Top Flite TOPA0220 - Manual (Page 19)

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3. Use a razor saw to trim the pushrods flush with
the fuselage sides. Fill any irregularities with
balsa filler.
IMPORTANT NOTES ABOUT SERVOS
The following steps show the installation of three full
size servos in the fuselage; one each for the elevator,
rudder and throttle. The wing also has two aileron
servos and one flap servo, plus a retract servo if you
are installing retractable landing gear. If you have a
computer radio and want to use some of its mixing
capabilities, there is adequate room in the fuselage
for a second elevator servo. The wing also has room
for a second flap servo. If you do install additional
servos it is recommended that you use mini servos
for their smaller size and lighter weight.
You MUST install your servos so that the servo arm
is located in the position shown on the plan. Install
the servo rails so that the servos you use will be in
the proper location.
Servo output torque is a consideration when you
select the servos that you will use. Standard size
servos have adequate torque for any control
function. If you are using mini servos you should use
two servos for the elevators that have at least 35 oz
in of torque each. The rudder servo should have at
least 42 oz in of torque. This will insure that the
control surfaces can reach full deflection at
maximum flying airspeeds.
We recommend Z-bends be used for the pushrods
where they connect to the servo arms. This results in
the most compact installation possible and will
reduce the possibility of a pushrod contacting
something close to it. As an alternative you can use
an L-bend with one of the supplied nylon Faslink
keepers. For making Z-bends we highly recommend
the Precision Z-bend Pliers from Great Planes
(GPMR8025). This tool makes very precise Z-bends
in tight areas and is one of those tools you wonder
how you ever got along without.
❏ 4. Locate a .074 x 36" [1.6 x 914mm] pushrod
wire. Bend a Z-bend (or L-bend) in the unthreaded
end of the wire. Make this bend close to the end of
the wire. Install a servo arm on the Z-bend. You may
need to drill the servo arm with a 5/64" [2mm] drill.
Insert this wire into the elevator pushrod tube where
the tube exits F3. DO NOT cut off the excess wire
where it exits the rear of the fuselage. This pushrod
wire will be used as locating jig for the elevator servo.
❏ 5. From the 1/4" x 3/8" x 36" [6.4 x 9.5 x 914mm]
basswood stick, cut two servo mounting rails to a
length of 2-5/8" [66.7mm]. These rails should be a
tight fit against the fuselage sides so that they can
hold the servo in position during the following steps.
❏ 6. Install one of the servo rails against F3. Place
the elevator servo in position on the rail and install
the second rail at the forward end of the servo. Install
the servo arm, with the wire attached, on the servo.
Refer to the note and photo below if you are using
full size servos. DO NOT glue the rails at this time.
Note: If you are using a full size servo, you will need
to cut a hole in the fuselage deck for the servo before
you can install the servo arm. Mark the deck from
inside the fuselage where you need to cut the hole.
Then, remove the servo. Transfer the location of the
hole to the top of the deck by pushing a pin through
the deck at the corners of the hole. Cut out the hole
from the top of the deck.
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