the clevise on the servo arm as close to the servo
centre as possible, and the clevise on the elevator
horn as far out from the elevator as possible - to
maximise the mechanical advantage, whilst still ob-
taining the maximum necessary aileron throws of
9mm up and down. Lengthen the servo arm exit slot
to clear the linkage on max. throws if needed.
IMPORTANT
: Do NOT use ball-joints or ball-links on
the plastic horn adapters. They will cause twisting,
and almost certain flutter ! This also applies to the
rudder linkage.
When the linkages are finally adjusted the servo
hatches can be held closed with small strips of clear
tape. It is not necessary to secure them with screws.
Some small triangles of very thin ply or fibreglass
sheet glued inside the corners of the servo bays
keep the hatches flush with the wing skin.
Flap Servos
The flap servos require a little patience to install and
set up, but result in a very nice system that is com-
pletely hidden within the wing.
The servos are fitted in 6mm thick milled liteply
mounts that you glue into the wing, sized to suit
‘standard’ sized servos, and we recommend that you
use servos with
not less
than 6kg torque as the
Hawk flaps have quite a large surface area. We pre-
fer to use a digital servo with at least 8kg torque, and
have installed JR 8311’s here.
If you want to use a single Rx channel and Y-lead
for operating the two flap servos, then you must fit
them both in the same orientation. In this case, then
the left flap servo will be fitted at the
inboard
side of
the hatch, and the right flap servo at the
outboard
side of the hatch, as shown in the photos here.
Of course it is even easier to use a ‘Matchbox’ (or
equivalent) on one servo so that you can reverse it,
and adjust centres and end-points to match the other
one perfectly - and in this case you can install the
flap servos in 'mirror-image' (like the aileron servos).
As with the aileron linkages, we also prefer to make the flap linkages parallel to the wing root - al-
though as they are fully hidden in the wing you can also choose to make them perpendicular to
the flap leading edges if you prefer. It’s your choice, and the angular difference is so small (6.5°)
that it does not affect the operation.
Carefully mark the line of both linkages on masking tape before starting. Centre both servos using
Fox Composites Co., Ltd.
9
(above) Secure flap servos to mounts
with allen-head screws for easy removal.
(below) Hold plywood mount at an angle
inside the hatch to screw the servo into
place when trial fitting. Right wing shown.
(below) Notice that the servo is at a slight
angle to the hatch sides, but parallel to
the wing root. Right wing shown.
