Make as generous a hatch opening as you can (above left) to make battery changes easy and damage free to the model. Jets generally make this easier with the long nose. The 800 mAh 2S battery goes as far forward as possible to
wedges inserted from either end to help tauten the plastic as it shrinks. After trim- ming, the canopy looks pretty good and is very light.
I held off making the nacelles because I hadn’t fully planned what I was going to do, as there were several options available. The basic structure would be two struts (fore and aft) going through the fuselage, separated by hard balsa, with mounts for the fans to bolt in. Other than that, I wasn’t sure. Even- tually I decided to make the casings for them non-scale, having them be little more than a simple balsa tube with a rounded in- let and kind-of-scale-like exhausts. The in- lets are simply half-rounded rings. The back of the nacelles is a ring of the same ID and OD, but only quarter round. The rear ring is friction-fit removable so that the card stock exhaust cone could be added after covering and the exhaust area tuned for improved performance if necessary.
If I had waited to start construction until the nacelles were designed, I might not be writing this article now! Instead, by having the whole model finished and covered, I really forced myself to finish the plane. They turned out not to be so bad after all. Using 1⁄64-inch ply soaked about three minutes in hot water and wrapped around a Z-56 glue bottle made the nacelle outside tubes simple. They were otherwise quite standard construction. A little out of the ordinary, I used Spek- trum A2000L servos with an AR6310. To do so it was necessary to change the connectors on the ends (fortunately the colors line up properly). These are much easier to mount on the wings for ailerons, and the alignment in the fuselage was very good for the eleva- tor. I also took advantage of the DX18’s channel mapping capability and put the sec- ond ESC control on the GEAR channel, but you could use a servo Y with no problem. Only rudder remained unused.
After everything was built and assembled, I still needed to make one more item—the landing gear fairings on the wings that are such a trademark of the A-10. These also serve another function for me—they protect the aileron horns from hitting the ground. Without a battery the almost-finished
FLYING MODELS
balance. The 182-gram AUW (above right) is reasonable considering the power units used and wing area. The large frontal area keeps this from being a speed demon.
model came in at 140 grams, a bit heavier than I had hoped and almost double the AUW of my other micros with similar wing area. When making the wires for the gear, I copied the MiG-15 setup and flipped the at- tachment area over so the wheel would be lined up as shown in the photos. What I didn’t think about, though, was that with double the model weight I should have used heavier wire. As soon as I put the finally-completed (150 grams now) model on the bench, the wheels bottomed out on their travel!
The wheel fairings slip over the covered
wing on the LE, and are glued in place at the TE. There’s nothing special about them, and they work very well at keeping the aileron horns off the ground.
Flying
The A-10’s first flight was a bit of a non- event. Michael Ramsey had the sticks and trimmed the plane while I drove the camera. The biggest thing he found was that there was significant diving as the throttle was in- creased. This was not unexpected, as the thrust line I built was parallel to the datum. I programmed a mix of throttle to elevator to give about 10% up elevator at full throttle. For a one-off model this is acceptable.
Other than that, the handling was very good. The noise of two EDFs running at al- most exact synchronization is strange to hear, but very satisfying. My concerns about power and weight were totally unfounded— the A-10 will fly in level flight for 10+ min- utes at half throttle! At full throttle it has plenty of oomph to get around the most hos- tile ground forces, and it glides nicely as power is cut for easy landings. After several outdoor flights, I had an opportunity to fly at the Armory (site of E- Fest). The A-10 was suited just fine, and I had no problems indoors. I also was able to ROG with no problem. While the facility was not a problem, my depth perception was—I “landed” on the wall. It would have been fine as a touch-and-go, but the wall I met had a cable for hanging banners. The cable snagged a nacelle and caused me a little repair work. I took advantage of the opportunity to adjust the thrust line a lit- tle.
If I were building another, probably the only changes I would make would be to fix the thrust line, and to use an AS3X receiver and servos. Hopefully this article will in- spire you to build yourself a model of the plane you’ve always wanted but never had formal plans for. You can do it!
PHOTO: YU CHAI
The UMX-size models are ideal for flying in your neighborhood backyards and ball fields. Stick to familiar size, power, and construction methods and you’re virtually guaranteed success! It doesn't have to be perfect scale to bring great fun from concept to landing.
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