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Composite-ARF YAK 55SP (3m span)
Due to the manufacturing tolerances
of the phenolic material you may find
that you need to sand small dimples in
the top surface (only) of the phenolic
arms where the steel clevises are fit-
ted, to make sure that they close com-
pletely and have free movement. A
drum sander with a rounded end (eg:
Permagrit) in a Dremel
makes this a quick task. The dimples
only need to be about 0.5mm deep.
See photo above.
The servo mounting tray should be
glued securely to the bottom of the
fuselage between the angled back
face of the muffler tunnel and the ring
bulkhead at the back of the cockpit.
Sand the ends of the tray if necessary
for a perfect fit, sand the inside of the
fuselage, and then glue in securely
with slow epoxy and micro-balloons
mixture, or Hysol.
The pull-pull cables that connect the
rear arm to the rudder horn should be
crossed, so that they exit under the
stabs. The slots that you need to cut
for the pull-pull cables to the rudder are 230mm (9 1/8") forward of the back edge of vertical fin
(immediately in front of the rear bulkhead) and 70mm from the bottom seam of the fuselage. Cut
out a small slot first with a very sharp knife, check the position using the pull-pull wire, and then
adjust and open up the slots with a small file as needed. The slots should be about 3mm high
and 35mm long.
Make the pull-pull wires from the hardware supplied, with a loop at the front that goes over the
hooks on the output arms, and a quick-link with threaded extender (turnbuckle) and locknut at
the rudder end. The ball-link is bolted in between the dual rudder horns with the M3 x 20mm bolts
and stop-nuts.
Pass the closed loop cable through the supplied 'crimping tubes' 2 times before squashing flat
with pliers. Make sure that the wires are tight, and check and adjust after the first few flights as
the cables straighten out. Even a small amount of slop will prevent your Yak from perfect track-
ing. You can glue a very small scrap of ply or balsa across the front of the slots on the servo arms
with a drop of CA to prevent the wires coming out of the slots accidentally, for example when the
rudder is removed for transport.
You can increase the lengths of the slots in the rudder L.E. in same way as for the elevators to
achieve extra throw if necessary.
or similar,
(above) Rudder servo tray glued into the fuselage
between muffler compartment & rear cockpit bulkhead.
(below) The slots for the cables are immediately in front
of the rear bulkhead, 230mm from the back of the fin.
19
techsupport@composite-arf.com
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