RCU Review: Great Planes Sukhoi SU-31 3D ARF


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    Contributed by: Mike East | Published: November 2007 | Views: 84801 | email icon Email this Article | PDFpdf icon
    Great Planes Sukhoi

    Review by: Mike East Email Me
    Flight Pictures and Video by: Bob Scheppele






    Great Planes
    Model Manufacturing Company
    P.O. Box 9021
    Champaign, IL 61826-9021
    Phone: 520.722.0607
    www.greatplanes.com



    Windows Media Player
    Sukhoi SU-31 3D
    VIDEO



    • Quality lightweight construction
    • Absolutely beautiful looking plane
    • Ready for glow, gas or electric
    • Lighter than advertised


    • One piece wing construction.

    The Great Planes Model Manufacturing Company has been providing quality kits for years. With the advent of the ARF, they have stepped it up and begun to produce some really "Great Planes". The U CAN DO phenom that started about 5 years ago was the beginning of my experience with Great Planes 3D ARF's and the Sukhoi SU-31 3D is their newest answer to our prayers for the 1.60/43CC class 3D plane.

    First off they really have done a nice job with the covering scheme and the look of the plane is just exquisite. The aggressive lightning bolt scheme and choice of colors could not possibly be any better for my taste. I have not seen a better looking plane out there in this size, I really haven't.

    Rollin' Rollin' Rollin'

    As we proceed you will see nothing but quality everywhere you look. The engineers appear to have really put their best foot forward in the design and construction of this plane.

    I don't want to give it away too soon, so let's get started and have a closer look at this beauty.




    Name: Great Planes Sukhoi SU-31 3D ARF

    Price: $399.99

    Wingspan: 77 in (1950mm)

    Wing Area: 1155 sq in (74.5 sq dm)

    Length: 70 in (1780mm) with spinner

    Flying Weight (advertised): 13-15 lb (5900-6800 g)

    Flying Weight: (actual)12 pounds 11oz

    Engine: 2-stroke 1.6-1.8 or 4-stroke 1.8-2.1 glow or 32-43cc gasoline engine or 63-62-250 out-runner brushless motor, ESC and battery

    Engine Used: OS 1.60FX

    Battery Used: NoBS Batteries 1800mah 6V NiMH


    Radio Used: 9C with Futaba 7CH FASST 2.4GHz module and receiver

    Servos Used: Futaba 9350's

    Channels Used: 6 total - (2)Elevator, (2)Aileron, (1)Rudder, Standard Throttle Servo

    Props Used: APC Props 18x6 Wide


    Items Used To Complete

    • 6 Channel Radio (Minimum) w/ 6 high torque metal gear servos and 1 standard for the throttle
    • (6) Futaba 9350 servos or equivalent
    • (4) 1 1/4' or 1 1/2" servo arms depending on your preference.
    • (2) Minimum 2000mah servo/receiver battery pack.
    • (2) 24" Servo Extensions
    • (3) 36" Servo Extensions
    • (2) 6" Servo Extensions
    • CA Adhesives
    • 5 and 30-min Epoxy
    • Various Standard Shop Tools






    As is typical with Great Planes stuff, the plane comes shipped in a stout box that protects the airplane from dings during shipping. When you open the box you will find that the parts are well packaged so that there is no way that things can move around in the box and become damaged during shipping. My Sukhoi arrived in pristine condition.

    Upon first inspection it is apparent that this is a very well constructed airplane and that a lot of care went into the design and pre assembly. The kit is very complete and has all the hardware needed to get the airplane ready to fly.



    All of the typical essentials are included and as you can see, the package also contains some premium upgrades like aluminum double servo arms, Robart style hinges, lots of heat shrink, a very nice aluminum spinner WITH hardware and just a whole lot of good stuff.

    The provided tank comes with the hardware to make a 3 line setup so that you can fill the tank without spilling fuel out of the carb and all over the inside of the cowl.





    Do not be alarmed by this rather large stack of wood. When I first opened the box I actually freaked out just a little at the thought of all that wood going into the plane. However after just a few minutes of reading I found that only a small portion is actually part of the permanent installation. The large rings are to make a cowl centering jig and only a portion of the rest of it is used depending on whether you go glow, gas or electric.

    The provided pushrods are thick and solid. They should be more than plenty to handle the control surface loads on this plane. The connections will require silver soldering which is something that is new to me personally in RC, but I have a handy dandy propane torch on hand so all I need to do is go pick up a little silver solder and I should be ready to sweat these connections together when the time comes.





    Anyway, again one thing is for sure. This plane is intended to be the best looking plane at the field. The paint and Monokote work is just exquisite and should lend itself to making this airplane a showstopper on the ground and in the air.

    One of the things that I like a lot is the completeness of the landing gear assembly. All the holes are drilled and blind nuts pre installed right down to the wheel pants so getting the plane on its feet should be a really quick and easy process.



    Here are a few more shots of the covering and paint. Absolutely beautiful work.

    You can see on the pic of the rudder that I slipped the hinges in place to show what we will be working with. I love these type of hinges. They provide an extremely strong hinge and very smooth, free movement.

    Finally, the last pic is a shot of the connecting spar for the wing, later on we will have to glue it together before assembling. Its a solidly constructed aluminum and plywood construction that should create an incredibly strong union of the two wing halves. This plane seems a little bit large to have a 1 piece wing and I was very surprised when I could not find a wing tube in the box. I am certain that the flight characteristics of the plane are going to make it well worth the effort to find a way to get the wing in my Expedition. Lets get going!


    Manual

    Click on the pic above to go to the manual.

    This is a nice manual. There is a lot of versatility in the plywood parts package. Only select pieces will be used depending on what engine/motor you select so be sure to read carefully. You should find that the exact parts that you will need are included in the box. Just follow the step by step instructions and you should find this to be an easy plane to complete.

    Let's go check it out!



    WING ASSEMBLY





    This airplane has a 77" solid wing. We will need to hinge the ailerons and then we will put the wing together. You will need 30 minute epoxy or Gorilla glue for the Robart style hinge installation.

    The first thing we need to do is go ahead and glue the center spar together. The spar is made of two aluminum inner spars and two ply wood outer spars. Just rough them up a little then glue them together with 30 minute epoxy. Be sure to get it lined up nice and straight and clamp it in place while it dries.





    While the spar is drying we can start on the hinging. This is a fairly simple process and if you do it right it's clean and goes together very easily. First put 1 drop of oil right in the hinge and wipe away the excess being very careful not to get any in the shafts of the hinge.

    Then lightly coat the inside of the hole and one side of the hinge shaft with 30 minute epoxy. I like to first put the hinges into the aileron and have the wing propped up on its edge. Once you get the hinges in the aileron, quickly put a light coat of epoxy on the other half of the hinge and slide the hinges into the wing. As you slide them in use small pieces of a paper towel to wipe away the excess epoxy as it puddles at the base of the hinge. When the hinges are in tight use a little alcohol on a paper towel to carefully wipe the rest of the epoxy from the hinge line.

    Now tape the hinge line in place and let it set for about 15-20 minutes. Once the glue has pretty well set start to work the hinge to be sure that it will move. After the epoxy is dry, I like to drop 1 small drop of acetone right into the hinge to dissolve any epoxy that might be in the hinge. Be sure not to use too much and loosen the glue on the hinge shaft. Then 1 last drop of oil on the hinge and you are ready to go.





    I will be using Futaba 9350 servos in this airplane. This is a metal geared digital servo that is fast and puts out 139 oz at 6 volts. Since we need 6 volts for optimal performance, I will be using a 5 cell NiMH battery pack from NoBS Batteries to provide power to the system. That way regulators will not be necessary and we can plug the battery in directly to the system.

    I will also be using a Futaba TM7 FASST 2.4GHz module and receiver for this plane.





    Locate the servo opening under the covering and carefully remove the covering to expose the hole. The use the supplied heat shrink to secure a 9350 to a 24" servo extension. Use the supplied string that is inside the wing to pull the servo extension through the wing and into place.

    Next, screw the servo in place with the name tag facing the aileron. We will need to use a very long servo arm to be able to achieve the throw that is necessary for 3D flight. If you are new to 3D the set up may seem a little unusual, but the set up techniques that are used are necessary to get the right mechanical advantage at the right point in the servo's range of motion.

    There is a plywood hard point located in the aileron beneath the covering that is set up for this sort of geometry. If you hold the aileron up in the light you should be able to easily see the hard point. Use the provided screws to mount the control horn in the location that you just measured out.

    For 3D airplanes you need to mount the control horn about 3/8" out from the side of the servo case so that at full surface deflection the servo is at its maximum mechanical advantage. To find this location simply lay a ruler against the side of the servo case and mark the aileron with a pen. Then measure out from the mark in the aileron 3/8" and make another mark. This will be the center line of the control horn.

    What this does is set up the servo so that with a 1 1/4" or 1 1/2" arm you get max mechanical advantage at full deflection. To get the throw you need you are going to have to use an extra long servo arm as mentioned. When you do this you decrease the mechanical advantage of the servo and risk stripping gears. That is why it is necessary to go with a higher than normal torque, metal gear servo like the 9350 for a plane this size. On 35% and 40% planes we use servos that have 300-400oz of torque, but this is necessary if you want to have an adequate servo and keep your 3D plane in one piece.





    Now that the servos are mounted, we can finish assembly of the wing. I left the aileron control linkage incomplete on purpose and will cover that later in the review. We will now join the two wing halves together.

    First test fit the center spar and be sure that you get a good fit and the wings fit tightly together. If not then lightly sand the spar and or the root ribs so that the wings fit flush together.





    Once you get a good fit install the anti rotation pin using medium CA or Epoxy and we are ready to join the wings. Tape the servo extensions so that they are out of the way. Paint a light coat of 30 minute epoxy in the spar tube holes on each wing, the root rib on one half and finally put a light coat on the spar. Slide the spar into 1 wing and then the other and bring the wings together carefully. Now now push the wing halves together tightly and carefully wipe away any excess epoxy with an alcohol soaked paper towel. Ideally if you put just the right amount of Epoxy there should be virtually nothing to wipe away. Tape the wing halves together tightly and allow to dry. Epoxy the wing alignment pins in the front of the wing leaving 5/8" exposed and allow to dry.

    Finally, locate the wing bolt reinforcement ply. Mark out the location and remove the covering. Epoxy the reinforcement plate in place and carefully drill through to complete the installation. That's it, the wing looks great.



    TAIL FEATHERS





    This airplane has a permanently installed 1 piece stab. So for this airplane we will need to remove the covering over the hole in the fuse to receive the stab. First locate and carefully remove the covering so that you can slip the stab into place when the time comes.

    Next install the wing and level the plane upright. Then slide the stab into place and using the wingtips as a reference center the stab in the fuselage. Once you have the exact same distance on both sides from the wing tip to the stab tip, mark all the way around where the stab meets the fuselage with a Sharpie or ball point pen.

    Remove the stab from the fuselage and prepare to remove the covering where the glue joint will be made. This is done so that a wood to wood glue joint can be achieved for maximum strength.





    I like to use a fine tip soldering iron to cut the covering. You can do it with an Xacto knife, but you run the risk of cutting and weakening the balsa. Once the iron is hot, carefully go around the perimeter of you marks on the top and bottom of the stab.

    Now you can remove the covering just slightly inside the pen marks, maybe 1/16". That way when you glue it up there will be no exposed bare wood.

    Once you have the covering removed you are ready to install the stab.





    Slide the stabilizer into place using the marks that you made before as a centering guide. If you removed the covering correctly you should just be able to see the pen marks. Now that you are sure you have a good fit slide the stab either way about 1/2" to expose the bare wood. Once you get the stab into place, mix up some 30 minute epoxy and lightly brush on the epoxy around the stab and slide through the fuselage so that the bare wood is just barely visible on the other side. Now again lightly coat the wood with epoxy and slide into position.

    Once you get to this point it is very important that you don't move the stab around much as the glue will get all over everything. If you see that you need more epoxy just slightly move the stab out and carefully brush the epoxy on. You should only need about 5-10 minutes to get to this point so you should still have about 5 minutes working time with the epoxy. While the epoxy is still wet re check you measurements and be absolutely certain that the stab is centered on the wing. The cut out for the stab on my plane were perfect, but you should setup the plane so that you can step back about 10' or so and look at the stab to make certain that it is level with the wing.

    Once you are satisfied that the wing is in the right place and hopefully with at least 5 minutes before the epoxy starts to set, wipe the excess epoxy off of the stab and fuse with denatured or 91% rubbing alcohol. If you use the epoxy sparingly there should not be any running down the fuselage. Just get your paper towel wet with alcohol and wipe along the seam. If you can get all the epoxy off now, there will not be any haze on the covering and it should look perfect.





    The last step is to install the hinges. Just follow the same steps as we used to install the hinges in the ailerons. The gap should be < 2mm. If you can get the gap tight you really should not need to seal the hinges. That's it. Lets see about getting the plane on its feet now.



    TAIL WHEEL INSTALLATION





    I think that GP is really on to something with this little tail wheel design. I really like the simplicity and the fact that it is engineered so that it cannot get loose, or wobbly or come apart. Here is how it works.

    First thing you need to do is to install the bushing into the under side of the fuselage. Just remove the covering, coat the bushing with a little medium CA and press it into the hole. Just be sure you don't get any CA into the bushing.

    The next step is to mark and mount the little retaining bracket for the tail wheel into place. Temporarily put the tail wheel into place and mark the holes in the bracket. Drill and harden the holes then screw the bracket into place. .




    Now place the collar under the bracket and slip the tail wheel in. You will need to drill a small hole in the rudder at this time to mount the guide post as well.

    Now coat the rudder guide post with a little Medium CA, then slip the tail wheel assembly into place. Tighten the nut on the collar using a drop of blue thread locker to make sure it does not come loose. Since the guide bar between the rudder and tail wheel is rigid, the whole thing should be held securely in place by the guide post in the rudder and the collar on the tail wheel.

    That's it, the tail wheel is ready to roll.



    LANDING GEAR INSTALLATION




    The first picture is a look at the landing gear plate. This plate has a very solidly designed but light weight structure that should be ample to support the plane during the roughest of landings.

    The gear installation is very simple and only requires one measure, mark and cut operation and that is cutting the axles to length. All you have to to is test fit the assembly and mark the length of the axles so that they just clear the wheel pants. See pic below left.





    With that done you will need to mark and grind a flat on the shafts for the outer collar so that you can secure the collar permanently onto the axle.

    Once you have the shaft ready mount the wheel onto the shaft and use a little blue thread locker to secure the wheel collars in place.





    As you can see in the pics above, the wheel pants are pre cut and the mounting holes and blind nuts are ready to go. All we need to do is locate the 4 4-40 machine screws and washers and bolt the wheel pants on. Again, be sure to use thread locker to secure the assembly.

    Finally, locate the 6 6-32 socket head bolts and washers and bolt the landing gear onto the fuselage. Again, be sure to use your thread locker.

    The last step is to install the gear plate cover. Just dot the bottom of the cover with some silicon, press into place and allow to dry. That's it, it's a very simple but very nice landing gear setup.







    PULL PULL RUDDER INSTALLATION





    If you are going to use a glow engine you will install the rudder servos in the bay under the canopy to help achieve the proper balance point. If installing a Gas engine, the rudder servos will go in the tail. For this application we are going with the pull pull system.

    As you can see, this will require some work using the provided pull pull hardware. You will need to have a couple of large round servo arms to connect to the provided aluminum double arms. You will need to mark and CAREFULLY drill the plastic arms and bolt them to the aluminum arms. I used the numbers on the round servo arm as a reference to make sure that the servo arm are in the exact same position on each servo. This needs to be extremely accurately drilled if you want a bind free operation so take your time and try to drill the holes as perfect as possible. Mark and measure as many times as necessary to get the two aluminum arms in exactly the same spot on the plastic arms. If the two servo arm's are off in relationship to one another by as little as 1/32" or less, the servos will inevitably bind as they deflect and that equals increased battery consumption and more wear on the servo.

    Turn the radio system on and check to be sure that the two rudder servos are at dead center. Use the provided hardware to connect the two servos together as indicated in the pic above and to the right. The connecting arms should be on the inner most holes on the servo arm.





    Install the control horns on the rudder on the pre installed hard point. As with all the control horns, be sure to remove the screws and harden the holes with thin CA before the final installation.

    Tape the rudder so that it is in the center position and DO NOT move the rudder stick once you begin connecting the pull pull cables while the tape is installed. The tape will help to make sure that your cables are properly aligned and the rudder in correctly centered.

    You can see the linkage hardware above. It's a standard cable pull pull. You will just need to make up the end connections per the instructions. I like to start out with one end of the cables clevis adjusted to the middle of it's range and the other end out as far as it will go. That way if you end up with a little bit of slack in the cable you have room to tighten it up after you are done. Although the rear servo arm is not offset, the instructions call for the cables to be crossed to get a better angle to the control horn. Since the horn is not offset, there will be a good bit of slack in the non pulling cable as you approach full deflection. Not to worry, although this looks bad the slack cable will go tight the instant that you reverse the direction of the control input.





    Finally, in regard to the pull pull hardware, to me this would be a great place to upgrade the hardware. Although the hardware is of the highest quality and this system works fine once you get it all done, it is my opinion that the use of pre made double servo arms with an offset rear arm would be a lot easier to set up and give you a much better chance at having a bind free, slop free setup. This is true especially if you are inexperienced or not real good at making very precise measurements. If you are going to use the provided setup, it also helps to understand how to use those tiny numbers on the servo wheel. They can really help to make sure that the servo arms center locations are exactly the same and in the right place relative to one another. There are a lot of places that you can be off a little and things still work fine but a rigid double servo pull pull system is not one of them. Be sure to take your time and get it just right so that you get the most out of your servos.



    PUSHROD ASSEMBLY





    Since most of you are probably not used to soldering your pushrods together, nor am I, I though that I would go over it briefly. You will need to get yourself some silver solder. I got mine from Radio Shack. You will also probably need to use a torch unless you have a really hot soldering iron because you will need to heat up the pushrod and clevis to about 430 degrees to get the solder to flow.

    To make the joint, cut the pushrod to length and sand the end of the pushrod to be soldered to rough it up and clean the surface. Then set the clevis on the pushrod and carefully apply heat to the PUSHROD, NOT THE CLEVIS and allow the metal to slowly heat. Lay the solder in the yoke of the clevis and when it all reaches the right temp the solder should flow into the joint.

    The keys are to start with very clean metal, add the heat slowly and don't overheat the metal or put the fire right where you want the solder to go. Let the heat conduct up the pushrod about 1/2" into the joint. That way you don't char and dirty the joint. If you do the solder won't stick. Once you figure it out it's a piece of cake, but it's not as easy as soldering copper wire together so take your time and if you can, practice on scrap pushrod and clevises if you can. Now, let's put those pushrods to use.



    ELEVATOR AND AILERON SETUP





    The elevator and aileron setup went pretty quickly and was an easy process. The first thing I did was use the provided shrink wrap to secure the servo leads to the extensions.

    For this plane I used the Great Planes 2" Aluminum arms since Tower was out of the 1 1/2" versions. I simply snipped the ends off and left the 1 1/2" hole then rounded off the ends on my sander. These are neat arms because they have inserts for Futaba, Hitec and Airtronics servos. If you look at the pics above and below you can just see the letters on the inserts.

    For all the control surfaces I used the stout Futaba 9350 metal gear digital servo. At 6V this servo puts out 139 oz of torque. As mentioned before, with the long servo arms that are needed to get 3D throws you need powerful servos to make sure that there is enough holding power to do the job with the decreased mechanical advantage. Although there are adequate metal geared non digital servo alternatives like the Futaba S3305, if you skimp and go with plastic gears or the typical size servo for a sport plane of this size you are going to end up with stripped servos, poor performance and possibly flutter. So be sure and get a good stout metal geared servo, regardless of what manufacturer you use.




    Once you get the elevator servos installed turn on the radio system and set the trim and sub trims to "0". Even if you are using a reversing Y harness this is necessary to start.

    Now with the radio on and the servos centered up install the servo arms at 90 degrees to the servo or as close as you can get. Once you have the arms on, if necessary use the sub trim to get the servos at exactly 90 degrees. If you are not using separate elevator servo channels hopefully your servos match. If not, take your time and get them as close as you possibly can. Trust me it's worth the trouble.

    Now, measure out from the fuselage and mark the center locations of the elevator control horns. They should be exactly the same distance out. With the elevator halves taped at neutral the control horns should both be installed so that the holes in the horn are exactly of the center of the hinge line. This is also crucial for ease of setup and to get balanced deflection from the 2 elevator halves. Even very slight variances can make matching the elevator halves travel virtually impossible.





    Once you have the horns installed its time to connect the servo to the control horn. Make up your push rods to the correct length with the clevis in the middle of the threads so that there is room for adjustment to get the push rod length just right.

    Now, if you have done your homework this step should be easy. With the elevator half taped at the counter balance install the pushrod. Adjust the length of the pushrod so that when you connect to the control surface the servo does not bind of buzz. When both ends are connected and the servo remains silent,,, you are done. All you need to do is connect the other elevator half using the same process and the two halves should be perfectly match and have identical travel.





    Now for the ailerons. I have found that for my style of flying I almost never need to use aileron differential so for this plane I am going to use a simple Y Harness single channel aileron setup. Just connect the extensions to the servo lead and feed them though the holes in the wing and connect the Y Harness and use heat shrink to secure the Y harness to the extension. As you can see I pushed the excess wire from the harness back into the wing and taped the Y harness to the wing to keep things nice and neat.

    Now set the trims and sub trims in the radio to zero and with the radio on, connect the servos to the control horns using the same method as with the elevators. Once you have the two ailerons servos hooked up remove the tape and they should be perfectly centered and be ready to set up your rates. Of course if you want to use flaps or spoilers there is no reason that you cannot setup a dual aileron system provided that you have a computer radio and the channels available to do the job. .





    Just a couple of final details. As you can see in the top left pic I ran the elevator servo leads in the bracing above the turtle deck. The places them so that they can never get close to the pull pull cables and minimizes the potential for interference both physical and electrical. Since I am using 2.4GHz I actually wrapped the leads around the antenna tube since i will not be using it. Neener neener to all you 72MHz guys!!


    OS 1.60FX ENGINE INSTALLATION


    The OS 1.60 is a power and lightweight 2 stoke option for the plane. Weighing in at just over 30 oz, this is a great alternative to ensure excellent power and optimize the overall weight of the plane.

    Combined with the Bison Pitts style muffler, we will have a great looking, sounding and performing power plant that should really throw the plane around.

    As you can see, with such a large front end on the Sukhoi, there is ample room for the engine and muffler. It easily fits inside of the cowl.

    OS 1.60FX 2 Stroke Engine
    Go to the OS Website

    A CLOSER LOOK

    The 160FX is the largest in the popular FX line of aircraft engines, but still boasts many performance features in the traditional short, compact FX design that accommodates tight installations. This power plant comes with a remote needle that can be mounted three ways: vertical, horizontal, and separate from the engine. It's engineered for low fuel consumption, with a wide, wing-shaped exhaust port that contributes to higher torque at lower rpm.

    Key Features

    • Easy-adjusting Type 60F carburetor offers good throttle response.
    • Includes a 3/8-24 size safety lock nut and smaller prop nut to fit APC propellers.
    • Can be flown on FAI fuel as well as glow fuels with up to 25% nitro content
    • Included E-5010 silencer provides quiet flight

    Specs

    • Type: 2-Stroke
    • Displacement: 1.60 cu in (26 cc)
    • Bore: 1.32 in (33.6 mm)
    • Stroke: 1.16 in (29.6 mm)
    • Weight: 32.6 oz (925 g)
    • Practical RPM:
    • Stroke: 1.16 in (29.6 mm)
    • Output: 3.7 hp @ 9,000 rpm
    • Prop Range: 15x12 - 18x12
    • Fuel: From FAI fuel up to 25% Nitro.
    • Muffler Type: Standard muffler or Pitts Style





    Mounting the engine is a very simple process. The first step is to locate the mounting template for the 160 on the back page of the manual, cut it out and tape it onto the fire wall using the marks on the fire wall as a guide.

    Once you have the holes marked and drilled you will need to install the blind nuts into the back side of the fire wall. I use my handy dandy magnet to get it down in there and get it started on the bolt. Speaking of bolts, I upgraded all the motor mount bolts to Grade 8 8-32 Socket head bolts from Micro Fasteners. Just use the mounting bolts and a couple of washers to pull the blind nuts into place. The plane comes with the motor mount for the 1.60 or a similar engine so just bolt it on, mount the engine and you are ready to proceed to the next step.





    Once you have the engine mounted its time to install the throttle control system. I used a standard Futaba servo for this plane. Locate the provided hardware per the manual.

    As you can see this is a tricky throttle linkage installation that requires some accurate bends to get the throttle arm connected to the servo. As far as I can see, there is no way around this when using the 1.60FX due to the location of the carburetor.





    The instruction manual provides good guidance on how to go about it, you just need to mark and drill the firewall for the pushrod and then carefully bend the pushrod around the engine head to get to the throttle arm connected. With a little tinkering I was able to get good balanced throttle resolution despite the awkward route of the pushrod to the throttle arm.



    FUEL TANK INSTALLATION





    I really like this tank. It's a good size for the plane and comes with a 3 line clunk system. That means we can fuel up without spilling fuel out of the carb because you fill the tank on a separate line from the carb supply line. The tank even comes with a fuel dot. That's a very nice detail touch.

    The stopper and clunk setup should look like the above pic. The tank should sit on its side so that it is taller than it is wide therefore you will need to use the longest piece of aluminum tubing and make a long bend to get the vent tube to the top of the tank.

    Next I used CA to secure a piece of 1/4" foam onto the tank mount and set the provided zip ties into place.




    With that done slip the tank into place pushing it as far forward as possible. You might need to trim off the ends of the motor mount bolts to keep them from touching and possibly wearing holes in the tank. Once you get everything in the right location, zip tie the tank into place.

    Finally locate the tanks rear brace. Follow the instructions and install the brace per the instructions. There is another brace for a gasoline fuel tank so be sure and get the right part.

    As you can see in the last pic, the stopper is not quite all the way through the firewall, you should be able to tell if you don't have it far enough forward because the rear brace will not fit correctly if you don't. Once the rear brace is installed you are done. That's it! Moving right along.



    COWL INSTALLATION





    When I first opened the box and saw all of the big fat wooden disc's pictured above I almost closed the box and shipped it back to Great Planes thinking they had lost their ever lovin' minds. However, they knew what they were doing and what they had done was come up with a nifty jig to center the cowl. What you do is tack the discs together with the one with the small hole on the bottom and the smaller discs on top. They are easy to center, just use the outside diameter for the big discs and the center hole for the smaller ones.

    The next step is it glue the cowl mounting blocks to the fuselage. This is where I messed up on the first go because I lost focus and did not read the instructions correctly. When you measure for the mounting block locations be sure to mark to mount the blocks in between the fins on the outside of the cowl. I succeeded in mounting the blocks in the dead center of the cowl fins on the first try, then had to carefully Dremel them off and re mount in the proper location. Just pay attention and use the cowl as a guide. The paint and covering are perfectly aligned so it's easy to do.

    Once you get the blocks in place tape the cowl centering template onto the cowl then follow the simple instructions in the manual for using tape and lines to layout the location to drill the cowl mounting screw holes. Oh, you will need to enlarge the hole a little in the template to get it to fit the motor shaft.




    For the guide lines to find the right location to drill this entails is making a 5" line on the tape that ends in the center of the block. Then you slip the cowl on and tape it in place. Then you just use the reference line, measure out 5", make your mark and drill the holes!

    Now this is where I modified the cowl mount a little. I hate using screws because they always wear out on me. So with the cowl still taped in place I enlarged the holes all the way through the mounting blocks to accept 4-40 bolts and blind nuts.

    As you can see I installed blind nuts in the backside of the mounting blocks so that I can take the cowl off as many times as I want and the holes will never wear out on me.





    Here is what you end up with. This is a great fitting cowl with an exquisite paint job. One of the prettiest I have ever seen to be honest. You will need to cut the underside of the cowl for the Pitts muffler, the side for the glow plug and the topside for the carburetor needle adjustment.





    The hole looks massive, but later on you will see that the very large spinner that comes with the plane looks great and really finished off the great look of the nose of the plane.



    CANOPY INSTALLATION





    Here is a look at the canopy installation. The canopy is a pretty good fit and the front edge is molded so that it lays flat on top of the hatch which really improves the fit and ease of installation. To install the canopy the first thing you need to do bolt the hatch to the fuselage to ensure proper alignment. The instructions called for using a drop of CA to glue the hatch bolts to the washer, I like this idea and it works great. That way you will never lose the washer when you remove the canopy bolts. Just be sure not to get any CA on the threads. Next, fit the canopy on the hatch so that it is centered and fits flush all the way around. When you get the plane you will see that the back of the hatch sticks up a little too far above the turtle deck and almost looks like a bad fit, but it is not.

    All you have to do with the hatch bolted in place is lay the canopy down so that it touches the fuselage at the front and rear and is centered on the hatch. Once I had it where I wanted it I taped it down into place and marked the perimeter with a fine tip sharpie. You can remove the ink with alcohol later so don't worry about the mark. Once you get it marked you can mark, drill and install the 4 screws. If you look closely you can see that there are 4 plywood hard points in the visible portion of the cockpit that are there to screw into. If you don't use these hard points your screws will inevitably vibrate out. Once you get the holes drilled and screwed, remove the screws and harden the holes with a little thin CA.





    Once you get the holes hardened the canopy is ready for permanent installation. All you need to do is use a little canopy adhesive or the adhesive of your choice and screw the canopy down into place and let it set until the glue is dry.

    Once the glue is dry you can go over the edges with a little alcohol or CA debonder and remove the pen marks. Be sure to avoid dousing the seams with anything. Just just a paper towel very lightly wet with your remover and lightly wipe.

    That's all there is to it. Its a done deal.



    PROP AND SPINNER INSTALLATION





    One of the best features of this plane is the provided 4" Aluminum spinner and the adaptor hardware to fit the OS 1.60. Just find it and bolt it on. Its a great looking and very high quality piece of hardware. Nuff' said.

    For this plane and engine in 3D service I decided to go with th 18x6 wide APC prop. This prop should provide excellent torque and provide the kind of response we will need to get this plane to perform 3D with the best of them.



    FINAL ASSEMBLY





    Here are a few shots of the final assembly steps. As you can see, the battery pack helps to balance the plane right on the 5 11/16" recommended cg when mounted on the provided plate just behind the motor box. I am using an 1800mah 5 Cell NiMH pack from NoBS Batteries for this plane. I should be able to get 3 flights out of this pack pretty easily, but if for some reason I do not I may switch to a pack in the 2000-2400mah range.

    For the switch I am using a heavy duty switch from Tower Hobbies. It is a little larger than a standard switch and has heavier wiring as well.

    I will be using a Futaba FASST 2.4GHz radio system for this plane as well. I have been using these for a few months and I really like everything about them. They are reliable and the response is just great. I don't think I will ever go back to 72MHz.





    The above right pic is a shot if the gear compartment from beneath the canopy. There is plenty of room and having access from both the hatch side and the wing side is really handy.

    The last step for me in the assembly process was gluing the belly pan to the underside of the wing. As you can see I used my soldering iron to cut the covering and after I marked my cuts with the pan taped in place I removed the covering and glued the pan on with 6 minute epoxy. The pan is a perfect fit and it really finishes off the look of the plane. That's it! We are ready to setup the throws, charge the batteries, and go fly!












    Well what a pleasant surprise. I had a good feeling about this plane when I was putting it together and boy did it live up to my hopes.

    First off, I try not to pre judge a plane by its weight, but rarely does an ARF come out LESS than the advertised minimum. This one did, and by 5 ounces. The lower advertised weight is 13 pounds and mine came out at 12 pounds 11 ounces which for the OS 1.60FX is nothing. The engine throws the plane around like a rag doll. Vertical is just ridiculous and pullout from a hover is just great. All I could ask.

    I have not had much calm air to fly in but the gusty winds have been a really good testament to the stability of the plane at the recommended CG. I found that the plane tracks very well and handles pretty crisp and clean for a plane of this size. I did find that the rudder is incredibly responsive with the twin 9350's driving and I ended up reducing the high rate rudder throw by about 10 degrees after the first couple of flights.

    The plane snaps well from inverted, upright and from knife edge and is easy to stop provided that you don't overdo the rudder. A light touch on the rudder is all it takes to get the plane to snap properly.

    3D is just fine with this plane, it seemed to settle in nicely to a harrier and is easy to hover. Inverted and upright spins are magnificent, they really are. I love the way this plane winds into a blender. Rolling maneuvers are going to be as good as the pilot is capable of executing them. The plane rolls very axially and the high rate ailerons are just right for rolling harriers and can still control a torque roll.

    Overall, I would give the plane a B+ for 3D and an A- for IMAC type flying. It pretty much does about all you could possibly ask for a plane of this size with a 2 stroke glow engine. It's a blast to fly and most certainly worth adding to your hangar of Great Planes,,,, planes!



    Check out the video to see her in action!

    Sukhoi SU-31 3D
    Flight Video (14mb) CLICK HERE

    Sukhoi SU-31 3D
    Flight Video (30mb) CLICK HERE











    In summary I just want to say that I appreciate the opportunity to review this fine airplane. Everything that comes in the box for the SU-31 3D exhibits the highest quality and an obvious effort by Great Planes to provide us with the a well built, solid performing 3D aircraft at a reasonable price.

    Although there were a couple of "wish list" items that I would have liked to seen done differently like pre install the cowl mount blocks and provide pushrods that are already cut and threaded to length, overall I have no complaints and feel that from a construction point of view this plane is a very good value for $399.99

    From a pure performance perspective I think that the engineers at Great Planes have done an excellent job of providing a great looking, excellent performing aircraft that is more than capable of meeting the 3D needs of the most discriminating pilots. I say give it a try, I am certain that you will be pleased with the overall fun and performance that the Sukhoi SU-31 provides!




    Great Planes
    Model Manufacturing Company
    P.O. Box 9021
    Champaign, IL 61826-9021
    Phone: 520.722.0607
    Website: www.greatplanes.com



    NoBS Batteries
    57 Cedar St . Suite 6
    Babylon
    , NY 11702-2350
    Phone 631-610-5169

    Website: http://www.hangtimes.com



    Futaba Corporation of America
    Distributed By Great Planes Model Distributors

    P.O. Box 9021
    Champaign, IL 61826-9021

    Website: www.futaba-rc.com/


    Comments on RCU Review: Great Planes Sukhoi SU-31 3D ARF

    Posted by: greengoose on 01/27/2008

    Posted by: Kostas1 on 09/25/2009
    Very nice review! I like the way you installed blind nuts on the cowl mounting blocks! Neat..... Kostas Greece
    Page: 1
    The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.

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