Carf-Models Composite-ARF Yak-55 SP Instruction Manual page 27

Composite-ARF Yak-55 SP (2.6m span)
parts supplied for each servo, using CA. Fix the servos into
the mounts with the 2.8mm Ø screws provided in the kit,
and place them on the hatch covers to check the alignment
so that the servo arms are in the centre of the slots milled
in the hatch covers, and also align with the aileron horn
slots. Don't forget to allow for the extra thickness of the C-
ARF servo horns that will be fixed onto the standard plastic
servo arms. You will need to make the slots in the servo
hatch covers a little wider, by 1mm or so.
Glue the servo mounts to the hatch covers with CA, and
then remove the servos, and reinforce the glue joints
between the servo mount and the servo cover plate with
slow (min. 30 minute) epoxy and milled fibre, with a nice
glue fillet all around (see photo). This is an important joint!
Rough sand the top surface of the 4 standard 25mm Ø
plastic servo arms, and one side of 4 C-ARF servo horns to
prepare for gluing. Then refit all 4 servos to the completed
hatch covers and install in the wing. Connect all servos to
your R/C and centre them. With the servos centred, insert
the C-ARF servo horns through the slots in the hatch covers
and glue them to the plastic servo arms with one or two
drops of thick CA, making sure that they are all at 90° to the
btm. surface of the wing using a small 90° set-square.
When the CA has cured, remove them and glue and screw
onto the plastic servo arms properly using the small sheet-
metal screws provided, in the same way as the elevator
and rudder servo horns. The servo covers are fixed to the
underside of the wing with 4 small sheet-metal screws pro-
vided. This kind of servo mount allows changing of a servo
within a few minutes, if needed.
Finally make up the linkages from the M3 x 70mm thread-
ed rods supplied, with 2 quicklinks and 2 x M3 locknuts for
each linkage. Don't forget to 'Loctite' the quick-link and
lock-nut on one end of each linkage. Please use the quick-
links and hardware supplied - do NOT use ball-links if you
use these C-ARF servo arms, because they will twist the
servo arm and cause flutter. This is a solid experience and
you should consider it a FACT.
Servo choice: We recommend using 2 high quality servos
(eg: JR/Graupner 8411) per aileron as the surfaces are
very large. The ailerons have enough torsional flexibility to
prevent servo damage if each pair is not perfectly matched.
Attention: To prevent severe wing damage during any pos-
sible aileron flutter, we highly recommend that you box the
4 servo cutouts between the bottom and top wing surfaces
with scrap 6mm (1/4") balsa, along both sides, glued with
epoxy, to stiffen the bottom wing skin. (see photo on right)
techsupport@composite-arf.com
(above) The completed aileron
linkage. Note locknuts and safety-
tubes (made from Tygon) used on
both ends of the linkage.
(above) View of the C-ARF servo
horns, shown fitted to standard
25mm Ø servo arms, and also a pair
of the standard C-ARF phenolic
control surface horns. Note gluing
surfaces roughened up with coarse
sandpaper to ensure good bond.
(below) Boxing of aileron hatch
cutouts with 6mm scrap balsa
sheet on both sides.
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