these to metal servo output discs, or to use full metal servo
arms (like those shown here from SWB) - and
not
the stan-
dard plastic output discs supplied with the servos. Secure
the phenolic servo arm extensions to the metal output discs
in the same manner as used for the elevators, centering the
servos with the R/C and making sure that all 4 arms are all
at exactly 90° to the side surface of the servos.
Assemble the servo mounts from the 3 CNC milled plywood
parts supplied for each servo, using thin CA, as shown in the
photos here, and P12. Fix the servos into the mounts with
the 2.9mm Ø screws provided in the kit, and secure your
chosen type of servo output arm to the servos.
Place the servos in their mounts on the inverted hatch cov-
ers to check the alignment so that the servo output arms
are exactly in-line with the pre-milled slots in the wing for
the control surface horns. The same principles apply here
as for the elevators, and you can adjust the slots in the
ailerons, or the slots in the hatch covers slightly, if neces-
sary, depending on your servo arm type. Tack the mounts
in place onto the hatch covers with a drop of thin CA.
When satisfied, glue the servo mounts to the hatch covers
permanently, with thin CA, and then remove the servos,
and reinforce the glue joints between the servo mount and
the servo cover plate with slow (at least 30 minute) epoxy
and milled fibre, with a nice glue fillet all around. These are
important glue joints!
Each servo hatch is fixed to the underside of the wing with
of the 4 sheet-metal screws provided, Ø2.9 x 10mm. These
servo mounts allow you to change a servo within a few min-
utes, if needed, easily within the time between 2 flying
rounds of a contest.
Control Horns
The slots for all 4 phenolic control horns are already partly
milled in the ailerons for you, but may be adjusted if
required. Extend the slots for the horns to least 20mm
deep, using a Dremel mill or small Permagrit file, checking
alignment with the linkage as you work.
Fit
just one
inner control surface horn to start with, using the
same method as described for the elevators. Trim the
length of one of the phenolic control arms so that the hole
for the clevise is approx. 23mm from the surface of the
aileron, and rough-sand the part that will be glued into the
balsa block inside the aileron. Ideally the hole in the horn
for the clevise should be exactly perpendicular to the cen-
tre of the hinge axis on the top of the wing.
Use a layer of parcel tape and clear wax to protect the
aileron surface. Install the corresponding servo and hatch,
Composite-ARF Extra 300SX
(2.6m span)
22
(above) Clevise hole for inboard
horns should be 23 - 24mm from
aileron surface, and perpendicular
to the aileron front edge.
(below) Make sure control horns
are perpendicular to aileron sur-
face and parallel to servo arm.
(above) Adjust position of servo
mounts on hatch covers so that
servo output arms align exactly
with phenolic aileron horns.
(below) View of aileron linkage,
with servo using metal disc, C-ARF
phenolic extension arm and the
included hardware.
