The stock Hobbistar 60 aileron linkage uses one clevis attached to a nylon torque-rod control horn. The aileron is aligned using two paint-mixing sticks clamped in place, and the control rod's other end is bent to pass through the servo's control arm with the arm centered. The bent section is then held in place by a nylon clip.

    This is fine, but experience has shown that the metal end expands the arm hole after roughly 100 flights. Also, the builder must enlarge the control arm's hole to fit the larger rod. If the hole is made even slightly too large, the ailerons will not be firmly held, with the usual bad results I've already mentioned.

    A better linkage system is shown. The control rod is attached to the torque rod's control horn using the standard nylon clevis and then cut in half. Another threaded control rod is connected to the centered servo arm. With the ailerons clamped in neutral, cut the servo's control rod where it meets the first rod. Apply solder flux to both sections and use a Du-Bro solder connector to make the joint. This control system will remain firm and positive during the aircraft's lifetime.

    We made several changes to the normal ARF wing construction while building the Hobbistar 60. Some may appear minor while requiring a great deal of work. If so, they are not mandatory and the aircraft performs well without them. However, service life is expanded and flying performance is increased with them. Only you as the pilot can judge their worth.

    Unless flaperons are going to be used, the wing is finished. Standard construction takes only approximately three hours of work and three more waiting for the epoxy to cure.

    You may have noticed a suspicious opening in the wing in a couple of photos. Those are homes for the two aileron control servos required for flaperon use.

    Why all the flaperon mentions? Twin aileron servos became useful with the introduction of computer transmitters. Using such a transmitter, a wing in which each aileron is controlled by a separate servo has several advantages.
 

Click on photo to view large image with caption

    Having independent aileron servos allows the pilot to adjust the aileron differential, which is where one aileron moves upward more than the other moves downward. Proper aileron differential improves rolling performance by helping eliminate adverse yaw, which is where the aircraft's nose first moves in the direction opposite the intended bank direction when ailerons are applied.

    Adverse yaw is most apparent with the flat-bottom wings that are prevalent on basic trainers. Although it is possible to adjust a single servo to provide some aileron differential, that is never as effective as using the transmitter's computer system.

    In addition to differential, twin aileron servos allow the ailerons to be used as flaperons, which are ailerons that also deploy downward as flaps. Flaperons slow the aircraft's landing speed while improving low-speed handling.

    Flaperons can also be deployed upward as spoilers to improve handling in high-wind conditions. Linking the flaperons to elevator input, as in a CL Precision Aerobatics aircraft, also makes for some interesting maneuvers and fun-flying.

    With two aileron servos, the control rods connect directly from the servo to the aileron without using torque rods. With sealed gaps and this control system, experiencing flutter is nearly impossible.   back to top

Next month I will cover flaperon installation. If you look at one of the photos with a sharp eye, you will spot a groove and a half-moon hole just behind the LE. If rubber bands are not your thing, you will want to learn more about this hole. We will also start fuselage construction next month.  MA