.
COVERING
General Instructions
We recommend that you cover the wing, fuselage, tail surfaces, and control
surfaces all separately before hinging and final assembly. This way, the parts
are much easier to handle. Before choosing the covering for your model, please
refer to the list of approved covering materials that has been included with this
kit. The open structure design of the Four-Star 120 wing relies partially on the
covering to aid in torsional stiffness, so it is very important that you use an
approved covering material.
Our Four-Star 120 prototypes were covered with either Sig Supercoat iron-on
plastic film or Sig Koverall fabric. Sig Supercoat is ideal for sport models
because it's lightweight and easy to apply. Sig Koverall is extremely durable and
adds tremendous strength to the structure with only a slight weight penalty over plastic films. Use Supercoat film if you're
looking for maximum performance with a 1.20 four-stroke or .90 two-stroke engine. If you plan on using a gas engine or an
engine in the upper end of the recommended engine range, Koverall would be your best choice.
The following instructions provide advice and procedures specific to covering the Four-Star 120 with either Sig Supercoat
or Sig Koverall. If you choose another brand of covering material, be sure to read the manufacturer's directions (supplied
with the covering) and follow them carefully.
Surface Preparation
A good covering job starts with good surface preparation. Regardless of what type of covering you choose, it won't hide
poor workmanship. Fill any small surface gaps or dents with a lightweight filler or spackling paste. Sand the entire model,
including the ailerons and tail surfaces, with 220-grit sandpaper, then again with 360 or 400-grit sandpaper.
Two areas of the fuselage require further preparation before covering the engine compartment and the cockpit. Since it's
too difficult to apply covering material to the engine compartment, it must be fuel-proofed using several coats of clear dope
or two coats of polyester (glass) resin, sanded between coats. Finish off the engine area with a few coats of colored Sig
Supercoat Dope. (Most of the Supercoat plastic iron-on films have a matching Sig Supercoat Dope color.)
The cockpit floor can be painted or covered with plastic film. The front of the headrest (HR) shouldn't be covered or
painted until after the fuselage stringer area has been covered, to help hide the seam. Cut the instrument panel from the
decal sheet and apply it to former T-3 to finish off the cockpit.
Covering with Sig Supercoat Iron-On Plastic Film
You will need four rolls of Supercoat (color of your choice) to cover the FourStar 120. You will need one big piece from
each roll (about 14-1/2"x42") to cover the wing. Use the rest of the film to cover all of the remaining parts.
Covering The Wing
Begin the wing by covering the wingtips and plywood hold-down plates. On the wingtips, run the covering material "around
the corner" about 1/8". Later, when the main top and bottom covering pieces are applied, they will overlap the wingtip
covering and can be trimmed at the wingtip corners, leaving a virtually invisible seam. Extend the covering material about
1/8" past the outside edges of the hold-down plates, again to provide an area for overlap.
Cover the main portion of the wing starting with the bottom and then the top so that the seams will be on the bottom where
they will be less visible. The top covering should overlap the full width of the leading & trailing edges. Wait until both the
top and bottom pieces of covering material have been sealed completely around their edges before shrinking the large
open areas between the ribs. Alternate between the top and bottom surface to avoid uneven shrinking which could cause
a warp. Your sealing iron or a special "heat gun" can be used (household blow dryers don't provide enough heat). Keep
the heat gun moving at all times or you may burn a hole in the covering. If you notice the covering material "ballooning up",
put a small pin hole in the bottom of each rib bay to allow the expanding air to escape. To maximize the torsional stiffness
of the wing, be sure to firmly bond the covering material to all of the spars and ribs by going over them again with your
sealing iron.
Cut an "X" pattern at the hatch openings on the bottom of the wing, then iron the excess material to the spars and hatch
rails. Don't forget to cover the outer surface of the plywood hatches, wrapping the covering around the edges about 1/8".
Summary of Contents for Four-Star 120
Page 29: ... ...
