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Reinforcing the Fuselage: Notice how nice the servos look in one of the photos, all in place and with everything connected. It is good to have an installed fuel tank as well, and the engine is comfortable nesting in its preinstalled mount. It seems a shame to disturb all of that nice work, but I am going to do just that.

    Experience has shown that some problems develop past the 100- to 200-flight mark that can be prevented at this point. You may consider 200 flights too many to worry about, but it represents only 10-20 weekends of five flights a day. That is less than one season.

    The servos are mounted on a thin plywood plate using small screws, which sometimes loosen after many flights. It is a good idea to center each servo's control arm—the part to which the control rod connects—and then remove the center screw and control arm and the four servo-mounting screws. Remove the servos, but leave them connected to the receiver.

    Hobby shops sell 1/8 x 1/2 spruce rails that are roughly 36 inches long. Cut two rails approximately 1/4-inch shorter than the inside width of the fuselage. Glue the two rails with thick cyanoacrylate onto the bottom side of the servo tray.

    Move the servos and wires out of the way, insert one rail through one of the two rear servo holes, and rotate it widthwise. Apply the adhesive and hold in place. It is best to position each rail slightly outside the plywood tray's servo hole so that the servo fits back into place easily.

    After installing the large rails, cut two smaller rails for the throttle-servo mount and install them. In the end, the bottom of your servo tray should look like the one shown. Drill through the existing servo mounting holes with a 1/16-inch-diameter drill bit, and then replace the servos and all connections. Make sure the servos are centered and all control surfaces are in their original positions. Do the same for the wing's aileron servo because it gets the most stress.

    All RTF aircraft feature bolt-on tail feathers. Hangar 9 trainers mount the vertical fin to the horizontal stabilizer using two bolts. Two additional bolts mount this assembly onto the fuselage, as shown. Hobbico RTFs use two long threaded rods mounted inside the vertical fin that pass through the stabilizer and are bolted to the fuselage bottom, as is also shown.

    Both systems provide perfect alignment but wear in time. Eventually the wood around the bolt holes distorts, enlarging the holes and allowing the stabilizer to rotate in position.

    The solution is to epoxy the stabilizer in place using the stock mounting system for alignment. Install the fin and stabilizer in place. You may find it easier to accomplish this using a 00 Phillips screwdriver to align the fuselage and stabilizer bolt holes first. After everything is in place, draw a line with a fine-point felt-tip marker onto the stabilizer's top and bottom where it meets the fuselage sides.

    Disassemble the stabilizer and fin, and cut away the covering 1/16 inch inside the lines on the top and bottom of the stabilizer. Use a sharp #11 blade, but be careful not to cut into the wood. Apply 30-minute epoxy to the fuselage plates that mount the stabilizer. Not much adhesive is needed since the only intention is to reinforce the stock mounting system. Install the vertical fin and stabilizer and let dry.

    I have never experienced a loose vertical fin, but you can epoxy it in place if you wish. Remember to remove any covering from the fin's bottom as you did on the wing center-sections. Connect the elevator and rudder control rods. Be sure to use the silicone "keepers" to lock each clevis closed.