Rudder
Trial fit the the double-sided phenolic control horn in the slot that is already milled in the base of
the rudder, mark the central part that will be glued in, and scuff it well with coarse sandpaper.
There is a balsa block underneath the horn position inside the rudder, and this should also be
scuffed with sandpaper or a small file. Adjust the milled slot in the rudder so that it is a little high-
er than the phenolic control horn thickness, so that all the glue is not scraped off the horn when
you insert it into the rudder !
Cover the rudder both sides around the slot area with
masking tape, wax the area, and then cut through the tape
to expose the slot with a sharp knife - in the same way as
described for the elevators. This makes it easy to clean off
excess glue afterwards. Glue the horn in position with slow
(min.30 minute) epoxy & micro-balloon mix, making sure
that it is perfectly centred and level in the rudder. When the
glue has cured, fit the rudder to the vertical stabiliser with
the 2mm steel hinge wire. Sand a small chamfer on the end
of the hinge wire for easier insertion through the phenolic
hinge posts, and if it is too tight use a little grease on the
wire. Check for smooth movement. You can increase the
lengths of the slots in the rudder L.E. in same way as the
elevators to gain extra throw if necessary.
The rudder servo mounting plate (and tank base) should be
installed in the plane
after
the engine and exhaust system
mounting are completed, but it is easier to assemble the
parts and install the servos outside the model now.
Glue the 2 milled plywood reinforcing pieces underneath
the servo cutouts in the balsa plate with CA, and glue the
plywood reinforcement onto the underside of the tank tray
(see also photo P8). Prepare, sand and assemble the other
milled composite balsa parts as shown above, using thin CA. Check fit of the complete assem-
bly in fuselage, and then apply a fillet of 30 minute epoxy to all joints and edges. It’s a good idea
to seal all bare edges of the fuel tank base with a coat of laminating epoxy now, or even thin CA,
in case of fuel leaks. Adjust the height of the vertical balsa bulkhead between the tank base and
servo tray, if necessary, so that the tank sits level when the plane is in level flight. The angled
balsa plate behind the rudder tray is optional, and can be used for locating your Powerbox or
Receiver if you wish. (photo P9)
Servos
The recommended choice of servos is similar to that for the elevators, either a pair of
JR/Graupner 8411/8511/8611’s or a pair of Futaba S9351’s.
Servo arms
The supplied ‘pear-shaped’ phenolic rudder servo output horns
must
be bolted to 1” or 1.25”
diameter metal servo output discs in the same way as the elevators. Please do
not
use the stan-
dard plastic discs for this, as there is a chance that the internal plastic splines can be stripped
by the current hi-torque servos - causing instant rudder flutter, and probable loss of your plane.
Fit the 2 rudder servos into the tray, with the output shafts nearest to the tailplane, and screw
into position using the 2.9mm Ø x 13mm long sheet-metal screws supplied. Fit the metal servo
Composite-ARF Extra 300SX
(2.6m span)
19
(above) Scuff up the gluing sur-
faces on the rudder horn and glue
into the slot in the rudder.
(below) The Tank base/Rudder tray
is assembled from the milled parts
included in the kit.
