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Composite-ARF Extra 300L (2.12m/84")
techsupport@composite-arf.com
inside the carbon tube. There is a small plywood reinforcing plate inside the stab that the bolts
will pass thru', and the centre of this is 100mm from the root. Apply some masking tape to the
bottom of the stabs and mark the centre line of the stab tube on it. Fit the carbon tube into one
stab, and drill a Ø 2.4mm hole 100mm out from the root of the stab, thru' the bottom surface, the
ply reinforcement, the fibreglass sleeve and the bottom of the carbon tube. Tap the hole M3.
Remove the carbon tube and glue in the M3 T-nut, using a thick mixture of 5 minute epoxy and
micro-balloons, with the M3 bolt temporarily in place to ensure alignment. Wax or oil the bolt first
!
Fit both stabs tightly to the fuselage, and then drill the hole in the other stab and spar tube, thread
and glue in the T-nut as before. Counterbore the holes in the bottom surface of the stabs for the
boltheads so that they fit almost flush with the bottom surface of the stabs, and put a piece of
clear tape over the bolt-heads for flight.
Note: Try to always leave the stab tube fixed in one stab, and never remove that one bolt, as it
is difficult to find the right position for the stab tube again if it is removed from both stabs!
Rudder
The rudder is hinged to the fin with a Ø 2mm
wire which passes thru' the 3 phenolic hinge
posts that are factory-installed and aligned. File
a point on one end of the wire, and a short 90°
bend on the other end and push it through the
rudder from the top, capturing the 3 phenolic
hinges on the way. Don't forget to secure the
bent end of the wire with clear tape for flight.
Trial fit the double-sided phenolic rudder horn in
the slot that is already milled in the base of the
rudder, and mark the part that will be glued in.
Remove it, mask the exposed parts and scuff
the centre part on both sides with coarse sand-
paper. Glue in place with slow (not 5 minute!)
epoxy and microballoons mix, making sure that
it is centred in the rudder. The front edge of the
phenolic horn should be flush against the back
of the balsa false leading-edge.
Servo: The rudder is a huge surface on the
Extra which definitely needs a hi-torque power
servo,
and
we
recommend
the
digital
JR/Graupner 8511/8611, or Futaba S9351, for
this very important control surface.
The servo is mounted in a CNC milled compos-
ite balsa plate, with a milled 3mm plywood rein-
forcement
glued
underneath
it,
and
2
balsa/glass stiffening rails, in the fuselage under
the canopy area. The exact position you chose
is up to you, but position the mounting plate at
18
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