TRICK R/C Zagi-XS

Model Airplane News, Nov 2004 by Stewart, John

High-performance fun that can take a hit!

With a decade of research and engineerIng behind it, the Trick R/C Zagi-XS gets high marks for both design and performance. This take-anywhere plane also has a wide flight envelope, so you can toss it into the back of your car for impromptu flights and look for thermals, practice aerobatics, or just enjoy some relaxing sport flying.

This kit features precision, wire-cut EPP foam wings, a lite-ply brace, carbon-fiber spars, an 180OmAh NiMH battery pack, a carbon prop with machined hub, balsa ailerons, colored tape, a hardware package, a Zagi-20 ESC, a Zagi-400 motor and a 23-page instruction manual. To complete the Zagi-XS, you'll need only a 3-channel radio with elevon mixing and 2 servos.

CONSTRUCTION

Even though it's an important factor, the goal weight of an aircraft is sometimes overlooked during the building process. With its battery pack installed, the finished Zagi-XS should weigh 25.5 ounces. One or 2 ounces in either direction will make a tremendous difference to flight characteristics, so think first before you apply that extra coat of spray adhesive or piece of reinforcing tape! It's a good idea to reinforce your model as suggested in the instruction manual, if you've never flown a flying wing before, intend to fly this plane in combat, or just need extra durability. If, however, you want maximum flight performance and flight times, build light. Since this was my first attempt at flying a model of this design, I reinforced the wing with fiber filament tape, as suggested in the instructions. The extra tape and spray adhesive added about an ounce.

* Wing. At first glance, the EPP foam wing-cores seem rather typical, but further inspection reveals that the servo bays, electronics compartment, spar slots and wingbrace channel are already cut at the optimal locations. This makes assembly much easier and takes the guesswork out of where to place your components. In fact, the instruction manual States that it is never necessary to add additional weight for balancing the aircraft if the recommended components are used.

After lightly sanding the wing-cores, I used 3M 77 to glue the wing halves together and to glue the plywood brace and carbon-fiber spars into place. To join the wing halves, apply a long bead of glue to the root of each wing and spread the glue with a small brush or a piece of stiff cardboard. When the adhesive is dry to the touch, use the foam beds from the wingcores as an assembly guide and join the wing panels; this method will ensure a perfeet fit.

Install the wing brace and spars by working a bead of 3M 77 into the appropriate grooves with a piece of stiff cardboard or scrap balsa. Apply a light coat of 3M 77 to each side of the brace and spars, and then insert them into the appropriate slots as instructed. Here again, the foam beds from the wing-cores are used as a guide. When everything is in position, place small weights on the wing assembly to keep I everything aligned, and let the assembly dry for a couple of hours.

* Electronics compartment. While the wing assembly is drying, your next step is to build up the electronics compartment. Cut out the black styrène pieces at the indicated edges, solder the motor to the ESC and hook up all the electronics and : servos for elevon or flying-wing operation. I really appreciated that the kit included a charging lead.

When properly set up, the Zagi-20 ESC features an arming procedure that is started with the throttle fully off. Move the throttle stick to full-on and then back to full-off. The ESC will emit a faint tone to signal that it is armed, and the motor will then turn on when the throttle stick is moved. I discovered that I had to : reverse the direction of the throttle on my radio so that the ESC would properly arm itself. This ESC is EEC-equipped and has a low-voltage cutoff.

* Servo pre-installation. The electronics-compartment cutout is completely removed from the wing assembly at this stage; push the servo cutouts out of the wing assembly just enough to make room to flush-mount the servo. Use a sharp hacksaw blade to make the portion of the cutout that protrudes from the bottom flush with the wing. The servo cutouts are designed to fit Hitec HS-81 servos, but they can be enlarged or shimmed to fit other servos.

* Taping the wing. Apply spray adhesive i to any surface that will be taped, and then use fiber-filament tape to secure the electronics-bay floor and to reinforce the wing in strategic locations. Colored tape gives your Zagi-XS its own distinctive look. The manual recommends that the model be | built with contrasting colors to make the plane easier to see. Use darker colors on ] the bottom; be creative.

* Final steps. When you prepare the j elevons for installation, make sure that you | sand a 45-degree angle in the leading edge; j if you don't, the downward movement of the élevons will be restricted.

The servo cutouts are designed so that the servos are attached by a press-fit. I wasn't completely comfortable with this method, so to provide additional security, I covered them with small pieces of colored tape that match the plane's color scheme. When my servos were in place, I used the provided pushrods and clevises to hook up the elevons.