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 current drain on your batteries. Therefore, glue a small
scrap of 1.5mm thick ply or balsa to the bottom of the tem-
plate 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
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
Composite-ARF SuperXtra 330L
(3.1m span)
19
(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 sservo arms
with at least 2 bolts each.
