Final Balance: The center-of-gravity (CG) point on the plans is the typical 25% back from the wing leading edge. The Scratch-One balanced perfectly with everything as shown on the plans. If for any reason you end up nose- or tail-heavy, just reposition the battery to achieve the correct balance. 

Motor/Battery Parameters: Motor current will average 10-12 amps on the eight-cell 1100 mAh NiMH battery pack. The rpm is 13,900 with the Gunther 5 x 4 propeller. Power to the motor is 90 watts. The calculated motor run time at full throttle is roughly six minutes, but at reduced throttle settings you could expect up to roughly 10 minutes.

Flying: Flying the Scratch-One was much the same as flying the Aero Craft Pogo, which was described in the September 2003 installment of "From the Ground Up." Since the Scratch-One has no landing gear, it is always going to be hand launched.

Although it's an ounce heavier than the Pogo and using the same power system, the Scratch-One seems faster in the air. That makes it easy to throttle back, thereby reducing the motor current and increasing flight time. I normally get 10-minute motor-run time with a lot of throttling back. On many occasions I've caught a thermal and increased my flight time to almost 15 minutes. The more time the model can stay in the air, the faster you are going to learn to fly.

Landings are slow with power throttled back or turned off, giving the beginner a chance to line up and judge distances properly. This airplane just doesn't have any bad habits.

I have been using the same Gunther 5 x 4 propeller on the Scratch-One. Without a landing gear I suspect that a propeller will get broken every once in awhile. In colder weather the plastic propellers can become much more brittle. If that is the case I recommend using a folding propeller assembly such as the Graupner 6 x 3, which can be obtained from Hobby Lobby.

Motor and Radio Control System (RC) Reference: The RC system and the electric-power-system components were previously described in this series. Rather than duplicate all of that data, I will list the "From the Ground Up" articles published in Model Aviation. You can also find them on the AMA/Model Aviation Web site (http://modelaircraft.org/mag/online features.htm).

The electric power system was described in the July 2003 "Introduction to Electric Power" installment starting on page 56. The Hitec RC system was described in April 2003's "Radio Control Systems—the Real Basics," page 54, and in May's "Radio Control System Installation," page 24. Further information was published in June 2003's "Radio Control System Operation" installment, page 46. A product review of the Hitec Neon system was published in the September 2003 issue. MA