INTRODUCTION
Hi people, my name is Anish Natekar I am a 2nd-year undergraduate student at IIT Goa majoring in Computer Science & Engineering and I recently build my first RC plane (FT Tiny Trainer) during my summer vacations using my research internship stipend. I will be telling you about the complete process of building an affordable RC plane in India in this blog.
Note: This blog is not sponsored by Flite Test, Vortex RC, or anyone whose content I have mentioned in the blog.
So what all kinds of RC plane designs are there and what should I build?
Take a look at this video by Flite Test explaining exactly what to pick.
In my case, I made the Flite Test Tiny Trainer. Here is a video by Flite Test about how to build the FT Tiny Trainer.
Some other beginner-friendly planes you might be interested in can be — FT Simple Cub, FT Simple Storch, FT Explorer, FT simple Soarer, etc.
Where can I get the designs from?
All the build plans will be given in the description section of the flite test video of the plane you want to build. For example, you can find the plans for the tiny trainer over here — FT_tiny_trainer tiled_plans.
Note: the tiled plans are the ones that are supposed to be printed on A4 size sheets whereas the normal plans are for a much larger paper.
What do these designs contain?
The above plans contain parts for the:
- Fuselage (Body)
- Vertical Stabilizer (Tail) + Rudder
- Horizontal Stabilizer + Elevators
- A 3ft Wing with Ailerons and a Dihedral ( up to 4 channel wing)
- A 3ft Wing without Ailerons and a Polyhedral (up to 3 channel wing)
- A Chuck glider Nose (2 or 3 channel) for unpowered flight.
- A motor glider Nose (3 or 4 channels) for powered flight.
- Something that is not included but has to be built is a mini power pod.
Materials
All Flite Test planes are made using 5mm thick foam board i.e. Dollar Tree foamboard or Adam’s Readi boards but in India, we do not have these companies or their products so it is important to get to know about what kind of foam is required.
XPS (Extruded Polystyrene, Depron is an XPS foam) — These kinds of foam are lightweight and easy to cut and fold. Vortex RC sells 5mm thick paper laminated foam boards called “Flight Board Pro” for building Flite Test models on their website — https://www.vortex-rc.com/product-category/building-materials/ You can buy 5 boards of 30inch by 20inch and 5mm thickness for Rs 455 to Rs 599 and it should be enough to build the FT tiny trainer plane. You can also get them from any other supplier near you. Flite Board Pro — FliteBoard Pro — Lightweight Paper Laminated Foamboard — Ideal for making DIY Radio Control Planes.
Warning: Polystyrene is not Cyanoacrylate (CA) safe so you have to glue it with a glue gun/hot glue or foam-safe CA glue. CA glue will dissolve Polystyrene foam leaving a big hole in the board.
EPP (Expanded Polypropylene) foam boards are strong, flexible, and lightweight. These come in blocks that are used for hot wire cutting parts of planes as well as sheets for making planes like the Flite Test models. This foam is Cyanoacrylate safe so you can use glues like Feviquick 203 or you can always use hot glue. This foam might be more expensive compared to polystyrene foam. Here is a video about EPP — EPP ( Expanded PolyPropylene ) Foam Blocks in India — Vortex-RC
EPS (Expanded polystyrene, low-density EPS is what we usually cal styrofoam) is a lightweight foam. This usually comes in blocks that are to be cut using a hot wire cutter but low-density EPS might not be suitable as 5mm thin sheets as it might break easily. When using this kind of foam you might consider reinforcing it using cello tape or lamination. Learn more about EPS from this video — All about EPS ( Expanded PolyStyrene ) Foam
Warning: Polystyrene is not Cyanoacrylate (CA) safe so you have to glue it with a glue gun/hot glue or foam-safe CA glue. CA glue will dissolve Polystyrene foam leaving a big hole in the board.
Coroplast sheets (plastic corrugated sheet) This is another lightweight material used to build model planes but the building techniques involved are different because unlike foam that is structurally isotropic in nature Corosheets are structurally anisotropic. Here is a video about building planes with Corosheets- How to build an RC airplane with COROSHEET
Balsa wood is a material that is heavily used in building airplane models for a long time but the designs for building balsa wood planes are different from that of foam board planes. Balsa wood is used to build a structural skeleton for planes, unlike foam board which is used to build a structural exoskeleton for RC planes. Learn more about Balsa — Premium AAA Grade Balsa Sheets, Sticks, and dowels available through Vortex-RC.com
Corrugated Cardboard used in boxes can be used but to get 5mm thickness you will have to stick multiple sheets over each other. Corrugated cardboard is also structurally anisotropic so you should be following some specific building techniques mentioned in the coroplast video. Cardboard is also not very strong or ware resistant so it should be laminated by cello tape to add to its strength as well as water resistance.
You can use other kinds of 5 mm thick foam/material if they are light enough to keep the total weight of the plane low enough that it can take off given the thrust of your motor and lift of its wings. You can compare it with the density of flight board pro material and make sure that it is not more than 2 times the density of flight board pro. I myself used a heavier foam board material I bought at a local vinyl printing shop.
Glues/Adhesives
When building an RC plane the most common kinds of glue that are used are Hot glue/Glue gun glue and Cyanoacrylate glue (CA) like Feviquick. Resin-based glues can also be used like Araldite but get the 5-minute setting ones. Cello tape is also really useful to reinforce parts of your plane, make it water resistant and fix any broken parts if you crash. Double-sided tape by 3M company is good to stick servos to the body of the plane as they hold the servos very strongly but remember to remove the stickers on the surface of the servos and you can use glues like Fevibond or Feviquick (Cyanoacrylate adhesive) around the of the servo for a little extra adhesion. Zip ties are useful in larger planes to reinforce landing gear, manage all electrical wiring inside the plane, etc.
Miscellaneous
Icecream sticks are useful to reinforce parts of your plane, fix broken parts, mount your motor to your plane body using screws and make the linkages for the control surfaces of your plane.
1mm to 1.5mm diameter steel rods are used to make the push rods of your plane that connect the servo arm to the linkages on your control surfaces. I wouldn't recommend going beyond 1.5mm diameter as cutting the wire becomes really difficult later.
2mm thick diameter wire is used to make your landing gears as it can handle more weight but it is difficult to cut and will require good wire cutters. Landing gear will also require small tires that can be built using foam or you can buy small plastic ones from a store.
Wooden skewers are used to mount the wing to the body via rubber bands giving which allows for the wing to be removed and stored while commuting to save space.
Thick rubber bands are used to mount the wing to the body using the wooden skewers this holds the wing strongly and allows for some flexibility to avoid damage during a rough landing.
Cost of materials
If you choose XPS foam or a material with a similar cost the total cost of materials can be between Rs 1000 to 2000 for a flight test RC plane like the Tiny Trainer depending on your local rates and what you might already have at home.
Electronics
Electric is the preferred mode of power for an RC plane, especially for beginners as fuels like nitro or gas might not be available all the time near you whereas you can charge your battery from your house and various other reasons.
What are the components required to build this plane?
Motor: A BLDC (Brushless DC) motor is preferred for good RC planes, drones, cars, etc. BLDC motors have a kV rating which tells how much RPM they can give per Volt applied to them. These motors are usually bought in a set with their respective propeller and ESC to give the optimal performance for example I got a set with a cheap unbranded 2212/10t 1400 kV BLDC motor, 30A rated Simonk ESC and a pair of 1045 (10 inches) propellers.
ESC: Electronic Speed Controller allows you to control the speed of the motor by varying a PPM (Pulse Width Modulation) signal given by your transmitter-receiver. The ESC has a max current rating on them specifying the max limit of current being pulled by the motor and if the motor pulls more current then it will burn the ESC. I got the 30A rated Simonk ESC with a 1400kV motor and 10inch prop but I wouldn’t recommend flying on full throttle as this can pull more than 30A of current resulting in the risk of the ESC catching fire. Some precaution I took was limiting the max throttle to 80% in the RC transmitter software, you can also just get an 8inch prop instead of 10inch as it pushes less air and acts as a smaller load on the motor, or get a 1000kV motor with a 10inch prop instead of a 1400kV motor as it will have a lower RPM and more torque reducing the current drawn for pushing air.
Battery: RC planes mostly use Lipo batteries as they are lightweight and can discharge a large amount of current required by the motor to keep the plane in the air. Lipo batteries are dangerous and you should be cautious when handling them. When charging never overcharge your batteries and stop charging when the total voltage reaches 4.2V per cell which for a 3S (3 cells connected in series) Lipo will be a total of 12.6V. Always charge your batteries at a low rate of around 1C using a special type of charger called a balance charger (if your battery capacity is 1000mAh then 1C is 1A or if your battery capacity is 2000mAh then 1C is 2A) manufacturers of the battery will have a limit for the maximum charging rate i.e. around 3C but for a longer lifespan 1C is the recommended rate of chagrin your Lipo batteries (i.e. it will take about an hour to fully charge). When discharging (flying your plane) please make sure that the maximum battery discharge rates are much higher than the maximum current that the motor can pull from it and make sure that you don’t go below 3.5V per cell as it can damage the battery and reduce its lifespan. If your battery is puffed up please do not use it and if it is puffed to its limits you will have to discharge it to 0V and go burry it somewhere as it is non-recyclable and can explode on any further use. When flying be careful of crashing as if any sharp object is able to pierce the battery then it will immediately catch on fire because when the packaging of the battery opens up due to cuts or being puffed up it exposes the thin Li sheets inside to air that has oxygen and moisture in it. Li is one of the most reactive metals so it reacts with water explosively giving a lilac/purple colored flame in a self-sustaining reaction i.e. it can continue to burn in environments without oxygen like underwater because the reaction generates oxygen. There are many videos of people intensionally causing Lipo batteries to explode to show how dangerous it can be. Flite Test: RC Planes for Beginners: Batteries and Safety — Beginner Series — Ep. 7
In my case, I bought a 3S 1000mAh 30C/60C Lipo battery from the Orange brand which is a common and well-known brand in India. The 30C is the maximum constant discharge rate of the battery which means that it can give a maximum constant current of about 30A and 60C is the maximum discontinuous/pulse discharge rate meaning that it can in certain situations give up to 60A for a very short amount of time. This is sufficient for my use case as the motor draws a maximum of 15A to 20A on 80% throttle generating 800g of thrust which is much more than required for a 400g to 500g plane to lift off.
Note: When storing your batteries during the off-season for a long duration make sure that they are always around a storage voltage of 3.7V per cell (11.1V total) and never go below 3.5V per cell as even when sitting around batteries lose voltage by discharging through the air slowly and various other reason so please always monitor your battery voltages regularly. Never use a battery that has a voltage of 3.0V or lower per cell as it will start to puff up soon.
PS: I might have scared most people by now but Lithium batteries like Lipo and Lion are used in many electronics and if treated well they work fine and never catch on fire. In the case of batteries get a good branded Lipo as with a brand comes reliability also considers buying a fireproof Lipo safe storage bag for storing your batteries in your house.
Battery Charger: The Lipo battery has to be charged using a balance charger that makes sure that all cells in a multicell Lipo battery while charging have almost equal potential differences. I bought a cheap 2S + 3S Lipo battery charger called the IMAX RC B3 pro balance charger from amazon. This charger charges at a constant rate of 0.8A which means for my 1000mAh Lipo battery it will charge at a rate of 0.8C.
Note: If you want to get into the hobby for the long run then I would recommend spending more on a better charger that is customizable and allows you to change the rate of charging while displaying the voltage details of your battery on a display.
Battery Voltage Checker: monitoring the voltage of your Lipo is extremely important as stated above that is why if you don’t have any tool to measure the voltage of your Lipo you should get a Lipo battery Voltage Checker. I got a pair of cheap Lipo voltage checkers from amazon,
XT60 to T adaptor: In my case, the plug of my Lipo and the plug of my ESC were of different types so got myself an adaptor to connect my battery to the ESC. The other alternative was switching the plug on my ESC to XT60 by desoldering it as well but I didn’t have a soldering rod with me at the moment.
Note: If you don’t want to get this adaptor and change the plug on either your ESC or Battery I would tell you to change the ESC plug over the battery plug as during the process of changing the battery plug if you short the battery by mistake it will result in a spark and the Lipo may not be usable again, Plus the XT60 connectors that are are on high discharge Lipo batteries are much better than the T connectors on some ESCs.
Servos: Servo motors are used to control the control surfaces of the plane allowing it to maneuver in the air about the three axes roll, pitch and yaw. I had a few sg90 9g micro servos already with me but Flight Test recommends using smaller 5g servos. You should still be able to fit 9g servos in the fuselage of the Tiny Trainer plane. In India, 9g servos are the most common ones and their prices are also lesser than 5g ones so you can use them if you like.
Transmitter + Receiver: These allow you to communicate with the plane from a large distance using Radio waves within a legal frequency of operation. The transmitter-receiver that I got was the Fly Sky CT-6B 6 channel 2.4 GHz <20dbm computer programmable transmitter-receiver. This is the cheapest branded 6-channel transmitter-receiver system I could find and it works well for RC planes, quadcopters, and cars. This transmitter says it works up to a max range of 500m to 1km within line of sight but you should not be flying above a height of 200m for many reasons that include low visibility and Indian Civil Aviation laws. This transmitter is an old model and requires 8 AA batteries to operate gives enough power for 7–8 flights that are not too much so If possible do consider upgrading to the newer FS i6 6 channel transmitter models by Fly Sky if you intend to fly for a long time and buy rechargeable AA batteries for your transmitter and a charger as well. This transmitter has 3 mixes allowing support for quadcopters, delta wing aircraft, flaperon support, etc.
Cost of Electronics
The electronic part I used can be bought on websites like robu.in and amazon.in for a total amount between Rs 6000 to Rs 6300 with half the cost coming from just the transmitter-receiver system. robu.in is a good website that delivers electronics at great prices and fast as well. They also have offered during off seasons or stock clearances resulting in discounts on various electronics and kits.
Mindset when Flying RC
When building and Flying RC always double-check and take necessary precautions when performing tests and flying as crashing is also a huge part of the hobby but because you have built your plane from scratch you have the advantage of knowing how to repair it and there are various sources on the internet to help you do so and keep you in the hobby for a long term.
Legal Restrictions
In India a few years ago the Civil Aviation department included RC planes under the drone category requiring any RC plane or RC quadcopter weighing more than 2Kg total takeoff weight to be registered and will require a license to operate. This plane weighs about 500g or less so it can be flown without any license within green zones i.e. areas more than 5km away from the nearest airport and below a height of 200m as above 200m is considered a yellow zone that requires permission to fly in. Please do take precautions before flying, for example, making sure that there is enough open space to clearly fly within line of sight, and in case of a crash it should not damage life and property. Having another person beside you can help make sure that you are not disturbed while controlling the plane in the air as once it is in the air you have to constantly be in control till you land it.
Building
The instruction for building the plane is provided in the flight test video Flite Test | Tiny Trainer BUILD. It mentions all techniques used to build this plane for example. A (above) folds, B (below) folds, Z bends for push rods, modified Z bends, score cuts, bevel cuts, dihedral, polyhedral, C.G. balancing, etc. So take your time going through the video as many times as you like.
I have not exactly used some of their components so I will be sharing my modifications in the Testing section. and some other useful content as well.
Testing
So I did mention that I built the Tiny Trainer and while building it I performed various tests and recorded their videos that are uploaded on YouTube as a part of a playlist for anyone to see.
I will be mentioning the test, all issues I faced, how I fixed the issues and what I learned from them.
Testing the FlySky-CT6B RC transmitter receiver with bldc motor and 9g servo
In this video, I have finished binding my transmitter with its receiver and installed the T6 config software to visualize and program my transmitter controls. In this video, you can see me moving the two sticks of the transmitter to control the BLDC motor and servo motor while also digitally showing the position of the sticks on my laptop that is connected to my transmitter via the given USB cable.
In my case, the transmitter didn’t come pre-bound with my receiver so It didn’t work right out of the box so to make it work you have to use the given binding to lead a black colored loop connector and connect it to the battery. Here is a video about binding and more — FlySky FSCT6B Binding/Connecting to Laptop/Channel Reversing and Tuning
Testing the Rudder with 9g sg90 servo
The rudder is hinged to the body by just cello tape. The wood connector is from the icecream stick of a choco bar I ate and the holes were made by roasting the end of the metal connector rod seen in the video over the gas stove till it was red hot to burn a hole through the wood and the same had to be done for the servo’s nylon plastic arm. The ice cream stick is stuck to the rudder by cyanoacrylate glue which makes a strong connection and doesn’t flex. There are two holes in the ice-cream stick because the other hole being farther away from the hinge didn’t give enough range of angle given the maximum range of the servo motor and so I had to make another hole much closer to the hinge.
3S lipo Battery discharge test from 12.2V to 11.4V at 50% throttle
Here you can see the seven-segment display showing the voltage of each cell of the 3S (1, 2, 3) Lipo as well as the overall voltage (ALL). The battery’s voltage at full charge is 12.6V (3x4.2V) and storage voltage is 11.1V (3x3.7V) and it is not recommended to go below 3.6V per cell i.e. 10.8V total as it can damage the battery and shorten its lifespan. The propeller pushing the air creates a very high load draining as much as 12A current at 50% power and providing around 400g of thrust (according to the internet). It is not recommended to use maximum thrust on a 1400kv motor and 10inch propeller because the current drawn can go more than 30A which is more than the max limit of the ESC so it is recommended to run at 50% to 80% power/throttle max. The battery and motor were cool enough to touch after the test (50% power for about 5 mins) so there should not be any overheating issue at all.
Elevator and Rudder testing with sg90 9g servos & added front landing gear
Elevator (horizontal) and Rudder (vertical) testing. Both are controlled by a 9g micro servo as shown in my previous rudder test post.
I also added landing gear (the red plastic tires) in front of the fuselage (body) and will most likely add one at the back. The landing gear was compulsory to add in my case because this plane is really heavy (around 500g I guess) for the wing span so it will require a run-up on the ground before it reaches a certain velocity to produce more lift than its weight. It also has a huge propeller (10-inch diameter) which requires it to be elevated so the blades don’t hit the ground while taking off and landing.
I also was regretting using a really dense foam material (A type of foam I got from a local vinyl printing shop) for the body which is at least twice as heavy as what I needed (extruded polystyrene type). It should be technically possible to fly this so that is why I didn’t want to abandon this structure just at that point in time. If it didn’t work I’ll have to make a lighter/smaller plane or just get some other lightweight material like cardboard, depron, polystyrene, coroplast, etc.
DIY front Landing gear testing
The video didn’t have rear landing gear so it took half throttle just to overcome static friction. This is why I had to add a rear landing gear allowing me to get going with much less throttle.
Aileron test using 2 channel mixing
The two servos are connected to separate channels that are mixed together. This was done because I didn’t want to buy a Y lead to control both servos to the same channel. The plane is completely done at this point all that is left is to convert the ailerons to flaperon using the remaining 2 mixes. A good thing to do is label the channels each servo has to connect to otherwise you will have to reprogram the channels or check them using trial and error.
DIY FT Tiny Trainer Maiden Flight Test :)
Let go of all anxiety and send it because it was not meant for show but meant to fly.
Waiting for better weather, To be continued …