Drone Racing Event

We are ecstatic to announce that SPARC Robotics, in collaboration with the Electronics Society of St. Stephen's College, Delhi University are going to host a great RC Event where people can come together and showcase their RC Skills and meet fellow fliers.

As some of you might know, RcHubIndia, under the name of SPARC Robotics has just released the very first 3D Printed frames in India.

You may have a look at the frame and the sales threads here -

http://www.rcindia.org/multirotors/discussion-sparc-250-3d-printed-frame

http://www.rcindia.org/for-sale/preorder-now-3d-printed-250-size-quadcopter-frame-manufactured-in-india

http://www.rcindia.org/free-donations-and-sweepstakes/3-multirotor-frames-at-stake

To showcase our frames to the great community at RcIndia, we have organized an event at St. Stephen's College, Delhi University which will also be a great opportunity to meet several fliers across Delhi and the neighbouring states.

The event has been divided into two parts - 

Exhibition - 

The Exhibition will showcase the process of developing the frames and how were they realized.

The Electronics Society of St. Stephen's College will showcase their achievements.

A special feature will be an introduction to 3D Printing technology and a look at the printer which started it all.

Competition - 

The competition will consist of two parts - 

1. Sprint - As the name signifies, the participants will sprint their copters over a long length of open track. This is a simple event which will test the acceleration and speed of the copter and does not require a lot of expertise in flying.

2. Obstacle Course - The second event will consist of a short and simple obstacle course in which the participant will have to maneuver their copter through tight spaces and complete in the shortest time possible.

Both the events will be simple but highly engaging to encourage participation from beginning fliers.

One of the event's main goals is to promote the hobby among people, and also to encourage interaction between the new and veteran fliers.

Anyone, from anywhere in India, and of any age may apply, they do not need to be a student.

If you cannot participate, you are encouraged to come anyway and meet with the fellow hobbyists and have fun.

Now for the fun part - 

There is no registration fee.

Every participant will get one complete 3D Printed frame for free!

Every participant will also get certificates from the college.

The Winners will get trophies and a 3D Printed 450 frame from SPARC robotics as a prize when they are released in December.

Note : More details about the competition will be released in the subsequent days and registration links will be put up.

The venue will be St. Stephen's College in Delhi.

The event will take place in the last week of October 2015.

Participants are required to bring their own multicopters and other equipment with themselves.

FPV Gear is not required for the event.

We expect to see you there!

Fellow Fliers - RcHubIndia

(contact rchubind@gmail.com for participation)

GUIDELINES:

Aerial photography (AP) has now become extremely popular specially with multirotor fliers. We routinely see amazing videos of fliers, not only from India but all across the world. 

Many have ventured into this as a progression from their traditional RC hobby but may have come into this as a new entrant, for the sole interest in photography and not RC . Many off the shelf products, like DJI, with its Phantom has aggravated this to a much larger extent.
I can say with confidence that those into AP can be grouped in two sections : RC-first and Photography-first interest. The interest part can be hobby or commercial

My concerns here target both of these groups, but the latter group the more. RC-First fliers would be aware of the traditional flight safety rules, but sometimes just being aware of the rules isn't enough. The photography first lot may not be even aware of the safety guidelines ! 

Also those of us who are aware may get carried away, by the superficially so called reliability of their systems . Superficial, i say because if a system works 100 out of 100 times, it cannot be guaranteed as reliable. There could be multiple points of failures which can be triggered by many factors, and many such points may be hidden out from the user unless they present themselves and at that point nothing much can be done, except witness the crash and damage. 
The flying equipment we use today is very complicated, has thousands of components, connectors and hundreds of thousands of lines of software code. All it needs to bring down a system is one single problem which may be completely obscured to the user !


''The other day, I went to the field to fly with my faithful Futaba 8FG . When i powered up my model I noted that it had substantial up elevator. Perplexed, I went to the Servo menu on my radio to see that almost full up elevator was given as a command, even with the stick neutral and the trims almost centered.

The gimbal and stick did not seem to have any mechanical problem, and when i moved the stick the center point changed randomly. The servo bar moved with the stick was usually offset and never centered. It was a very nervous moment - Imagine what this could have done, with someone flying a multi rotor, only to have it come flying back at them with no stick movement !! 
Or for that reason go flying anywhere else ! 

The stick was smooth, and the radio has had no history of problems or handling problems.

Of course i would never fly with such an equipment, so went home and opened the radio. Everything inside was clean and factory set.

The gimbal was connected to the motherboard with a cable with connectors on each one. One end plugged into the gimbal and the other into the main board. i noted that when I touched these connectors, the servo output varied.

So, I took of the connector, cleaned it with some iso propyl alcohol, and after drying, put it back and all the problems were gone ! 
The centering works fabulous ! ''

Gimbal Signal for the stick being generated by the position of Potentiometer connected to the stick axle, this is bound to happen even if there is a small amount of oxidation in the Plug connectors of the potentiometer which will vary the balance of the potentiometer, which can easily happen due to any ingress of moisture, sweat or fuel with Nitro with overtime usage. Only way to eliminate this is to remove the plug connectors and directly soldering the three wires to the main board further to be doubly sure can give a coat of lacquer to the exposed solder conductors. 

Where an internal connector issue, complete hidden away from the user, on a reputed brand radio can cause a complete control problem leading to crash and damage/injury to people. I shudder to think what this could have caused had a multirotor been flying over a wedding with hundreds of people ! This problem alone, if presented when the multi rotor was flying, would have resulted in an uncommanded flight leading to a crash, possibly over people, and causing serious injuries. The pilot would have no answer, since none of his 'obvious' actions caused the crash  
Yet the pilot should be termed liable, since his action alone caused the crash - Flying over people, when it is completely against the safety guidelines. 

My concerns here are firmly rooted in the ground and I am not speculating something out of the blue. A few months back, I was at a wedding, and saw a multiorotor do aerial photography. It flew over people, many times as low I could feel its prop wash. The flier was more concentrated on getting the 'right shots' than on keeping the model away from people. 


Truly an appeal to all AP fliers - Please take this very seriously. Rules are not meant to be just posted, read and forgotten. Since no one is enforcing the safety rules on us we should undertake this responsibility ourselves and observe strict regulation in the benefit of our community  

I do sincerely hope that no such incident takes place, but this might not be the case, unless measures are taken by people to understand and observe self regulation. 
Commercial interests should never come in way of safety measures , and hope our small community takes heed of this .


Some Guidelines:
The new breed of multi rotors and AP-first pilots need to be aware of things like : 

A. Where to fly and where NOT to fly - 
20 km around airports - NEVER to fly. 
Over groups of people - NEVER to fly.

Even if getting close up or good shots are paramount - NEVER to fly over people.

B. Always have a flight plan before flying

C.  Always have a spotter having a visual reference of the multi copter

D. NOT to fly under any influence of alcohol.

E. LEARN to Manually fly a multi-copter. 

F. REMEMBER at all times that GPS, and all its related safety measures ( IOC, RTL etc ) can be lost in a split second. Hundreds of factors affect GPS and I cant list enough incidences have come  across. For the un-initiated, heres one -  solar flares cause a wipe out of GPS signal. I have first hand experience of this. 

G. Keep your model ALWAYS in Line of Sight.

H. ALWAYS have a flight plan before flying. Do not fly and then think. 

I. MAKE Check-lists. It is easy to forget things which may lead to catastrphc failures, when under commercial pressures.

J. Do Thorough PRE Flight and POST flight inspections. KNow the failure points, critical points on your machine.

K. DO NOT TRUST the Auto pilot features. Even if its the best.  Remember they CAN fail. and when they will, and safety guidelines are not followed, injury will happen.

L. Always have a first aid kit in your flight set. You can carry a zillion equipment, wires and connectors and not a small box with first aid ? When a prop cut happens, it will be essential to stop bleeding.

Happy flying all !

Multirotor tutorial

Multirotor becoming very popular nowadays. It's real fun and pleasure to see them flying, however making them at home from scratch is tough job. If you are thinking to make one then this tutorial might help you. You don't need to ask someone or search over forums or blogs to troubleshoot your issue. Here i am trying to put everything together for you. It comes from my personal experience and time i spent searching over google so it might help you to build your multirotor without any hassle. I would like to thank RCGroups, RCIndia and buddies LazyZero, Ron, er9xuse for their help and support. Here i will post some basic tips of selecting motor-prop combinations, battery, esc etc.
If you are making it for school, college or university projoct make sure you have enough time for testing and debugging. KK boards are known for plug and play functionality but still fine tuning your multirotor needs time.
I would also like to warn you that don't take multirotor lightly, they are monsters and can ruin your day within seconds. So be careful when you are testing them.
So where to start and how to select parts for multirotor? Here i am trying to put everything step by step.

PURPOSE
Before you start buying parts you should have rough idea, for what purpose you want to make your multirotor? People make them for fun flying and hovering, stunts, AP(Aerial Photography), FPV(First Person View) and Heavy Lifting. You just can't make one multirotor that can do everything for you and if you are completely new to this thing you should first learn hovering and some basics of multirotor flying. So here we assume that we are making multirotor for beginner flying that can probably lift 200-300grams payload so you can hooked up light weight camera for onboard video recording(not FPV) in future.

TYPE, SIZE & WEIGHT OF MULTIROTOR
There are many types of multirotor people make nowadays. Some of them are Monocopter, Twincopter, Tricopter, Quadcopter, Y-6, Hexacopter, X-8, Octocopter. I found that less rotors more precision requires to build them. That's why FPV lovers use hexa or octocopters so if one motor fails, they can safely bring it down to the surface. But more rotors means you have to invest more money. As a beginner quadcopter is good to start. Tricopter is good as well but you will have to deal with yaw mechanism which is tricky if you are building it from scratch. So here we will start with quadcopter. Quadcopter or also called Quadrotor has 4 rotors and it has two flight configurations. X config and + config. In X config two arms will face front side while in + config only one arm will face front side. If you are making Quadcopter with plus config you can tune your quadcopter easily by single axis tuning method which we will learn later. Small and light weight quacopters can do stunts better while big quadcopters can lift heavy payload like cameras with gimbal and fpv gear. So here we assume we are making normal medium size Quadcopter with plus config and 1000-1100grams AUW(All Up Weight) for funflying. AUW includes battery and everything. Basic formula you should keep in mind that weight of multirotor should be half of the total thrust.
Total Thrust = 2x AUW
In short to lift 1000gram quadcopter we need 2000gram thrust. We will learn about thrust later.

FRAME
One of the most important part of multirotor is its frame because it supports motors and other electronics and prevents them from vibrations. You have to be very precise while making it. 
ARM:
You can make arm from any material like CF, PVC pipes, Aluminium or Wood but make sure it has enough strength to withstand impact and rough landings. Frame weight should be around 200-250grams. I would recommend you to go with aluminium channels/beams as they are cheap, strong and easily available at any local hardware shop. You can cut, drill them easily at home.
CENTER PLATE:
Ceter plate holds the arms and supports FC, receiver and other sensors. You can use 2-3mm glass fibre, plywood, aluminium sheet or any plastic sheet material but make sure they are stiff, strong and light weight. You can put some holes to reduce weight.
LANDING SKID:
If you want to attach landing skid, buy any RC helicopter landing skid or you can build your own skid from scratch. It's all upto you. 
FASTNERS:
Use M3 nut-bolts of different length to assemble frame and motor mount.
SIZE:
There is no thumb rule for size of the frame but for medium size quadcopter 450mm to 550mm motor to motor frame is enough. If your frame is too big compare to your power setup(motor-prop, esc, battery)it will add extra weight while if it's too small props will fight with each other.

Making frame is truly depends on your imagination, skill and availability of material. But it's fun building frame from scratch and you will learn many things from it. If you want to get rid of all these diy things you can simply buy readymade frame from the market but it might put big hole in your pocket. In our case we want to build quadcopter so make sure the angle between two arms is 90 degree and also check that arms are not twisted.


FC(Flight Controller)
There are many FCs out now in the RC world. Some of them are KK, MultiWii, Ardupilot, Naza, Naze, Rabbit, WKM and many other. Advanced FCs have more features and advanced sensors like gyro, accelerometer, sonar, GPS, Magnetometer. But as we know "more power comes with more responsibility and difficulties" so if you are newbie you should start with gyro only. Hobbyking v1, v2.1, v3.0 boards/KK boards have gyro sensor only but still they are best beginner boards in the market to learn and undestand science behind multirotor. So here we are assuming that we are going to use HK board. You can buy any board v1, v2.1 or v3.0. The only difference between them are ATMEGA chip. V1 has 4kb flash memory, V2.1 has 16kb memory while v3.0 has 32kb flash memory. One more reason to use these boards is they are cheap, reliable and easily available at any hobby store. It won't burn your pocket. If you crash and damage your board you can buy another and there are lots of posts and videos available describing how to use them.


MOTOR
One of the important part of multirotor is its motor. It's a part of power system. Infact whole power system depends on selection of motor so you should be very careful while selecting motor. We use Brushless motors for multirotor. Brushless motor comes with some important specifications. You will see these specifications on the page if you are purchasing it online. So it makes our job simple. For motor selection some important specifications are.
kV
Max current(A)
Shaft dia
Thrust
Weight
Lipo(3S-4S)
Suggested prop
For multirotor application 600-1200kV motors are good. Below 600kV even better. Low kV means you can swing big prop. Big prop means it can move more air and you will get more thrust. 
kV = RPM/V
If you have 600kV motor and 3S battery to supply power, RPM of of motor at NO LOAD would be
600 x 11.1(3S battery) = 6660 RPM.
Max current rating is another important factor while selecting motor. Selection of ESC and battery depends on this value(we will learn it later). It should be able to run on both 3S and 4S lipo battery. Shaft diameter helps you selecting prop adapter. Now we are coming to the thrust. In most cases you will see value of the thrust motor can produce with suggested prop on the website. If you remember we learned that to lift 1000 grams quadcopter we need total 2000grams of thrust. And quadcopter has 4 motors, so each motor should be able to produce atleast 500grams of thrust to satisfy our need.
4 motors x 500grams thrust = 2000grams thrust.
One more thing is Watt.
Watt = V(Voltage) x I (Ampere)
More Watt more power so you should also consider that while selecting motor.
But when it comes to selecting motor you will notice that there are many options available for motor selection and it's really confusing, so which motor is best for multirotor application? Well you should consider few more things other than specifications. Some of them are
Motor Mount: Well motor mount is one more important factor you should keep in mind while selecting motor for your multirotor. Motor mount comes under tensile force especially when you are swinging big prop and if motor is not fitted properly it might come off during flight and i am sure nobody wants to see such things happen. So make sure that motor you are purchasing has good mount that can hold motor properly under heavy load and same way you can fit that mount easily on the frame. However you should always precheck before flight that all connections and fastners are properly fitted. Get one spare motor. So i hope i have covered everything for motor selection.

PROPELLER
We always neglect this plastic piece. Just because it's cheap? Who knows!! But in multirotor application contribution of prop is remarkable. Specifications of prop are easy to understand and they are dialmeter and pitch. Type of prop is important as well but we will see effect of diameter and pitch on flight of multirotor. Generally we see prop with the specification of
7x3.5
8x4.5
9x5
10x3.8
10x4.5
10x6
11x4.7
12x3.8
First value is diameter of prop and second value is pitch. Both are in inches.
Diameter: Virtual circle that prop generates.
Pitch: Amount of travel per revolution.
As we see above our motor runs at 6660 RPM at NO LOAD. But when you mount prop on it, RPM will be reduced. Here we will take example of two props 10x3.8 and 10x6. When you mount 10 inch diameter prop RPM of motor will be reduced to 3600 RPM (Revolutions Per Minute).
60 Revolutions Per Second.
Our 1st prop has 3.8 inch pitch. Means per revolution it will travel 3.8inch. So
60 x 3.8 = 228 Inch/Sec = 5.7 m/sec
For 2nd prop, it has 6 inch pitch.
60 x 6 = 360 Inch/Sec = 9.1 m/sec
So we can say if we have 10x3.8 prop our quad will climb in the air at 5.7 m/sec, while with 10x6 prop climb rate will be incread to 9.1 m/sec.
Bigger dia prop can produce more thrust.
So which prop is best for our multirotor?
Generally you will get suggested prop value in motor specification, so you should go with it and buy 1-2 pair extra. But what if prop value is not given. You will see kind of table with different props, Volts, Amp, Thrust and Efficiency. Here you will have to try trial and error method. But it doesn't mean you swing 13x3.8 prop on 1700kV motor.
Lower kV motor can deal with bigger prop. With increasing kV value size of prop will be decreased. So you will have to keep this in mind. For multirotor you should go with low pitch prop if you need more stability and less vibrations. How to balance prop? We will see in next part.

ESC(Electronic Speed Controller)
ESC supplies power from battery but not constant, it varies according to input signal. ESC also has BEC(Battery Eliminated Circuit). BEC is nothing but 5V output from ESC that can power up receiver, servomotor(for camera gimbal) and FC. But how to select ESC for our multirotor? Well it's really simple. You only need to keep in mind that Ampere rating of ESC should be higher than max amp rating of motor. For example the motor we selected draws maximum 15Amp so your ESC rating should be higher than 15amp. Say 18-20Amp. Still confused? Here is simple forumla. Thanks to Sai sir(rcforall) of RCI.
ESC = 1.2-1.5 x max amp rating of motor
1.2-1.5 x 15 = 18-22.5A
So you can select ESC between range of 18A to 22A. But please note it's note thumb rule. You can go with either 18-20A or 25A (it might be bit over powered). Whichever ESC you choose make sure it has programing facility(throttle range, battery mode etc). Go with quality ESCs check user reviews and buy 1 spare.

BATTERY
This beautiful monster eats quality food. If you don't feed them they refuse to fly. So how to select battery for your multirotor?
For that maximum Amp rating of motor comes first. If you remember our motor draws max 15amp. We are working on quadcopter and it has 4 motors, so all 4 motors will draw
4 x 15amp = 60Amp.
Now let me explain few specifications of battery. You will see them on battery and website as well.
mAh
C discharge rating
2S, 3S or 4S.

mAh:
1000mA = 1A
You can compare mAh rating of battery with petrol tank of your vehicle. Big tank more petrol you can fill and more you can drive. The same way more mAh rating gives you more flight time.
C Discharge Rating:
Maximum current(A) at which battery can be discharged at particular time.
1S, 2S, 3S & 4S
1S = 1 cell of 3.7V
2S = 2 cells in parallel x 3.7V = 7.4V
3S = 3 cells x 3.7V = 11.1V
4S = 4 cells x 3.7V = 14.8V
4S means more power than 3S. If you remember we discussed that
Watt = V x I
Here we are increasing value of Volt so watt will be increased. Our motor draws max 15A. So watt value for 3S and 4S will be
At 3S battery 11.1 x 15 = 166.5 Watt
At 4S battery 14.8 x 15 = 222 Watt
but make sure your motor and esc are capable of handling 4S.
Generally you should go with 3S battery only.
Now as we know we need atleast 60A current. So here we will take example of two batteries.
2200mAh 25C
2200mAh 40C
Which battery is good for our multirotor? Let's see
2200mAh = 2.2A
2.2 x 25C = 55A
2.2 x 40C = 88A
We need atleast 60A so 2200mAh 40C is good for us. Go ahead and get it.

I hope you have gathered enough confidence to build your own multirotor from scratch. Next part will be even more interesting. So stay tuned.

Hacking Servo

The theory behind this hack is to make the servo think that the output shaft is always at the 90 degree mark. This is done by removing the feedback sensor, and replacing it with an equivalent circuit that creates the same readings as the sensor being at 90 degrees. Thus, giving it the signal for 0 degrees will cause the motor to turn on full speed in one direction. The signal for 180 degrees will cause the motor to go the other direction. Since the feedback from the output shaft is disconnected, the servo will continue in the appropriate direction as long as the signal remains.

The result of this is a really nice compact gearhead motor with built in electronics. The interface to this motor unit is a 1 wire control line, +5 volts for power, and a ground. All of this for around $15, which is an outstanding deal.

As for the details, there are actually only two modifications to make to the servo:

• Replace the position sensing potentiometer with an equivalent resistor network.
• Remove the mechanical stop from the output shaft.

You will need a few supplies:

• Small philips screwdriver for opening the case
• A soldering iron
• A desoldering pump or solder wick for removing the potentiometer
• A sharp knife or wire cutters for removing the mechanical stop
• Two 2.2k resistors (actually, anything between 2.2k and 3.3k will work, as long as they are equal values)

The following steps will help you make the modifications:

1. Open the case by removing the 4 screws located at the bottom of the servo. The bottom plate should come off easily. Remove the top of the case. You will find a set of gears under the top case, a several blobs of white grease. Try hard to save the grease by leaving it on the gears.



2. Be careful to note how the gears are arranged, and remove them from the top of the servo. I usually place them as the are supposed to sit. The large fine tooth gear in the middle does not need to be removed. See the picture below.



3. Locate and remove the two small philips head screws on the left shaft in the picture above. These screws go through the top case and into the drive motor.


4. Next, you need to remove the circuit board from the case. To do this, you will probably need to press down hard on the brass shaft on the right side. This is the top of the position potentiometer. I find that pressing that brass shaft against the edge of the workbench helps push it through.


5. From the bottom, very carefully pry up on opposing corners of the circuit board. The board should slide out with the motor and potentiometer attached. You should end up with the following parts on the table.



6. Now for the actual modifications. You will need to desolder the potentiometer from the board. I usually cut the long leads off a quarter inch or so from the bottom. I then use solder wick on the back side of the board.


7. Once the pot has been removed, you need to wire in the resistor network in its place. To do this, place the resistors side by side and twist one pair of leads. Solder them together, but leave one of the leads long enough to make a 3 wire part. Then replace the pot with this 3 wire pot. As seen in the picture below, the pot has been replaced by the resistor network.



8. Now, reassemble the circuit board into the case. Note that the pot is now missing, so only the motor will protrude through the top of the case.


9. Before reinstalling the gears, you will need to modify the gear with the output shaft so the mechanical stop is removed. The mechanical stop is a small tab of plastic on the lower gear surface. In the picture below, you can see the tab on the left gear. This should be cut down flush with the surface. Try to get all of the tab removed, as is shown with the gear on the right side.



10. Replace the gears as they were when you took the motor apart, replace the top of the case, the bottom plate, and the two screws.


11. You are done!

The motor should now be able to turn all the way around. Connect a control horn, and carefully apply enough pressure to make the horn turn around. Feel for any mechanical problems, such as a gear catching on the cut off section of the tab. You should not feel any catching or resistance. It would be best not to play with turning the servo by hand too much. This device is not intended to be driven from the output shaft, and it may cause undo wear and tear on the servo motor.

Engine Break-In Procedure

CAUTION
The instructions that are supplied with a new engine should be read thoroughly and followed for breaking in and maintaining the engine. If the instructions are not available, these instructions can be used for standard 2 - cycle engines. 

Although engine manufacturers have excellent Quality Control systems, there is always a chance that a new engine has small metal filings that can permanently damage an engine if not removed. Prior to being broken in, an engine should be inspected and cleaned to assure that all metal filings and dust are removed. This is done by simply removing the backplate and flushing with new, clean fuel. Any further attempts to disassemble could result in the warranty being voided. At this point, the owner has done as much as can be expected to reduce the chances of damage and any other damage will be covered as a warranty defect. 

Modern 2 - cycle engines can produce a surprising amount of thrust. Regardless of whether the engine is mounted on a stand or the model, the mount must be secure so that the engine cannot lurch forward when it is initially started. Disregarding this safety warning can result in serious, permanent injury. 

FUEL TANK MOUNTING
The fuel tank should be located as close to the engine as possible with of the tank level with the carburetor needle valve assembly. The fuel tank system must sealed to eliminate the possibility of fuel or air leakage. If the muffler has a pressure tap, it should be connected to the pressure inlet of the fuel tank. The tank should be mounted on high quality foam rubber to reduce fuel foaming during the break-in operation. Fuel foaming can adversely affect the operation of the engine resulting in improper break-in. 

FUEL
A good quality, commercially available fuel containing between 5% and 10% nitromethane and 20% castor oil is recommended for breaking in a new engine. A fuel with a castor/synthetic lubricant blend may be used but may less effective if the engine should suddenly run lean as the last of the fuel is used. If the oil content is less than 20%, medical grade castor oil can be purchased at a drug store and added to bring the oil level to the appropriate level. 

PROPELLERS The size of the propeller used for the break-in period is not nearly as important as that used for actual operation. The size chosen should allow the engine to turn at optimum revolutions per minute without stressing the engine or allowing it to overheat. A prop chart recommends a good starting point. Although it might not be the ideal prop, it will be adequate for breaking in the engine. 

CAUTION
It is extremely important to check the balance of a propeller before attaching it to an engine. An unbalanced propeller can cause substantial damage to an engine. 

GLOW PLUG
The type and quality of glow plug used in the engine varies from one type engine to another. If no plug is recommended, it is best to start with a very high quality R/C long-type plug such as Thunder Tiger, K&B 1L, or O.S. No. 8. Fox plugs have a colder heat range and may work on some of the cooler running engines but can cause frustration in attempting to break-in some of the modern ABC engines. It the engine slows down excessively or dies when the glow plug driver is removed, this might indicate that the heat range of the glow plug is too low. 

BREAK-IN PROCEDURES
Most engines produced today do not require a prolonged break-in period. Refer to a prop chart to determine the proper propeller size for break-in. With the propeller installed securely to the engine, the glow plug installed, the fuel lines connected, and the tank filled with fuel, the break-in operations can begin. The idle mixture screw and/or idle stop screw should not be adjusted during the initial break-in period. This will only serve to complicate the process. All adjustments during break-in will be made to the needle valve. The initial setting is made by turning the needle valve clockwise until resistance is felt. This is the fully closed position. Forcing the needle valve beyond this point can damage the carburetor. The needle valve is then turned counter-clockwise about 2 - 2 1/2 turns to open the port to good starting point. 

Using the transmitter or throttle pushrod, the throttle is opened to 1/2 to 3/4. Without the glow plug battery connected, a finger is placed over the carburetor opening and the propeller is rotated counter-clockwise 2 - 3 turns or until fuel flows through the fuel line into the carburetor. A 1.5 volt ignition battery or power panel is connected to the glow plug. The throttle opening is then reduced to 1/4 - 1/2 open. The propeller is the flipped counter-clockwise using a "chicken stick" or electric starter. The engine should fire after a few seconds. After the engine starts, leave the glow plug battery connected and advance the throttle to full open. At this point, the engine should be running very rich, i.e. dense smoke and/or heavy oil residue coming from the exhaust. 

After the engine runs for a minute or two, the needle valve is closed 1/4 turn clockwise and the glow plug clip is disconnected. The engine should be allowed to consume the entire tank of fuel at this needle setting, making sure the engine remains rich. After the first tank of fuel is depleted, the engine should be allowed to cool for a few minutes. During the second tank of fuel, the engine is run at alternate throttle settings, 1/2 throttle for 30 seconds, full throttle for 30 seconds, and back to 1/2 throttle, until about half the fuel is consumed. At this point, the throttle is slowly advanced to full and the needle valve is closed slowly, about 1/8 turn at a time, until maximum revolutions are reached. Finally, the needle setting is turned about 1/8 turn counter-clockwise to avoid an overly lean running condition and the balance is consumed. The engine is allowed to cool again and the tank is refilled. Without resetting the needle valve, a third tank of fuel is run through the engine while alternating the throttle position ever 30 seconds to 1 minute between 1/4, 1/2, 3/4 and full throttle. At this point, the engine is ready for the first flight. The engine is not broken in completely at this point so care must be taken to avoid running the engine overly lean.

Propellor Selection Chart

2-Stroke Engine

ENGINE SIZE	PREFERRED SIZE	ALTERNATE SIZE
.049	6 x 3	5 1/4 x 4, 5 1/2 x 4, 6 x 3 1/2, 6 x 4, 7 x 3
.09	7 x 4	7 x 3, 7 x 4 1/2, 7 x 5
.15	8 x 4	8 x 5, 8 x 6, 9 x 4
.19 - .25	9 x 4	8 x 5, 8 x 6, 9 x 5
.29 - 30	9 x 6	9 1/2 x 6, 10 x 5
.40	10 x 6	9 x 8, 11 x 5
.45	10 x 7	10 x 6, 11 x 5, 11 x 6, 12 x 4
.50	11 x 6	10 x 8, 11 x 7, 12 x 4, 12 x 5
.60 - .61	11 x 7	11 x 7 1/2, 11 x 7 3/4, 11 x 8, 12 x 6
.70	12 x 6	11 x 8, 12 x 8, 13 x 6, 14 x 4
.78 - .80	13 x 6	12 x 8, 14 x 4, 14 x 5
.90 - .91	14 x 6	13 x 8, 15 x 6, 16 x 5
1.20	16 x 6	16 x 10, 18 x 5, 18 x 6
1.50	18 x 6	18 x 8, 20 x 6
1.80	18 x 8	18 x 10, 20 x 6

4-Stroke Engine

ENGINE SIZE	PREFERRED SIZE	ALTERNATE SIZE
.20 - .21	9 x 6	9 x 5, 10 x 5
.40	11 x 6	10 x 6, 10 x 7, 11 x 4, 11 x 5, 11 x 7, 11 x 7 1/2, 12 x 4
.45 - .48	11 x 6	10 x 6, 10 x 7, 11 x 7, 11 x 7 1/2, 12 x 4, 12 x 5, 12 x 6
.60 - .65	12 x 6	11 x 7 1/2, 11 x 7 3/4, 11 x 8, 12 x 8, 13 x 5, 13 x 6
.70	12 x 6	11 x 7 1/2, 11 x 7 3/4, 11 x 8, 12 x 8, 13 x 5, 13 x 6
.80	13 x 6	12 x 8, 13 x 8, 14 x 4, 14 x 6
.90	14 x 6	12 x 10, 13 x 8, 14 x 8, 15 x 6
1.08	16 x 6	15 x 8, 18 x 5
1.20	16 x 6	14 x 8, 15 x 6, 15 x 8, 16 x 8, 17 x 6, 18 x 5, 18 x 6
1.60	16 x 6	15 x 6, 15 x 8, 16 x 8, 18 x 6, 18 x 8, 20 x 6
2.40	18 x 10	18 x 12, 20 x 8, 20 x 10
2.70	20 x 8	18 x 10, 20 x 8, 20 x 10
3.00	20 x 10	18 x 12, 20 x 10

Decorating is equally important

TWO COLOR COVERING

The introduction of heat-shrinkable plastic covering has saved a lot of labor and time for many modelers. Plastic coverings require far less effort and skill than the silk and dope or silkspan and dope coverings of the past. A tight, glossy, attractive covering job can be achieved by anyone with the right tools and a little patience.

As with any other covering methods, there are inherent drawbacks to plastic covering. One of the major problems is that of applying trim sheets to the completed covering surface. Several methods have been devised to overcome the problem of applying the trim sheets without having bubbles appear later. Some of them work far better than others but there is no assurance that bubbles will not eventually appear. This is especially true with large trim sheets. The larger the area, the greater the chance that trapped moisture will expand and cause bubbles.

Sometimes, the need arises for a multi-color covering pattern that requires large but relatively simple trim patterns. In this case, there is a viable alternative to using large pieces of trim. The pattern can be cut from the covering material and joined into a single piece before it is applied to the model. The method described is for a two (2) color pattern but can also be applied to more complex patterns such as the scallop, stripe, and sunray patterns used on a typical Citabria. It can even been used for camouflage patterns that have sharp edges between colors.

The process begins with deciding how the pattern is to be laid out to achieve the desired results. Illustration 1 shows a Thunder Tiger Trainer 40 that was recovered with red and white material to duplicate the original color scheme as closely as possible.

The closed surfaces of the fuselage, stabilizer, and fin are covered using normal practices. The white of the fuselage is cut to the desired shape allowing a 1/4" overlap and applied. The red is then cut to shape and applied with the overlap.

The open bay of the wing requires a different process. There is no surface onto which the edge of the white covering can be sealed before the red is applied. In this case, the white and red pieces are joined together before they are applied to the wing. The bottom of the wing is solid white and is covered prior to beginning the layout of the top surface.

Templates for both the white and red patterns are cut from a heavy card stock to ensure that the patterns are the same on both upper wing surfaces. The template for the lighter color, white in this case, must be cut 1/2" larger to allow the darker, red, to be joined with an overlap. The overlap can be as little as 1/4" but this leaves no margin for error when applying heat to shrink the material. An additional 1" to 2" allowance is made on the outer edges to allow handling and pulling the finished material when it is being applied to the wing. This is normal practice for all plastic covering materials. The amount of this allowance is left up to the discretion of the builder. The templates are laid over the covering material and used to cut the outlines of the pieces that make up the final piece. Illustration 2 depicts the layout for the pieces of covering material used on the left wing of the Thunder Tiger Trainer 40.

The right wing panel covering sheet is made by flipping the templates over on the covering material and cutting the pieces exactly opposite of those for the left wing.

After the covering pieces are cut, they must be joined together before covering can begin. This is a critical stage. The joint must be strong enough to resist being pulled apart when the heat is applied to shrink the covering material. The backing material can be left in place on the lighter color material but part of the backing must be remove from the darker material to allow the joint to be made. This is accomplished by pulling the backing material loose along the edge that will be joined and cutting it with scissors roughly 1/2" to 1" from the edge. This allows room for working with the edge but the majority of the adhesive surface remains protected from contaminates.

A solvent such MonoKote Trim Solvent or acetone is used to activate (soften) the adhesive along the overlap. A soft brush, like a camel hair artist's brush, that is the width of the overlap is used to apply the solvent. The solvent must be applied evenly over the entire length of the overlap. After only a few seconds, the adhesive will be sufficiently tacky so the parts can be joined. The lighter covering should be held in place on a flat surface so that it will not move while the darker piece is being joined. Illustration 3 shows the light and dark pieces joined with a 1/2" overlap.

Care must be taken to place the overlap joint at precisely the desired point with a minimum of movement required. Any movement can cause the adhesive to smear over the surface of the lighter covering. After the joint is made, it is pressed down with a squeegee to ensure that no air is trapped in the overlap. Although the solvent will evaporate very quickly, it should be allowed to sit overnight to be sure that it has adequate time to "gas out".

After the covering sheets are made, they can be used to cover the wing panel using normal covering practices with one exception. The corners are tacked down with a covering iron then the edges are pulled into place and tacked down. Illustration 4 shows the finished covering sheet laid over the wing panel.

When heat is applied to shrink the covering, extreme care must be take to avoid over-exposing the edge of the darker material to the heat. Although the edge is joined, it is still a raw edge and is subject to pulling back. The solvent welded joint should hold up to normal shrinking without pulling apart at the seam.

After the covering is applied, it is trimmed along the outer edges to complete the process. To further accentuate the color scheme and to help protect the raw edge, pin-stripe tape can be applied over the raw edge at the seam. Illustration 5 shows the left wing panel completed. If the wing is one piece, the covering of the opposite wing panel is allowed to overlap at the center of the wing.

With proper planning, almost any multi-color trim scheme can be applied in the same was as the two color scheme described. Using this method is more work but the advantages far outweigh the disadvantages. There is a slight reduction in the weight of the covering but this is relatively insignificant. There is far less chance of bubbles appearing. Reheating to tighten the covering results should it become loose has much better results. Builders who have had problems before that his method virtually eliminates those problems.

SILKSPAN COVERING

Over the last four (4) decades, the choices of covering materials for models have expanded steadily and R/C modelers have quickly adopted the new methods. Modelers involved in other disciplines, especially control-line stunt, are not as eager to change their methods of finishing models. There must be a reason for this. The primary reasons are that it is easy, cheap, fun, and above all, beautiful. Silkspan, the primary covering material, is lightweight, accepts nearly all paints readily, and will never sag, bubble or wrinkle. It goes on just as easily over either sheeted structures or open framework.

Silkspan is primarily used on smaller models like Old Timers, 1/2A glow and small electrics, but it is also an excellent surface preparation for sheeted surfaces even on giant scale warbirds. There are two (2) primary disadvantages to using silkspan; it is easier to tear or puncture than plastic coverings and requires much more time and effort to finish.

R/C modelers could learn a few things about finishing their airplanes from control-line modelers. These people can make the most phenomenal finishes and keep them light enough so that the model is competitive. Maybe this is in part the reason that control-line stunt models are scored on appearance and R/C pattern planes are not.

The stunt community in general frowns upon anything that irons on. The purpose of covering the balsa structure with silkspan is to hide the grain, not fill it, and to add strength. It makes a tremendous difference in strength. According to Windy Urtknowski, a guru of stunt model finishing, there is no way to fill balsa grain at an effective weight. He says he has tried covering with glue and sanding it off, but that the grain reveals again after sitting in the sun for a while.


The steps required to achieve that fabulous finish are:

1. Sand everything as smooth as possible with 400-grit paper.


2. Brush 3 coats of clear nitrate dope thinned as little as possible but still resulting in good paint flow. These coats must provide a reasonably waterproof seal so that when the wet silkspan is applied, the underlying structure will not warp due to the moisture.


3. Again, sand everything as smooth as possible with 400-grit paper.


4. Start the covering with the bottom of the wing. Lay the wing on a clean work surface and trim a sheet of silkspan to oversize allowing 1" to 2" of excess around the perimeter. Wet the silkspan with water until it is completely saturated. This will cause it to swell and wrinkle.


5. Gently lay the silkspan sheet over the surface to be covered. Start lifting and smoothing the silkspan until all wrinkles are removed and it is pulled fairly taut. Use wet brush to help to force bubbles toward the edges being careful not to tear the silkspan. Even wet, it is surprisingly tough.


6. Using a sheet 240-grit paper, sand the edges on the down-stroke only to feather away the excess silkspan. The silkspan can be easily worked around compound curves, leading edges and wingtips.


7. Once the silkspan is trimmed and while it is still damp, brush on a coat of nitrate dope that is thinned 50%. The dope is this highly thinned so that it will partially dissolve the dope that is already on the bare balsa. This will bond the covering to the airframe.


8. Cover the rest of the wing and then the fuselage following steps 4 thru 7. Overlap the successive pieces so that there are no gaps.


9. Brush 3 more coats of clear.


10. Sand everything as smooth as possible with 400-grit paper.


11. Make a sanding sealer using equal parts of thinner, clear dope, and corn starch or unscented talcum powder.


12. Brush on a thin coat of the sanding sealer over any remaining pits or dings.


13. Sand off as much sanding sealer as possible with 400-grit paper.


14. Sand everything as smooth as possible with 400-grit paper.


15. Spray a coat or two of 50/50 clear/thinner to seal the filler coats.


16. Sand this lightly with 600-grit paper.
The ultimate goal of this process is to make all of the surfaces as flat as possible then use the dope and silkspan to make it smooth. The trick up to this point is to use as little thinner as possible in the mix. Thinner changes the shape of the wood taking away from the flatness of the wood and requiring more sanding. The trick to finding flaws is to sand in a room with only one light source. Hold the model up to the light and bounce the light off the working surface on at an oblique angle. This will make even he slightest flaw visible. This technique is called candling. All flaws must be corrected at this point; otherwise they will be even more visible after the color coat is applied. Silver primer is very important to an award winning finish, especially when translucent paints, such as candy apple automotive paints, are used.

17. Spray a coat of silver dope. Allow it to dry for about a week. The longer it dries, the easier it is to sand to a smooth finish. If the paint balls up while being sanded, it did not time to dry sufficiently. Stop immediately and allow a few more days for it to dry.
Normally, the reaction when the silver is sanded will be frustration. Every flaw is highlighted. Sand off as much of this silver as possible and correct all flaws with sanding sealer.

18. Apply a second coat of silver.


19. Again, correct all the flaws.


20. Continue this process on the surface has the appearance of machined aluminum. The silver dope is actually used ultra fine filler coat.
Note: Do not spray different colors over each other. This adds weight and makes the color harder to apply. For example, do not paint the entire surface white and put blue trim over the white parts. Mask the areas that are to be painted white and spray it. Remove the masking and allow this coat to dry thoroughly. Mask over the white and spray the blue trim. The silver dope is a perfect base for all colors and saves weight. Finishing this way takes a lot of work and time but the results are incredible. 
21. Mask and spray the lightest color paint first.


22. Mask and spray the remaining colors.


23. Sand the color coats to a dull finish with 1200-grit paper, paying close attention to smoothing the edges as much as possible without through the color coats.


24. After an even, smooth surface is achieved, spray about 4-6 coats of clear over the entire surface.


25. Let this cure at least a month. The harder the paint, the shinier it will be and the longer it will keep its shine.


26. Rub the whole plane with fine rubbing compound.


27. Rub the whole plane with Gorham's Silver Polish.


28. Wax it 2-3 coats with fine automotive wax.
This covering technique is lighter than most of the plastic film coverings, will never wrinkle, and is quite easy although time consuming to do. The results that can be achieved from this method are incredible and unattainable with film coverings.