.
FINISHING AND FLYING
19.
Covering And Painting The Framework
The completed Cub framework can be
covered with Sig Koverall, Sig Silk or an
iron-on type of covering material (either
plastic or fabric). Whatever type of
covering you desire to use, it will not
conceal a rough framework. Be sure all
surfaces are smooth before proceeding!
The manufacturer's directions for
applying iron-on coverings are packed
with the material. Follow these closely,
for different types of material have
different iron temperatures and
techniques of application.
The rest of these instructions describe
the use of Sig Koverall, which is a
polyester based synthetic fabric ideally
suited to quarter-scale models due to its
low cost, workability, and toughness.
Silk is applied in the same way, but it
costs much more per yard. Koverall is
highly recommended for the Cub - all of
our prototype models were covered with
it.
Brush an unthinned coat of clear Sig
Supercoat or Sig Lite-Coat Dope over all
parts of the framework that will contact
the covering. When dry, resand with fine
sandpaper to remove any fuzz or raised
grain. Brush on a second coat and sand
again.
Hints On Covering The Fin Fillet
On the full-size Piper Cubs, the
fuselage and fin are covered with
one continuous piece of fabric. It
bridges from the top stringers of the
fuselage sides up to the fin bottom
rib, producing a beautiful fillet.
The construction of this model Cub
duplicates this feature. Your
covering material should bridge from
the sheet balsa Tail Fairings up to
the fin bottom rib. This may at first appear to be a difficult job to do, but it's
much easier than you'd think.
If you're using a dope-on type covering, proceed as follows:
1.
Cut a piece of material that will cover the entire left side of the fin and
left side of the fuselage top (all the way forward to the wing T. E.
Crosspiece).
2.
Dope the edges of the covering down along the fuse 3/16" x 3/8" Top
Stringer, the 1/4" sq. Corner Stringer, and the T.E. Crosspiece. Pull out
any large wrinkles or sags in the fabric.
3.
Straighten out the rear end of the covering and adhere the bottom of it
to the Tail Fairing. Work the material smooth and dope it down to R4
and the fin bottom rib. Use plenty of pins to hold securely until dry.
4.
Apply three extra coats of clear dope along the fabric stuck to the fin
bottom rib. Let dry between coats.
5.
Finish sticking down the remainder of the covering piece ot the top of
the fin.
6.
Now repeat the steps to cover the right side of the fin and the fuselage
top in the same manner.
When dry, resume following the rest
of the written instructions for doped-
on coverings. Be careful when
applying the pre-color clear dope
coats over the entire model that you
don't soften the bond of the fabric to
the bottom rib and let it pop loose.
It's best not to put any dope of the
fin bottom rib while painting the
surrounding fin and fillet areas.
If you're using an iron-on type of covering, apply it basically the same as
described above with one exception. Lap and adhere the fillet covering piece
over onto the top side of the fin bottom rib and cut it off there. Then, after
shrinking the fillet area tight, cover the top part of the fin with a separate piece.
Overlap it slightly onto the fillet covering. If you try to do the job in one piece,
the heat of shrinking the entire area will always pop the covering loose from
the fin rib.
The bottom of the wing is a good place
to start covering. Cut a piece of Koverall
about 1/2" larger all around than half of
the wing, with the grain running
lengthwise. (The grain of woven
materials run parallel to the finished bias
edge.) Dip the piece of covering in
water, let the excess water run off, and
then lay it on the wing. Go around the
edges, pulling out the wrinkles and
stretching the material smooth. Brush
clear dope around the edges. This will
soak through the fabric and adhere it to
the dope already dried into the
framework. Let dry before trimming off
the excess material with a sharp razor
blade. Check for any rough areas or
places that are not stuck down properly
and apply more dope.
Use the same process to cover the top of the wing, the fuselage, and the tail surfaces. Be sure to read "Hints on Covering
the Fin Fillet".
After all covering is done, allow the water to dry out of the fabric and wood. If the Koverall is slack or baggy in any places,
use a hot air gun or hair dryer to shrink it tight (read Koverall package instructions).
Next give the entire model a coat of Lite-Coat clear dope. Thin the dope until it brushes on easily and flows out smoothly.
Brush the dope on sparingly over the open framework areas. If too much is applied, the excess dope may rub off the
brush, run completely through the covering and puddle against the covering surface on the other side.