Model Tech Magic: A 3D performer not even Houdini could top!

Model Airplane News, Sep 2003 by Royer, Erick

I marked the location for the throttle pushrod, drilled the hole and installed the pushrod tube. I used a Hitec HS-81 mini-servo right behind the fuel tank for the throttle. I used a Z-bend to connect the pushrod to the throttle arm on the carburetor and then attached the other end to the servo arm with an E-Z connector.

Tail feathers. Now it was time to install the tail surfaces. I positioned the horizontal stabilizer and vertical fin on the fuselage and marked the position of the fuselage sides on the tail surfaces. I then removed the covering inside these lines, and, using my Great Planes

Woodpecker, I prepared the exposed balsa for epoxy. Using 5-minute epoxy, I attached the tailpieces to the fuselage. Make sure that the stabilizer remains parallel to the wing's trailing edge and that the vertical fin rests at a perfect 90-degree angle to the stabilizer. Be sure not to get epoxy in the pushrod exit when you glue the stabilizer into place.

Radio gear. I used Hitec HS-425BB servos for the rudder and elevator. These are standard servos that work well, given the control-surface sizes. If you decide that you need more power, you can switch to a Hitec HS-605BB servo. The elevator servo is flush-mounted on the servo tray, and the rudder servo is mounted on support blocks that are epoxied to the servo tray. I used a set of long control horns from Du-Bro and had to cut the ends so they wouldn't contact the fuselage sides. These horns will provide maximum control-surface throw.

Next, I attached the control horns to the rudder and elevator with the included bolts and nuts. I found it easier to slide the pushrods into their respective tubes and attach the clevis to the control horn first. With all the control surfaces and servos centered, I made a Z-bend where the rods should be attached to the servo arms. (The manual suggests that you make an L-bend and use a keeper, but either method will work fine.)

FINISHING UP!

At this point, the model is pretty much ready to go. The last two components to install are the battery and receiver. I placed the receiver next to the throttle servo and routed the antenna wire along the bottom of the fuselage. Before I installed the battery, I thought it would be a good time to balance the model.

The manual states that the CG should be 115mm behind the leading edge of the wing. I set my Great Planes CG Machine to 115mm and placed the plane on it. To my dismay, the model was very nose-heavy. I began to position the battery in various places on the fuselage to see where it would balance. I ended up cutting a hatch for it on the bottom side of the fuselage, about 3 inches behind the servo tray. I used a 6V, 100mAh battery. The plane then balanced perfectly.

The last step is to set up the control throws and the radio. I use two rates on my Futaba 9C radio. I have low rate set to the measurements indicated in the manual, but I decided to set the high rates to maximum deflections. I'm counting on the extra control throw for 3D maneuvers. 1 did use 50-percent-negative exponential on all channels at high rates; this keeps the controls soft near the center, even on high rates.