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airplane, you may wish to adjust the thrust slightly to compensate
for your particular engine/prop combination. We suggest "sneaking
up" on such adjustments by using 1/64" plywood shims directly
between the motor mount bases and the firewall, on the left side of
the centerline. Do not use washers, as these will typically bury
themselves into the plywood, giving you little or no adjustment.
Used in the manner described, these 1/64" plywood shims will give
you about 1 degree of thrust change. With the shims in place, fly
the airplane again to see if you have achieved your goal. If you still
need further adjustments, either use another piece of 1/64" ply for
a second shim or remove the existing shims and use a piece of
1/32" plywood for the new shims. Again, fly the model to see if you
have achieved the desired effect. In this manner you will quickly
find the optimum thrust adjustments for your particular airplane.
FLYING
If you have carefully followed this assembly manual, you should
have no real problems in test flying your EXTRA 300XS. Try to
choose a calm day for the first flight. Good conditions will help in
correctly evaluating the flight performance of the model. Begin
your test flight by making sure the engine is properly set with a
reliable idle, a strong top end, and smooth transition performance.
We always set our engines to run a little on the rich side and
suggest you do the same.
Holding up elevator, taxi the model to get a feel for how it handles
on the ground. Make sure you have positive left and right turning
ability. If not, make any adjustments needed to achieve positive
ground control. Once you are satisfied with the taxi tests, line the
model up with the centerline of the runway, nose into the wind.
Hold a little up elevator and advance the throttle smoothly - do not
throw the throttle open all at once! The airplane should roll forward
smoothly, tailwheel on the ground. As speed builds, slowly back off
the elevators and use just a little rudder, only as needed, to
maintain a straight takeoff run. The tail will come up as flying
speed is reached and a little up elevator will lift the EXTRA off the
ground.
Maintain a straight outbound flight path, climbing at a shallow
angle until a safe maneuvering altitude is reached. If the model
requires trim, fly it to a reasonable altitude before trimming. Make
your control inputs smooth and avoid jerking the sticks.
At altitude, make any trim changes needed to achieve hands off,
straight and level flight. From our experience, this will take very
little trim input, if the model was assembled and balanced properly.
Once you're comfortable, make a few circuits around the field to
get the feel of the controls.
The airplane should demonstrate
smooth flight characteristics without jumpiness or over sensitivity.
At altitude, try a roll. Then try another roll to the opposite side.
Properly trimmed, the EXTRA will roll smoothly and very axially
For initial test-flying and familiarization purposes, we suggest a
starting balance point of 27%, approximately 4-3/8" behind the
leading edge of the wing at the side of the fuselage. (By the way,
this translates to about 2-3/4" aft of the leading edge at the wing
tip, for those of you who prefer to balance your airplanes that way).
As we all know, as the balance point is moved aft, an airplane
will become more responsive in all axis, but it will be especially
noticeable to a model pilot in "pitch" (up and down). We have flown
the EXTRA at the 30% location and found it to be manageable,
with excellent aerobatic capabilities. However, we did notice an
increase in pitch sensitivity and had decrease the elevator throw to
compensate.
"Softening" elevator response with a reasonable
exponential percentage also works. In the end, the final balance
point and control throws you use will depend somewhat on how
you like to fly. Some pilots like their models extremely reactive,
others strive for more smoothness. The EXTRA 300XS is an very
capable aerobatic machine and can be tailored to fit your style. We
therefore suggest that you begin with the 27% CG location and
experiment from there.
The best means of shifting the CG fore or aft is to locate the
battery pack where it is needed to achieve balance. If doing this
does not work and more weight is needed, consider using a larger
(and therefore heavier) battery pack. Try to avoid adding useless
weight. If you need more weight in the nose, try a heavier spinner
or replace the light wheels with heavier after-market wheels. If
your model is nose heavy and battery shifting does not work, you
can make significant changes in balance with lead stick-on
weights. These are unsightly, but should be considered until such
time as you have flown the model and are happy with the CG.
Once that's done, the weights can be placed inside the fuselage by
simply removing the elevator servos and placing the weights inside
and securing them. With the elevator servos back in place, the
weights are hidden. For reference, our EXTRA 300XS prototypes,
using either the Irvine 1.20 or 1.50 and also the Saito 1.50
4-strokes, required no additional weight to achieve balance.
Finally, the aerobatic performance of your EXTRA will benefit
greatly if you balance the airplane laterally as well as fore and aft
(eliminate the "heavy wingtip" syndrome).
Lateral balancing
requires that the model be suspended upside down, using
substantial chord or fishing line. Loop the line over the engine
propeller shaft and the other end over the tailwheel bracket. Hang
the model from the ceiling or a rafter, leveling it in side view. With
the model secured in this way, observe the wings. Ideally they
should be level, without one wing lower than the other. If one wing
panel is lower, it means that it is somewhat heavier than the other.
When flying the model, this imbalance can cause the model to
"pull" to the heavy side, especially in loops and up line maneuvers.
To make the airplane track true, the light wing panel needs weight
at the tip to balance it level with the other panel. Again, this can be
done with stick on weights, which could later be hidden. Always
secure weights firmly in place.
ENGINE THRUST ADJUSTMENTS
Your airplane has been carefully built to produce a firewall that is
"zeroed out". This is to say that there are no thrust adjustments
built into the fuselage. This has been purposely done for several
reasons. First, factory built thrust adjustments can be problematic
and may not produce exactly what your engine and prop
combination needs. Our models have all been flown extensively
with no thrust adjustments at all - this means that our models have
zero right thrust and zero downthrust. These models fly beautifully
and we suggest that you begin the trimming process with these
settings. Later, as you gain more experience and time on your