refer figure). During this procedure take care of polarity. Otherwise, there won't be any power coming out.
Step 5: Control Surfaces:
we are controlling the rudder and both elevator using a single servo motor. The only reason of doing so is to reduce weight, which is the key element of this project. There is another servo which controls the elevator. I have used 1mm carbon rod as pushrod to move control surfaces.
Here one control element which is different from typical RC plane is throttle. As we are using some sort of digital control which can either turn on or off our motor. A switch is operated by a servo motor which connects or breaks circuit in-between coreless motor and solar panel. That’s how we can turn on or off a motor.
here our control surfaces are operated by battery power. so power loss will not result in crash. power loss may be the result of atmosphere change or high tilt angle of plane.
Step 6: Attaching Motor:
To empower our plane we have two coreless dc motor which is extracted from toy quadcopter. These two motors are connected to each other in parallel such that after connecting this motor to solar panel both motor rotates in opposite direction to each other. And also attach prop such that both push air backward.
attaching a motor to the wing is very easy and strength forward. just make a cut on wing apply some amount of hot glue. as these motor are very low thrust motor hot glue works perfectly.
Step 7: Preparing Plane for Flying:
connect all servo motors to the receiver check weight and thrust of the plane. in my case weight was 250g and thrust was around 50-80g.
than the most important part is to set CG. there should be 5cm distance in between the front end of the wing and CG. this "5cm" is just a starting point to set CG precisely. refine the position of it by doing some trail and error.
Step 8: Conclusion:
things to keep in mind:
• A good stiffness of wing is must, without it cells may get easily damaged during hard landing.
• also, apply some dihedral at the tip for easy control.
• stick cells properly. there must not any gap in between cells and wing, that introduces extra drag.
• use a good amount of glue during sticking cells, vibrations of the wing can easily loose wing.
this plane flies nice even in mild wind. but difficult to fly at the slight high-speed wind. it is also difficult to fly it if the day is cloudy.
• this plane has low thrust (not always 70g) so it can not gain height very fast but takes the time to do so. so be patient and rise it slowly and smoothly.
• during turning, sudden power drop can be felt. so be prepared for that.
• this ON/OFF control of motor can not give a good feel of flying but still works fine.
• we are using one battery to control servos which need to be charged by electric charger which is not very good for " solar plane" . it must charge from solar energy itself.