c) Recheck the position of the cowling and make any
adjustments needed to get it back in perfect position, securing
the tape to hold it in place.
d) Now drill another pilot hole for the upper screw on the
other side of the cowling. Install the screw.
e) Repeat this process to install the two bottom cowl
mounting screws. Remove all the tape.
❑
33) Mount a suitable propeller on your motor with the
included spinner. Be sure to balance the prop before installa-
tion.
CONGRATULATIONS!
Your Sbach XA-41 EP is completely assembled. However, it is
NOT ready for flight! There are a few very critical pre-flight
tasks we must perform before flying. These are extremely
important and should be approached with patience and care.
PRE-FLIGHT
BALANCE
Balancing your airplane may be the single most important step
in preparing it for flight. All airplanes, model or full-size, must
be accurately balanced in order to fly successfully. An airplane
that is not properly balanced will be unstable and will most like-
ly crash.
NOT ALL SBACH XA-41’s WILL BALANCE THE SAME
It is impossible to produce a model airplane kit that will auto-
matically have the correct balance point. Not everyone uses
the same motor or radio gear - and all those items can vary in
weight! Even propellers of the same size can vary as much as
a 3/4 oz. between different brands. That’s why every model
must be balanced before flying. Don’t feel that whatever the
balance point your model came out at is "good enough".
Check carefully and make whatever adjustments are required.
Trying to fly an out of balance model is dangerous!
Preliminary: All the parts and components that will be in the
airplane in flight must be installed in their correct positions.
This includes all the radio gear, the propeller, battery pack, etc.
Every piece of essential equipment must be installed, ready for
flight.
BALANCE POINTS FOR SPORT/PRECISION PATTERN
The following table lists inch measurements and the equivalent
percent of MAC (Mean Aerodynamic Chord) for typical range
of balance points for sport and precision pattern flying.
Note: Measurements are aft of the leading edge of the wing, at
the fuselage sides.
DISTANCE
% MAC
2.83"
=
28%
3.04"
=
30%
3.24"
=
32%
BALANCE POINTS FOR 3D
The following table lists inch measurements and the equivalent
percent of MAC (Mean Aerodynamic Chord) for typical range
of balance points for sport and precision pattern flying.
Note: Measurements are aft of the leading edge of the wing, at
the fuselage sides.
DISTANCE
% MAC
3.24"
=
32%
3.44"
=
34%
3.65"
=
36%
If you are unsure where to start, a balance point approximately
3" aft of the leading edge is a safe bet for initial test flights. After
test flying, you can adjust the balance point to fit your flying
style. Remember, it has been said that a nose-heavy model
may fly poorly; however a tail-heavy model may fly only once.
Keep in mind that an aft CG is good for 3D aerobatics, but a
more nose-heavy CG is often better for precision flight and is
much easier to land gracefully. It's best to start out toward the
nose-heavy side, and then re-adjust as flight testing indicates.
When you experiment with CG location, move the CG only
small amounts, 1/8 inch or so, at a time. A small change in CG
can have a large affect on flight characteristics.
Fine Tuning The Balance Point For Advanced Aerobatics
For aerobatic flying you’ll want a "neutral CG", one which will
usually provide very little (if any) throttle/pitch coupling. The
nose will stay put when power is increased/decreased. The
nose will not drop much during turns. When you roll a neutral
CG airplane inverted, the airplane neither climbs nor dives. In
contrast, a slightly nose heavy airplane usually requires you to
hold some "down" elevator to keep the airplane flying straight
while inverted.
An easy way to test for neutral CG is to do the "roll inverted"
test. Trim your plane for your Sbach for straight and level
hands-off upright flight at about _ throttle. The Sbach should
be able to fly straight and level with no control input. Once you
are satisfied with the trim in upright flight, you need to test it
inverted. With sufficient altitude, pull the Sbach to a 45 degree
up line, establish this line and immediately roll the aircraft
inverted. The plane should hold the 45-degree line for about
2-3 seconds before slowly dropping towards the canopy. If
instead it wants to climb, you are tail heavy and should move
the battery forward until it holds the line. If the Sbach wants to
drop sharply, you are too nose heavy and should move the
battery aft until it holds the line. It may take a few tries of
adjusting the battery pack to find the sweet spot for the CG, but
the time to do this will make the plane fly much better.
For less-experienced RC pilots, the neutrally balanced
airplane can be challenging to fly. For instance, the nose
doesn't drop as the plane slows down; the plane usually
descends in a level attitude. Hence, there are typically no
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