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Let’s Talk Giant Scale

These mechanisms mount to the fuselage and have composite anti-rotation devices as part of the units. They protrude from the fuselage as it is inserted into the wing. In the root rib, the builder must install a fiber tube in the exact same location as the anti-rotation pin. Then, to change the incidence, an adjustment screw located on the mechanism allows the wing to be adjusted up and down to increase, or decrease the incidence.

For airplanes with once-piece wings, you can simply insert a shim, like a washer, underneath the wing installation bolts. Inserting a washer under the rear attachment bolts between the wing and the fuselage, you will give a positive incidence adjustment. Placing a washer under the front bolts will provide a negative incidence adjustment.

If you wish to install an adjuster in
the tail, you will need an Adjustable Stab
Bracket. This is secured within each sta-
bilizer half and has two screws, located
both below and above the central portion
of the bracket, where a joiner rod is to be
inserted. This rod is the anti-rotation pin
and it must be glued into the fuselage at a
fixed point. Loosening the top screw and
tightening the bottom screw provides a
positive incidence adjustment.

Installing the stabilizer bracket

Since the horizontal stabilizer on the ZN Line Extra 330S is foam and sheeted with balsa, one of the last steps was to install the root rib on each stabilizer half. However, before doing this, I wanted to ensure that the adjustable stab bracket was properly secured to the rib. When installed, this bracket must sit flush with the root rib so only the root rib ever contacts the fuselage. To do this, I made a mount plate out of 1/8-inch light ply with a carbon laminate and spaced it out from the root rib by the depth of the adjuster. By using light ply and boxing in the area around the bracket, the bracket was now ready to be installed.

Once it is in position, mark and drill out two holes and install two 4-40 Tee Nuts. This allows the bracket to be replaced, and Tee Nuts installed with Medium ZAP CA ( franktiano.com)will not become loose over time.

Since the bracket was installed on the chord line of the stabilizer, finding out where to mount the pin should not be difficult. Drill a hole that is the same size as the pin then make two 1/8-inch light ply supports and glue them on the inside of the fuselage. Glue them in place with a mixture of 30-minute epoxy and microbal-loons. When cured, we can drill the anti-rotation pin alignment holes. Roughen the area of the pin that will make contact with the fuselage and the reinforcement plates, and epoxy the pin in place. Again, use an epoxy and micro balloon mixture.

Now that one stabilizer half is complete, repeat the steps above for the second half. Check the stabilizer incidence and make any necessary adjustments with the two setscrews.

Final thoughts

Finding the right incidence can be a challenging task, but if you take your time in trimming out your aircraft and seek the advice of experienced modelers, you’ll find it is easier than you think to produce a try flying aircraft. 