GREAT PLANES PT-20 Instruction Manual page 29

3. Without glue, test fit the CJ's between the top and
bottom spars of one wing panel. Hold the wing panels
together with the CJ's in position. Make sure the CJ's fit
between the top and bottom spars and that the LE, TE and
the spars meet. Examine all the joints carefully. There
should be no gaps between any of the parts, especially
the top and bottom spars. If necessary, make small
corrections with your bar sander, checking progress
regularly to avoid "over correcting." You may need to
shorten both ends of the CJ's slightly to allow the wing
halves to meet.
4. With CJ's temporarily holding the wing halves
together, test fit the rest of the joiners.
5. Use medium CA to glue the die-cut balsa rear center
ribs 1C to each other and the front center ribs 1A-A
(or 1A-B) to each other.
A. Remove the die-cut piece for the wing dowel in the
front center ribs 1A-A (or B). Use the die-punched lines
as a guide to extend the notch to the front of the center
ribs and remove the rest of the wood.
B. Temporarily install a 3/16" x 3/16" bottom
forward spar in the right wing panel. Fit the 1A forward
center rib assembly on the spar, then fit the FJ between
the rib and the main spars. This should temporarily hold
the rib in position for the next step.
C. Draw two lines on the end of the LE to match
the spacing and angle of the slot in the rib.
D. Remove the spar and the center rib. Wrap a
piece of 150-grit sandpaper around one of the 1/4"
dowels included in this kit or use a round wood rasp to
sand half the diameter of the dowel hole in the end of
the LE.
E. Do the same procedure for the other wing panel.
F. Temporarily join the wing panels with the forward
center rib. Test fit one of the 1/4" wing dowels into the
center rib and make sure you have made the grooves
deep enough in each leading edge. Cut the dowel off
3/4" in front of the leading edge. Disassemble the wing
halves and remove the center rib.
You will need several small C-clamps (or modeling clamps)
and a few clothespins or office spring clips for the next few
steps. Clear a space on your work bench long enough to
accommodate the soon-to-be-joined wing.
IMPORTANT: Perform a "test run" of steps 7 through 16
without any glue so you understand where to position
all the joiners, how many clamps you will need and
where to place them. Do not attempt to join the wing
halves with anything but 30-minute epoxy – you'll need
the working time to be sure that all the joiners are
accurately positioned and the clamps are properly set.
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