Acroduster wings are built of wood. The design utilizes a web-and-capstrip wing rib design, using birch plywood rib "webs" enclosed by grooved 1/4" spruce capstrips. The ribs are glued together in a jig.
Remember, though, that the Starduster and Acrodusters have a rather elegant elliptical wing shape. This means that the ribs are going to end up being a lot of different sizes! Fortunately all ribs are the same size for all four wings. To build them, you first cut and build a wing rib jig to fit the smallest sized wing rib. Build four of these ribs. Then, enlarge the jig to fit the next-sized rib. Build four more. Complete the process until done!
There are nine fullsize ribs per wing on the Acroduster, for a total of thirty-six. Add thirty one more noseribs, and you end up with a lot of ribs! They actually took nearly six months to complete.
The two rib jigs are shown on the work table in the picture. I built one
jib, which would be modified as work progressed for four sizes of
fullsized ribs, and a second jig for the sixteen ribs in front
of the aileron bays. For these locations, the wing's elliptical shape
is given by merely changing the size and length of the aileron ribs, all
are the same from the rear spar forward. The two jigs are closed
tightly using the wooden cams along the bottom of each jig.
A night's rib building would consist of gluing up a couple of
aileron bay ribs and a couple of fullsize ribs, with waxed paper in between,
then clamping shut the jig to let the glue (T-88 epoxy) dry overnight.
The next day, take the four ribs out, and now nail and glue on the plywood
stiffeners and nose pieces, etc. 1/4" aircraft nails were used for this,
their only purpose being to hold the glue joints in close intimate contact!
The fittings at the left attach to the wing spars and anchor the aluminum drag and anti-drag "truss tubes", a critical structural wing member. These are constructed from 2024-T3 aluminum "U" channel extrusion. The fittings were cut quite easily on the little bandsaw, then each was sanded smooth until the edges shined on the belt sander. Then over to the drill press jig to drill the various 1/4" holes.
Making a good hole in aluminum takes more than just
drilling with a 1/4" drill (such an approach would lead
to a somewhat out-of-round, rough hole, and you want
a more precision fit in aircraft work). I first drill
these with a small pilot drill, then a "D" drill bit,
which is just a bit smaller than 1/4". Then REAM the
hole to its exact 1/4" size using a reamer.
Reamer?
What's that? Indeed, this was one of those hard things
to figure out when I first started homebuilding. Reamers
are used in precision metalworking and fabrication, you
can't find them at Home Depot! I finally got a catalog
from a machine tools outlet, Rutland Tool and Supply,
and purchased my "chucking reamers" there.