Great Planes Piper J-3 Cub 40 Kit - GPMA0160 - Manual (Page 15)

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27. Place the die-cut 1/8" balsa triangular Gusset
(CUB4W01) in the corner formed by the #4 rib and the
tapered TE. Securely glue it in place.
(Photo taken at a later stage of completion.)
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28. Glue the 1/2" x 3/4" x 1" basswood Wing Strut
Mounting Blocks (CUB4W22) to the outboard side of the
second #6 rib. They should be flush with the bottom of the rib
and positioned as shown on the plans. Cut four 1" long pieces
of 3/8" balsa Triangle (CUB4W24) and glue one piece on top
of each mounting block. There are six of these blocks
included in this kit, two of which are (CUB4F20). The strut
mounting blocks must be down flat on the building surface
when gluing it to the rib. The front block will be flush with the
bottom of the rib, but the aft block will be 3/32" below the
bottom edge of the rib because the balsa sheeting has not yet
been installed in the bellcrank bay.
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29. Use the die-cut 1/8" ply Spar Gauge (CUB4F09)
to mark where to cut the spars and TE off. Hold the gauge
flat against the work surface and line it up with the centerline
on the plans. Mark along the almost vertical edge and then
cut the spars off along these lines. This will make the top
spar slightly shorter than the bottom spar to allow for the
dihedral angle. In addition to the spars, mark and cut off the
bottom TE sheet and the tapered TE at the wing centerline.
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30. Remove the wing panel from the work surface and
install the 1/8" x 1/4" x 33-1/2" Bottom Forward Spar
(CUB4W12) following the same procedure used in step 25.
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31. Go back to step 4 and build the other wing panel.
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1. Using the die-cut 1/8" ply Front Spar Joiner (CUB4W07)
and the die-cut 1/16" ply Forward and Aft Main Spar Joiners
(CUB4W05), test fit (DO NOT GLUE) the two wing panels
together. With the center of the wings resting on the work
surface, block up both wing tips 5/8" (1/2" for the clipped wing)
as measured from the work surface to the bottom of rib #7.
Check the fit of the spars and the TE to make sure they meet
up nicely without producing any sweep in the wing. Take the
panels apart and sand the spars or TE’s if necessary to achieve
the correct alignment. NOTE: The holes in the die-cut 1/8"
plywood Front Spar Joiner and the holes in the die-cut 1/16" ply
Forward Main Spar Joiner must be centered on the centerline
of the wing. Make sure you trim the ends of the spar joiners as
needed to allow the wing panels to come together and the
spars to touch. It is typical to have to trim 1/16" from the ends
of the joiners. It is also likely likely that you will have to deepen
the notches in the #2 ribs slightly to allow the joiners to slide
fully into place.
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2. Glue the three die-cut 1/8" plywood Dihedral Braces
(CUB4W07) together as shown in the photo.
Joining the Wing Panels
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