RC sailplanes strive for efficiency, especially competition models like discus launch gliders. Efficiency comes in many forms; it can be in launch height, how well the glider floats and penetrates, or even the setup of the linkages. Offsetting flaperons on a DLG uses all of the servo's deflection to maximize the control surface throw, torque, and accuracy.
What is a flaperon, and what does it do?
The flaperon is a single wing control surface on a wing-half that combines the functions of the flaps and ailerons. Flaperons control three things:
The camber of the wing to control the amount of lift produced,
Banking input, and
Brakes to slow down the glider.
These three functions require different deflections. The flaperons only move up or down by several mm for camber control, approximately 15mm for banking input, and up to 80 degrees of down deflection for brakes. Therefore, the flaperons require significantly more downward deflection than upward deflection based on these requirements.
What is the best way to offset the flaperons?
So, what do you do? Do you set the servo horn to control horn radio closer to 1:1 so you get excess deflection in both directions, then clip the extra upward movement through the radio settings? No, because while this will provide you with the travel you need, it comes at the expense of lower accuracy and torque. In other words, you will have a hard time setting up the model, so it is repeatable, and it will likely flutter on launch.
You need to mechanically offset the flaperons during the assembly process for best results. Mechanically offsetting the flaperons provides you with the up and down deflection required with no excess while increasing the accuracy and torque. Instead of using the neutral point of the servo and flaperon as the base of the installation, this method uses the maximum up deflection required and maximum up servo movement as the base. After the installation, the flaperons are offset from neutral, and you can use your radio to bring the flaperons back to flush with the wing.
While the process is simple, it can be hard to visualize. Watch our tutorial video to see precisely how to offset the flaperons on your DLG mechanically.
