Radio Control Flying for the Casually Interested
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Introduction
The hobby world of Radio Control (RC) covers a huge variety of vehicles: Boats, cars, airplanes, helicopters, balloons, tanks, and a lot more. Almost anything that rolls, flys, floats or crawls has been modeled and converted to RC. Many of these general areas are split into special interests. RC hobbiests are often involved in more than one area. When its to windy to fly an airplane, they just grab their boat or car and head to the nearest pond or track.
This page is meant as a skeleton introduction to RC flying. Its designed to give enough information to understand what RC flying is about. I hope it may interest someone to try it. For those who become hooked or just want to know more about the hobby, try my RC links section in my bookmark page. More about the author.
Who can fly RC model aircraft?
Anyone can fly RC. You don't need a radio license, or a pilots license, or even understand anything about flight or electronics. However, it doesn't hurt to have these skills. If you stay in the hobby long enough you will acquire some degree of knowledge in each of these areas.It is a good idea to join an organization such as the AMA (Academy of Model Aeronautics or SFA (Sport Flyers of America). These U.S. national organizations offers through membership, insurance for modelers. Why insurance? The average powered model might weigh five and a half pounds, and have a flying speed of 30 miles per hour. On the nose will be two sharp-edged blades spinning at 2,000-28,000 rpm. Accidents happen, no matter how careful you are. There are radio failures, control surface failures, and many pilot errors. Thus, a model airplane can be a dangerous projectile, and must be treated with respect. Occasionally people do get hurt, and property gets damaged. Yes, there have been a few deaths in this sport over the years. Most accidents occur to the flyer himself, such as getting some part of your body to close to the propeller, or burning yourself on a hot engine cylinder. Another common variety of accident is gluing body parts together with todays fast setting superglues, or getting them in your eyes.
So even though anyone can fly, a lot of common sense is needed. Safety is something we think about all the time. You must be a responsible person, not only to yourself, but to others. This means that young children should be very closely supervised. I have seen several five year olds fly, but never alone.
Do I need to be a mechanical engineer to fly RC aircraft?
You don't have to be a tool stud to fly and build RC models. With that said, if your total committment to tools is a hammer, screwdriver, and pair of pliers, I would think twice about getting into the hobby. Or maybe your a phone handyman. These are people who are always saying how they fixed something, but whose favorite tool on their workbench is a phone to call in a repairman. Personally, I know a number of people in each category, but I don't know anyone in RC like that. I doubt they would find the hobby fun. Some mechanical aptitude is a necessity. Planes need to be built and rebuilt. Engines need routine care and maintainence, even to the point of being disassembled. Dexterity with small tools is useful, but can be learned. (Of course, you can't have too many hand tools or power tools to make any task go easier and faster.) A workshop is nice, but for some its a luxury item. Many people use their dining room table, a spare bedroom, or even a closet. The worst problem in these cases is the glares from loved ones. For those with a little ability, you will learn a lot more. When you start talking with other flyers about problems or interests, you will discover many useful tips and techniques. You would be suprised how many household and job related problems I have fixed with my RC knowledge.Who flys RC model aircraft?
The bug to fly can strike anyone. I see bikers flying and building right along side doctors. The only thing that separates them is language, and sometimes money. Yes, the more expensive equipment is often found with those with higher paying jobs. But the greatest ingenuity in building often lies with those with less money to spare for the hobby. The biggest problem for everyone I know in the hobby is finding the time to fly and build.What kinds of RC planes are there?
There are as many types of models as there are full scale types of planes. After all, these are models. In addition, there are model airplanes which have no counterpart in full scale. They range from ugly, nearly formless stick- like models to ultrasleek pattern ships. The wingspans can vary from 12 inches to 24 ft monsters. They can be powered by combustion engines or electric motors no bigger than a fat thumb to powerful chain saw engines. Speeds can be from a few miles per hour for a glider or some trainers, to nearly 200 miles per hour in jets or racing planes.Many of the RC planes are specific to certain types of flying that people are interested in: Trainers for newbies or advanced flyers just relaxing, sport and aerobatic ships for general hotdogging, pattern ships for precision aerobatics, scale aircraft modeled in exquisite detail after full size aircraft, gliders, slope soarers, midget and quickie racers, helicopters, and, of course, jets. Take a look at some of these links for examples of different models.
What do you need for this RC flying thing?
There are six basic ingredients to flying:Enthusiasm
Enthusiasm may sound strange as an ingredient, but you'd be surprised how many people give up after a few flights. Enthusiasim wanes fast when, even though you fly Boeing 777's for a living, and tool around in a P-51 for enjoyment, your looking at your model spread over twenty square meters of ground. Knowing the basics of flight certainly helps you understand what your plane is doing, but you haven't got time to consider many options when your model is heading straight down under full power. Here's an experiment: See how many logical arguments you can have with yourself in one second.One of the most common problems is that beginners forget that the plane is supposed to come back. I have witnessed many crashes by first flight beginners who were afraid to ask for help and weren't noticed in time. Typically, they have about an even chance of getting off the ground. Then they have to turn. Maybe half of them will actually complete the first turn successfully. With the rest, the plane often drops its nose and gyrates into the ground. Half of those who make it through the first turn, might make it through a second. But now the plane is coming straight at them. Whoa, the controls seem reversed. Goodbye orientation, hello ground. Well, in the end maybe one in a hundred beginners is capable of successfully completing a flight with a typical powered trainer. Forget the bravado and start with the attitude that you are not the one in a hundred. Its not just a hand-eye coordination problem, its learning to coordinate the amount of stick throw on the transmitter with the reaction by the plane in a very short amount of unforgiving time.
Thus, you need plenty of enthusiasm to sustain you through the learning period and subsequent crashes. It also helps to have a comforting loved one. There is one axiom in RC flying - you will crash. Some crashes are minor, some are spectacular. Sometimes its only a dinged wing, sometimes the plane is in more pieces than the original kit. I know people who carry large garbage bags with them just to make sure they get all the pieces. And you do want all those pieces. Its amazing what you can put back together with today's modern adhesives.
Money
No matter how creative you are, you will need money for this hobby. A beginner can expect to pay about $400 U.S. to be completely outfitted. This includes accessories to keep everything running. Yes, that is a lot of money. (At least to me!) Remember much of that money will buy equipment that will far outlast your first plane, and maybe even your interest in the hobby. My oldest radio is nine years old and still works well. It has been repaired several times (mainly the receiver after bad crashes), and its on its fourth set of rechargable battery packs. My oldest engine is the same age, and still kicks a lightweight plane around well enough for me.Airplane
Just about everyone wants to start in the hobby with a nice warbird, or some sleek aerobatic screamer. I did. Forget it, it doesn't work that way. The more responsive the plane the quicker your responses need to be. A well designed sport or aerobatic plane goes where you want it, and stays that way. Beginners need something more forgiving. They need to think small, simple, and slow. A typical trainer will have a 50 to 60 inch wing span, and weigh four to seven pounds when ready to fly. The majority of models that we fly are in this range. A typical trainer has a thick, flatbottom wing situated high on the fuselage. Plenty of dihedral (the amount of angle the wingtips are raised relative to the center point of the wing) is built in. This is a very stable configuration, and has a tendency to right itself if left alone.Once past the trainer stage the choices depend on your interests and abilities. Most people move up to sport planes. These can be based on full scale aircraft, but many are not. They have flying characteristics of intermediate level. Typically, they have generous wing areas with moderately thick airfoils. The wing may be semi-symmetrical (more curvature over the top of the wing) or fully symmetrical. They can do a large range of aerobatic maneuvers, and for many people this is the class they stay with.
Another popular area is the 1/4 scale or giant scale. These model are impressive in size, power and price. Wing spans must be at least 1/4 scale of a full size aircraft, or a minimum length of 80". Weights are in the range of 10 to 45lb. A plane in this range can easily be a $600 (US) investment. Usually flyers wait until they have several years experience berfore advancing to this level.
Gliders are also popular. They have long thin wings with thin airfoils. Many have multiple dihedral. Getting gliders aloft is usually done with a device called a high start. It consists of a something like 100 ft. of surgical tubing that is stretched out and the glider attached. Up elevator is applied when the glider is let go. To release from the tow line, the glider will dive to slip a holding ring from a pin on the plane. Another more expensive variant is a powered winch. Other methods of gaining altitude consist of a power pod attached to the glider. A tiny, glow-engine engine is attached to the glider wing. The engine carries just enough fuel to get the plane up to several hundred feet.
Electric sailplanes are also becoming popular. In this case an electric motor powered by rechargable cell packs drives a propeller. The motor is used only to gain altitude, then is shut down.
It is not uncommon for gliders to have 30 minute flights or more. The trick is to find thermals (rising pockets of warm air) so that they can regain altitude. This is exactly what some brids, such as hawks or eagles do.
The construction of RC models alone would fill many pages. There's just to much for a simple page like this. Generally, there are three classes of construction. Commercial kits, almost-ready-to-fly (ARFs), and scratch built.
Commercially prepared kits vary widely in the building materials they contain. In smaller planes, balsa wood is the predominant material. Its high strength coupled with its low density still makes it one of the best materials for producing light weight, rugged structures. Where high strength and ruggedness is needed, such as in firewalls (where the engine is mounted) or wing saddle areas, aircraft plywood is used. This type of plywood is a little different than regular construction plywood. It has many thin close grain plys. In large models, the proportion of plywood to balsa increases and the balsa parts are thicker than for smaller models.
Wings can be shaped in a variety of ways. They can be "built up" from wood with ribs and spars just as in full scale aircraft. Or foam insulation board can be used to make a wing. The material is cut to the desired shape and size with a "hot wire". This foam core is then sheeted with thin balsa planks, cap strips, or thin wood veneers.
Fiberglass is commonly used for many large scale models both to form fuselages and to sheet wings. Even carbon fiber composites are being used, especially in gliders, to strengthen the long wings.
Almost-ready-to-fly (ARF) kits are gaining in popularity. These models may have built-up or foam core wings. Their main characteristic is that the wing halves, fuselage and tail surfaces are already built for you. In many cases, the parts are even pre-covered. The only gluing that needs to be done is to join the wing halves and glue the stabilizer and fin surfaces on the plane. In some cases the control surfaces: the ailerons, rudder, and elevator, are even installed at the factory.
Both wood kits and ARF kits often contain some hardware in addition to the material to construct the basic framework. This can be from as little as nothing to nearly complete hardware including, wheels, landing gear, engine mounts with all screws and nuts, plastic cowling, plastic canopy, plastic turtledecks, hinges for control surfaces, and even fuel tank.
The final type of plane building is the scatch built. Many modelers would consider this the ultimate level. The builder starts with a set of plans, either of his own design or commercially prepared. He purchases all material to his specifications, makes his own jigs and cutout masks to construct the aircraft. Anything goes here.
Some fliers cheat a little and just mix and match, taking an airfoil from standard kit plans and a fuselage from another kit plan. Both kinds of building usually require a fairly well equiped workshop.
In all these modes of building, glues are the most important fastener. A variety of glues is used: common wood glues, epoxies, contact cements and superglues. Cyanoacrylates or super glues are becoming a favorite of many modelers. These glues produce strong joints very fast, keeping building time to a minumum. There are a number of different formulations for specific uses. Often a kit will require more than one type of glue. For instance, where high strength is needed such as in firewalls, epoxy glues are recommended.
There are many different techniques used to cover airframes. With balsa and foam models, the most common covering material is a thin heat shrinkable polyester. This material, which comes in a large variety of colors, has a heat activated adhesive to fix the material to the balsa. Small irons (even clothes irons) or heat guns are used to attach and shrink the material. First, the covering is tacked down to the airframe with the iron, and then the iron or heat gun is used to shrink the covering between the tacked down areas. The result is a very tight covering. Older methods such as dope and close weave cloth are also still used.
Building time varies enormously. It depends on how efficient the builder is, how complicated the kit, how intricate the covering design and exterior detail. A typical built-up kit may take 100-150 hours to get to the ready-to-fly stage. An ARF can take from 10 to 40 hours. A scale airplane with exquisite detail, such as seat belts for a scale pilot and hand painted instrument panel, can take over a thousand hours.
A message to parents who have an interested son or daughter: [For parent trying to justify the expense - begin cut here.] This is a great hobby for parents and kids. Building a plane and learning to fly together is a great experience. Building a model teaches the importance of reading plans and following instructions. It is a great way to introduce working with simple tools to a child. Many tasks do not require heavy manual labor. [End cut here] However, building a plane is a tedious job requiring careful attention to detail. Most kids get bored very easily, and 15-30 minutes is often their tolerance limit for construction. This is especially true during the early building phase, where very little seems to be done that looks like it will ever turn into an airplane. Tolerance is also more limited in the summer months. Be prepared to be patient. You may also find that for some stages of construction, it isn't worth trying to keep the child around.
I built one plane with my younger son, when he was 12. I had crashed his trainer in mid-summer, and needed to get something in the air fast to continue his training. I opted for a ARF trainer. The parts go together fast, and a little bit of work makes a wing, or fuselage fast. But, I found that the tedium and fanagling of radio installation was way beyond his attention span. At 13 he is now building a balsa kit, and although his attention span is longer, he has many other interests. So the building phase is going to be much longer than for me.
Radio System
Most flyers purchase their radios. Things have changed dramatically since RC first began in the 1930's. Gone are the fifty pound transmitters with twenty foot antennas, and several pound receivers. Todays equipment is all based on solid state electronics. The basic radio system of today consists of a transmitter, receiver, servos and battery pack. The transmitters are proportional, i.e. a certain amount of transmitter stick movement causes a proportional change in the models control surface. The reciever, servos, and battery pack are installed in the plane. The transmitter is what the "flyer" has in his hands.Radio systems have a number of "channels". Each channel can be assigned to a certain function, such as controlling ailerons or throttle. Radio systems commonly have four or six channels in the lower price range, large models may use up to nine channels or more. Radios with microprocessors are also becoming more common. These marvels can allow mixing of the various controls to achieve a custom effect such as a aileron/rudder coordinated turn, or a snap roll. The most common type of transmitter set up consists of two main control sticks. Moving the left stick up or down controls the throttle. Side motion controls the rudder. Moving the right stick up or down controls the elevator, and left to right movement the ailerons. The receiver, which is placed in the aircraft, is generally small, weighing only a few ounces. It derives its power from a Nicad rechargable battery pack. The receiver not only picks up the signal from the transmitter, but decodes the signal and tells the appropriate servo how much to move. It is the servo that moves the control surface. There are additional "trim" controls on the transmitter to fine tune the control surfaces. These trims move the planes servos only a few percent.
Their purpose is to overcome any minor imperfections in the planes flying surfaces to achieve optimum flight conditions or "hands off" level flying.
How can there be more than one plane in the air at a time? Transmitters transmit on specific frequencies, just as different radio stations transmit on different frequencies. There are over forty different frequencies alloted to model aircraft. When a flyer goes to a flying field there is a frequency board or a transmitter impound area. The frequency board tells him what frequencies are being used, and whether his transmitter's frequency is in use. If it is in use, he must wait for the other flyer to give up the frequency.
Engines
Most engines used for RC flying are 2-cycle, single piston, air cooled engines. That is they fire on each stroke. They have displacements ranging from 0.010 to over 2.5 cubic inches. In the U.S. vernacular of RC flying a "40" size engine has a 0.40 cubic inch displacement. Engines in the range of 30 to 90 are the most common. Glow ignition is used to ignite the fuel. Unlike the familiar spark plug, glow plugs consist of a platinum alloy spring, which glows continuously like the more familiar toaster element. This ignites the compressed fuel. Initially, a battery is used to keep the plug hot, but once the engine is running, the fuel combustion keeps the plug hot, and the battery can be removed. These engines turn from 3000 rpm at idle up to about 28,000 rpm in the highest performance class.
Four-cycle glow engines are also used. They are more like the familiar car engine and have a true cam and valve system. These engines turn around 2,500 to 11,000 rpm. Many people like these engines, because of their more realistic sound. They have a less annoying pitch than the two cycle engines.
All these engines have adjustable carbareuters to throttle the fuel mixture at both idle and high speed. The fuel for glow engines is a mixture of methyl alcohol, oil, such as castor oil, and nitromethane.
In addition, regular two and four cycle ignition engines are used on larger models. These engines are similar to chain saw or weedwacker engines, but modified to take the different forces generated by a propeller. These engines burn gasoline.
Critical Accessories
A plane, an engine, a radio are what most people think is all that is needed. Well, its pretty close, but there are some accessories which can make problems a little less frustrating. Lets not forget fuel. Oh, and then we need something to transfer the fuel to the fuel tank in the plane. You didn't forget the battery for the glo-plug, did you? New engine a little onery starting? Maybe you should have taken up golf.Well there are ways to solve all these problems. Fuel can be despensed with either hand cranked pumps or small electric pumps designed to be compatible with glow-fuel. Engine starting can be greatly simplified by using modified motorcycle starter motors sold specifically for RC use. Often all these defenses against frustration are powered by 12V motorcycle batteries with power panels to control pump, starter, and gloplug. All this equipment along with an assortment of tools is often placed into a flight box.
Hints for Success in RC Flying
First off let me start with etiquette: Even if you never fly yourself, please, please, never, never laugh or rudely comment if you see a model airplane crash. Consider the amount of work and caring that went into the model. When someone spends over a hundred hours putting together a model, and the model is gone in a few seconds, it is extreme bad taste to make fun out of it. If the model is repairable, it can easily mean a few to twenty hours work to repair. (I once spent forty hours rebuilding an airplane only to have it crash on the first flight after the rebuild.)Start with a glider or trainer. Yes, dream and drool over the P-38, but forget it for now. You'll see why on your first flight.
If at all possible, learn to fly with an instructor. With his help your much more likely to take your new plane home in one piece. Most clubs have designated instructors to help new flyers both fly and build their aircraft. To find out about clubs in your area, just go to the nearest flying field that you know of and ask around. Very few flyers are snobs. They will be happy to clue you in on clubs and other flying sites in the area. In many cases if you ask very nicely, a flyer will assist you on the spur of the moment. If he refuses he is more than likely not snobbish, just cautious. This is true of even many advanced flyers. They just don't feel comfortable teaching. Don't take it personally. A word of caution here; actions speak louder than words. First, watch how a person flys before asking him to help. Is he watchful of others? Can he fly well, but safely? Does he seem to follow the rules of the field? Spend some time picking the right person to ask.
Remember fly safely, check your equipment and plane each time before you fly. You have a wonderful aircraft, that can let you soar to amazing feats. But it is also a potentially dangerous machine. Keep alert, and keep your equipment in good shape.
Finally, there is nothing quite like your first solo flight, where you takeoff, fly and land all by yourself. Its a moment that you will bore your family and friends with for at least a week. Its a personal accomplishment that only someone who has done it can fully understand. Yes the pounding heart, weak knees and the sweating palms are also part of the experience. They will be there even after many flights.
