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SIG SUKHOI SU-31 ARF, Assembly Manual, Page: 15 / 26

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15

screwing the servos in place. When done, temporarily unscrew the
elevator servos so you can install the radio "Y-harness" chord in
the next step.

IMPORTANT: While you have the elevators servos out, flow some
thin CA into the screw holes in the plywood to toughen up the
threads. Let dry.

❑

11) As mentioned earlier, to make the elevator servos function

properly you will need to either:

(a) electronically reverse one of the elevator servos internally

and use a standard Y-harness (and possibly another short 
extension chord)

(b) use the " MIRACLE Y™ Servo Reversing Y Adapter" to 

obtain mirror image elevator action

Install your Y-harness chord through the canopy opening, back to
the two elevator servo cutouts. To avoid a clutter of chords and to
keep them away from the pull-pull cables, route the y-harness
chord through the upper part of the rear fuselage.

Plug the 

elevator servos into the Y-harness ends at the servo cutouts,
securing all connector plugs with tape.

Then reinstall both 

elevator servos, pulling the excess chord lengths towards the front.
Use plastic "cable ties" or small spots of silicone adhesive to 
lightly fasten the extension chords (or the " MIRACLE Y™" control
pot) in place to the model structure, to keep them from flopping
around during flight and possibly coming unplugged. Finally, plug
the chord into your radio system to check the action of the 
elevator servos. Make any corrections that may be required.

❑

12) Hinge the elevators to the stabilizer at this time. Be careful

to correctly identify which elevator goes on the right side of the 
airplane and which goes on the left. Look for the plywood control
horn mounting pads, that are inset into the BOTTOM side of each
elevator, underneath the covering. After installing the hinges, wipe
off all excess glue from the hinge line with alcohol, and then tape
the elevators to the stabilizer in neutral position and allow to dry.

❑

13) Locate one left and one right Metal Control Horn and eight

M2.6 x 10mm Metal Screws. Hold one of the control horns in 
position on the bottom leading edge of the appropriate elevator.
The horn should be as far forward as possible so that the holes in
the horn line up directly over the stab/elevator hinge line. Also be
sure the control horn lines up with the elevator servo output arm.
Mark the horn's hole locations on the elevator with a fine-point
marker pen. Drill a 3/64” dia. (or #56 drill) pilot hole for each screw,
then screw the horn in place.

Repeat this procedure on the 

opposite elevator.

IMPORTANT: After you finish mounting the control horns for the
first time, take them back off. Then put a few drops of Thin CA into
each screw hole in the elevator. The Thin CA will soak into the
threads in the wood, and when it dries the holding power of the

b. When satisfied with the alignment, use a felt-tip pen to mark

the fin location on top of the stab. Take the fin off and carefully
remove the covering material from the stab just inside of the lines.

c. Apply slow-drying epoxy glue to all the mating surfaces and

then put the fin back in place on the fuselage. Wipe off any excess
glue with alcohol. Recheck the alignment, adjust as needed, and
then let dry.

❑

9) Locate the molded plastic tail fairing. Trial fit the fairing in

place onto the fuselage. Trim as needed to seat the fairing in 
contact with the fuse, the top of the stab and around the fin. Once
satisfied with the fit, mark the location of the fairing onto the fuse,
stab and fin with a felt-tip pen. Remove the fairing. Use a sharp
#11 blade to cut away the covering just inside of the lines, 
exposing the wood. Apply a coat of glue to the inside of the 
fairing where it will contact these areas.

Install the fairing, 

pressing it firmly in place to make sure it contacts all gluing areas.
Clean up any excess glue with alcohol and use tape to secure the
fairing in place. Allow to dry.

❑

10) Mount the two elevator servos in the fuselage now, using

the rubber grommets and screws that were supplied with your
radio system. It's best to mark the servo mounting hole locations
on the plywood first, then drill 1/16" dia. pilot holes, before 

Summary of Contents for SUKHOI SU-31 ARF

Page 1: ...elevator servos will be mounted on opposite sides of the fuselage in exact mirror image to each other i e with the pushrods coming off the top of each servo in direct line with the control horns This is done so the geometry of the servos pushrods and horns is exactly symmetrical on both sides providing the exact same response to control inputs for each elevator This is very important in an all out...

Page 2: ... authority than the small er engines It is simply a matter of how you want to fly the airplane RECOMMENDED ENGINES 2 STROKE GLOW ENGINES 1 50 2 10 cu in 4 STROKE GLOW ENGINES 1 80 2 70 cu in GAS ENGINES 2 4 cu in GLOW ENGINES GAS ENGINES Our preferred engine for the SUKHOI is a 2 4 cu in gas engine Our hands down favorite is the FIRST PLACE ENGINES FPE 2 4 cu in gas engine available from SIG Weigh...

Page 3: ...er climate you may notice that some wrinkles might develop after removing the covered parts from their plastic bags If that is the case there is no need to be alarmed The covering is not defective This is perfectly normal and has nothing to do with the covering material or how it was applied It has to do with the wood beneath the covering Wood takes on or loses ambient humidity Your SUKHOI ARF was...

Page 4: ...ool with Selection of Sanding and Grinding Bits Soldering Iron and Solder Large Fuel Tubing WING ASSEMBLY Before starting actual construction trial fit both wing panels onto the Hardwood Wing Joiner and the Aluminum Tube Rear Wing Joiner Check to see that the wing panels fit together in proper alignment and that both root ribs come into firm straight contact with each other If the Hardwood Wing Jo...

Page 5: ... and to check servo travel Make sure both servo output arms are 90O to the servos and that they are long enough to clear the wing s bottom surface during extremes of travel a Now attach 12 long servo extension chords to both aileron servos Note Be sure to put a piece of tape around the connecting plugs so they can t come apart while hidden in the wing b Feed the servo extension chords into the win...

Page 6: ...F 1 show the exact locations Drill completely through the foremost wing structure including the hardwood wing joiner that the hinge can be pushed in far enough for the pivot point to line up with the front V point of the aileron leading edge We recommend enlarging the opening of the hinge holes slightly with a hand held 1 4 dia drill bit You only need to twist the drill bit in about an 1 4 or so C...

Page 7: ...m of the wing where the side flanges make 11 Use slow drying epoxy to install the two hardwood dowels into the front of the wing First trial fit the dowels into the holes without glue to make sure they can be pushed in far enough You want to end up with about 1 2 of dowel remaining exposed in front of the plywood former Take the dowels back out and apply plenty of epoxy glue inside the two holes S...

Page 8: ...e servo output arms on the output shaft to exactly 90O upright when the servos are neutral c Test the action of the servos making sure the output arms move freely and that they move in the correct directions for left and right aileron action d Turn off the radio system and disconnect the aileron servos from the Y harness 18 Locate one left and one right metal control horn and eight M2 6 x 10mm Met...

Page 9: ...er engine installations will be similar 1 You need to purchase a suitable engine mount not supplied to fit your particular engine and the appropriate mounting bolts blind nuts not supplied to attach the mount to the firewall A wide variety of after market engine mounts are available Many of them are one piece and sized to fit a particular engine We recommend that you choose aluminum mounts for eng...

Page 10: ...he front of the firewall carefully aligning it with the horizontal and vertical thrust lines Mark the mount s bolt hole locations on the firewall with a pencil Drill holes completely through the firewall at those locations for the mounting bolts Finally bolt the engine mounts in place being sure to glue the blind nuts into the back of the firewall 3 With the engine mount bolted on the firewall pla...

Page 11: ...2 CYCLE GASOLINE ENGINES Gasoline engines like the FPE 2 4 pictured here fit best in the SUKHOI when mounted inverted You will need to purchase mounting bolts and blind nuts to fit your particular engine installation 1 The FPE 2 4 gas engine measures 5 from the prop drive washer to the back of the engine mount while the SUKHOI is designed with a firewall to prop washer distance of 6 Consequently y...

Page 12: ...back edge of the cowling uncovered for the next step NOTE The SUKHOI has lots of room inside the cowling and the engines that we have used fit completely inside except for the muffler pipes and the spark plug of the FPE 2 4 gas engine 3 With the cowl securely taped in place use a 3 64 or 56 dia bit to drill pilot holes in the fuselage centered in each of the four pre drilled holes in the cowl Moun...

Page 13: ... the bottom of the SUKHOI cowling to allow engine cooling air to properly flow through and exit the cowl Cooling a fully cowled engine is not difficult although many modelers have trouble doing it It s relatively simple if you follow one basic rule Simply stated the total square inches of area you have for air exit must be equal to or slightly more than the square inches of area you have in the fr...

Page 14: ... fin Let dry 8 Trial fit the fin in place on the fuselage The bottom of the fin should rest on the high point of the stabilizer a View and measure the alignment of the stabilizer to the entire airplane from several different angles Make sure that the fin is absolutely 90O upright on the fuselage and that it is aligned straight with the centerline of the fuselage not turned left or right 3 Next bol...

Page 15: ...n and eight M2 6 x 10mm Metal Screws Hold one of the control horns in position on the bottom leading edge of the appropriate elevator The horn should be as far forward as possible so that the holes in the horn line up directly over the stab elevator hinge line Also be sure the control horn lines up with the elevator servo output arm Mark the horn s hole locations on the elevator with a fine point ...

Page 16: ...eutral position Attach the solder link ends of the elevator pushrods to the servo output arms Adjust the threaded R C links to fit into the middle hole of each elevator horn Remove the tape holding the elevators in neutral and test the movement of the elevators with your radio Adjust as required to get both elevators exactly at neutral if you are using the Miracle Y splitter chord you can turn the...

Page 17: ...f masking tape hold the clear canopy tight against the base and fuselage while the glue dries b With the rudder and tailwheel both in neutral position apply a small amount of tension to the spring and use the pliers to make a 90O bend at the tailwheel steering arm hole Insert the wire into the steering arm and make another 90O bend back toward the center of the spring forming a loop Do the same fo...

Page 18: ...ed to its characteristics you will likely change the control throws to suit your style of flying But you have to start somewhere and this is where you begin These movements provide the SUKHOI with very smooth control inputs without the immediate need for exponential We suggest starting out with these movements as your low and high rates You can easily play with more control throw after you become ...

Page 19: ...ur style We therefore suggest that you begin with the 27 CG location and experiment from there you have had time to shift it around into exact position Once you have it in position squeegee the excess soapy water out from under the decal Mop up the water with a dry cloth Squeegee repeatedly to get as much of the water out from under the decal as possible After setting overnight the decal will be s...

Page 20: ...ing the model this imbalance can cause the model to pull to the heavy side especially in loops and up line maneuvers To make the airplane track true the light wing panel needs weight at the tip to balance it level with the other panel Again this can be done with stick on weights which could later be hidden inside the wingtip If you need to move your balance point fore or aft slightly the first met...

Page 21: ...nput You will also discover that your SUKHOI has outstanding inverted flight characteristics Our prototypes require only the smallest amount of down elevator to maintain level inverted flight Assuming you re comfortable and getting used to the airplane take it to a safe altitude and throttle back to get a feel for the slow flight and stall characteristics Properly balanced and trimmed your SUKHOI ...

Page 22: ...22 SUKHOI SU 31 LOG BOOK Engine Prop Flying Weight Wing Loading Balance Point Aileron Travel Elevator Travel Rudder Travel Date of first flight ...

Page 23: ...23 ...

Page 24: ...ing the most power at a reasonable cost First Place Engines are your best choice for large gasoline powered model airplane power plants All engines use piston and cylinder assemblies from world renowned manufacturers such as Husqvarna and Sachs Makita insuring long life and easy operation Using state of the art CNC machines First Place produces all other major components from high quality billet a...

Page 25: ... 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 ...

Page 26: ...The color and markings of this ARF kit do not duplicate one particular full scale Sukhoi SU 31 Rather they are a realistic selection of markings typically seen on many full scale aerobatic airplanes 26 ...

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