PHOTOS: DAVE LOCKHART
The beautiful lines of the original model are faithfully replicated in this new ARF version (above left). The color scheme and bold colors enhance the striking lines of the Dirty Birdy on take-off roll (at left, bottom), nose wheel beginning to break ground. DirtyBirdyon approach (above). The Dirty Birdy is solid and tracks well on landing approach.
modification here that should extend the life of the cowl mounting points. Rubber backed washers were used on the mounting screws, and five screws were used instead of the sug- gested four. The rubber backed washers are available at
www.microfastners.com or 800- 892-6917. The specific ones used here are product
number FWRBS04, Bonded Steel Washers.
There are a few things to note in the fuse- lage. The pushrods are 1⁄16-inch steel rod. The elevator, rudder, nose wheel, and throt- tle rods in my kit had a coating of some kind on them which made them slightly sticky in their casings. Wiping them with alcohol took care of that.
Throttle and nose wheel pushrods require bending to fit as shown in one of the photos. Note the nose wheel rod gets a slight bend near the nose wheel arm to reduce binding at extreme right and left travel. Slight widening of the nose wheel exit hole in the firewall will also help. Mount servos in the pre-installed tray. Verify that elevator pushrod collar retainers do not rub on the elevator servo case. The radio receiver, switch and battery could be installed now, but let’s not do that quite yet. This is a good time to check bal- ance of the plane, before deciding where to install those components. Verify all other parts—engine, prop, spinner, nose wheel, receiver, servos and linkages—are in their correct locations. And, if you elected to defer the stabilizer install step, temporarily in- stall the stabilizers. Use the two spar tubes, and slide the stabilizers on. If not already done, slip the elevator and rudder pushrods into their respective casings. Check for bal- ance at the manual recommended 513⁄16 inch- es (or 148 mm) behind the leading edge of the wing. That measurement is behind the “leading edge”, not behind the 11⁄4-inch notch in the leading edge.
My model was definitely nose heavy, so I looked for ways to minimize the amount of
FLYING MODELS Neoprene
tail weight that would be needed. I found space behind the servo tray and ahead of a fuselage former that was an ideal location for the battery. With battery in that spot, about 11⁄2 ounces of tail weight was needed to get the balance to the recommended loca- tion. Those using a tuned pipe in lieu of a muffler may not need tail weight. It’s now time to permanently install the stabilizers. Or is it? Might a removable sta- bilizer be of interest to you? Perhaps to facil- itate shipping or transportation of the plane? While test fitting the stabilizer tubes to the sockets in the fuselage and stabilizer halves, I saw that they fit so perfectly, there was al- most no need to glue them in permanently. So we have the final modification of my Birdy to consider. I epoxied a light plywood pad to the inside bottom of each stab half to receive a self-tapping screw. I found the fuselage is sufficiently thick to retain the screw on the fuselage side. One nylon landing gear strap on each side completes the installation.
Final surface setup
I used the mechanical linkage adjustments to set control surfaces to neutral. Recom- mendations are in the manual for control sur- face travel, both high and low rates, and are good. If you are not using a computer radio, set throws between the recommended high and low rates. Set the control surface throws using mechanical linkage adjustment to get as close to possible to the recommended throws.
If you are using a computer radio, then use the End Point Adjust function to fine tune each surface. I also chose to add some exponential control to soften the control re- sponse near neutral for all three axes. How much expo is a matter of personal prefer- ence. A good starting point is 20% for ele- vator and ailerons, and 25% for rudder/nose wheel. Futaba radios use a negative (–) expo number to soften center. Let’s prepare for the maiden flight:
Balance point set to 513⁄16 inches behind leading edge of wing. Check.
Control throw sets to manual recommen- dations. Check.
Flight controls respond in proper direc- tion. Double Check.
Radio system range checked with engine running. Check.
Flight and transmitter batteries freshly charged. Check
Fuel tank full. Check
Engine full throttle mixture set a few hun- dred rpm less than peak. Check Engine idle around 2,700 with reliable throttle up. Check Local field procedures and take-off direc- tion observed. Check
Completing those items will contribute to an unexciting test flight, which is the best kind!
That is what I got with the Birdy. It need- ed only very minor trim with the transmitter. Loops, rolls, point rolls, inverted flight, were great as is to be expected of the Birdy. It is comfortable and fun to fly; time to land came all too soon. Landing the Birdy was easy. Speed bleeds off reasonably quickly. You may find flying the final approach with two or three throttle notches up from idle makes the approach easier.
After further flying, I found the recom- mended balance point very good and have not changed it.
For typical Pattern maneuvers the low rates provided smooth response and suf- ficient authority for landing and take-off. Further flight testing showed the model has a slight tendency to pull toward the canopy on right and left knife edge flight. With a computer radio, a mix of a few per- cent of down elevator with left and right rudder could be used to eliminate the pull. I’d suggest starting with 3% down elevator.
Enjoy your Dirty Birdy, I certainly have! 59
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