Building Tips – Elevon control

Most of us are delighted when our model just responds to radio signals and performs properly. Typically, we use a “lever” style transmitter (Tx) and on a twin motor vessel, if seeking individual motor control, one motor is controlled by the up/down movement of each lever. This works well but has some limitations. Both hands need to be used and rudder effect is easily masked by inadvertent motor operation. This is particularly apparent on faster models with a brushless motor installation.

          There was an article published in “Model Boats” magazine in March 2019 suggesting another approach. All of our RC equipment was generally developed for model aircraft, for that is where the volume market is. However, sometimes features are offered that boaters would not usually use. On some of the more sophisticated Transmitters (Tx) both “Elevon” and “V-tail” mixing are available. These link two radio functions together so one control lever can operate both features. I will describe the “Elevon” as it is the one I use on my Flysky Tx, although both functions are offered.

          “Elevons” are control surfaces on delta wing aircraft where the functions of elevator and aileron are combined. My Tx is the “Mode 2” style where elevator and aileron controls are on the RH lever. In aircraft with separate wings and tail, the Forward/Back stick movements operate the 2 elevators and cause the aircraft to pitch up or down, and side/side movements operate the 2 ailerons and cause the aircraft to roll. When the ‘elevon’ control method is used, the same stick movements cause the same aircraft motions but operate only 2 elevons.

          On a model boat, elevon control puts both ESCs on the RH control lever. Moving the lever up operates both screws in the forward direction and down into reverse. Going from side to side speeds up or slows down either motor, so the boat goes in the direction the lever dictates. Rather more intuitive than before. After setting this function up and then testing it, I decided it works well. This was accomplished by:

•  Establish the Tx Stick mode, mine was # 2.
• Considering Elevon, determine which layout allows the Aileron and Elevator controls to be operated by the same lever.
• Use ‘Elevator’ for throttle (fwd & astern) and ‘Aileron’ to “turn”. The ‘Aileron’ will accelerate the motor on the outside of a turn.
  
• Reallocate channels on the Tx so Port & Starboard motor ESCs become channels 1 & 2 respectively. Use these channels on the Rx for the appropriate ESC.
  
• Select “Elevon” mode on Tx.
  
• The RH lever now controls both motors.
  
• The LH lever (side to side) can now be used for rudder and the up /down function for any other feature needing proportional control. I use it for the centre brushed motor on my triple screw model.
  
• Your Radio instructions should give detailed information on setting up the radio.

Rowen has used this technique on his models to control brushless motors. He found that using differential motor control for steering could be difficult. The brushless motor response is so rapid it is impossible to do anything gently. For steering he tends to use rudder control on the LH stick when running at slow speed or when in confined waters, and turns using Elevon differential motor control on the RH lever at speed or on open water. Differential control will probably be smoother when using brushed motors.