Years of testing, development and evolution have moulded today's competition pattern ship, yet to the untrained eye the design cues aren't always obvious. Mike Williams, highlights a few key details
Selecting the right propeller is essential (and good research vital) to gain maximum efficiency for F3A requirements. Pattern models need to fly at a constant speed no matter which direction they’re travelling. In this respect, a propeller designed specifically for maximum power and down-line braking will help.
Electric power has come to dominate F3A over the last couple of years. Reliability aside, outrunner motors swing large props that help to slow the model where necessary, i.e. on a down-line, and contribute to a constant speed.
Servos that centre accurately and move with precision are paramount in helping to achieve the smooth flying style that F3A demands. Surprisingly, servos with plastic gear trains are common as the stress loads imposed by schedule manoeuvres are minimal. Moreover, the mesh of metal gear servos tends to display a certain amount of movement which can lead to deviations in the air.
The canaliser was first devised by World F3A Champion Christophe Paysant Le-Roux to provide a greater change in airflow over the rudder. This helps make the rudder more effective, keeping rolls more axial, especially when in the knife-edge position. There are different shapes and sizes of canaliser but they’re all designed with the same function in mind.
Most F3A designs now employ an anhedral tailplane arrangement. This is designed to change the lateral stability making roll manoeuvres more linear with less need for aileron differential and rudder correction.
Trailing edges, particularly at the rudder, often have thicker profiles. This helps change the airflow, which in turn makes for much smoother tracking, especially in windy conditions. Some rudders also feature a flared trailing edge, designed to stop fish tailing.
The fuselage is designed with a deep side profile that tapers little towards the tail. This is to maximise lift and to produce a better, more linear knife-edge capability.
Control surfaces differ from freestyle or 3D aircraft in that they’re far smaller. Models such as this don’t require huge deflections to perform smooth graceful manoeuvres.
Whilst standard covering materials are usually applied (this Wind 100 uses Oracover), it’s interesting to note that serious competitors keep their machines very clean in a bid to reduce drag.
Tiny wheels and spats are employed in an attempt to keep the weight and drag down to an absolute minimum. Sizes no bigger than 1.5” are common, even on 2m models. That said, wing loadings are comparatively low so undercarriages get an easy life.
Undercarriage fairings produce lift and help the model track straight. Of course, some competitors like them simply because they add a neat finishing touch to the aircraft.
Featured pattern ship
This is Gary Beaven’s SebArt Wind S 110e, a popular, 1.7m, electric machine designed by F3A World Champion Sebastiano Silvestri. The model suits both the beginner or intermediate pilot and is used by many for regular competition work. A full ARTF, Gary’s model uses a Hacker A50 16L 272Kv brushless outrunner swinging an 18 x 12” APC-E prop with power from eight Li-Po cells via an 80 amp ESC. A 1300mAh two-cell Li-Po battery provides power for the receiver and five servos, this via a PowerBox switch that also regulates the voltage. On the servo side, two JR DS8321s (9kg torque) drive the elevator with JR DS8411s (11kg torque) employed on rudder and ailerons.
WIND S 110E Specification
Manufactured by: SebArt (Italy)
Wingspan: 68” (1740mm)
Rec’d motor: Hacker A50-16L
Functions (servos): Aileron (2); elevator (2); rudder (1); throttle (via ESC)
By Martin McIntosh
by Martin McIntosh
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