SIG Sbach 300
Hitec HS-82MG servos are installed into each wing panel (above left) followed by the control horn and pushrod. Screw holes are pre-drilled to minimize
Moving on, you install the rudder and ele- vator servos in the forward fuselage. Again, a very slight elongation of the slots was re- quired to drop in my Hitec HS-82MGs. After attaching the clevises, the long pushrods are inserted through the rear of the fuselage and attached to the servo arms via the in- cluded snap keepers. Again I found the stock Hitec arms to be too short, so I substituted longer ones. I finished the radio installation by securing a Futaba R617FS receiver on the forward end of the radio tray. Motor installation comes next. The SIG Sbach features an adjustable firewall to ac- commodate the tremendous variation of brushless motors available nowadays. A 32-size brushless motor is required, and there are many motors in this class to choose from. The one I chose, a 4250-800Kv model rated at about 700 watts, is available from Value Hobby. The manual gives a 51⁄2-inch dimension to properly locate the motor’s thrust washer ahead of the first fuselage former and line up with the cowl. Attach your motor of choice to the firewall. Then fix the firewall in place with CA and some included balsa
assembly time. The horizontal stab (above right) is epoxied into place on the fuse. The covering in the center section is already removed for you.
triangle stock. My particular motor required the addition of 1⁄4-inch nylon standoffs to reach the required distance. Once the fire- wall is glued in place, mount a 50- to 60-amp ESC to the outside of the motor box. The in- cluded hook and loop straps are then in- stalled in the battery tray slots. Secure the canopy to the large hatch using
canopy glue. The canopy-to-hatch fit was ex- cellent, and I added just a few small pieces of masking tape to hold it in place overnight to dry. No sort of cockpit floor or backing is included, but it would be easy to do so if de- sired. Since I plan to use the Sbach for most- ly 3D flying where every ounce counts, I left the cockpit as is.
Next is the installation of the cowl. Install the included plastic spinner and your prop to aid the cowl alignment. The cowl has pre- drilled holes to ease assembly, and with lit- tle effort I had a perfect spinner-to-cowl fit. Thanks to all of the pre-fabrication, total as- sembly was done in one long weeknight. At this point the Sbach is nearly ready to fly! Before attempting a maiden flight I went over the Sbach and set the center of gravity and throws per the manual. For the CG, the
manual has six different suggestions de- pending on your flying style, be it sport or 3D. SIG recommends a 4S 2500 to 4000 mAh battery and the weights of these packs can vary greatly.
For 3D flight, using a smaller, lighter pack and a further aft CG will achieve the best results. This will result in an airplane that is much more responsive and maneu- verable, but also touchier and less stable. If sport flying is more your style, a heavier pack and a more forward CG will give you a plane that feels a lot more like it is “on rails.” I set my balance point for the middle 3D setting of 37
⁄16 inches from the leading
edge. I achieved this by moving my 4S 2650 mAh pack as far forward as possible. Upon testing my power system, it immedi- ately became apparent that the stock plastic spinner was not centered and wobbled, caus- ing immense vibration. I would say that the included spinner is almost unusable, except that after repeated removal, rotation, re-in- stallation and tweaking of the tightness of the two spinner screws, I found a combina- tion that gave vibration-free rotation. I may swap this spinner out for an aluminum one
The included tailwheel assembly is installed (above left). It is very sturdy to help endure those harrier landings. The outrunner motor and ESC of your choice
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are installed on the firewall (above right). My motor required small standoffs even with the firewall fully forward.
APRIL 2014
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