GREAT PLANES Extra 300S Instruction Manual page 10

3. (Refer to this sketch while you align the stab.) Slide
the stab into the fuse. Align the centerline you marked with
the slot for the fin. Measure the stab on both sides of the
fuse to make sure it is centered (A=A).
4. Remove your cowl if it's on the fuselage. Insert a
T-pin into the top, middle stringer over the firewall in the
front of the fuselage. Tie a small loop at one end of a 40"
piece of monofilament string and slip it over the T-pin.
5. Fold a piece of masking tape over the other end of
the string and draw an arrow on it. Slide the tape along the
string and align the arrow with one end of the stab. Swing
the string over to the other end of the stab. Shift the stab
and slide the tape along the string until the distances
between both ends of the stab and the front of the fuse are
equal (B=B). Now your stab is centered and square with
the fuse.
6. Use a felt-tip pen to mark the sides of the fuselage on
the top and the bottom of the stab. Remove the stab from
the fuselage.
7. Use a fresh #11 blade to carefully cut through the
covering 1/16" inside the lines you marked on the top and
bottom of the stab that indicate the fuse sides. Do not cut
the wood under the covering! This will weaken the
structure and may cause the stab to fail in flight.
Remove the covering from the center of the stab within the
lines you cut.
8. Reinstall the stab in the fuse. Bolt the wing to the fuse
with two 6-32 x 1-1/2" bolts and flat washers. View the
fuselage from the rear and make sure the stab is parallel to
the wing as shown in the sketch (A=A). If the stab is not
parallel to the wing, remove the stab and carefully sand
the fuse where it interferes with the stab, allowing the stab
to become parallel to the wing. Reinstall the stab and
recheck alignment from behind the fuse. Sand the fuse as
necessary until the stab is parallel with the wing. Proceed
carefully and remove only a small amount of material at
a time.
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