What is Free Flight?

A free flight model is one that the operator has no direct control of once it has been launched. This does not mean that the model is allowed to fly in a way that is uncontrolled, let me explain.

The model is designed with in-built stability, commonly the wings are set at an upwards facing 'V' angle (called dihedral) and the centre of gravity (C.G), the longitudinal balance of the model is at or around the main-spar of the wing.
The rudder (or fin) is set to give a circular glide and the thrust-line of the engine (if powered) is set to offset the torque of the propeller.

The time that the model is in the air is controlled by:
Limiting the time that the engine is allowed to run on power models.
Terminating the flight by operating a mechanism that changes the angle of the tailplane (or wing on some models) putting the model into a safe stall resulting in a controlled descent.

Types of model

Free flight models can be classed in one of three main categories:

Glider

The model in it's simplest form can be a 'chuck' glider or can be towed into the air with a towline.

Rubber powered

The model is powered by a propeller driven by a rubber motor, in it's simplest form a rubber band, but normally many strands of specially produced rubber.

Power

The model is powered by an internal combustion (piston) engine with either glow plug ignition, compression ignition (Diesel), or spark ignition (on some vintage models).

Construction

Free flight models are generally of simple open frame construction, traditionally using mainly balsa wood with some plywood and covered in tissue paper.
However contest models can use more sophisticated methods of construction using modern materials such as carbon fibre and kevlar.

Contests

Free flight duration contests are judged on the model's flying performance and are scored on the model's flight time. This can result in some very long flights with models regularly flying distances of over 2 miles.
Finding the models after long flights can be a problem and thus most people use binoculars and a compass to track the model whilst it is in the air.
However in major contests where flight times of 10 minutes or more are common many models are lost when the owner loses sight of it. This problem has been overcome in recent years with the use of radio tracking equipment. A very small transmitter is carried by the model and the signal is picked up by a directional receiver.

Crookham member Phil Uden winding up the rubber motor of his F1B (international class rubber) model.
As you can see the torque (turning force) required is very large and needs a special "winder".
Note the tension (stretching force) in the motor!, necessitating the model to be held in a "winding jig" that is secured to ground with cords and stakes.
(Photo: Rod Kenward)

BACK

John Thompson launching his F1C (international power class) model at Middle Wallop.
The engine only runs for 5 seconds from the time of release, but by then it may be 500 feet high.
Note the bicycle, a very necessary part of the contest flyer's equipment.
(Photo: Rod Kenward)

BACK

John Thompson starting his F1C (international power class) model.
This very specialised American engine (Nelson 2.5 cc glow plug) turns a carbon fibre propeller at over 30,000 rpm on the ground, and gets even faster as the model accelerates.
(Photo: Rod Kenward)

BACK

(Photo: Rod Kenward)

Jack Allen with his vintage spark ignition powered pylon model. Note the ignition contact breakers on the front of the engine just behind the propeller. They are connected to a small ignition coil that operates on 3-4.5 volts and supplies approximately 5,000 volts to the spark plug.

BACK