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SIG SUKHOI SU-31 ARF, Assembly Manual, Page: 16 / 26

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SIG SUKHOI SU-31 ARF Assembly Manual Download Page 16

16

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17) Mount the T-shaped Metal Rudder Horn onto the bottom of

the rudder with two M2 x 9mm PWA Screws, as shown here.

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18) Hinge the rudder to the fin with epoxy glue. Clean off any

excess glue and allow to dry.

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19) Locate a 4-40 x 4-5/8" threaded pushrod for the rudder, plus

a 4-40 solder link, a 4-40 threaded R/C link and a 4-40 hex nut.
Solder the solder link onto the unthreaded end of the pushrod.
Thread the hex nut onto the threaded end, followed by the R/C link.
Use your radio to center the rudder servo and then mount the
servo output arm in place at 90° to the servo body. Tape the 
rudder to the fin in neutral position. Attach the solder link end of
the rudder pushrod to the servo output arm. Adjust the threaded
R/C link to fit into the middle hole of the rudder horn. Remove the
tape holding the rudder in neutral and test the movement of the
rudder with your radio. Final rudder throw adjustment and locking
the R/C links in place with the hex nuts will be made later.

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20) The two Coiled Steering Springs can now be installed 

on the tailwheel, connecting the tailwheel's steering arm to the 
T-shaped metal horn mounted on the bottom of the rudder.

a. Use needle nose pliers to bend loops in one end of each

spring to hook into the holes of the T-shaped rudder horn.

threads will be much stronger. Use Thin CA only, not medium or
thick CA. Let the Thin CA dry completely before remounting the
control horns onto the elevators.

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14) Locate the two 4-40 x 2-3/4" threaded pushrods for the 

elevator, plus two 4-40 solder links, two 4-40 threaded R/C links
and two 4-40 hex nuts. Make two elevator pushrod assemblies by
soldering a solder link onto the unthreaded ends of the pushrods.
Thread a hex nut onto the threaded ends, followed by an R/C link.
Use your radio to center the elevator servos and then mount the
servo output arms in place at 90° to the servo body. Tape the 
elevators to the stabilizer in neutral 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 pot adjustment 
screw to achieve exact neutral very easily). Final elevator throw 
adjustments and locking the R/C links in place with the hex nuts
will be made later.

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15) Mount the rudder servo 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 screwing the
servo in place.

IMPORTANT: After the initial mounting, remove the rudder servo
and flow some thin CA into the screw holes in the plywood to
toughen up the holes. When dry, screw the servo back in place.

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16) Locate one left Metal Control Horn and four M2.6 x 10mm

Metal Screws. Mount the control horn on the right side of the 
rudder, about 3/8” up from the bottom, as shown in the photos.
Notice that the control horn should be as far forward as possible,
up against the front edge of the rudder, so that the pivot holes in
the control horn line up with the hinge line. Mark the mounting hole
locations on the rudder with a fine-point pen. Drill a 3/64” dia. (or
#56 drill) pilot hole for each screw. Then screw the horn in place.

IMPORTANT: After mounting the control horn for the first time,
take it back off and flow some thin CA into the screw holes in the
rudder. The Thin CA will soak into the wood and toughen up the
threads. Let the Thin CA dry completely before remounting the
control horn onto the rudder.

IMPORTANT SAFETY ISSUE: You may have noticed in the
last picture that we installed a short length of fuel line tubing
over each R/C link, as insurance against the link popping
open and coming off in flight. It’s a good idea to do this to all
the R/C links you use in all of your models.

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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