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Composite-ARF YAK 55SP (3m span)
Horizontal Stabs
The stabilisers are finished at the factory, and
only need the servos and linkages installing.
Insert the Ø 20 x 435mm long aluminium tube
spar in the fuselage sleeve, and slide on both
stabs. The 10mm carbon anti-rotation dowels
fit into the carbon tube in the fuselage and the
alignment and incidence has already been set
in a jig at the factory for you. The stabs are
retained on the aluminum tube with an M3 x
16mm allen bolt thru' the bottom surface of
each stab, and these are already factory
-finished.
The elevators are hinged to each stab using
the Ø 4mm aluminum tubes provided. Make
sure there is no burr on either end of the
tubes, and chamfer one end slightly with fine
sandpaper to make it easier to get them
through the holes in the phenolic hinge plates.
Be careful inserting them, and if they are a bit
stiff, then use a little grease on the tubes.
Don't use too much force, otherwise a pheno-
lic hinge post inside might break loose. Leave
the tubes a bit too long during assembly, and
cut them to exact length when the model is fin-
ished. We supply the hinge tubes with quite a
tight fit in the phenolic hinge posts - but after
the first 2 or 3 flights they will free up com-
pletely and give smooth movement.
During final assembly, secure the inboard
ends of the hinge tubes with small pieces of
clear tape on the root end of the elevators
before flight.
Servos
The elevators are designed specifically to be
controlled by a single very high torque digital
servo in each stab, and we strongly recom-
mend that you only use a JR8711 or JR8811
servo. Do not substitute a servo with lower
torque, such as a 8511 or 8611, as it might not
be sufficiently strong enough to prevent flutter.
If using Futaba servos, we recommend that
you use S9152's (or better), but you will need
to open up the milled cutouts in the plywood ribs as these are a bit wider than the 8711 or 8811
servos. The Futaba S9351 is not strong enough to be used in the stabs. The servos should be
installed with the output shafts nearest to the trailing edge of the stabs.
techsupport@composite-arf.com
(above) Elevator horns, spar tubes, stab secur-
ing bolts, anti-rotation dowels and servo arm
slots are all factory-finished.
(below) A single JR8711 or 8811 servo is
installed in the milled mount in the ply rib, and
connected using a 1.5" SWB metal servo arm,
and the linkage hardware supplied.
(below) Milled 3mm thick plywood doublers are
included for both the JR8711/8811 and the
Futaba S9152 servos. JR8811 and SWB 1.5" servo
arm shown here.
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