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SIG Four-Star 120 Building And Flying Instructions Download Page 15

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Mounting The Wing To The Fuselage

 
NOTE: The wing must be completed through step 18 before proceeding.

 
48.

 

a. Trial fit the wing to the fuselage. Align the wing (see the General Alignment 

Diagram on page 20 of "The Basics of Radio Control") and make accurate 
pencil marks on both the wing and fuselage so that the wing can be 
returned to the same position later.  

b. Locate the two 5/16" dia. x2" wing dowels and sharpen one end of each to 

a point - keep the point symmetrical and centered. Push the dowels into 
the holes in F-2 so that only the points remain sticking out into the wing 
opening. Slide the wing into position, making sure it is centered on the fuselage. When you remove the wing, there 
should be two small indentations in the leading edge. 

 
49.

 

a. Drill 1/8" holes through the leading edge at the indentations. Re-drill the holes, this time with a 5/16" drill bit, and 

continue drilling straight through the lite-ply wing dowel supports that are already installed in the wing. Keep the drill 
aligned as best you can with the wing center line.  

b. Remove the wing dowels from F-2. Put a piece of wax paper over the face of F-2 and reinsert the dowels, forcing 

them through the wax paper. Push the dowels in only 3/8", leaving most of their length exposed.  

c. Trial fit the wing in position, sliding it onto the dowels. Check to see that the wing seats properly on the fuselage. If 

not, slowly enlarge the holes in the leading edge until it does seat properly. 

 
50.

 
When satisfied with the fit of the wing and the wing dowels, coat the inside of the holes in the leading edge with epoxy. Slide 
the wing back into position on the dowels. Also apply epoxy to the aft end of the wing dowels and the wing dowel supports 
by working through the openings in the bottom center sheeting. Hold the wing in place until dry, then remove the wing and 
fill any gaps around the dowels with another application of glue.
 

 

 

 
51.

 

a. The two 3/4"x3/4"x1-1/2" basswood wing hold-down blocks key into pre-

cut notches in the -fuselage doubler. For an accurate fit, the side of each 
block that contacts the fuselage needs to be beveled slightly to match the 
aihedral angle of the wing. Temporarily tape the wing in place on the 
fuselage, then check the fit of the blocks by working through the lightening 
holes. The blocks should seat firmly against both the fuselage side and the 
top surface of the wing.  

b. Again working through the lightening holes, install the wing holddown 

blocks in the notches, making certain they are in full contact with the wing 
upper surface. Tack glue the blocks to the fuselage with slow CA, then 
remove the wing. Finish gluing the blocks in place using medium CA.  

c. Cut two 1-1/2" lengths of 3/4" balsa triangle stock to brace the wing hold-down blocks. Glue the triangle braces firmly 

to the top of the holddown blocks and the fuselage doublers. 

 
52.

 

a. Fit the wing in place on the fuselage and check its alignment one last time. 

When you are satisfied that it is aligned correctly, tape it so that it can't 
move.  

b. Carefully mark the drill locations for the wing bolts. Visually confirm that a 

hole drilled at the marks will pass through the approximate center of the 
basswood hold-down blocks.  

c. Drill through both the wing and the wing hold-down blocks with a #7 (or 

13/64") drill bit. Keep the drill perpendicular to the bottom surface of the 
wing so the heads of the nylon wing bolts will seat flush against the 
plywood plates. 

Summary of Contents for Four-Star 120

Page 1: ...but its reputation quickly spread Novice flyers suddenly looked like pros and experts couldn t believe how slow it could land without stalling Instructors began calling us with stories about training people to fly R C with the FourStar 40 even though it s never been promoted as a trainer Clubs even began using it for one design pylon races ...

Page 2: ...s the finest blend of building and flying characteristics to be found in a sport model of this size Personally I ve had more fun with the Four Star 120 than any model I can remember There s no doubt in my mind that you ll enjoy it just as much Engines Propellers and Mufflers There is a tremendous variety of engines available in the size range specified for the Four Star 120 A good 1 20 size 4 stro...

Page 3: ...d when the two parts to be joined are in perfect contact with zero gap Capillary action pulls this glue deep into the wood resulting in a very strong bond and it dries in just a few seconds Thin CA can be used to tack assemblies together but these joints should be glued again later with medium or thick CA Thin CA is also necessary for installing EASY HINGES Sig CA Medium Our medium thickness CA is...

Page 4: ... into which pins can be easily pushed Don t hesitate to use plenty of pins during assembly to hold drying parts in their correct position When pinning and gluing parts directly over the full size plans cover the plan with wax paper to prevent gluing the parts to the plans Don t use a ball point pen for making marks on the model during construction If not sanded off these ink marks will show throug...

Page 5: ...ize Printed Plans 1 Photo Illustrated Instruction Booklet 1 The Basics of Radio Control Booklet 3 10 x27 Color Decals Hardware 2 2 Flat Washers for tailwheel wire 10 2x3 8 Sheet Metal Screws 8 for hatches 2 for tail brace wires 8 2x3 4 Sheet Metal Screws for control horns 2 4x1 2 Sheet Metal Screws for tailwheel bracket 4 8x1 Sheet Metal Screws for engine 3 2 56x1 2 Mounting Bolts for tail brace w...

Page 6: ...at the proper dihedral angle 20 then glue it to the spars and the trailing edge sheeting c Add the remaining wing ribs three W 1 two W 2 and six W 3 to the wing panel 4 a Use the SHEAR WEB IDENTIFICATION diagram on sheet two of the plans to identify the three types of pre cut balsa shear webs SW 1 SW 2 SW 3 that are used in the wing panel The vertical wood grain is important for maximum wing stren...

Page 7: ...ng edge Notice that one end of the support is pre cut to match the dihedral angle of the inboard W 1 rib 8 Form a 14 long aileron servo lead tube by wrapping one of the supplied pieces of 8 1 2 x14 plain white paper around a broom handle Temporarily tape the tube together slide it off the broom handle and into the 1 holes in the wing panel Position the outboard end of the tube flush with the outer...

Page 8: ...ps 2 through 14 to build the opposite wing half Joining The Wing Panels 16 a Trial fit the two wing panelswith the die cut 5 32 plywood dihedral brace installed between the main wing spars Be certain that the dihedral brace is not preventing the panelsfrom making solid contact with each other at the center If necessary trim or sand the dihedral brace for a snug fit The dihedral angle of 20 per win...

Page 9: ...ct the strength of the CA A second coat of CA will help fill in the weave of the fiberglass resulting in a smoother surface Rub the second coat with your finger protected with plastic wrap keep it moving to smooth out the glue Use a fan to keep the CA fumes away from your face 4 When dry sand lightly to remove any rough spots Try not to sand into the fiberglass tape itself Ailerons 21 Sand the tra...

Page 10: ...n tell later which hatch goes with which wing panel 27 a Since servos come in many sizes you need to make a custom servo tray from lite ply and basswood to fit your particular servo Cut a hole in the die cut lite ply aileron servo mount to fit your particular servo The forelaft dimension of the hole should be about 1 16 larger than the length of your aileron servo b Cut two 3 8 sq x4 basswood serv...

Page 11: ...a 31 The plywood hatch will need an opening cut into it for the aileron pushrod Again the exact size and shape of this opening will depend on the shape and position of your pushrod You can make a nice looking slot by drilling two holes then connecting the edges with knife cuts When you are done with the hatch remove the aileron the aileron control horn and the aileron pushrod The servo can be left...

Page 12: ...unt far enough forward for the propeller to clear the fuselage cheeks mark the engine mounting holes then drill at each of the marks If you plan on using the four 8 x1 sheet metal screws provided in the kit use a 9 64 dia drill bit The sheet metal screws are self tapping and won t loosen from engine vibration If you prefer machine screws can be substituted but you ll have to drill and tap the moun...

Page 13: ...o check its alignment Even if some of the plywood is badly warped the interlocking parts are designed to be self aligning If there are any persistent warps or twists now is the time to fix it Once the fuselage is glued it can t be re aligned Double check that the opening at the back end of the fuselage is square with the fuselage top If necessary gently twist or push the parts in the desired direc...

Page 14: ...oublers and against the back of F 1 then glue it in place b Trim the die cut lite ply nose triplers as necessary to fit then glue them firmly to the fuselage doublers and F 1 c Glue the small top deck formers T 1 T 2 and T 3 into their notches in FT 46 a Bevel the top edge of the fuselage sides with a sanding block to provide a firm seat for the fuselage top deck when it is installed Notice that t...

Page 15: ...tion on the dowels Also apply epoxy to the aft end of the wing dowels and the wing dowel supports by working through the openings in the bottom center sheeting Hold the wing in place until dry then remove the wing and fill any gaps around the dowels with another application of glue 51 a The two 3 4 x3 4 x1 1 2 basswood wing hold down blocks key into pre cut notches in the fuselage doubler For an a...

Page 16: ...rly meet but not cross at the notch in F 5 Glue a scrap of balsa below the tubes to hold them in place d Apply glue either slow CA or epoxy to the outer tubes at the push rod exit slots from both the inside and the outside of the fuselage e Use a single edge razor blade to trim the outer pushrod tubing flush with the outside surface of the fuselage 57 a The nylon push rods must be supported at eac...

Page 17: ... complete the stabilizer frame 62 The stabilizer is sheeted on both sides with 1 16 balsa Cut two pieces of 1 16 x4 x30 balsa as shown in the diagram and glue the parts together to make two stab skins BUILDER S TIP Use Sig Bond for gluing the sheets and sand the joints smooth BEFORE attaching them to the stabilizer frame Sanding the skins after attaching them to the framework can result in a rippl...

Page 18: ...to their final shape b Draw a line on both sides of the fin trailing edge 3 8 below the fin base c Apply slow CA or Sig Bond to one entire side of the fin frame except for the area below the line that you have just drawn d Repeat the above step for the other side of the fin 70 When dry trim the sheeting flush with the fin frame Use a sanding block to sand the fin leading edge round Finish the fin ...

Page 19: ...nd smooth Done properly this installation should be completely trouble free 73 The balsa tail fairing blocks can now be glued to the fuselage using the stabilizer and fin to position them accurately Cut two 4 lengths of 3 4 balsa triangle stock to serve as tail fairing blocks Make sure your fin is centered on the fuselage as viewed from above then carefully glue the fairing blocks to the back of F...

Page 20: ...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 S...

Page 21: ...he fin trailing edge all the way to the bottom Covering with Sig Koverall And Dope Koverall is a polyester base heat shrinkable synthetic fabric much like the covering used on full scale aircraft only lighter Its toughness and relatively low cost make it ideally suited to giant scale and giant sport models One large package of Koverall SIGKV003 48 x 5 yds is plenty of material to cover the Four St...

Page 22: ...ig products from the start and you ll be rewarded with a classy finish that is rugged and easy to repair Applying Decals The supplied decals can be used over any type of finish as long as the surface is clean If needed replacement decals are available from SIG order SIGDKM265A SIGDKM265B and SIGDKM265C Cut out the decals with sharp scissors leaving about 1 32 to 1 16 of clear at all edges and roun...

Page 23: ...t draw cut lines on the bottom of the stabilizer at the fuselage sides and on the top of the stabilizer at the tail fairing blocks Remove the stabilizer and cut away the covering between the lines exposing the bare wood underneath Use a sharp knife to cut the covering material try not to cut into the balsa sheeting Use the same method to expose the area under the tail fairing blocks b Permanently ...

Page 24: ...ce wires will provide enough extra strength to put your mind at ease while you re wrapping the model around the sky Four 2 56 x10 threaded rods are provided to serve as tail brace wires Four standard RIC links 2 56 thread inside and four solder clevises unthreaded are also provided for the ends of the tail brace wires Take each link and cut off the side that has the pin in it a Dremel tool with an...

Page 25: ...ed portion remains exposed The metal rod will help prevent the nylon tubing from buckling under flight loads Thread a 4 40 hex nut and the R C link onto the end of the pushrod until the rudder is in neutral Tighten the hex nut against the clevis to help reduce any slop in the linkage Repeat this procedure for the elevator push rod this time cutting the threaded rod to an overall length of 4 1 2 If...

Page 26: ...e of Success in R C A model engine or radio that is not prepared and working properly on the ground before takeoff will not improve in the air it will get worse There is no point in attempting to fly until everything is 100 correct RECOMMENDED CONTROL SURFACE MOVEMENTS For test flying the following are suggested ELEVATOR 1 UP and 1 DOWN RUDDER 1 1 4 LEFT and 1 1 4 RIGHT AILERON 5 8 UP and 5 8 DOWN...

Page 27: ...es them fairly well It does however require a balance point near the rearward limit a lot of control throw a lot of power and a lot of altitude The exact setup will vary from model to model so you ll need to experiment To do a flat spin you must first enter a normal spin throttle up to full power then slowly move the aileron stick to the opposite side To recover chop the throttle neutralize the ai...

Page 28: ...ely want you to share WARNING DANGER Important Read These Warnings A model airplane motor gets very hot and can cause serious bums Do not touch the motor during or after operation Keep clear of the propeller it can cut off a finger or put out an eye Make sure the propeller is securely fastened in place and is not cracked Model airplane fuel is flammable and poisonous Take the same precautions whil...

Page 29: ... ...

Page 30: ...E 1 800 524 7805 Weekdays 7 00am 4 30pm Central Copyright SIG Mfg Co Inc SIG MFG CO INC Montezuma Iowa 50171 0520 LIMIT OF LIABILITY In use of our products Sig Mfg Co s only obligation shall be to replace such quantity of the product proven to be defective User shall determine the suitability of the product for his or her intended use and shall assume all risk and liability in connection therewith...

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