SIG Four-Star 120 User manual

Specifications:(cont.) Imperial Metric
Wing Loading: 22 oz./sq. ft. 67 g/sq. dm
Radio Required: 4 Channels with 5 servos
Engine Required: .90 - 1.20 2-Stroke 15 - 20 cu. cm
1.20 - 1.50 4-Stroke 20 - 26 cu. cm
Kit Number: SIGRC65ARFR (Red) or
SIGRC65ARFY (Yellow)
* Calculated at full span, including fuselage
** Flying weight can vary with use of different engines, battery packs, & equipment
RADIO EQUIPMENT:
The FOUR-STAR 120 ARF requires a typical four-channel radio
system and five servos. We recommend you use ball bearing type
servos of at least 60 oz./in. of torque for the two ailerons and for
the elevators. We suggest using a metal gear servo of at least 100
oz./in. of torque for the rudder. The throttle can be driven by a
typical standard servo.
We have used and can highly recommend the Hitec radio
systems. These are affordable and reliable radio systems that offer
all the features for this and the many other R/C aircraft in your
future. For reference, this assembly manual will show the
installation of a Hitec radio system, using the upgraded servos
mentioned earlier. In addition, you will need two 12" servo lead
extensions, one 6" standard aileron servo Y-harness and one 36"
heavy-duty servo extension for the elevator servo. Due to the size
of the model itself and the fact that it uses five servos, we suggest
using an aftermarket airborne battery pack of at least 1000 mAh
capacity.
Last, many of the following assembly steps will require the use of
the radio system for the purpose of testing movements, etc. Before
you begin assembly, place your radio system on charge to be sure
it is ready to use during assembly.
ENGINE SELECTION:
The FOUR-STAR 120 ARF offers you the ability to use a wide
range of engine types and sizes. The airplane has been designed
to produce excellent performance when using the recommended
engine sizes. Do not use engines larger than those
recommended.
The FOUR-STAR 120 ARF flies very nicely using 4-stroke engines
in the 1.20 to 1.80 cubic inch displacement range. 2-stroke
engines in the .91 to 1.20 cubic inch displacement range will also
provide plenty of power and performance. For example, either the
AVIASTAR®1.20 or 1.50 glow engines would be fine choices for
this model. Aviastar®engines are powerful, ringed engines with
oversize ball bearings. These high quality engines are both
affordable and very reliable. Whatever engine you choose, take the
time to carefully break it in according to the manufacturer’s
instructions. A good running, reliable engine is a minimum
requirement for the enjoyment of this or any other R/C model
aircraft.
Use only the propellers suggested for your particular engine. We
also suggest using the larger diameter, lower pitch propellers
listed for your engine by the manufacturer. Such props tend to
provide very good pulling power during maneuvers, without a lot of
excess speed. An 18" diameter propeller is about as big as you
can use and still have adequate ground clearance. Lower pitch
props are also of help in controlling your landings. The FOUR
R
1
FOUR-STAR 120 ARF ASSEMBLY MANUAL
INTRODUCTION:
The SIG FOUR-STAR 120 ARF combines the great classic looks
and performance of the original Four-Star kit series, in an almost
ready to fly package. The FOUR-STAR 120 ARF is easy to fly
and makes an ideal choice for your first large low wing airplane.
Intermediate and advanced flyers will also appreciate the
maneuverability and smooth handling characteristics of this very
honest flying design. All of this makes the FOUR-STAR 120 ARF
the sport model that you will want to take to the flying field every
time!
With the control throws set at the suggested low rates for the first
flights, you will be able to easily get airborne, throttle back, and
enjoy a truly nice flying, gentle R/C model. As your skills and
confidence build, the control movements can be dialed up to match
your abilities for more advanced aerobatics. The FOUR-STAR 120
ARF is a capable aerobatic model. Inside and outside loops, rolls,
inverted flight, snap maneuvers, and great spins are all well within
the Four-Star 120's flight envelope.
The FOUR-STAR 120 ARF kit has been engineered to get you into
the air as quickly as possible with a R/C model that will truly last.
The airframe has been expertly built and covered with SIG
AeroKote®. This premium covering material is both rugged and
easy to repair. The provided self-adhesive decals are high quality
Mylar®and really serve to compliment the already striking color
scheme.
This assembly manual has been specifically sequenced to get your
FOUR-STAR 120 ARF assembled and into the air quickly. We
strongly suggest that you read through this manual first, to become
familiar with the various parts and their assembly sequences. The
proper assembly and flying of this R/C model aircraft is your
responsibility. If you are new to the sport/hobby of radio control, we
urge you to seek the assistance of a qualified person to help
you assemble this model airplane. If you do not understand
a particular assembly step or sequence, do not guess - find
qualified help and use it.
Specifications: Imperial Metric
Wing Span: 81 in. 2057 mm
Wing Area*: 1205 sq. in. 77.7 dm2
Length: 65 in. 1651 mm
Flying Weight**: 11.5 - 12 lbs. 12.5 kg

STAR 120 ARF has a fairly low wing loading and may tend to float
in ground effect during landings.
A lower pitch prop has a "braking"
effect in such circumstances and will get the airplane down to the
ground nicely.
We have made it a point to paint the tips of our
props with a brightly colored paint to make the prop arc visible.
Finally, always be sure to balance your flying props carefully to
minimize vibration and possible engine bearing problems.
COVERING MATERIAL:
Your FOUR-STAR 120 ARF has been professionally covered using
SIG AeroKote®. This high quality covering material is well known
for its ease of application, light weight, and consistency of color. If
you live in a dry climate, you may notice that some wrinkles might
develop after removing the various covered parts from their plastic
bags. This is perfectly normal in low humidity climates. Your model
was built and covered in a part of the world with fairly high
humidity and therefore, the wood was carrying a fair amount of
moisture. When exposed to drier air, the wood typically loses this
moisture, dimensionally shrinking in the process. In turn, this may
cause some wrinkles. However, wrinkles are easy to remove by
simply using a hobby type heat iron.
We suggest covering the iron shoe with a thin cotton cloth, such as
an old T-shirt. This prevents scratching the film. The iron should
be set to about 280Oto 300OF. To avoid the seams from creeping
during the shrinking process, first go over all the seams, heating
them well and pressing them down with a cloth until cool. Use the
heated iron to lightly shrink the material in the open span areas -
do not press on it. Then lightly iron the material back down to the
wood. You can also use a hobby type heat gun to re-shrink the
covering but you must protect all seams and color joints to prevent
unsightly creeping. A good way to do this is to roll up a damp
paper towel and cover the seam with this while you apply the heat
gun on the adjacent areas. For reference, your FOUR STAR 120
ARF was covered with SIG AeroKote®in one of the following color
schemes.
AeroKote®#SIGSTL330 BrightYellow with AeroKote®#SIGSTL433
Yellow & Black Checks
or
AeroKote®#SIGSTL311 Bright Red with AeroKote®#SIGSTL413
Red & White Checks
REQUIRED TOOLS:
For proper assembly, we suggest you have the following tools and
materials available:
•A Selection of Glues - SIG Thin and Medium CA Glue
SIG Kwik-Set 5-Minute and
30-Minute Epoxy
•Thread Locking Compound, Such As Loctite®Non-Permanent Blue
•A Selection of Screwdrivers, Both Blade and Phillips Types
•Pliers - Needle Nose and Flat Nose
•Diagonal Wire Cutters
•Small Allen Wrench Assortment
•Hobby Knife With Sharp #11 Blades
•Scissors
•Heat Gun, Heat Iron & Trim Seal Tool for Model Coverings
•Soldering Iron, Solder & Flux -
StaBrite®Silver Solder & Flux Recommended
•Power Drill With An Assortment of Drill Bits
•A 90
O
Triangle or Square
•Masking Tape
•Paper Towels
COMPLETE KIT PARTS LIST:
The following is a complete list of all parts contained in this kit.
Before beginning assembly, we suggest that you take the time to
inventory the parts in your kit.
❑BAG #1 Horizontal stabilizer and elevator - hinged but not
glued - 4 hinges per side - 3/8" (9.5 mm) gap in
covering in center of stab. top and bottom - wire
joiner installed and glued - hard points for braces
installed but not opened - all parts built up and
sheeted over then covered
❑BAG #2 Vertical fin and rudder - built-up, sheeted structure -
4 rudder hinges in place, not glued - hard points
installed for bracing but not opened - factory covered
❑BAG #3 Left wing panel - ailerons installed with 6 hinges but
not glued, held in place with tape - aileron servo
hatch/mount taped on bottom - tube for servo lead
installed - receptacle built into main spars to receive
aluminum joiner blade - locator dowel installed
towards trailing edge - hold down tab at l.e. of root rib
- servo lead hole in top sheeting but not opened
❑BAG #4 Right wing panel - same as bag #3 except for locator
dowel socket towards trailing edge
❑BAG #5 Fiberglass wheel pants - 1 left, 1 right - painted to
match covering w/ 2 each M3 blind mounting nuts
installed in each pant
❑BAG #6 Fuselage with canopy installed with six screws - black
frame painted on canopy - cockpit floor covered in
gray - spacer block installed in tail to protect stab.
openings - servo tray installed inside - servo mounts
provided under horizontal stab. but not opened -
fiberglass tube for servo lead installed - antenna tube
installed - pull-pull cable exit guide tubes installed -
4 blind nuts for landing gear installed - two 1/4-20
blind nuts for wing hold down installed - hole for neck
of fuel tank in firewall - thrust lines marked on firewall
- firewall and cowl cheeks fuel proofed - cowl drain in
bottom of cowl not opened.
4 each M4 Blind Mounting Nuts installed in firewall
2

3
❑BAG #7 Aluminum landing gear wrapped in foam padding -
painted yellow or red drilled for axles and wheel pant
bolts - drilled for fuselage mounting bolts.
❑BAG #8 Misc. parts bags.
❑Sub bag A 2 each 4" dia. (102 mm) foam wheels
❑Sub bag B 2 each Blue foam - 3/8" x 3" x 7-3/4"
(9.5 x 76 x 196 mm)
❑Sub bag C
Sub bag 1C 1 each 3" (76 mm) dia. spinner
assembly - white cone with
black plastic back plate
Sub bag 2C 2 each PA3 x 12 mm Phillips head
sheet metal screws
❑Sub bag D 1 each Plywood bolt plate for wing
center section, 2 bolt hole
drilled but not open
2 each 1/4-20 x 2" Nylon Wing
Mounting Bolts
❑Sub bag E 1 each Fuel tank - 16.9 oz. (500 cc)
square with offset neck - fuel
line and clunk weight inside -
10 mm square x 105 mm balsa
tank retainer
(25/64" sq. x 4-1/8")
Sub bag 1E 2 each 3 mm aluminum tubes -
40 mm (1-9/16") and
60 mm (2-3/8")
1 each Rubber stopper
2 each Zip Ties
1 each 3 mm I.D. x 20 mm silicone
tube
❑Sub bag F 1 each Wing Joiner Blade -
4.7 mm x 29.72 mm x 391mm,
Hardened Aluminum
(.185" x 1-11/64" x 15-25/64")
❑Sub bag G 2 each Plastic coated pull-pull cable -
1 mm dia. x 1 m long (.039 x 39")
2 each Z-bend pull-pull cable fittings
2 each
Threaded pull-pull cable fittings
2 each Nylon RC Links with metal pins
2 each D6 x 5 mm Blue Fuel Tube
4 each Copper swage tubes
❑Sub bag H 2 each Axles - 5 mm dia.x 47 mm with
M8 lock nuts (.197 X 27/32")
4 each Wheel Collars - 5.1 mm ID
w/ setscrews
4 each
M3 x 12 mm Phillips Head Bolts
4 each
M4 x 16 mm Phillips Head Bolts
❑Sub bag I 8 each T2 x 12 mm PWA Screws
❑Sub bag J 2 each 1/4" ID Wing Bolt Washers
❑Sub bag K 3 each
M2 x 18 mm Phillips Head Bolts
3 each M2 nuts
6 each M2 washers
2 each T2 x 8 mm PWA Screws
❑Sub bag L 8 each
M2 x 18 mm Philips Head Bolts
2 each M2 nuts
❑Sub bag M 1 each
Aileron Gage - laser cut plywood
1 each Laser-cut Pushrod Guide
❑Bag #9 Wire Parts: 1 each 2.5 mm x 152 mm (.098 X 6")
rod threaded 4-40 on one
end-Elevator pushrod
2 each 2.5 mm x 128 mm (.098 X 5")
rods threaded 4-40 on one
end-Aileron pushrods
2 each D2 x 202 mm
(.071 X 7-15/16") rods with
plastic fittings at each end
2 each D2 x 254 mm
(.071 x 10") rods with plastic
fittings at each end-Stabilizer
braces
❑Bag #10 Tail Wheel Assembly, including:
3 each T3 x 12 mm PWA screws
2 each T2 x 10 mm PWA screws
2 each Tail Wheel Centering Springs
1 each “T”Bar
❑Bag #11 Motor Mount Assembly, including:
4 each
M4 x 12 mm Phillips Head Bolts
4 each M4 Flat Washers
4 each M4 Split Ring Washers
❑Bag #12 Control Horns, including:
3 each Left Control Horns
2 each Right Control Horns
3 each
#4-40 R/C Links (ailerons [2], elevators [1[)
3 each #4-40 Solder Links (ailerons [2], elevators [1])
3 each #4-40 Nuts (ailerons [2], elevators [1])
2 each 1/4 - 20 x 2”Nylon Bolts
❑Bag #13 Throttle Linkage Bag, including:
1 each .130 x 15" (3.3 x 380 mm) Inner Nyrod
1 each .060 x 18" (1.5 x 457 mm) Flex Cable
1 each 2-56 Nylon R/C Link
1 each Pushrod Connector
1 each Pushrod Connector Connector Keeper
1 each 4-40 x 1/8, Socket Head Cap Screw
❑4 each Decal Sheets
❑1 each Assembly Manual
Hardware 101:
Every modeler has heard stories about "inferior" foreign
hardware - we certainly have. While some of this might be
deserved, the fact of the matter is that much of this comes from
people who failed to use the right tools for the job. A case in
point is the common Phillips screwdriver. These things come
with bits in all shapes, sizes, and angles. If you use a Phillips
screwdriver that has too small of a bit for the screw or bolt, it will
almost always "roach" out the head of the screw or bolt under
the pressure of installing it. The same is true if the screwdriver
bit is too large. One size does not fit all! Slotted screws,
installed with under or oversize screwdrivers, can also suffer
from this same kind of abuse. From experience, we can also
tell you that magnetized screwdrivers are great for this
project. Having the right tools available for the job can make
a big difference in making the job all that much easier and
enjoyable.making the job all that much easier and enjoyable.

4
WING ASSEMBLY:
The FOUR-STAR 120 ARF wing has been designed to be a strong,
easy to assemble, two-piece unit to ease transport in today's
smaller vehicles. For more precise control authority, each wing
panel has its own aileron servo. While working on the wing panels
during the upcoming steps, we suggest that cover your workbench
with a protective blanket or foam rubber sheet. This precaution will
minimize unnecessary dings, dents, or scuffing of the covered
parts.
Aileron Servo Installation & Aileron Hinging:
For the following steps you will need:
•The left & right wing panels with their ailerons, hinges,
and servo hatch mounts
•The main aluminum wing joiner blade
•The aileron servos (at least 60 oz./in. of torque)
•Two 12" aileron servo lead extensions
•One 6" standard "Y" harness with connectors to fit your
radio system
•After-market extra strength servo output arms - this manual
shows our use of the DuBro #672 servo output arms for
Hitec servos
❑1) Start by first checking the fit of the two wing panels. Slide
the joiner blade into the receptacle in one of the panels and then
fit the opposite panel in place, sliding the two panels together at the
center section. The rear locator dowel should fit into the hole in the
opposite panel. Once satisfied, separate the two panels for now.
❑2) As received, the aileron servo hatch/mounts are taped onto
the bottom surfaces of each wing panel - remove these hatches
from the wing panels. Fit one of your aileron servos onto the hatch
mounting beams. Check to be sure that the servo arm will fit into
the provided slots. Open up the slot as required for a good
clearance fit. Repeat this process with the opposite servo and
hatch/mount. Place a 1/16" (1.5 mm) spacer shim between the
servo and the hatch and mark the beams for the four servo
mounting screw holes. Remove the servos and shims and drill
pilot holes for your servo mounting screws, using a #50 (1.8 mm)
bit.
The servo hatch/mounts
each have four mounting
holes - one in each corner.
Use a sharpened dowel
to open up these holes,
through the covering. Place
the hatch/mounts back
into their appropriate wing
panels and use a power drill with a 1/16" bit to drill pilot holes into
the wing panels for the retaining screws.
❑3) On the top center of both wing panels, just inboard of the
center wing rib, you will now need to remove the covering over the
servo lead exit holes, using a sharp #11 blade.
❑4) Install a 12" servo lead extension to both of the aileron
servos. We suggest securing these connections with a piece of
heat shrink tubing. Next, install the rubber grommets and brass
eyelets, that came with your radio system, into the servo mounting
lugs.
❑5) Using the mounting screws that came with your radio
system, mount the servo onto the hatch/mount. Using your radio
system, center the aileron servos, making sure the trims are at
neutral. Install an extra long servo arm onto each servo, making
sure it is centered in the slot and is at 90Oto the servo case. Once
satisfied, install the servo arm retaining screws into each servo.
Unplug the servos from the receiver and turn off your radio system.
Feed the servo extension leads through the tube inside the wing
and pull the connector out of the hole at the top center of the wing
panel. Use the eight T2 x 12 mm Phillips Head screws (Bag 8, Sub
Bag I) to install and secure the two aileron hatch/mounts into each
wing panel.
❑6) The ailerons are now hinged to the wing panels. Note that
the installation method for these hinges will be the same for all of
the control surfaces on this model. Press the six CA hinges into
the slots in each aileron leaving 1/2" exposed. Use two pins in the
center of each hinge to keep them centered when inserting them
into the corresponding slots in the trailing edge of the wing panel.
❑7) Carefully insert the hinges into the trailing edge of the wing
until the pins are tight against the trailing edge, setting the proper
gap between the aileron and the wing. Adjust the ailerons as

5
needed to align the tip with the wing tip, in top view. The aileron
should now be in the proper position for permanently hinging it in
place.
❑8) Flex the aileron down slightly and hold it in this position with
a piece of masking tape. Remove the pins from one hinge and
apply 4 drops of thin CA directly onto the hinge. We suggest using
a fine tipped applicator on the glue bottle to better control the flow
of glue - excessive glue can run through the gap and mar the
backside of the wing. Repeat this process on the remaining five
hinges. Remove the masking tape holding the aileron and turn the
wing panel over on your bench. Again flex the aileron and hold it
in position with a piece of tape. Apply four drops of thin CA glue to
each exposed hinge. Remove the tape, allowing the aileron to
return to the neutral position. Because it takes a little time for
the glue to fully wick its way through the hinge surface and
surrounding wood, allow 10 minutes or so before flexing the
aileron. Hinge the remaining aileron to the remaining wing panel
using the same procedures just described.
❑9) After sufficient time has passed, firmly flex the now-hinged
ailerons to free their movement. Also, pull on the aileron, at each
hinge location, to make sure that each hinge is firmly adhered in
place. Any clean-up required for CA glue drops, can be done with
SIG Debonder and a soft cloth.
Installing the Aileron Control Horns and Pushrods:
For the following steps you will need:
•1 each Left Hand Nylon Control Horn, Long with Back Plate
•1 each Right Hand Nylon Control Horn, Long with Back Plate
•2 each 4-40 x 128 mm Threaded Rod
•2 each 4-40 Threaded R/C Links
•2 each 4-40 Metal Solder links
•2 each 4-40 Hex Nuts
•4 each M2 x 18 mm Phillips head bolts
•Soldering Iron, Flux & Solder
•Laser-Cut Aileron Gage
❑1) As shown, use a square to locate the mounting position of
the control horn on the aileron. A perpendicular line from the
aileron hinge line intersects with the servo arm. Mark the leading
edge of the aileron at this point and then draw a line from this point
1" (25.4 mm) back, toward the trailing edge of the aileron
❑2) From Bag 12, locate one left and one right control horn. The
base of the control horn should be positioned toward the inboard
(fuselage) end of the wing. Place the control horn on the bottom
of the aileron with the upright arm of the horn next to the line, with
the linkage holes in the upright arm directly over the hinge line.
Mark the position of the horn mounting holes in the base plate onto
the aileron.
❑3) Use a power drill and a 5/64" drill bit to drill holes through
the aileron at the control horn mounting locations just made. Use
two of the M2 x 18 mm sheet metal screws to attach the control
horns to each aileron. The screws seat into the nylon retaining
plate, included with each control horn. After the screws are
securely in place, the excess screw tips can be trimmed using a
pair of side cutters. The remaining stubs can be filed or ground
flush to the retaining plate.

adjust the aileron pushrod R/C links as required to achieve uniform
contact with the bottom surface of the aileron gage.
Now, test the movement of the ailerons with the transmitter to
make sure the are moving in the correct directions - right stick
movement should cause the right aileron to move up. Once
satisfied, unplug the servos, turn off the radio system and set the
wing panels aside for final assembly later.
FUSELAGE ASSEMBLY:
Fuselage Preparation:
To avoid damage, we suggest that you remove the canopy from the
fuselage and set it and its mounting screws aside for now. Next,
the fuselage has several openings that have been covered over
and now need to be opened up. These are;
a) The oil drain hole in the bottom front of the engine
compartment
b) The two pull-pull rudder cable exit holes on each side of the
fuselage beneath the horizontal stabilizer at the tail
c) The antenna tube exit hole on the bottom rear of the
fuselage, located about 6-1/2" forward of the tailpost.
Using a hobby knife with a sharp #11 blade works well in making
these openings. In the case of the oil drain opening, we suggest
sealing the exposed wood with a few drops of thin CA glue to
prevent oil from penetrating the wood.
ENGINE INSTALLATION:
For the following steps you will need these parts:
•Your Engine
•Engine Mounting Hardware (not included)
•2 each Glass-Filled Engine Mounts
•Fuel Tank Assembly
•Fuel Tubing (not included)
•3" Dia. Spinner Assembly
•Your Propeller
•4 each M4 x 25 mm Phillips Head Bolts
•4 each M4 Flat Metal Washers
•4 each M4 Split Ring Washers
•1 each 1/8" dia. x 15" Inner Nyrod Tubing
•1 each 1/16" dia. x 18" Flex Cable
•1 each 2-56 Nylon R/C link
•1 each 2-56 Threaded Coupler
•1 each Pushrod Connector w/Setscrew
•1 each Pushrod Connector Keeper
•1 each Plywood Pushrod Guide
❑4) Thread one of the 4-40 hex nuts all the way onto one of the
4-40 x 128 mm threaded aileron pushrods. Thread a 4-40 R/C link
onto the pushrod, centering its threaded barrel, leaving an equal
amount of threads on each side. Clean the opposite end of the
pushrod with fine sandpaper and then slip a 4-40 solder link in
place.
❑5) Plug the aileron servo connector into the receiver and turn
the radio system on. Tape the aileron in the approximate neutral
position. Install the solder link into the outermost hole in the servo
output arm and install the threaded R/C link into the outermost
hole in the aileron control horn.
The solder link is now soldered to the aileron pushrod. We like and
recommend the use of Stay-Brite®silver solder and flux for such
connections. Apply a drop of flux to the solder link/pushrod and
apply just enough solder to allow it to "flow". When the joint has
cooled, remove the pushrod and thoroughly clean the solder joint
and lightly oil to prevent rust. Remove the tape holding the aileron
in position. Repeat this process on the opposite wing panel and
aileron pushrod.
❑6) The ailerons are now set to their neutral positions using
the provided laser-cut plywood Aileron Gage, found in Bag 8, Sub
Bag M. As shown, this gage is held against the bottom surface of
each wing panel, centered on the hinge line. Temporarily join the
wing panels and plug the aileron servo leads into the receiver
with the transmitter aileron trim at neutral. Using the aileron gage,
6
3/8”
IMPORTANT NOTE: The motor mounts provided with the Four
Star 120 ARF kit are of excellent quality and designed to work
well with both 2-stroke and 4-stroke engines up to 1.50
displacement. DO NOT use any engine larger than these with
the supplied motor mounts. DO NOT mount your engine on
these motor mounts by drilling and tapping them for bolts or
screws! These mounts should be drilled for clearance of the
engine mounting bolts and the engine itself should be secured
to the mount arms with bolts, washers, and lock nuts. Tapping
threads into these motor mount arms may weaken them,
potentially causing them to fail.

mount arms and mark the firewall with the appropriate position for
the throttle pushrod.
❑8) Remove the engine from the mounts and use a #29
(3.4 mm) bit, drill a hole through the firewall at the marked location.
You will also need to drill a new hole through the fuselage former
at the leading edge of the wing and the former in the approximate
center of the fuel tank compartment, on the opposite side of the
factory drilled hole. The throttle cable housing tube is now glued
into position in the holes in the firewall and two fuselage formers.
Position the engine compartment end of this tube flush with the
forward face of the firewall.
❑9) In the case of a 2-stroke engine installation, the hole for the
throttle cable tube needs to be drilled through the firewall. This
hole is located between the motor mount and the fuselage side, on
the throttle arm side of the engine. Use a #29 (3.4 mm) bit to drill
this hole. Now feed the throttle housing tube through the firewall
and through the holes in the two fuselage formers - leave about 1"
of tubing in front of the firewall. With the tubing now positioned, use
thick or medium CA glue to secure it permanently in place to the
firewall and fuselage formers.
Fuel Tank Assembly & Installation:
❑1) The 500 cc (16.9 oz.) fuel thank supplied provided with this
kit is now assembled. We suggest using a simple two-line fuel
7
❑1) Note that four M4 blind mounting nuts have been factory
installed behind the firewall. The spacing of these nuts, in
conjunction with oblong motor mount holes provides crankcase
mounting widths from 1-11/16" to 2-1/4" (42.8 to 57 mm). Such
spacing adjustment covers most recommended engine sizes for
this model. If the crankcase width of your engine is outside of
these dimensions, or you are using an alternate engine mounting
system, you will have to modify this bolt pattern accordingly.
NOTE: The engine and tank compartment were fuel-proofed
during the production of this model. However, if desired, these
areas can be additionally fuel-proofed. To do this, use a brush to
apply a coat of surfacing resin or clear polyurethane varnish to
these areas, as well as, the inside of the wing saddle in the radio
compartment. Be sure to brush the resin up to the covering edges.
❑2) Bolt the engine mounts in place on the front of the firewall
using the M4 x 25 mm Phillips Head Bolts. Put a M4 flat washer
and a M4 split ring washer on each of four M4 x 25 mm bolts, apply
a little thread locking compound to the threads and install the two
motor mount arms to the firewall - do not tighten in place yet.
❑3) As previously mentioned, the motor mount arms can be
positioned to adjust to the width of the engine's crankcase. Place
your engine on the motor mounts, moving the arms as needed to
accept the engine. Also, center the spinner backplate to the
fuselage in the top view. When everything appears correct, tighten
the motor mount bolts to the firewall.
❑4) Use a punch or a pencil to mark the engine's mounting
screw locations directly onto the motor mount arms. To make
these hole position marks easier to see, a neat trick is to use white
or silver plastic model paint or paint marker to paint the tops of the
motor mount arms.
❑5) Remove the engine and drill four clearance holes for the
bolts that will hold the engine to the mounts. Do not tap these
holes as doing so may weaken the mounts.
4-STROKE INSTALLATION DETAILS:
NOTE: If you are installing a 2-stroke engine, move ahead to
Step 9 in this section.
❑6) When installing a 4-stroke engine, note that the throttle
cable housing tube must be relocated. Start by pulling the throttle
housing tube out of the firewall and fuselage.
❑7) Install a pushrod connector into the outermost hole of the
throttle arm on the carburetor. Place the engine on the motor

❑5) To ease the
removal of the tank at a
later time, make a pull
tab at the rear of the
tank by wrapping a
loop of reinforced
strapping tape around
the front of the tank
allowing a 1" (25.4 mm)
tab to extend at the
rear.
❑6) To install the tank in the fuselage, first apply a generous
bead of silicone sealer around the neck of the tank. Install the tank
into the fuselage tank compartment. Make sure the offset neck of
the tank lines up properly with the round hole in the firewall. Firmly
press the tank body to the firewall and allow the silicone sealer to
set before proceeding.
❑7) Glue the provided 10 mm sq. x 103 mm balsa tank retainer
strip into position against the fuselage sides and firmly against the
rear of the tank. Trim as required to obtain a snug fit against the
fuselage sides. We suggest using a drop or two of thin CA glue to
both sides of the retainer strip, where it contacts the *fuselage.
This secures the strip nicely, but still allows it to be easily removed
should the need ever arise.
Final Engine & Throttle Linkage Installation:
❑1) Install the engine to the motor mount arms, using
appropriate sized socket head bolts, lock washers, flat washers,
and lock nuts (not provided).
❑2) Now is the time to address any modifications or clearance
holes that may be needed for your particular engine installation in
the nose of the fuselage. These may include muffler clearance,
system in this airplane.One fuel line is connected to the fuel
pick-up (clunk) line and to the engine's carburetor. This same can
then be used to fill the tank. The second line is the overflow line,
used when filling the tank. After the tank is full, this fuel line is then
connected to the pressure tap on the engine muffler, providing
muffler pressure to the tank when it is running.
❑2) Note that the rubber stopper has three holes molded into
the flanged side but not opened up on the interior side. Two of
these holes will be used for the fuel lines and need to be opened.
Insert the two aluminum tubes through these holes until about 1/2"
(12.7 mm) protrudes from the flat end of the stopper.
❑3) Gently bend the longer overflow tube upwards towards the
top of the tank on the inside. Cut the end of the short piece of
silicone tube at a 45Oangle. Slip this tube over the vent tube and
adjust until it just makes contact to the top of the tank. Make sure
the opening in the end of the tube does not become blocked by the
top of the tank. Adjust the length of the longer silicon tube to the
clunk weight, allowing the weight to move freely inside the tank and
so it is about 3/8" away from the back of the tank when at rest.
Install this tube on the other aluminum tube inside the tank.
❑4) Install the stopper assembly
into the neck of the tank and
secure it with a zip tie over the
flange on the tank neck.
In front view, the neck should be
offset slightly to the right and the
overflow tube should go to the top
of the tank.
8
MODELER’S NOTE: Whenever we assemble a new tank or
refit an older tank with new fittings, we make it a practice to
pressure-check the finished tank before installing it in the
model. This is simple to do. Simply install a couple of lengths
of fuel tubing onto the tank overflow and fuel line tubes. Then
submerge the tank into a pot of water. Blow into one or both of
the fuel lines and look for any "bubbles" coming from the tank
body. Make any fixes necessary and then install your fuel tank
with confidence.

❑8) If your engine installation is a 4-stroke type, all of the
previous instructions apply with the exception of the throttle cable.
From inside the fuselage, insert the unprepared end of the throttle
cable into the housing tube, feeding it all the way up to the engine
compartment and through the hole in the pushrod connector on the
carburetor arm (previously installed).
Connect the nylon R/C link into the outermost hole in the servo
output arm. Glue the throttle tubing support to the side of the
fuselage.
Use your radio system to adjust the throttle servo movement to
achieve true "low" and "high" throttle settings, with no binding.
Once satisfied with this initial set-up, tighten the setscrew in the
pushrod connector. Trim any excess throttle cable, as needed and
reinstall and tighten the servo output arm retaining screw.
❑9) With the engine installation now complete, the provided
3" dia. spinner assembly can be installed to the engine. First,
measure the outside diameter of the propeller shaft on your
engine. The center hole in the spinner backplate must be drilled
out to clear the prop shaft of your particular engine. This is best
done using a drill press.
Slip the spinner backplate onto the prop shaft of the engine,
needle valve holes, etc. These can be easily made using a
Dremel®Tool and sanding bits. Once these openings or clearances
have been made, any exposed wood should be fuel-proofed. This
can be done using thin CA glue, clear dope, or surfacing resin.
Finally, cut and install two lengths of fuel tubing, connecting the
fuel tank pick-up line with the carburetor and the tank overflow line
with the pressure tap in the engine muffler.
❑3) Prepare the throttle servo for installation by first installing
the rubber grommets and brass eyelets into the mounting lugs.
Place the throttle servo into the appropriate opening in the
fuselage servo tray and mark the four mounting screw locations
onto the servo tray. Remove the servo and drill four pilot holes for
the servo mounting screws. Place the servo back into the servo
tray and use the screws provided with your radio system to secure
it in place. Connect the throttle servo to the receiver and use
the radio to make sure the throttle arm is moving in the proper
direction to obtain high and low throttle settings at the carburetor.
Remove and reposition the servo arm as needed to achieve equal
fore and aft movement. Slip the laser-cut plywood pushrod
housing tube guide over the throttle tube.
❑4) The throttle cable is now prepared. Solder the 2-56
threaded coupler onto one end of the 1/16" dia.x 18" throttle cable.
Thread the 2-56 nylon R/C link onto the threaded coupler until
1/16" of threads are showing inside of the link.
Carefully note that if your engine is a 2-stroke type, the end of the
throttle cable with the soldered coupler and nylon R/C link will be
located at the carburetor throttle arm. Conversely, if your engine is
a 4-stroke type, the nylon R/C link will be located at the throttle
servo.
❑5) In the case of a 2-stroke engine installation, install the
pushrod connector with setscrew in the outermost hole of the
servo arm. Now insert the unprepared end of the throttle cable into
the nylon tube at the firewall and feed it back into the radio
compartment and into and through the pushrod connector on the
servo arm.
❑6) Using thick or medium CA glue, position and glue the
plywood pushrod tubing support directly to the side of the fuselage,
about 4" ahead of the servo.
❑7) With the carburetor fully closed and the servo rotated to the
idle position, tighten the setscrew in the pushrod connector,
locking the cable in place. Using your radio system, adjust the
servo end points to achieve full throttle servo travel with no binding
at either end of the throttle cable. Once satisfied with this initial
set-up, reinstall and tighten the servo output arm retaining screw.
9

❑3) We suggest bolting the wing to the fuselage before gluing
the stabilizer in place. Doing this provides good visual reference in
squaring and leveling the stabilizer to the fuselage during its
installation. Slip the stabilizer in place, being careful to align the
centerline on the stabilizer with the centerline of the fuselage. Also
make sure the trailing edge of the stabilizer is parallel to the
trailing edge of the wing.
❑4) With the fuselage on a flat surface, stand back and view the
model from the rear. The stabilizer should be absolutely aligned
with the wings, without leaning to one side or the other. If it is
leaning, lightly sand the high side of the mounting surface in the
fuselage until the stabilizer is level with the wing.
❑5) Again, using a felt tip pen, mark the position of the fuselage
sides onto the bottom of the stabilizer. Next, mark the location of
the outer top edges of the stabilizer fairings onto the top of the
stabilizer. Remove the stabilizer from the model.
❑6) Use a hobby knife and a #11 blade to carefully remove the
covering from the stabilizer to expose the wood structure for gluing
purposes. Trim the covering about 1/32" or so inside the marker
lines. It is very important that the wood beneath the covering is not
scored or cut during this process. In the fuselage stabilizer slots,
trim the covering away from each slot surface, leaving 1/32" or so
of covering.
followed by the propeller. This assembly is now firmly tightened in
place using the engine thrust washer and prop nut. The spinner
cone is then placed over the propeller and its rear face fitted into
the groove in the backplate. The spinner cone is then secured to
the backplate using the two provided PA3 x 12 mm Phillips head
sheet metal screws.
Note that some propeller makes or types may be too large to fit into
the molded recesses in the spinner cone. In this case, some
trimming of the cone recesses may be required. Use a sharp #11
blade to "shave" the prop openings until the prop fits properly. Be
sure to only remove as much plastic as needed to fit over the
propeller and that the openings are equally opened on each side
of the spinner cone.
TAIL SURFACE INSTALLATION:
For the following steps you will need:
•1 each Horizontal Stabilizer & Elevator Set - hinged but not glued
•1 each Vertical Fin & Rudder Set - hinged but not glued
•1 each Nylon Control Horn - Left
•1 each Nylon Control Horn - Right
•2 each M2 x 15 mm Phillips Head Bolts
•2 each M2 Nuts
❑1) At the top rear of the fuselage, in the horizontal stabilizer
slots, you will see a small wood block occupying the space where
the stabilizer will fit. This block is only in place to protect the top
stabilizer fairings. Remove this spacer by slipping it straight back
and out of the stabilizer slots. Exercise care when handling
the fuselage, making sure that the two stab fairings do not get
damaged.
❑2) As shown, use a felt tip pen or marker and a small square
to clearly mark the centerline of the stabilizer onto its top surface.
10

slips into the rear of the fuselage. Press the fin firmly into place
and use a clean paper towel and denatured alcohol to clean up
and remove any excess or oozing glue.
View the model from the rear, making sure the vertical fin is
absolutely 90Oupright to the stabilizer. If necessary, use a length
of masking tape to pull and hold the fin into proper alignment.
Allow the epoxy to fully cure.
❑11) The rudder is now hinged in place to the trailing edge of the
vertical fin and tailpost, using the four provided CA hinges. The
hinging process is the same for the rudder as it was for the
elevators and ailerons. As before, allow about 10 minutes for the
thin CA glue to fully wick across the hinge surfaces and into the
surrounding wood. After sufficient time has passed, briskly flex the
rudder left and right to free its movement.
❑12) The two rudder pull-pull control horns are now positioned
and installed to the rudder. Note that these two control horns will
be installed to the rudder in mirror image relationship. From the
bottom leading edge of the rudder, measure up and make a mark
at 1-1/8" (28.5 mm). This mark represents the top of the control
horn, with its mount base facing downward. Hold the control horn
in place to the rudder, with its vertical linkage holes aligned with
the leading edge of the rudder. Use a marker pen to transfer the
two control horn mounting hole locations to the surface of the
rudder. Use a power drill and a 5/64" bit to drill two perpendicular
holes completely through the rudder at the two marks just made.
The left and right rudder control horns are now mounted to the
rudder, using the provided M2 x 15 mm bolts and M2 nuts. Tighten
the nuts firmly and place a single drop of thin CA glue on the bolt
ends at the nuts.
PULL-PULL RUDDER SYSTEM:
The following parts will be required for these steps:
•2 each Plastic Coated Steel Pull-Pull Cable - 1 meter long
•4 each 3 mm dia. x 8 mm Brass Swage Tubes
❑7) The stabilizer is now glued in place into the slots at the rear
of the fuselage. For this step, we suggest using 15-minute epoxy
to allow sufficient time to position the stabilizer accurately and to
make any final adjustments that may be needed. In top view, the
stabilizer must be aligned squarely to the fuselage and the wings.
Any excess epoxy can be easily removed with a clean paper towel
and denatured alcohol. With the stabilizer in its final position, allow
the epoxy to cure completely before continuing.
❑8) With the stabilizer now installed, the elevators are hinged
in place to the trailing edge. To do this, use the exact same
procedures and methods described earlier during the hinging of
the ailerons. Remember, allow 10 minutes or so for the CA glue to
fully wick its way over the hinge surfaces and into the wood. After
sufficient time has passed, briskly flex the elevators to free up their
movement.
❑9) Fit the vertical fin and tailpost in place between the two
stabilizer fairings and into the slot at the rear of the fuselage. With
the fin firmly in place, again use a felt tip pen to mark the position
of the fin base onto the top of the stabilizer. Also mark the location
of the two stabilizer fairings onto both sides of the fin. Remove the
fin from the model.
Using a #11 blade, carefully remove the covering from the top of
the stabilizer, between the marks just made. Likewise, carefully cut
and remove the covering from both sides of the fin, exposing the
wood for gluing purposes between the two fairings. As mentioned,
be careful to not cut or score the wood beneath the covering.
❑10) The vertical fin can now be glued in place at the rear of
the fuselage, again using 15-minute epoxy to allow reasonable
working time. Apply glue to the exposed wood on both inside
surfaces of the fairings and to the bottom of the fin where it
contacts the stabilizer. Also apply glue to the fin tailpost, where it
11
XX

mounting screws that came with your radio system. Reinstall the
servo into the tray and secure it in place with the mounting screws.
❑2) Note that the pull-pull cables will be prepared with two
different types of connections at each of their ends. At the rudder
horns, the cable connections consist of a threaded stud with a hole
at one end for the cable. At the servo output arm ends of the
cables, the connections consist of a metal wire with a Z-bend and
a hole at the other end for the cable. The rudder ends of both
cables are prepared first.
Slide one of the copper swage tubes onto one end of one of
cables, holding it with your fingers. Now thread the cable end
through the small hole in the end of the threaded stud cable fitting,
leaving 4" to 5" of the cable extending past the hole. Loop the short
end of the cable back through the swage tube, then loop it around
again and through the swage tube for the third time. Firmly pull out
all of the slack that you can in the cable. Use needle nose pliers
or a crimping tool to now firmly crimp the copper tube at its center.
Use diagonal cutters to trim the excess cable away from the swage
tube. Repeat this procedure on the remaining cable end.
12
•2 each Z-Bend Cable End Fittings
•2 each Threaded Cable End Fittings
•2 each R/C Links - Nylon with Metal Pins
•1 each Left Nylon Control Horn
•1 each Right Nylon Control Horn
•1 each Heavy-duty rudder servo output arm
(DuBro #672 arms shown)
❑1) Prepare your rudder servo for installation into the fuselage
by first installing the rubber grommets and brass eyelets into its
mounting lugs. Place the servo into the center opening in the
fuselage servo tray, with its head facing forward. Use a pencil or
marker pen to mark the mounting hole locations onto the servo tray
and remove the servo. Drill four small diameter pilot holes for the
MODELER’S NOTE: In the next few steps, you will assemble
and install the rudder pull-pull system. When setting up a
pull-pull system for any flight surface, such as the rudder, it is
important to maintain the best possible geometry between the
two cable connections on each side of the output arm and the
cable connections at the two opposing rudder control horns.
The goal is to try and make the distance between these two
connections as similar as possible. In the case of the Four-Star
120 ARF, we used a Dubro #672 "Super Strength Long Servo
Arm" set for our rudder servo. The distance between the
outermost attach points in the DuBro servo arm measures 2".
Therefore, at the rudder horns, it is necessary to connect the
left and right rudder cables as close to 2" apart as possible.
Also note that in our pull-pull rudder installation, the two cables
cross each other inside the fuselage.
Note - DuBro makes these aftermarket servo output arms for
virtually any servo brand and type.

❑6) With the fuselage upside down on your bench, choose one
of the rudder cables and slide a copper swage tube onto its end
and hold it with your fingers. Pass the end of the cable through the
hole in the end of one of the Z-bend connectors and then pass the
cable end back through the swage tube. Connect the Z-bend end
of the coupler to the side of the servo arm that is opposite to its
connection at the rudder horn (remember, the cables cross each
other in the fuselage). Repeat this same procedure for the second
pull-pull cable. Take up the slack in the cables and slide the swage
tubes up close to the rigging couplers. The radio system should
still be on, holding the servo in neutral. Both cables should be taut
- not tight. Loop the cable end back around and through the swage
tube and pull it tight. Firmly crimp the swage tube at its center,
locking the cable. Repeat this process with the remaining cable
and swage tube. Use diagonal cutters to remove the excess cable
at the swage tubes.
❑7) With the radio system still on and the rudder still being held
in the neutral position, adjust the threaded R/C links until they both
feel uniformly taut - not tight. Remove the neutral restraint holding
the rudder and test the movement and centering of the rudder.
Make any adjustments necessary and turn off the radio system.
ELEVATOR SERVO INSTALLATION:
The following parts will be required for these steps:
•1 each 4-40 x 152 mm Threaded Pushrod
•1 each 4-40 Threaded Metal R/C Link
•1 each 4-40 Metal Solder R/C Link
•2 each 4-40 Hex Nut
•1 each Long Control Horn and Backing Plate
•2 each M2 x 18 mm Phillips Head Bolts
•1 each Elevator Servo (not supplied)
•1 each Heavy Duty Long Servo Arm (not supplied)
•1 each Servo Extension Cord - 36" Heavy Duty (not supplied)
•Soldering Iron, Flux, & Solder
❑3) Thread the two white nylon R/C links onto these fittings until
about 1/16" of threads protrude through the center of the link.
❑4) Feed the unprepared ends of the cables into the pull-pull
exits built into each side of the fuselage at the rear, about 1-1/2"
below the leading edge of the stabilizer. Feed the cable ends
through the fuselage to the rudder servo location. Take up all the
slack until you can connect the R/C links to the outermost holes in
the rudder control horns.
❑5) Remove the standard output arm from your rudder servo
and install a heavy-duty
2-arm output arm, such as
the DuBro unit described
earlier. Connect the rudder
servo to the receiver and turn
the radio system on. Center
the rudder trim and then
reposition the output arm on
the servo to position the two
arms at 90Oto the servo
body, as shown. Once
satisfied with the position of
the output arm, reinstall the
retaining screw to hold it in
place.
To hold the rudder in the neutral position with the vertical fin,
temporarily tape or clamp the rudder in neutral alignment.
13
MODELER’S TIP: Because the pull-pull cables were coiled
and packaged at the factory, they have a tendency to curl inside
the fuselage, as they are being fed into the exit holes. If
necessary, make a simple pulling hook from a coat hanger to
reach down inside of the fuselage, snagging the cable loops
and pulling them out into the servo compartment.

❑1) First, prepare the elevator servo for mounting by installing
its rubber grommets and brass eyelets. Next, plug the 36" servo
lead extension into the servo lead. We always suggest placing
heat shrink tubing of these connections to prevent them from
coming apart inside the fuselage.
Locate the elevator servo opening on the left fuselage side
immediately beneath the stabilizer at the leading edge. Use a
#11 blade to remove the covering over the elevator servo
opening/mount. Feed the free end of the servo extension through
the elevator servo opening and start it into the fiberglass guide
tube inside the fuselage. Holding the fuselage vertically, nose
down, feed the extension all the way down the tube until it comes
out in the radio compartment. Once servo lead and extension is
completely inside, fit the elevator servo into the opening with its
head forward, toward the nose. Hold the servo in place and drill
four small diameter pilot holes for the mounting screws. Secure the
servo in place using the screws that came with your radio system.
❑2) The elevator control horn is now installed. On the bottom of
the stabilizer, at the elevator hinge line, measure out 1" from the
left fuselage side and mark this location onto the elevator with a
marker pen. Place a small square on the elevator hinge line and
draw a 1" line on the elevator at 90Oto the hinge line. Place a ruler
on this line and use a marker pen to mark a point at 3/8" back from
the hinge line and another at 5/16" back from the hinge line. These
two marks are the locations for the two elevator control horn
mounting bolts. Drill holes through these two locations, using a
power drill and a 5/64" bit. Mount the elevator control horn to the
bottom of the elevator using two M2 x 18 mm Phillips Head bolts
threaded into the nylon backing base on the top of the elevator.
❑3) Plug the elevator servo into the receiver and turn the radio
on. Make sure the transmitter elevator trim is in neutral. Next,
make sure the elevator servo is moving in the correct direction
for up and down elevator movement. If necessary, reposition the
14
output arm on the servo, making sure it is at or near 90Oto
the servo body, pointing straight down. Reinstall the output arm
retaining screw into the servo.
❑4) Thread the 4-40 hex nut all the way onto the threaded end
of the elevator pushrod. Thread the metal 4-40 R/C link onto the
pushrod, centering it on the remaining pushrod threads. Hold it in
this position by hand-tightening the nut up against its back side.
Lightly sand the opposite end of the pushrod with sandpaper.
Install the metal R/C link into the outermost hole in the elevator
control horn. Slip the 4-40 solder link onto the sanded end of the
pushrod and install it into the outermost hole of the servo output
arm. As you did with the rudder, secure the elevator in neutral to
the stabilizer with tape or a clamp. Apply a little StaBrite®silver
solder flux to the pushrod/solder link joint and use solder to secure
the solder link in place to the pushrod end.
❑5) Remove the tape and/or clamps holding the elevator in
neutral. Test the action of the elevators using the radio system.
TAIL BRACE INSTALLATION:
The following parts will be required for these steps:
•2 each 1.8 mm x 202 mm Threaded rods with plastic fittings
at each end
•2 each 1.8 mm x 254 mm Threaded rods with plastic fittings
at each end
•3 each M2 x 18 mm Phillips head bolts
•3 each M2 Nut
•6 each M2 Flat washers
•2 each T2 x 12 mm Phillips head sheet metal screws
❑1) Both the stabilizer and the vertical fin have pre-drilled holes
with hard points for mounting the tail brace assemblies. These
holes now need to be found and opened. On the stabilizer, these
holes are located about 8-9/16" out from the vertical fin, about
1/4" ahead of the hinge line. On the vertical fin these holes are

6-25/32" up from the horizontal stabilizer and again 1/4" forward of
the hinge line.
❑2) At the bottom rear of the fuselage, on each side, one 1/16"
dia. pilot hole needs to be drilled for the T2 x 12 mm bottom brace
attachment screw. These holes are located 1-1/4" forward of the
rudder hinge line and 1/4" up from the bottom of the fuselage.
❑3) The plastic end fittings are much easier to work with if you
pre-bend their ends to the approximate mounting angles, where
they meet their mounting surfaces. Lightly warming them with
a heat gun and then bending them with round nose pliers
accomplishes this nicely.
❑4) Working first with the two shorter bottom braces, we
suggest first pre-threading the plastic fittings onto each end of the
wire. Then thread the fittings in or out to adjust the final hole-to-
hole length of the finished brace. Mount the two bottom braces to
the fuselage sides using the two T2 x 12 mm Phillips head sheet
metal screws, as shown in step 2.
❑5) The two longer top braces are made next. Pre-thread the
fittings in place to each end of the wire braces. Thread the fittings
in or out to adjust the final hole-to-hole length of the finished brace.
❑6) Place an M2 washer onto one of the M2 X 18 mm bolts.
Insert the bolt through one of the top brace fitting ends and then
through the hole in the top of the horizontal stabilizer. On the
bottom of the stabilizer, slip the free end of the bottom brace onto
this bolt. Add another M2 washer and a small amount of thread
locking compound. Thread an M2 nut all the way in place onto the
bolt end, clamping the top and bottom fittings firmly in place to the
top and bottom of the stabilizer. Repeat this same procedure on
the opposite stabilizer side.
❑7) Finally, the same bolting procedure is used to mate the two
remaining brace fittings to the hole in the vertical fin. Make sure
15
that the surfaces are all square with each other. If not, adjust the
length of the braces to correct. The completed assembly should
look like this.
INSTALLING THE TAILWHEEL:
For the following steps you will need the following kit parts:
•Tail wheel assembly, Bag 10
❑1) With the fuselage upside down on your work surface, place
the metal rudder "T"- horn on the bottom surface of the rudder with
the "T" oriented toward the front of the model. Center the T-horn
on the rudder and line its leading edge up with the rudder as
shown. Mark the two mounting hole locations for the T-horn onto
the rudder. Drill pilot holes for the two T2 x 10 mm PWA mounting
screws. Mount the T-horn in place to the bottom of the rudder.
❑2) Place the main tail wheel leaf spring onto the fuselage at
the very rear. Make sure it is lined up with the fuselage centerline
and that it is as far back as shown in the photos. Mark and then
drill the three 3/32" (1.75 mm) pilot holes into the fuselage bottom,
along the centerline.
Place the shorter secondary leaf spring under the primary leaf
spring, lining up the mounting holes. Use the three provided
T3 x 12 mm PWA screws to secure the leaf springs firmly in place
to the fuselage.
❑3) Install the two steering centering springs to the arms of the
metal T-horn on the rudder. Needle nose pliers work best for
making the loops in each end of the spring wires. It’s important
that both springs be bent identically, resulting in the same overall
length, thereby centering the tail wheel with the rudder in neutral.
Also, the two centering springs should be under some small
tension when they are installed. This keeps them "loaded" under
all steering loads. Do not over stretch these two springs. Just a

16
little tension is all that’s needed.
MAIN LANDING GEAR & WHEEL PANT ASSEMBLY:
For the following steps you will need the following kit parts:
•1 each Formed Aluminum Main Landing Gear
•2 each Fiberglass Wheel Pants
•2 each 5 mm x 47 mm Axle Shaft with M8 Threaded End
•2 each M8 lock nut
•4 each PM4 x 16 mm Phillips Head Bolts
•4 each M3 x 12 mm Phillips Head Bolts
•4 each 5.1 mm I.D. Wheel Collars with Set Screws
•Thread Locking Compound, such as Loctite®Non-Permanent
Blue
❑1) Install the two main wheel axles into the two large holes at
the bottom of each landing gear leg. Secure the axles in place to
the landing gear legs with the two M8 lock nuts. Tighten these nuts
firmly.
❑2) Slip a 5.1 mm wheel collar onto each axle, followed by the
main wheels. Slip the remaining wheel collars in place onto each
axle. Locate the outer wheel collar close to outer end of the axle,
with its setscrew facing straight down. Snug the setscrew lightly in
this position to the axle. Slide the wheel out to the outside wheel
collar, followed by the inside wheel collar. With the setscrew facing
straight down, snug the setscrew in the inner wheel collar lightly
against the axle, leaving sufficient "play" to allow the main wheel to
roll freely.
❑3) In this step, the proper relationship between the two main
wheels and their wheel collars will be established with the
fiberglass wheel pants in place.
Place the appropriate left and right wheel pants over the main
wheels, down to the wheel axles and against the landing gear leg.
Temporarily mount the wheel pants to the landing gear legs, using
the four M3 x 12 mm bolts. Just lightly tighten these bolts to secure
the pants.
Looking down into each wheel pant opening, observe the position
of the wheels within the wheel pants. If required, reposition the two
wheel collars and the wheel to center them within the pant
opening. Once both wheels are centered and roll freely, firmly
tighten the wheel collar setscrews to secure the wheel in place.
The four M3 x 12 mm wheel pant mounting bolts can now be
tightened in place.
❑4) With the landing gear/wheel pant assembly now complete,
it is mounted to the fuselage using the four provided PM4 x 16 mm
mounting bolts. As always, we suggest using thread-locking
compound on these bolts.
RECEIVER, BATTERY PACK, & SWITCH INSTALLATION:
All flight control servos and the throttle servo have now been
installed and tested. The remaining tasks are the installation of the
receiver, battery pack and switch. Of all these components, the
heaviest is, of course, the battery pack. The battery pack can be
positioned in the fuselage in any location required to achieve the
proper Center of Gravity (C.G.). Note that the model will be
balanced for the correct CG location a bit later in this manual.
Receiver: We wrapped our receiver in foam sheet with rubber
bands. We then wedged it under the servo tray. The foam wrapped
MODELER’S TIP: When installing wheel collars, we always
suggest the following precautions. First, use a file or a Dremel®
Tool and a carbide cut-off disk to file or grind a small "flat" into
the axle, where the wheel collar setscrew will be tightened.
Second, remove the setscrews from each wheel collar and
apply a little thread-locking compound to their threads. These
two simple steps almost always prevent wheel collars coming
loose.

17
placement purposes. We suggest the following procedure to apply
these decals.
Carefully and completely cut out the decal. Remove the decal itself
from the sheet using tweezers. Use a product such as SIG Pure
Magic Model Airplane Cleaner or Windex®to spray the general
area of the model that will receive the decal. Also spray the
adhesive side of the decal as well. Lightly position the decal in
place on the model. The liquid cleaner allows the decal to slide
easily into the desired position, as long as you don’t press down on
it. Once the decal is in position, hold it lightly in place with your
fingertips and use a paper towel to gently dab the excess liquid
away. Use a small squeegee to now set the decal in place,
removing all excess liquid and any trapped air bubbles from
beneath the decal. The SIG 4" Epoxy Spreader - #SIGSH678 - is
perfect for this job. Remove any excess fluid with a dry paper towel
and allow the decals to set overnight. They will be solidly adhered
to the model without any air bubbles.
CONTROL SURFACE TRAVEL:
The following surface control movements for the Four-Star 120
ARF model are based on our experience with our prototype
models. These movements have provided us with a very smooth
flying model. We urge you to use these initial low rate surface
movements for your test flight set-up and then change them
incrementally to best suit your own particular flying style. Note that
the following control movement measurements are made at the
widest point on the control surfaces.
SURFACE LOW RATE TRAVEL HIGH RATE TRAVEL
ELEVATORS: 3/4” UP - 3/4” DOWN 1-1/8" UP - 1-1/8" DOWN
AILERONS: 3/4” UP - 3/4” DOWN 1-1/8" UP - 1-1/8" DOWN
RUDDER: 1” LEFT - 1” RIGHT 2” LEFT - 2” RIGHT
We have used and can recommend the use of exponential to
smooth out the flight characteristics when using the high rate
recommendations. We used 40% to 50% of expo to achieve very
smooth control response.
CENTER OF GRAVITY:
Establishing the correct Center of Gravity (C.G.) for this or any R/C
aircraft is critical to its ultimate success in the air. Measured from
the leading edge of the wing, next to the fuselage side, the
recommended starting balance point range for the Four-Star 120
ARF is 4-1/4" to 4-3/4" (108 to 120 mm).
Mark the above C.G.range onto the tops of both wing panels using
receiver can also be placed directly onto the servo tray and held in
place with a pair of zip-ties. The receiver antenna is routed through
the internal antenna tube, factory-mounted in the fuselage.
On/Off Switch: We chose to mount our onboard switch
assemblies inside the fuselage, directly to the forward end of the
servo tray. We then used a length of 1/16" dia.music wire from the
switch lever, through the fuselage side, making a neat remote
on/off end with a simple L-bend. Of course the switch can be
mounted to the fuselage side by cutting a small rectangular
opening in the fuselage side to accept the switch and then
mounting it in the traditional manner.
Battery Pack: Our prototype Four-Star 120 ARF models both had
their 1000 mAh battery packs placed in the nose of the fuselage,
beneath the fuel tank. With heavier engines, the battery pack can
be moved back as needed to achieve the correct C.G. location.
Always wrap the battery pack in foam to protect it from vibration.
OPTIONAL PILOT FIGURE:
Many modelers enjoy the look of a nice pilot figure in the cockpit of
their models. We're no different and decided to install a pilot in our
own FOUR-STAR 120 ARF models. We chose a Williams Bros.
1/4”scale "Sportsman" (Williams Bros. P/N 62600) figure to pilot
our models. After assembly, we painted the figure with plastic
compatible paints and added a few details to make him a bit more
believable.
We installed the finished pilot into the cockpit area, using
15-minute epoxy. From beneath the figure's base, we glued a
piece of 1/16" plywood to the wood. After the glue set, we drilled
pilot holes for two #4 x 3/4" sheet metal screws (not provided) and
secured these screws through the pilot holes and into the base of
the pilot figure.
Now that the airplane is essentially complete and your optional
pilot figure is in place, the canopy can now be reinstalled onto the
fuselage, using the 6 screws and plastic washers that were
removed and set aside earlier in the manual.
DECAL APPLICATION:
As mentioned earlier, the Four-Star 120 ARF decals are high-
quality Mylar with a very aggressive adhesive. The individual
decals are not die-cut and must be removed from their carrier
sheets using a hobby knife and a sharp #11 blade or scissors. A
straight edge makes this easier in the case of the longer graphics.
For location purposes, use the box art photos as a guide for

120 ARF begins moving forward, back off of the up elevator input
and use the rudder as required to correct any engine torque and/or
wind induced deviations from a straight take-off run. At takeoff
speed, use a slight amount of up elevator to lift off, using ailerons
to keep the wings level. Climb to a reasonable altitude before
making any trim changes.
Although not intended as a primary R/C trainer, the FOUR-STAR
120 ARF is a very forgiving design that allows you to fly at relatively
low speeds. With the control movements set at the measurements
provided in this manual, the airplane should exhibit smooth,
predictable control. Try a few loops and rolls. Inverted flight is
easy, requiring a little down elevator for level flight. The FOUR-
STAR 120 ARF also performs nice inside and outside loops, snap
rolls, Immelmanns, stall turns, Cuban eights, and spins. Of course,
it is not a pattern aircraft, but with practice, there isn’t much that it
won’t do. As with any aircraft, getting consistently good results is
usually just a matter of practice.
Still at altitude, throttle the engine back to idle. This will give you a
good idea of the glide characteristics. While still at idle, steadily
increase up elevator input to get a feel for the stall characteristics.
The FOUR-STAR 120 ARF tends to stall very gently, with the nose
dropping straight ahead with little tendency to drop a wing. This is
great information to have when setting up your first landings.
Landing the FOUR-STAR 120 ARF is typically a pleasure. We
suggest using a standard landing approach, beginning with a
throttled back downwind leg and base turn to the final approach
into the wind. During final approach, keep just a little power on the
engine until the airplane is over the end of the runway. In
crosswind conditions, a little rudder input will likely be needed to
keep the airplane lined up with the runway. The FOUR-STAR 120
ARF is best landed in the three-point position. As long as we’re on
the subject, no landing gear system is bulletproof. Your FOUR-
STAR 120 ARF has a great landing gear system that has proven to
be very tough on both grass and asphalt flying fields. However, it
can be ripped off during less than desirable landing approaches,
poor field conditions, failure to flare, and just plain "brain fade". If
this happens, simply epoxy the landing gear block back in place
and learn to be more careful the next time. After landing, always
remember to hold up elevator when taxiing, to keep the tail wheel
firmly to the ground.
We sincerely hope that your FOUR-STAR 120 ARF will provide you
with many, many enjoyable flights. We also hope that this has been
a pleasurable kit for you to assemble and fly. Please operate your
airplane in a safe, responsible manner with constant regard to
other flyers, spectators, and property.
trim tape or a non-permanent marker pen. As shown, we balanced
our Four-Star 120 ARF models upside down, using a simple
padded C.G. fixture.
When balancing the model at the predetermined C.G.location, the
model must balance level. If the nose hangs down when
suspended at the proper C.G. location, it means that the model
nose-heavy. Likewise, if the tail hangs down, the model is
tail-heavy. If either of these conditions exists with your model, it
must be corrected.
In the case of a nose-heavy model, the correction to make it
balance level is fairly easy. The heaviest component in the model
is typically the battery pack and this can be repositioned a further
back in the model as needed to achieve the correct balance. In the
case of a tail-heavy model, weight has to be brought forward in the
fuselage to achieve the proper balance. There are several ways to
do this but the easiest is to move the battery pack as far forward in
the nose of the model to achieve the correct C.G. point. In the
unlikely event that more weight is needed, you might consider
adding lead weight into the nose or using a "Heavy Hub", available
commercially from Harry Higley Products. In any case, it is
imperative that the correct C.G. location is established before you
fly the model.
FLYING:
If you have carefully followed the assembly instructions in this
manual, test flying your new FOUR-STAR 120 ARF should be a lot
of fun. When it comes to test flying a new model, we always advise
modelers to choose a calm day with little or no wind. These
conditions allow you to better evaluate and more accurately adjust
the trim requirements for your airplane. As we’ve mentioned
before, a good running, reliable engine is a must for the ultimate
success of your airplane. Take the time to solve any engine
problems before you try to fly.
Always make it a part of your pre-flight routine to check each
control on the airplane, making sure the surfaces are moving in the
correct directions. Also check each control linkage to be sure they
are secure and that nothing is loose. With all the controls checked,
make a range check with your radio system, using the procedures
provided by your radio system manufacturer.
After starting and warming up the engine, hold full-up elevator (to
keep the tail wheel firmly on the ground) and taxi the FOUR-STAR
120 ARF out to the take-off position on your flying field. Line up the
airplane facing into the wind and along the centerline of the
runway. Hold a little up elevator and smoothly advance the throttle
- do not slam the throttle full open all at once. As the Four-Star
18

19
LIMIT OF LIABILITY
The craftsmanship, attention to detail and actions of the builder/flyer of this model airplane kit will
ultimately determine the airworthiness, flight performance, and safety of the finished model. SIG MFG. CO.’s
obligation shall be to replace those parts of the kit proven to be defective or missing. The user shall
determine the suitability of the product for his or her intended use and shall assume all risk and liability in
connection therewith.
CUSTOMER SERVICE
SIG MANUFACTURING COMPANY, INC. is committed to your success in both assembling and flying the
FOUR-STAR 120 ARF kit. Should you encounter any problem building this kit, or discover any missing or
damaged parts, please feel free to contact us by mail or telephone.
SIG MANUFACTURING COMPANY, INC.
P.O. Box 520
401-7 South Front Street
Montezuma, IA 50171-0520 USA
PHONE: [phone]
FAX: [phone]
SIG WEB SITE: www.sigmfg.com
SIG E-MAIL: [email protected]
WARNING! THIS IS NOT A TOY!
Flying machines of any form, either model-size or full-size, are not toys! Because of the speeds that
airplanes must achieve in order to fly, they are capable of causing serious bodily harm and property
damage if they crash. IT IS YOUR RESPONSIBILITY AND YOURS ALONE to assemble this model
airplane correctly according to the plans and instructions, to ground test the finished model before each flight
to make sure it is completely airworthy, and to always fly your model in a safe location and in a safe
manner. The first test flights should only be made by an experienced R/C flyer, familiar with high
performance R/C aircraft.
The governing body for radio-control model airplanes in the United States is the ACADEMY OF MODEL
AERONAUTICS, commonly called the AMA. The AMA SAFETY CODE provides guidelines for the safe oper-
ation of R/C model airplanes. While AMA membership is not necessarily mandatory, it is required by most
R/C flying clubs in the U.S. and provides you with important liability insurance in case your R/C model should
ever cause serious property damage or personal injury to someone else. For more information,
contact:
ACADEMY OF MODEL AERONAUTICS
5161 East Memorial Drive
Muncie, IN 47302
Telephone: [phone]
AMA WEB SITE: modelaircraft.org