Composite-ARF CARF-Models Spitfire Building Instructions page 21

Wing assembly (Servo installation)Cont.
Use a 1/2'(13mm) square piece of
1/8" (23mm) at the rear of the pocket
to screw down the cover
Wing assembly (Pocket
reinforcement)
Do not skip this step, it is
necessary to reinforce the servo
pocket or flutter of the control
surfaces will occur. Using 1/4"(6mm)
balsa make up the reinforcements
as shown. Be sure the grain of the
balsa runs from the top skin to the
bottom. Use photo as a guide to
locate balsa blocks. Measurements
are shown in the photos as a starting
point. Light sanding of the block may
be required for a good fit. Once the
blocks are fit scuff the wings and
glue in place.
On the top side of the wing, 2 1/2"
(63MM) in front of the spar tube we
need to make an exit hole for the
wires and air lines. It's best to split
the hole between the top and side to
make installing the wing easier. See
photos below
Composite-ARF Spitfire 21