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SIG SUKHOI SU-31 ARF, Assembly Manual, Page: 11 / 26

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SIG SUKHOI SU-31 ARF Assembly Manual Download Page 11

11

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4) The throttle pushrod is a standard 2-56 size steel R/C rod

(not supplied). On the threaded end of the pushrod we used a 
Du-Bro #367 Swivel Ball Link (not supplied) to connect to the
carb's throttle arm. At the servo end of the pushrod we used the
brass pushrod connector assembly that is provided in this kit.
Assemble it to the servo arm as shown in the drawing. Plug the
throttle servo into your radio system and test the action of the
throttle setup, checking for proper movement. Make sure there is
no binding.

NOTE: The carburetors on gas engines are notorious for having
a short amount of "travel", requiring limited servo movement. You
will probably find it best to mount the brass pushrod connector in
the innermost hole of the throttle servo arm.

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5) Drill a small hole in the fuselage former right in back of the

throttle servo to pass the servo chord into the radio compartment.

FUEL TANK AND HATCH
VERY IMPORTANT!  The fuel tank parts provided in this kit are
intended for use with glow engine installations. If you are using a
gas engine, you will need to substitute a gasoline compatible fuel
tank stopper (such as Du-Bro #400 Gas Stopper) and gasoline
compatible fuel tubing (such as Du-Bro #800 Tygon Fuel Tubing)
for those items supplied in this kit. The fuel tank bottle itself is
gasoline compatible.

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8) From the firewall, insert the bare end of the steel cable

through the nylon tube. When you get it all the way in, insert the
end of the cable into the pushrod connector on the servo. At the
other end, connect the solder link to your engine's throttle arm.
Finally cut the cable to length inside the fuselage, leaving about 1"
of extra length behind the brass pushrod connector. The extra
length will be useful when setting up the throttle travel limits later
on.

GENERAL GUIDELINES ON THE INSTALLATION OF

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.

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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 you will have to put a 1" thick spacer (not supplied)
between the firewall and the back of the FPE engine to achieve the
proper 6" total distance. SIG has a set of laser-cut 1/4" thick 
plywood spacers specifically for the FPE 2.4.

They are part

#SIGSH802 (2 spacers per package, so you will need 2 packages
to achieve 1" total spacers). You will also need 10-32 x 1-1/2"
mounting bolts & blind nuts (not supplied).

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2) Position one of the plywood spacers on the front of the 

firewall, carefully aligning it with the horizontal and vertical thrust
lines. Mark the mounting bolt hole locations on the firewall with a
pencil and then drill the holes completely through the firewall. Bolt
the engine and spacers onto the firewall and glue the blind nuts in
place.

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3) A pre-cut plywood servo tray is provided for mounting the

throttle servo. Decide on the best location for the tray based on
the location of your engine's throttle arm. Note that the location
and direction of movement of the throttle arm on a gas engine
varies tremendously from engine to engine. So it is not possible
for us to show you a "best" method for all gas engines. We can
only show you what worked well with the FPE gas engine we used.

With the FPE 2.4 gas engine, we found it easiest to mount the
throttle servo right behind the bottom of the firewall - see photos.
It's actually a very simple trouble-free arrangement.

Glue the

plywood servo tray in place at an angle that will provide a straight
shot from the servo arm to the carb's throttle arm. Mount the 
throttle servo in the tray using the grommets and mounting screws
supplied with your radio system.

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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