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Composite-ARF Yak 55 (2.1m/83")
dard sized servos.
NB: Screw the servos into place with the Ø 2.9 x 13mm
screws provided in the kit - not the standard screws that
come with the servos.
The slots for the supplied phenolic elevator horns are
already partly milled in the elevators, but you will need mill
them deeper - to at least 13mm (1/2") depth so that the phe-
nolic horn fits into the balsa block in the eleva-
tors right up to the small shoulders on the horn.
It is important that both horns are in identical
positions in relation to the hinge axis to give
equal elevator movements. It is also important
that the horns are directly in line with the servo
arm, so that there are are no twisting forces on
the phenolic arms. Depending on what type of
servos and arms you chose to install, you may
need to add thin plywood shims to the inside
surface of the root rib to position the servo
exactly in line with the elevator horns.
Do NOT use single-sided ball-links on the plas-
tic servo arms or phenolic control-surface horns
to obtain the correct alignment, because they
will twist the arms & cause flutter. This is a solid
experience and you should consider it a FACT.
Adjust the position of just one of the slots slight-
ly, forward or backward as necessary, so that the
clevise holes in the horn are exactly perpendicu-
lar to the hinge axis when the elevator is in the
neutral position. When horn fits fully into the slot,
put a layer of plastic parcel tape over the area of
the milled slot, wax it, and then cut through the
tape with a sharp knife to allow the horn to be
glued into the slot. This stops excess glue get-
ting on the surface of the elevator, and makes
the clean-up easy and quick! Rough up the glu-
ing surface of the horn, and glue it into the slot
with 30 minute epoxy and microballoons.
When the glue has fully cured on the first horn,
remove the tape, and make a horn alignment
template from thin plywood (see photo in wing
section) and a 1.6mm drill or piece of wire, and
use it to install the horn in the other elevator,
adjusting the slot position as needed. This
method ensures identical elevator throws.
Make up the elevator linkages from the 60mm
long M3 threaded rods, with 2 clevises and 2 x
techsupport@composite-arf.com
(above) Use waxed parcel tape to protect
the painted elevator surface while gluing in
the control horns.
(below) Adust the position of the servo or
the slots slightly if necessary to make sure that
the linkages are directly in line.
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