V-Tails and Elevons
angled stabilizer surfaces.
To get the appropriate movement out of the surfaces of a V-Tail or elevon plane (such as a Zagi-5C flying wing), the elevator-rudder or elevator-aileron controls are mixed together with either a mechanical device, electronic servo mixer, or a common function now built into most modern transmitters.
In the 'old' days (pre-1980 or so), mixing was accomplished via mechanical fashion. For elevons, it was common to see a linkage known as a 'sliding servo' mechanism. This is where the V-tail or elevon surfaces were connected to the aileron servo arms and an elevator servo arm was connected to the aileron servo itself. The aileron servo moved the elevons like a normal aileron linkage, but the elevator could also pull or push the ailerons up or down by physically moving the aileron servo on a sliding tray.
How the Mixing Works
physically moves the aileron servo on a tray.
There were also little plastic, mechanical mixers (available from Du-Bro and other manufacturers) that you'd put between the servos and the tail surfaces or elevons. They accomplished the same thing, but at the penalty of less surface movement (throw) and the mixers tended to be a bit 'sloppy' or inaccurate.
These days, mixing is accomplished right at the transmitter — some non-computer radio systems even have built-in V-Tail or Elevon options just by turning on a switch.
Sizing a V-Tail
There's a long-standing 'belief' about sizing a V-Tail using the 'projected area' of a conventional tail. This has proved to be a rather inadequate method. For equivalent control 'authority', a conventional, T, or V-Tail should all have the same TOTAL area. This is because of the need to use full rudder and full elevator at the same time. If you make a V-Tail with the same PROJECTED area, you can make the same elevator force OR the same rudder force, but not both simultaneously. For certain maneuvers (such as recovery from a spin), this difference can be very significant.