Great Planes Piper J-3 Cub 60 Kit - GPMA0162 - Manual (Page 14)

TWO WARPED SPARS INSTALLED
THIS WAY WILL RESULT IN A
STRAIGHT WING
TWO WARPED SPARS INSTALLED
THIS WAY WILL RESULT IN A
WARPED WING
D D 5. Without gluing, place ribs R3 through R7 and the
laminated R7/R7B (but not R2 or R8) on the spar in their
locations as shown on the plan If building the clipped wing
version, discard one of the R4 ribs.
NOTE: Rib 3 does not contact the plan since the center
section will be sheeted later.
D D 6 Slide the trailing edge sheet against the notches in
the bottom of the ribs The outer tip of the sheet should
match the plan and the "overhang" should be at the
center section.
D D 2 Locate all four 1/2" x 1/2" x 40" basswood spars.
Examine them carefully for possible imperfections Look for
knots, soft spots, diagonal grain and any other
imperfections If possible, position each spar so the
imperfections are on the outer half of the wing panel
(toward the tip) where they will be least affected by high
stress If the spars are warped slightly, try to "balance them
out by installing the warped spars in opposite directions
(see sketch).
D D 7 Position the die-cut 1/8" balsa outer trailing edge
at the rear of ribs R5 through R7.
D D 8 Mark a line on the trailing edge sheet against the
entire length of the outside of the outer trailing edge and rib
R5 As you mark the line, make sure all ribs and the outer
trailing edge are lying flat on the sheet.
D D 3. Do not use any glue until step 15. For now,
we're just making preparations and familiarizing
ourselves with the layout Place one of the 1/2" x 1/2" x
40" basswood spars on the wing plan and pin the spar
down with crossed T-pins as shown in the sketch We
recommend crossed T-pins at every rib bay (the space
between the ribs) NOTE: Align the end of the spar with the
outboard edge of wing rib R8 at the wing tip.
D D 4. Locate a 3/32" x 2" x 40" balsa trailing edge
sheet. It is supplied slightly wide so you may trim it to
straighten any bowed edges Using a straightedge, trim the
piece to 1-29/32". Set the trailing edge sheet aside for now.
D D 9. Remove the sheet and use a straightedge and
knife to cut along the line. Save the scrap piece.
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