milled slot to suit your
servo. Shown installed
here is a digital
JR3401 servo.
Centre the servo with
your Tx, set the travels
to maximum, and fix a
short servo arm onto it
at 90° to the servo
case as shown. Screw
the servo into place,
with the output shaft
towards the leading
edge of the Fin.
Route the extension
cable upward and for-
ward, thru' the milled
hole in the front balsa
spar, and then down
and out of the bottom
of the fin. Apply some
masking tape to the
outside of the fin (left
side) and carefully
mark the position of
the servo arm centre-
line on it. Extend this
line onto the rudder,
exactly perpendicular
to the leading edge.
Drill a Ø 2.2mm hole
right thru the rudder,
on this line, 10mm
from the leading edge
and tap M3 for the
control horn in the same way as for the elevators and ailerons. Screw the M3 threaded rod into
the threaded hole, and secure with a drop of 30 minute epoxy and microballoons through an 8mm
hole drilled in the bottom of the rudder. Make up the linkage as shown, using your choice of hard-
ware (M2 or 2 x 56 UNC). Cut a small slot in the outer skin of the rudder, as shown, and lengthen
the slot until you can fit the linkage as shown and obtain throws of 15mm both sides.
The fin is secured to the fuselage with a M4 x 25 bolt at the front, that screws into an M4 T-nut that
has been fitted into the fin already. The hole has been drilled in the fuselage for the bolt, but can
be adjusted if necessary. Cut a small reinforcing plate of 3mm plywood, 20 x 30mm, and drill a
4mm hole in the centre of it. Wax the M4 bolt thread. Pass the M4 bolt thru’ the hole and screw it
up into the stab from inside the fuselage. Make any small adjustments to the Fin position now, so
that it is straight with the fuselage centreline. Glue the plywood reinforcing plate to the inside of
the fuselage with 30 min. epoxy and micro. Secure the rudder servo extension cable to the side
of the fuselage and make sure that it cannot come into contact with the hot thrust tube.
Fox Composites Co., Ltd.
8
(above) Rudder is controlled by min. 4kg mini-servo servo screwed
to factory-installed plywood mount. Use a short servo arm and adjust
control horn to give 13 - 15mm throw each way.
(below) Fin is secured to the stabiliser with Ø7mm spar rod that fits
into a fibreglass tube, and an M4 bolt at the front into a T-nut in the
base of the fin - all factory-finished for you.
