(3/4 - 1 ounce) of lead in the leading edge of the outer
mass-balance area in each elevator half, which helps to
prevent any chance of flutter that could destroy your Xtra.
(see photo on page 19)
Although the JR8511/8611 servos are about 1 mm longer
and wider than the 8411 type, you will find that both sizes
will fit in the milled servo cutouts in the rib without problems.
The elevators are hinged to each stab using the 4mm Ø
aluminium tubes provided. Make sure there is no burr on
the end of the tube, and you can chamfer the end slightly
with fine sandpaper to make it easier to get them through the
holes in the phenolic hinge plates. Be careful inserting them,
and if they are a bit stiff, then use a little grease on the tubes.
Don’t use too much force, otherwise some of the phenolic
plates inside might break loose. Leave the tubes a bit too
long during construction, and cut them to exact length when
the model is finished. During final assembly, retain both
ends of the tubes with a small piece of clear tape on the
root and tip ends of the elevators.
NB: To fit the dual servos in each stab you must fit the outer
(tip) servo first, using a long (30cms/12”) screwdriver,
inserted through the inner servo hole in the root rib to tight-
en the bolt that holds the servo arm onto the servo shaft.
To fit the outer servo, proceed as follows: Mill out a slot in
the fibreglass tip of the stab., as shown, to allow the servo
to fit in the milled hole in the rib that is already built in dur-
ing manufacture. Note that the servo is fitted
inverted
, with
the servo shaft nearest to the leading edge of the stab. You
will need to drill a hole of about 6mm (1/4”) in front to get
the screwdriver though to tighten the front servo screws.
Use the 2.9mm Ø x 13mm screws provided in the kit,
not
the standard screws provided with the servos. You can
cover these holes in the tip of the stabiliser moulding with
pieces of self-adhesive film afterwards if you wish. You may
need to grind 1mm or so off the inner end of the phenolic
hinge plate that projects inside the false trailing edge of the
stab for enough clearance to install the servo.
Mark and mill out the slot in the bottom of the stab for the
servo arm. The slot should be approx. 4mm wide and 55mm
long, and the back of the slot should be about 50mm from
the trailing edge of the stab. If using JR8411 servos and C-
ARF servo arms, then the centre of the slot should be
exactly 16mm inside the servo rib, which can be seen in the
false trailing edge. In any case, start the slot a bit smaller
than this, and enlarge until correct.
At this point you should fit the elevator to the stab, and
make the control surface horn alignment template from a
Composite-ARF SuperXtra 330L
(3.1m span)
18
(above) The outer servo is fitted
into the stab inverted, against the
factory-fitted rib. Note the hole in
the tip leading edge for access to
the servo securing screws.
(above) Cut the slot for the C-ARF
servo output arm.
(below) Horn template for outer
horns is made using the inner ele-
vator horns for identical throws.
(above) Completed stabiliser and
linkages showing the mandatory 2
servo set-up, also showing the
20mm Ø stab spar tube and anti-
rotation pin.