project. Modelers who have much more experience than I do
employ other methods using many different types of materials.
The wing I will cover has an 88-inch
span. Not counting the wingtips, the actual
foam span is roughly 80 inches. I chose
3/32 x 4 x 42 balsa sheets to make the wing
skins. You can purchase the balsa sheets
in common sizes of 36-, 42-, and 48-inch
lengths. I purchased mine from Balsa
USA.
Because wood is not an exact science,
the edges needed to be sanded lightly so
that the sheets would butt up nicely to
each other. This is important because a
successfully glued joint requires an
accurate fit.
You will need masking tape and your favorite glue. I prefer
3M Scotch Blue Painter’s Tape because it is flexible and has
medium adhesion. Medium adhesion means that it can be
IT’S NEARLY MAY and spring has sprung! It’s time to finish
those winter projects and get ready for the flying season.
I’m working on a 1/4-scale model that
uses foam-core wing panels. I thought it
appropriate to photograph and document
some of the building techniques I use; I
hope you find it helpful.
Expanded-bead foam for models has
been around for a number of years. Some
modelers like to use foam, while others
prefer the traditional stick-building
method. Whether it’s foam or balsa, we all
intend to achieve a model that flies well.
Foam has some excellent advantages:
it’s strong, inexpensive, and easy with
which to work. Additionally, foam wings consist of few parts and
are extremely accurate when made correctly. I’ll write more about
foam-wing construction in the coming months.
Following is the way I made the balsa skins for this particular
Making balsa skins for a foam-core wing
[[email protected]]
Radio Control Giants Sal Calvagna
Also included in this column:
• New five-color lozenge fabric
from Wildmann Graphics
• Armand Francoeur’s Balsa
USA Spad 13
The edges of the balsa sheets are sanded lightly to ensure a good
fit and taped together with masking tape.
A small amount of wood glue is applied to the opened balsa joint
using a large plastic syringe.
When the sheets are flattened, the excess glue is squeezed from
the joint and cleaned with paper towel.
Wildmann Graphics manufactures the five-color, lozenge-pattern
fabric in lighter and darker versions.
May 2008 119
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120 MODEL AVIATION
Armand Francoeur of Westford, Massachusetts, displays his Balsa
USA 1/4-scale Spad 13.
Armand’s Spad 13 handles nicely in the air, and ground control
was improved with the addition of a gyro.
removed easily once your project is completed. This tape works
well for making wing skins.
I use an aliphatic resin—wood glue—for the skins. Wood glue
is easy to clean off and sands nicely. I have used cyanoacrylate in
the past, but unless you’re careful with its application, cleaning
and sanding can be a chore. When using cyanoacrylate in the past,
I have left a slight ridge at the glue joint between two sheets of
balsa.
As I mentioned, you need to start by sanding the balsa sheet
edges so they fit together nicely. Tape the balsa sheets together. I
used five sheets to make one wing skin.
When the balsa is taped, carefully turn the entire assembly
over and lay it flat on the work table. One at a time, lift the panels
where they are taped together to expose the balsa joint. You can
place something such as a large closet dowel under the taped joint
so that the balsa sheets’ edges are exposed.
I filled a plastic syringe with glue and applied the adhesive to
the joint. Easy does it; a little glue goes a long way. When the
joint is filled, lay the sheets flat. Excess glue will be forced from
the tight-fitting joint. Wipe the excess with a paper towel and
repeat the process for the rest of the joints.
I was pleasantly surprised to find that the completed wing skin
could be handled in approximately 20 minutes. The combination
of a tight fit and a small amount of glue accelerated the drying
time.
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