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SIG SUKHOI SU-31 ARF, Assembly Manual, Page: 7 / 26

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SIG SUKHOI SU-31 ARF Assembly Manual Download Page 7

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14) Locate the two nylon wing bolts. Mount the wing in place

on the fuselage, using the nylon wing bolts. The nylon wing bolts
should pass freely through the holes in the wing and thread into 
the blind nuts that are pre-installed in the fuselage. If the wing
does not assemble cleanly and freely to the fuselage at this point,
you need to find the cause of any binding and fix it now, before 
proceeding.

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15) With the wing mounted to the fuselage, check the fit of the

1/8" thick plywood part WF-2. This part is to be glued to the 
trailing edge of the wing.

Before gluing, carefully remove the 

covering material in the area where WF-2 contacts the wing, so
that you will have a good wood-to-wood joint. Then glue WF-2
securely in place on the wing.

NOTE: In order to allow the wing to slide on and off easily, it's best
to have a slight gap (1/16" maximum) between WF-2 and the 
adjacent fuselage former. Tape or tack glue a piece of scrap 1/16"
thick wood or cardboard to the backside of WF-2 to serve as a
temporary spacer while you are gluing WF-2 to the wing.

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16) Set the molded plastic wing fairing in place on the bottom of

the wing to check the fit. The plastic fairing should contact the
wing surface and plywood formers WF-1 and WF-2. If WF-1 and
WF-2 are keeping the sides of the fairing from contacting the wing
surface, you may need to sand them down a little bit. When 
satisfied that the fit is good, put a bead of silicone adhesive on the
side flanges of the fairing that will contact the wing and on the
edges of plywood formers WF-1 and WF-2.

Carefully set the 

plastic fairing back in place. Tape it to the wing in a few places to
keep it from moving. Clean off any excess silicone that oozes out
by first scraping it off with a clean flat stick, and then wiping the
smears with a rag soaked in methanol or CA debonder. Let dry
thoroughly.

OPTIONAL: If you'd rather use glue instead of silicone adhesive
to hold the fairing to the wing, be sure to strip the covering 
material off the bottom of the wing where the side flanges make

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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. Smear some glue on the end
of the dowels and then re-insert them into the holes. Wipe off any
excess glue. Visually check to be sure the dowels are straight in
the wings and not at angles. Allow to dry.

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12) The wing can now fitted to the fuselage. First engage the

two dowels at the front of the wing into the two holes in the 
fuselage former.

If you cannot get both dowels into their 

respective holes at the same time, it may be that one of the holes
is just slightly off (left to right) due to a misalignment in the 
manufacturing process. If this is the case, it shouldn't be off very
much, and you should be able to correct it easily. Use a sharp 
#11 blade in your hobby knife to adjust ONE of the holes slightly
to the left or right to achieve a good fit. Once the wing dowels 
properly engage, press the rear of the wing in place into the wing
saddle and check the overall fit before proceeding.

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13) Locate the two 1/8" x 3/4" x 3/4" plywood wing bolt plates.

The wing bolt plates are already pre-drilled in the center to pass
the nylon wing bolts. Notice that there are also holes for the wing
bolts pre-drilled in the rear center section of each wing panel. Hold
one of the wing bolt plates in position on the BOTTOM of the wing,
aligning the hole in the plate with the bolt hole in the wing. Use a
pencil (or fine tip marker) to draw the outline of the plate onto 
the wing. Do the same for the other wing bolt plate, marking its
location on the bottom of the other wing. Use a hobby knife to 

remove the covering material on the wing, about 1/16" inside the
wing bolt plate outlines. CAUTION: Be careful not to cut through
the balsa wing sheeting!  Then glue the wing bolt plates to the
wing with CA glue, carefully aligning the bolt holes. Make sure
there is no excess glue inside the holes and let dry.

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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