Final Setup: I covered setting up the
control surfaces, throttle, and trim settings in detail in the second
part of this series of articles. To recap, all control surfaces must
first be in the neutral, centered position. Turn on the transmitter and
center all the trim tabs. All servo output arms must be in the center
Since our servos move in a curve, any offset from center will
result in "differential" control-surface movement. An elevator will move
more up than down if the servo arm were offset. This is true of all
control surfaces and can make for a difficult-to-understand flight
Once the servo arms are centered, disconnect the pushrods at
the control surface. Clamp the control surface in neutral using two
straight pieces of wood and two modeling clamps. Align and clamp the
ailerons with the wing's TE. Adjust the clevis until it can easily be
inserted into the control horn without pressure.
The control surfaces
are now in neutral. This is the time to set movement direction and
Most instructions specify the amount of movement in
inches of travel. The Hobbistar 60's elevator should move 7/8 inch in
either direction. Set the fuselage on a flat surface and adjust the
amount of movement.
In this example if the elevator moves too far,
relocate the pushrod clevis into the next hole away from the control
surface. Or you could move the servo connection inward toward the center
of the servo arm. Reverse these operations if there is too little
Sometimes relocating both connections is required to get the
proper amount of control-surface travel. On a computer radio leave the
connections alone and set the amount of travel using the transmitter.
Experience has shown that changing the amount of travel on the
transmitter by more than 30% sets up a problem. In these situations
transitions from left to right aileron or up- to down-elevator become
somewhat "sudden," making smooth transitions difficult. Use a
combination of transmitter and mechanical clevis adjustments to
eliminate excessive transmitter settings.
I also previously covered
setting the throttle in detail. The basic idea is to fly with the
throttle trim lever set on "high," then lower it to "half" to land, and
have engine shutoff set for full low trim. The reason for the "high"
trim flight setting is that many analog, noncomputer transmitters
require maximum throttle trim to achieve complete throttle-arm movement.
Although various engines and installations may differ, a good starting
point is usually 2,800 rpm at high throttle trim, 2,300 at the middle
trim setting, and 0 rpm at low trim. This usually means the throttle
barrel should be open approximately 1/16 inch at the middle trim
After completing all the assembly work and setting
control-surface travel, step back from the assembled aircraft, take a
deep breath, and concentrate. Think of nothing but the control surfaces
and move the aileron transmitter stick all the way to the right. The
right aileron should move upward, and the left aileron travels downward.
If not, fix it.
It is always surprising how these settings somehow just
change during the building process. Give all the control surfaces, and
the nose wheel, this final check to ensure proper movement.
Click on photo to view large image with caption
On the Flightline: All the checks and settings were done on the Hobbistar 60,
so I loaded the airplane, all the field gear, and Frank Costelloone of
the best in-air photographers aroundinto my Suburban and headed out to
the field to see if all the extra work was worth it. At the field we
unloaded everything and assembled the airplane. The bolt-on wing paid
for itself right then.
I switched on the transmitter and then the
onboard radio system. Always turn on the transmitter before the flight
radio, and turn it off last when shutting down. This prevents possible
servo damage and jitters from stray signals.
We took a short walk
(roughly 100 feet) with the antenna collapsed and tested the radio
connection. After that test was passed, we checked control-surface
movement again to make sure everything was connected during assembly.
The flight data we obtained tells the performance story and is detailed
in the sidebar, but there is a great deal the data does not accurately
portray. Piloting the modified Hobbistar 60 left some strong
The stock Hobbistar 60 is a fine advanced trainer; it's
stable yet responsive, with a maneuver repertoire that is well above
average for its class. The modified version feels more solid, flies
faster, has more positive responses, and has an even wider maneuver
envelope than the unmodified version.
The O.S. Max .61 FSR is a fairly
powerful engine, even by today's standards, and takeoff required less
than a 100-foot ground roll. Climbout was steady, with just a touch of
right rudder, at approximately 1,900 feet per minute despite a strong
crosswind. At that climb rate the airplane reached "fun time" altitude
We left the throttle at maximum and quickly noticed one
performance difference in comparison to the stock Hobbistar 60s that we
have flown. The modified model was faster at full speed, yet it was
RealTree Systems' Flight Data Recorder was set for
testing low-speed aircraft, and the modified Hobbistar 60 quickly passed
its 70 mph maximum reading. My guess would be a top speed near 75 mph.
This is roughly 10 mph faster than most stock Hobbistar 60s can reach.
Lowering the flaperons reduced the top speed to 67 mph. Although the
airplane remained steady at this rate, it did feel "loose" and required
constant small corrections to maintain heading. Pitch control became
more sensitive as well. But then, flaperons are not meant for high-speed
flight. Their advantages are best used in the slower speed spectrum.
slowed the airplane, and the flaperons started to perform their magic.
Yes, they lowered approach and landing speeds, but the real difference
was in the model's stability and control responsiveness at low
airspeeds. Even at less than 30 mph, the modified Hobbistar 60 remained
steady and responsive, especially to aileron inputs.
remained almost as effective during the approach as they did at higher
airspeeds. The sluggishness that is so common at low speed was greatly
reduced when the flaperons were down.
Altitude control during the
landing approach was improved, and spot landings became predictable. The
entire approach could be flown more slowly, but it was rock steady. With flaperons it was possible to start the approach as much as 75 feet
higher than normal, yet land the aircraft at runway center without
increasing speed during the steeper approach.
The flaperons allowed this
advanced airplane to fly and land at basic-trainer airspeeds. Not bad
for a few hours' work.