Great Planes PT-40 MkII Kit - GPMA0118 - Manual (Page 40)

the top of the wing at the front of the wing bolt plate (start at
the trailing edge of the wing if you are building the rubber
band-on wing). Pull the tape around the leading edge
(CAUTION: Work in a well ventilated area when applying
the CA). Wick thin CA into the cloth and wing sheeting while
holding the cloth tightly in position. Turn the wing over, then
pull the cloth around the LE toward the TE and glue in
position.
❏
2. Cut off any excess cloth, then lightly sand the surface
to smooth off any glue bumps.
Well, you’re through the framing stage and you’ve given life
to a box of balsa. It’s really going to fly! Have you decided
on your color scheme yet?
Refer to the Expert Tips below, then fill any scuffs, dents or
gaps in the balsa with HobbyLite balsa filler. After the filler
has fully hardened, sand the entire fuselage with
progressively finer grades of sandpaper, ending with 320-grit.
Slightly round the corners of the fuselage.
Fuelproofing may be done either before or after covering.
❏
1. Remove the engine mount, fuel tank, landing gear and
any other hardware you may have installed in the model.
❏
2. Fuelproof the engine and fuel tank compartments and
any other areas that may be exposed to fuel (such as the
landing gear rails, the tops of formers F-2 and F-3, the
inside of the fuel compartment hatch). You can use any
fuelproof paint such as K&B Superpoxy, model airplane
dope or 30-minute epoxy. Pay special attention to the
firewall. Refrain from allowing paint or epoxy to clog the
blind nuts. Apply petroleum jelly to the threads with a
toothpick. If you get some on the wood, be sure to clean it
off with rubbing alcohol before fuelproofing.
SPECIAL NOTE: Do not confuse this procedure with
“checking the C.G.” or “balancing the airplane fore and
aft.” That very important step will be covered later in
the manual.
Now that you have the basic airframe nearly completed,
this is a good time to balance the airplane laterally
(side-to-side). Here is how to do it:
❏
1. Temporarily attach the wing, engine (with muffler) and
landing gear to the fuselage.
❏
2. With the wing level, lift the model by the engine
propeller shaft and the fin (this may require two people). Do
this several times.
❏
3. If one wing always drops when you lift the model, it
means that side is heavy. Balance the airplane by gluing a
weight to the inside of the other wing tip. Note: An
airplane that has been laterally balanced will track
better in loops and other maneuvers.
Balance the Airplane Laterally
Fuelproofing
C. You must use a flat sanding block of some type when
sanding flat areas such as fuselage sides/top/bottom, tail
surfaces, etc. (more details on this subject are located in
the front of this manual). If you don’t have a bar sander
use a flat block of hard wood or something similar.
D. Most important – don’t neglect the sanding job.
While you should inspect your work frequently to make
sure you are not over-thinning the wood (more of a
concern on 1/16" wing sheeting), you should be able to
remove all the uneven glue joints in the structure (such
as the fuselage sides) with enough sanding.
E. Sanding across the grain removes more wood but
leaves sanding marks. Sanding with the grain leaves a
better finish. You may rough sand across the grain but
finish sanding with the grain.
FINISH-SANDING
Many beginners (and some experts) start out with a
sound structure and good glue joints but end up with a
model that doesn’t look its best. One area where some
fall shor t is in the sanding depar tment. It’s not
necessarily the
technique of sanding but how much
sanding that’s important. Below are some tips to help
your finished model live up to (or compliment) the
building job you have done so far:
A. You should wear a particle mask when you are going
to do lots of sanding.
B. Keep your sandpaper fresh. When it becomes worn or
clogged replace it.
EXPERT TIP EXPERT TIP EXPERT TIP
Final Sanding
FINISHING
40
REPAIRING SURFACE “DINGS”
Many surface blemishes in the balsa of a framed model
are caused by glue bumps or wood chips on your
building table. This type of dent in the balsa may be
repaired by applying a drop or two of window cleaner or
tap water to the dent, then running a hot sealing iron
over the spot to expand the wood fibers. After the
surface has dried, sand the expanded area smooth.