FOUR-STAR 120 RC65 COVERING
We recommend that you cover the wing, fuselage, tail surfaces, and control surfaces all separately before hinging and final assembly. This way, the parts are much easier to handle. Before choosing the covering for your model, please refer to the list of approved covering materials that has been included with this kit. The open structure design of the Four-Star 120 wing relies partially on the covering to aid in torsional stiffness, so it is very important that you use an approved covering material.
Our Four-Star 120 prototypes were covered with either Sig Supercoat iron-on plastic film or Sig Koverall fabric. Sig Supercoat is ideal for sport models because it's lightweight and easy to apply. Sig Koverall is extremely durable and adds tremendous strength to the structure with only a slight weight penalty over plastic films. Use Supercoat film if you're looking for maximum performance with a 1.20 four-stroke or .90 two-stroke engine. If you plan on using a gas engine or an engine in the upper end of the recommended engine range, Koverall would be your best choice.
The following instructions provide advice and procedures specific to covering the Four-Star 120 with either Sig Supercoat or Sig Koverall. If you choose another brand of covering material, be sure to read the manufacturer's directions (supplied with the covering) and follow them carefully.
A good covering job starts with good surface preparation. Regardless of what type of covering you choose, it won't hide poor workmanship. Fill any small surface gaps or dents with a lightweight filler or spackling paste. Sand the entire model, including the ailerons and tail surfaces, with 220-grit sandpaper, then again with 360 or 400-grit sandpaper.
Two areas of the fuselage require further preparation before covering the engine compartment and the cockpit. Since it's too difficult to apply covering material to the engine compartment, it must be fuel-proofed using several coats of clear dope or two coats of polyester (glass) resin, sanded between coats. Finish off the engine area with a few coats of colored Sig Supercoat Dope. (Most of the Supercoat plastic iron-on films have a matching Sig Supercoat Dope color.)
The cockpit floor can be painted or covered with plastic film. The front of the headrest (HR) shouldn't be covered or painted until after the fuselage stringer area has been covered, to help hide the seam. Cut the instrument panel from the decal sheet and apply it to former T-3 to finish off the cockpit.
Covering with Sig Supercoat Iron-On Plastic Film
You will need four rolls of Supercoat (color of your choice) to cover the FourStar 120. You will need one big piece from each roll (about 14-1/2"x42") to cover the wing. Use the rest of the film to cover all of the remaining parts.
Covering The Wing
Begin the wing by covering the wingtips and plywood hold-down plates. On the wingtips, run the covering material "around the corner" about 1/8". Later, when the main top and bottom covering pieces are applied, they will overlap the wingtip covering and can be trimmed at the wingtip corners, leaving a virtually invisible seam. Extend the covering material about 1/8" past the outside edges of the hold-down plates, again to provide an area for overlap.
Cover the main portion of the wing starting with the bottom and then the top so that the seams will be on the bottom where they will be less visible. The top covering should overlap the full width of the leading & trailing edges. Wait until both the top and bottom pieces of covering material have been sealed completely around their edges before shrinking the large open areas between the ribs. Alternate between the top and bottom surface to avoid uneven shrinking which could cause a warp. Your sealing iron or a special "heat gun" can be used (household blow dryers don't provide enough heat). Keep the heat gun moving at all times or you may burn a hole in the covering. If you notice the covering material "ballooning up", put a small pin hole in the bottom of each rib bay to allow the expanding air to escape. To maximize the torsional stiffness of the wing, be sure to firmly bond the covering material to all of the spars and ribs by going over them again with your sealing iron.
Cut an "X" pattern at the hatch openings on the bottom of the wing, then iron the excess material to the spars and hatch rails. Don't forget to cover the outer surface of the plywood hatches, wrapping the covering around the edges about 1/8".
|Covering The Fuselage|
The fuselage should be covered with six pieces in the order described here:
The trickiest part of covering the fuselage is the stringer area. Start by applying one edge of the covering to one of the fuselage sides, overlapping 3/16" onto the side covering. Drape the material over the stringers, pulling out any major wrinkles. Carefully tack the material to the other fuselage side,then trim off the excess, again leaving a 3/16" overlap. To avoid slicing into the material underneath, slide a piece of thin cardboard under the excess stringer covering before cutting it with a knife. Use a straight edge to make a nice, straight cut.
Go back over the side seams with your iron, then seal the material to HR at the front as well as F-6 and the tail fairing blocks at the rear. Trim away the excess covering at the rear flush with the edges of the fairing blocks and F-6. At the front, leave a 1/8" overhang forward of the headrest (HR) to iron around the corner. Seal down the overhang to the front of HR (you may find that slits in the overhang every 1/4" or so will help during this step). Now you can use a heat gun or iron to shrink the rest of the material over the stringers.
Covering The Tail Sufaces And Ailerons
The stabilizer, elevators, fin, rudder, and ailerons should each be covered with two pieces of material - bottom first, then the top. Iron the material from the center out to avoid trapping air bubbles. Be sure to cover the back edge of the 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-Star 120. It can be applied to the structure using dope or Sig Stix-It, and heat-activated adhesive.
Whichever application method is used, you should first brush two coats of clear dope onto the framework wherever the covering material makes contact (even the edges of the wing ribs). If you plan to use dope for the entire finish, use Sig Lite-Coat (low-shrink butyrate dope) for the first two coats. If you plan to use enamels or epoxy colors, use Sig Nitrate dope. Lightly sand after each coat to remove any raised grain or fuzz.
Applying Koverall With Dope
The bottom of an outer wing panel is a good place to start covering. Cut a piece of material about an inch larger all around the panel, with the grain running spanwise. (The grain of woven materials runs parallel to the finished bias edge.) Lay the Koverall on the wing, pulling out any major wrinkles. Koverall shrinks up considerably under heat - there's no need to worry about such things as packaging fold creases because they will come out easily with the iron. Brush clear dope around all the edges. This will soak through the fabric and adhere it to the dope already dried into the framework. Allow the dope to dry before trimming off the excess material with a sharp razor blade. Check for any rough edges or places that are not stuck down properly and apply more dope. Let dry.
Applying Koverall With Stix-It
Directions for using Stix-It are on the can. The basic procedure is to apply Stix-It around the edges of the framework where you want the covering to attach. When dry, the fabric can be ironed-on around the edges where the Stix-It was applied.
|Shrinking And Sealing Koverall|
After both sides of a surface are covered, shrink the Koverall evenly with an iron or heat gun (be sure to read the Koverall package instructions). The fabric. is now ready to be sealed with clear dope. The dope that you apply to the top of the fabric will soak through and bond with the dope underneath, firmly cementing the Koverall in place.
Thin the dope until it brushes on easily and flows out smooth (about 25% to 30% thinner). The first coat should be applied sparingly to avoid puddles underneath the fabric. The second coat will seal most of the pores of the Kove rail , and from then on running. through will not be a problem. Sand the model VERY LIGHTLY with FINE sandpaper after the second coat is dry. You may need three to five coats of clear dope on the Koverall before going to color, depending on how heavy the coats are. Use your own judgement about when you've applied enough clear dope. Keep in mind that weight can build up fast when you're painting! Don't bother trying to completely fill the weave and avoid using heavy sanding sealer or primers. The goal is to hide the seams and provide "an even base for the color paint.
Finishing With Supercoat Dope
(Complete the model through step 83 of "FINAL ASSEMBLY" before applying the color dope to your model.) The best results can usually be obtained by spraying the color coats of dope with spray equipment. Thin the dope for spraying by mixing in an equal amount of Sig Supercoat Dope Thinner. Apply two or three coats, starting with the lighter colors, followed by darker trim colors. Mask off your trim scheme with low-tack drafting tape, then seal the edges of the tape with clear dope (applied with a small brush) before applying the trim color. A final coat or two of clear dope over the color dope will add a nice gloss to the finish. Stick with Sig products from the start and you'll be rewarded with a classy finish that is rugged and easy to repair.
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 rounding the corners as you cut. Wet the surface on which the decal will be placed with soapy water (use dishwashing detergent). Place the decal on the model and squeegee the water from underneath with a balsa paddle. This procedure allows time for repositioning and prevents air from being trapped under the decal. Allow several hours to dry.
INSTALLING EASY HINGES
Sig's famous EASY HINGES have been included with your kit to hinge all of the control surfaces. Each ultra-thin hinge is actually a three-part laminate - a tough plastic inner core sandwiched by an absorbant wicking material. They have been chemically treated to slow down the reaction of thin CA (which is normally instant), to allow the glue time to soakall the way to the ends of the hinge and into the wood surrounding it. Once the glue has dried, the hinge cannot be pulled from the structure without tearing wood out with it! We recommend that all surfaces be covered before hinging.
Using a No. 11 X-Acto blade (or similar), cut slots approximately 1/2" in depth and slightly wider than the hinges. Cut eight slots in the stabilizer and eight matching slots in the elevators at the locations shown on the plans.
After all of the slots have been cut, insert EASY HINGES halfway into the stabilizer slots. DO NOT GLUE THE HINGES YET! Next, carefully slide the elevators onto the hinges. You'll find it easiest to slide the elevators onto the hinges at an angle, one at a time, instead of trying to push it straight onto all of the hinges at once. Don't be concerned if the hinges aren't perfectly straight or centered in the slots - they'll work regardless of their final position.
Install two 4" main wheels on the aluminum landing gear using the hardware as shown on the plans. Use a drop of CA or thread locking compound on the inner nut to keep the assembly from vibrating apart. Once the wheels have been attached, the landing gear assembly can be bolted to the fuselage using three 8-32 x 3/4" mounting bolts.
Optional Tail Brace Wires
We've flown our prototypes extensively without tail brace wires and have never had any problems. However, tail bracing is such a common feature on large sport models that it seemed appropriate to include them as part of this kit. If you plan on using a typical 1.20 4-stroke engine (or .90 2-stroke), you don't really need the braces. If you're leaning towards bigger engines with more power and vibration, the tail brace wires are probably a good idea. For just a small increase in weight, complexity, and drag, the tail brace 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 abrasive cutoff wheel works best). Enlarge a hole in the remaining half with a 3/32" drill bit. Use a vise to hold the clevis while you drill - not your hand!
Assemble two upper tail brace wires and two lower tail brace wires as shown on Sheet 2 of the plans (see the full-size "Tail Brace Wire Assembly" diagram).
Fit the wires to the model by bending the end of each link to sit flat against the model sUrfaces. Adjust the threaded links and jam nuts until the wires are snug, but not pulling the tail surfaces out of shape. Use three 2-56 x1/2" machine screws and three 2-56 hex nuts to fasten the links to the fin and stabilizer. Attach the bottom ends of the lower brace wires to the bottom of the fuselage, just ahead of the tailwheel bracket, using two #2 x 3/8" sheet metal screws.
NOTE: The remaining sections of these instructions concerning engine and fuel tank installation, radio installation, pre-flight checkout, and flying, provide information that is specific to the FOUR-STAR 120. For a more in-depth look at any of these subjects, please refer to "The Basics of Radio Control" booklet also included with this kit. In particular, it is strongly recommended that you go through the "Pre-Flight Checklist" in Chapter 7 carefully before attempting to fly.
Engine And Fuel Tank Installation
Engine installation on the FOUR-STAR 120 is simply a matter of bolting the engine and engine mount in place on F-1. Install the throttle cable on the carburetor arm and assemble the push rod connector on the throttle servo arm. The exact position of the cable in the push rod connector will have to be adjusted after the rest of the radio has been installed.
|Like most SIG kits, the fuel tank in this model is installed from the rear of the fuel tank compartment rather than through a removable hatch. This choice was made for several reasons. A hatch opening makes the nose weaker and it's very difficult to keep oil from leaking in around a hatch.|
A method of fastening the hatch must be built into the fuselage, adding to the complexity and construction time of the model. Besides, modern plastic fuel tanks are virtually indestructible under normal use when installed properly, so they seldom need to be removed for maintenance.
|A 16 oz. to 20 oz. fuel tank is recommended for the FOUR-STAR 120. The Sullivan 16 oz. slant tank fits well, as do the DuBro 16 oz. and 20 oz. tanks. Most engines will require the tank to be mounted as high as possible in the fuselage. Use foam rubber under the fuel tank as necessary to position it properly.|
Screw the nylon control horns onto the rudder and elevator as shown on the plans, then re-install the inner nylon push rods that you prepared in step 58. Snap a 4-40 R/C link onto the rudder horn, then cut off the excess nylon tubing, leaving a 1/8" gap between the end of the tubing and the R/C link. Cut a 4-40 x 8" threaded rod to an overall length of 5-1/2", measuring from the threaded end. Install the threaded rod in the nylon tubing, smooth end first, so that approximately 5/8" of the threaded 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 you look closely at the photo, you should be able to see that a short length of fuel tubing has been slipped over the R/C link. The purpose of this is to keep the link from popping open during flight, which could cause a loss of control. For safety, install fuel tubing "keepers" on ALL of your R/C links and solder clevises. Without them, your model probably won't pass the standard safety inspection performed at most fly-ins.
Hook up the ailerons by installing control horns and the aileron push rods. The servo leads will probably require short extensions to reach the center "V" harness which is required to connect the servos to the receiver. Radio manufacturers generally have these items available as stock equipment. It's best to keep the extensions as short as possible since excessively long wires have been known to cause radio "glitches" under certain conditions.
Use the die-cut lite-ply Aileron Positioning Guide (APG) to set the ailerons at neutral. Adjust the R/C link on each aileron push rod until the APG seats perfectly against the bottom of both the wing and aileron.
A typical radio installation is shown in the photo. Always wrap your receiver and battery in foam rubber and position them forward of the servos. If you use a lightweight engine, you may need to install the batfery under the fuel tank to achieve proper balance. Use a scrap balsa stick or rubber bands to keep them from moving around during flight.
|Notice that the aileron connector wire and the charging jack are left accessable, but are tucked away enough so that they can't interfere with the servo arms and linkages. The switch is mounted internally on a scrap piece of plywood and actuated by a piece of music wire that extends through the fuselage side. The antenna has been routed away from all other wiring and out the fuselage bottom.|
IMPORTANT! For first flights, make certain that the model balances with an empty fuel tank somewhere between 3-7/8" and 4-1/2" aft of the wing leading edge. If it balances too far back, add weight to the nose as necessary. Trying to fly with the balance point too far aft is much more dangerous than the slight increase in wing loading caused by adding lead to the nose. To balance the Four-Star 120, you may find it easiest to support it upside down with your fingertips on the inboard section of the wing.
Be certain to range check your radio equipment according to the manufacturer's instructions before attempting the first flight. A lot of problems can also be avoided if your engine has been well broken-in and the idle adjustments perfected on a test stand or in another airplane before installation in the new model.
Before flying, you should adjust all of your push rod linkages so that the control surfaces are in their neutral position when the transmitter sticks and trim levers are centered. When you get to the field, don't be surprised if the elevator and rudder are .suddenly misaligned. Temperature and humidity changes can cause the nylon pushrod tubes to expand or contract slightly. Use the trim levers on the transmitter to return the control surfaces to neutral, and do the final trimming in the air.
The control surface movements listed here are recommended for the first flight of your FOUR-STAR 120. These movements will provide the model with a fair degree of aerobatic capability if it's balanced correctly. Test flights may indicate a need for slightly more or less movement, depending on individual model performance and personal preference.
Remember the Golden Rule 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."
Like it said at the beginning, the Four-Star 120 was designed with flight performance as one of its top priorities - and we weren't disappointed! If you've never flown a plane that is this large, you are definitely in for an eye-opener. Lots of modelers will tell you that "bigger flies better" and in many ways, we would have to agree! Compared to smaller sport models, like the Four-Star 40, the "120" is every bit as capable aerobatically. The main difference is that maneuvers with a bigger model are larger, slower, and smoother than those performed by a typical AO-size model. The slower maneuvering speeds not only make for more impressive aerobatics, they give you more time to think and make corrections. These are the kind of advantages that can make any pilot look terrific!
The Four-Star 120 is a fun aircraft to fly, but it is not a basic trainer. If you have little or no R/C flying experience, we strongly suggest that you get an experienced pilot to help you fly your model until you're comfortable with the controls. Contact your local club or ask your hobby dealer for the names of good fliers in your area and suitable flying locations.
When all of your equipment is working properly, it's time to fly! First, you may want to practice taxiing the model while holding "up" elevator to avoid nose-overs. If you've never flown a taildragger, this kind of practice is time well spent. The Four-Star 120 handles much better on the ground than most taildraggers. You would really have to be "behind the stick" to do a ground loop with this model!
When you're ready for takeoff, point it into the wind and apply throttle. Release the "up" elevator as it accelerates. Like with any model, you'll probably need a touch of right rudder to keep it going straight because engine torque will try to make it drift to the left. When you reach flying speed, pull back slightly on the elevator stick for a gentle liftoff.
|If you're using a relatively large engine, don't expect the takeoff roll to last very long! With its big wing, the Four-Star 120 will lift off quickly and reliably.|
The control surface movements listed on page 22 are fairly tame - most modelers will want to increase the movements as they become more familiar with the flying characteristics of the model. Experiment with different control throws and balance points until the plane flies exactly the way you want. Make any changes, especially to the balance point, gradually. We recommend that you shift the balance point no more than 1/4" at a time. In general, moving the balance point forward will make the model more stable, slowing down snap rolls and spins. Moving the balance point back increases its sensitivity to control inputs; but if carried too far, the model can become completely unstable and uncontrollable. The balance range shown on the plans is a safe area to use for test flights. Don't exceed the rearward limit unless you are a very experienced pilot.
Aerobatically, the Four-Star 120 can do any trick in the book. The primary aerobatic maneuvers listed on the back of "The Basics of Radio Control" are no problem for this model. Here's how the Four-Star 120 handles some of the more advanced maneuvers:
You'll need to hold just a touch of "down" elevator to keep the model flying level while inverted. Climb to altitude and try some slow-speed inverted flight with your Four-Star. It truly flies as well upside down as it does right-side up!
A proper spin begins with a stall. Just as the model stalls, chop the throttle, hold full "up" elevator, and deflect both the rudder and ailerons either left or right. Once spinning, the "120" can easily be thrown from a left spin into a right spin and back again. To recover, simply release the controls, then gently pull out of the ensuing dive.
A flat spin can be fatal for most models, but the "120" actually does 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 ailerons, apply opposite rudder and down elevator, and wait! A fully developed flat spin may take two to five rotations to recover, so don't start the recovery procedure too late! This maneuver is very difficult and is definitely only recommended for highly skilled pilots.
Knife edge flight is achieved by rolling the model 90 deg. so that the wing is vertical, then holding the nose up with rudder. Since the Four-Star 120 doesn't have the neutral stability of a pattern ship, it requires a modest amount of "up" elevator to maintain heading during knife edge flight. With enough rudder deflection and power, the Four-Star will actually climb in knife-edge, using only the side of the fuselage for lift.
The Four-Star will actually "yaw" through a 360 deg. turn without ever banking the wing. From level flight, simply hold full rudder and some "up" elevator to keep the nose up. Some aileron correction may be necessary during the turn to keep the wings level.
Needless to say (but we will anyway), when you attempt a stunt for the first time, give yourself plenty of altitude and clearance from other people. Fly safe! You may need the room to recover from a messed up maneuver.
When landing, the Four-Star 120 may tend to "float" a bit more than models you have flown in the past, so be ready to go around if it looks like you're going to overshoot the runway. As with any new airplane, it may take a few flights to get a feel for the correct approach and landing speed. Remember to keep your control inputs smooth and gentle to avoid overcontrolling. When you are certain the model will make it to the runway (even if the engine quits), bring the throttle to full idle and concentrate on keeping the wings level during final approach.
| Slow the model down during the entire approach by slowly feeding in "up" elevator. Just before the model touches, flare the landing by
carefully feeding in more "up" elevator. Hold the model just inches off the ground until your elevator stick is pulled all the way back. The Four-Star 120 should settle in for a perfect "three-point" landing
with a short rollout.|
If your model always seems to make a nice landing approach but bounces when you touch the ground, you are simply trying to land too fast. If you're concerned about stalling during the approach, try doing some fake landing approaches about 50 to 80 feet high to build your confidence. You might be surprised at how slow the "120" will actually fly without stalling.
One caution about flying your Four-Star in front of other active R/C pilots. Unless they have one of their own, they will very likely want you to share!
The top view and side view drawings are provided for modelers who wish to develp their own personalized color and trim scheme for the FOUR-STAR 120. Make several copies of this drawing so you can draw out a few different ideas before deciding which one you like the best. This drawing is 1/10th actual size.
|We sincerely hope that you enjoy building and flying your SIG Four-Star 120. If you have any questions, comments, or problems with this kit or any other SIG product, please call us.||
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