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Composite-ARF SuperXtra 330L (3.1m span)
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
piece of thin scrap plywood as shown here. Make the tem-
plate to fit the inner horns, which are already installed at the
factory, and drill a 3mm hole in the plywood that exactly
lines up with the 3mm holes in the double horns. Check that
it's correct by putting an M3 bolt through the horns and the
template. Notice the small 'hook' at the back of the template
to set the position from the trailing edge of the stab.
The elevator is 3mm thinner at the position of the outer servo
than the inner servo and (as it is centre-hinged) so the horns
must project out of the elevator 1.5mm more for the outer
servo than for the inner/root servo. This important to get the
same throws from each servo, and prevent them working
against each other, and possibly stalling, causing a big cur-
rent drain on your batteries. Therefore, glue a small scrap
of 1.5mm thick ply or balsa to the bottom of the template
and use it to set the position of the outer horns while you
glue them in place.
Now mark the position of the slots on the elevator for the
techsupport@composite-arf.com
(above) Completed stabiliser and
linkages showing the mandatory 2
servo set-up, also showing the
20mm Ø stab spar tube and anti-
rotation pin.
(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.
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