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Composite-ARF SuperXtra 330L (3.1m span)
outer control surface horns. Mill the slots with a dremel until
the horns fit properly and can be temporarily joined with
one of the ball-links provided and an M3 bolt though the
horn alignment template as shown. Put a layer of masking,
or clear, tape over the area of the milled slot, wax it careful-
ly, and then cut through the tape with a very sharp knife to
allow the horns to be glued into the slots. This stops the
glue getting on the surface of the elevator. Scuff up both
sides of the phenolic horns with coarse (60 grit) sandpaper
or a Permagrit tool to ensure a good glue bond, and glue
them in with slow epoxy (minimum 1hr cure) mixed with
milled fibreglass, or a filled thixotropic epoxy (eg:
Loctite/Hysol 9462 or BVM Aeropoxy). Check that horn is at
90° to the surface of the elevator, and wipe excess glue off
before it cures.
Important Note: The C-ARF phenolic servo arms supplied
with the kit have to be attached to the servo output discs,
but if using the 8511/8611 servos it is mandatory to use
metal (aluminium) servo output discs for this - and not the
standard plastic output discs supplied with the servos, as
the extreme torque of these digital servos can strip the
plastic splines from the inside of the disc - which will result
in immediate flutter and destruction of your SuperXtra.
We also highly recommend that you also use aluminium
output discs when using the JR8411 servos, or other simi-
lar hi-torque digital servos. Several reputable after-market
accessory companies make suitable aluminium discs, but
you must check that the CNC machined splines fit the servo
output shaft tightly, with a minimum of play. Fit the discs to
the servos and use a little Loctite on the retaining bolt in the
centres. Centre all 4 elevator servos using your R/C and
attach the phenolic servo arms to the outside of the metal
discs temporarily with a couple of drops of CA, making sure
that the servo arms are at exactly 90° to the bottom surface
of the stabs using a set square. Then remove the arms and
discs, drill through both, and secure with at least 2 small
bolts, washers and locknuts (M2 or equivalent size).
Make up the linkages from the hardware supplied, using
M3 threaded rods (90mm for inner servos, 65mm for outer
servos), with a quick-link and M3 nut at the servo-end, and
a ball-link in between the double horns secured with an M3
bolt and locknut. Add short pieces of Tygon fuel tube, or
similar, to make sure the quick-links cannot open in flight !
The last job is to fit the M3 stab retaining bolts and blind
nuts. Inside the stabs you will see the small plywood rein-
forcement plates between the spar sleeve and the bottom
surface of the stab. Mark the bottom of both stabs in the
centre of this plywood. Install the aluminium tube into 1
stab, and drill a 2.4mm hole right through the stab surface,
the plywood plate, sleeve and into the 20mm aluminium
techsupport@composite-arf.com
(above) Slots cut in elevator for
outer dual control surface horns.
(below) Add 1.5mm scrap ply to
the bottom of the horn alignment
template for correct positioning of
outer elevator horns.
(above) We strongly recommend
that you partly mass-balance the
elevators with 25-30grams lead in
each as shown here.
(below) You must use aluminium
discs on the servos, especially if
using the 8511/9611 servos, fixed
to the C-ARF phenolic servo arms
with at least 2 bolts each.
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