TYPES OF AEROMODELS

Aeromodels can be basically classified into 2 types:

• Static and
• Flying

Static model aircrafts are not intended to fly. They are commonly built using plastic detail parts, photo etched brass, and wire, though other materials such as wood, metal, and paper are also often used. Some static models are scaled for use in wind tunnels, where the data acquired is used to aid the design of full scale aircraft.

Flying aeromodels are, as suggested by the name, model aircrafts capable of actual flight. While static models lay more emphasis on the external appearance of an aircraft, flying models need considerations of weight, balance and strength as well. Shape considerations tend to focus more on the aerodynamics or flight characteristics of the model than just the external looks such as paint and finish. Different building materials may be used for building flying aeromodels but they should have a good weight-strength ratio. Balsa wood and polystyrene foam meet these criteria and are choice materials for construction. Also, bits of glass fiber cloth, plywood and some plastic moulded parts such as propellers and spinner cones may be incorporated in the design. Just like the static models, it is always a good idea for beginners to go for kits rather than trying to build models from sheets of balsa wood!

They may be classified very basically as:

• Powered or
• Unpowered,

depending on whether they have a source of power (such as a motor or an engine) to assist their flying.

Also, depending on the method by which they are controlled in flight, flying aeromodels may be classified as

• Free flight models (with only built-in controls)
• Control-line models or
• Radio-controlled models

UNPOWERED AEROMODELS 

These are without a power plant and fly only using the initial force supplied during launching.

The chuck gliders are launched in the air by the chucking action of the hand and are often flown indoors. Hence they are also known as 'Indoor models' Some chuck gliders are made using sheets / blocks of 'thermocol'. These tend to float in air for longer time and have longer wings and higher lift compared to other models of this class. The critical aspect of such aeromodels is the design of the wing, as this decides the time of flight of the model.

Catapult models are also similar to chuck models, except they are launched from a hand-operated catapult, rather than a chuck of the hand. These models are swift, have a longer range and are suitable outdoors. Catapult models need to be stronger than chuck gliders, hence are made of wood / plastic and not thermocol. They are basically model planes which take-off with the aid of a rubber string hooked to it. The tension in the string pushes the model forward when released. These models are usually made out of balsa. The success of the flight depends on the shape of the wings (aerofoil).

Tow-line models are gliders which are launched using a long line with a ring hook, in the open against the wind direction. The launcher runs against the wind after the helper releases the aircraft. Once in air, the aircraft rapidly gains height until it is at the top most point called the 'zenith'. The model automatically detaches from the tow-line as the ring hook slips and glides back to earth in wide circles. The fin is off-set a couple of degrees while constructing, to aid the glider to descend in circles.

POWERED AEROMODELS:

Free flight models are aircrafts fitted with an internal combustion, reciprocating engine (usually small compression ignition engines of capacity around 0.75 cc). They are launched in an open field and gain height as a virtue of pre-set elevators, as long as the engine is running. Calculated amount of fuel is filled in the tank to gain a desired height. When the engine cuts, the free flight model glides back to the earth, freely, just like a glider! http://www.parmodels.com/free_flights.htm

Rubber powered models are simplest class among the powered aeromodels. They also fall in the category of 'Indoor models' and are similar to chuck gliders, but made of balsa wood. They have a propeller which drives power from the unwinding of a twisted rubber band. Special rubber powered motors are also supplied with some kits. They also come under free flight models.

Control-line models are a stepping stone towards the radio-controlled models and are usually fitted with compression ignition engines from 1 - 3.5 cc capacity and are controlled by means of two metal cables, which control the elevators of the aircraft. A fixed rudder position in the design of the aircraft ensures that the aircraft flies in circles around the flyer but pulling away, to keep the control line taut at all times. Depending on the flight characteristics and the ease of maneuvering, the control-line aircrafts may be trainers or aerobatic models or speed models. Trainer models are sturdy and have low speeds and sluggish controls to allow a beginner to gain experience in flying powered aircrafts. The aerobatic models are light weight, overpowered and have sharp controls which allow the flyer to perform in-flight aerobatics with the model. Speed models are racing models, generally used in competitions and are dedicated to very high speeds. Some of the aerobatic and speed models are powered by glow-plug engines for an extra boost of power. 

More about 

control line model:  http://www.go-cl.se/clinf.html 

control line competitions: http://dkd.net/clmodels/links.html

Radio controlled models fly like real aircrafts and are a keen aeromodeller's ultimate dream. They are remotely controlled by means of a radio transmitter. The receiver fitted in the aircraft picks up the transmitted signals and manipulates the flight controls to fly and even perform aerobatics. Generally a 4 channeled radio with 4 servos fitted on the aircraft gives the flyer (pilot) control of the elevators, ailerons, rudder and the throttle. The more the channels on your radio the finer control you can exert on the aeromodel. These models are powered by a single / multi-cylinder glow plug reciprocating engine. There is a huge variety of engines available in several price ranges differing in their engine capacities, types (some are 2-stroke engines while others are 4-stroke), cylinder configurations, throttle controls and accessories. Some advanced models also incorporate jet engines or solid rock motors which use a solid propellant.

Types of RC planes: Powered sailplanes are popular choices for electrically-powered planes since a relatively low amount of power is required to sustain flight. This corresponds to long flight times of 10-20 minutes and more. Some gliders are capable of high speeds and advanced aerobatics, others are designed for seeking and circling in hot air packets called thermals. The smallest sailplanes are about 4-5 feet in wingspan and can fly effectively as pure gliders or with .049 engines or 50-100 watt (035 class) motors. They require the smallest radio equipment due to their small fuselages. Standard-class sailplanes are the next largest at slightly over 9 foot wingspans. Sailplanes larger than this are classified as open class gliders. Relatively few of these planes are powered, but could be modified to accept 200-400 watt (15 to 40) electric motors as desired.

Trainers are used to learn flying rc models. Although the easiest way to learn to fly R/C planes is through sailplanes, many opt for the more traditional Cessna-like trainer approach. Most trainers are gas-powered, but several kits also come in an electric flavor. Most of these planes are designed for 100-250 watt (05-15) motors and have wingspans of 3-5 feet. They generally fly somewhat faster than the typical sailplane, but still slowly enough for the novice to comprehend the situation and respond correctly. Trainers are generally high-wing planes with flat-bottom airfoils and plenty of dihedral for positive stability and high lift at low speeds. Most good trainers, if placed in an unusual or hazardous attitude, will recover on their own if there is sufficient alititude.

Sport and Aerobatic models: After mastering the basics of flight, many modelers seek planes that are less overtly stable than trainers and hence make better aerobatic planes. Such planes range from 3-9 foot wingspans with 100-1500 watt (05-90) motors. Unlike sailplanes and trainers which utilize a flat-bottom airfoil, most sport planes use semi-symmetrical and symmetrical airfoils. This can sacrifice some lifting capability but usually improves handling in gusty wind conditions and during aerobatic maneuvers. The plane tends to be neutrally stable -- they "go where they're pointed"; i.e. they don't self-recover from bad situations as readily as trainers.

Pylon racers: Some pilots choose to design low drag planes that will go as fast as possible. Such planes typically have 3-4 foot wingspans and use 200-400 watt motors, reaching speeds well in excess of 100 mph! Some gas kits can achieve speeds of 200 mph. By comparison, typical sport planes fly at 40-60 mph, sailplanes from 20-60 mph.

Scale models: Exact scale models of all varieties of civilian and military planes are also popular targets for model airplane enthusiasts. Details are easier to implement in larger models, so such planes tend to be above 5 feet in wingspan and have high power requirements (300+ watts). Civilian planes with light wing loadings, such as the classic J-3 Cub, and multiengine models as displayed above, are excellent electric flyers. Ducted fan models: For those who like special challenges, you can model jet aircraft with electrics as well! Electric ducted fan models are a new exiting and challenging part of the hobby.

Ducted fan models powered by an electric motor have only been possible for a couple of years. Contrary to typical prop planes, where a "slow"-turning, high torque motor is desired, in ducted fan models high RPMs are needed on relatively few NiCad. Fortunately, R/C car aficionados use high speed motors for racing purposes often with "only" 6-7 cells. Also, motors used in pylon racers are also frequently suitable for ducted fans.

RC Helicopters: R/C helicopters are an interesting aspect of the hobby. Such models can hover and move exactly like their full-size counterparts -- in addition to non-scale abilities such as inverted flight and stunning aerobatics. Relatively few electric helicopters have entered the market due to the short flight times (you can't exactly glide a helicopter). Helicopters tend to be more complicated and costly to build and maintain, a trait which R/C helicopters also inherit.