Great Planes Extra 300S 60 Kit - GPMA0236 - Manual (Page 13)

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6. From a 3/32" x 3" x 24" balsa sheet, make shear
webs to fit from ribs R3 through R8, with an additional web
aft of the spars between R3 and R4. Hint: Use a #11 hobby
knife to hold the cut shear webs while putting glue on the
web and put the webs in place.
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7. Glue the 1/8" x 1/4" x 36" balsa bottom rear spar
in place butting it against R1. Remember we are building
the wing upside-down so the bottom spar is on the top now.
Note: It is necessary to bevel the root end of the spar so it
will fit well against R1.
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8. Pull the 1/8" x 1/4" x 36" balsa top rear spar up
into the notches in the ribs and glue in place. Trim the ends
of the rear spars off at the wing tip.
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9. Make marks on the ribs 3/8" forward of the rear spar.
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10. Glue a piece of 1/16" x 3" x 36" balsa sheet on
the TE of the wing, aligning the LE of the sheeting with the
marks you made in step 9.
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11. Glue the 3/32" x 5/8" x 30" sub LE on the LE of
the ribs, centering it vertically and leaving the excess at the
root of the wing.
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12. Use a razor plane and/or a sanding block, shape
the sub LE so it aligns with the tops of the ribs and the
shape of the airfoil.
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13. Glue a 1/16" x 4" x 32" balsa sheet to the forward
half of the main spar. Note: Make sure the sheeting hangs
over the tip rib and the center of the wing slightly.
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