RCU Review: Great Planes Reactor Biplane .61 GP/EP

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    Contributed by: Mike Buzzeo | Published: September 2009 | Views: 54590 | email icon Email this Article | PDFpdf icon
    RCUniverse.com Review of The Great Planes Reactor Biplane
    Mike Buzzeo

    Email Me

    Great Planes
    Model Distributors

    2904 Research Road
    Champaign, IL 61826

    • Pre-Hinged Ailerons
    • Sturdy, lightweight Construction
    • Superior MonoKote® Finish
    • Excellent Flight Characteristics
    • Balancing Jig Included

    • A few minor mistakes in the manual.

    Skill Level:

    Time Required to Build:

    Frustration Level:

    What do these ratings mean?

    A few years ago, the release of the Great Planes "Reactor" made the 3D world stand up and take notice. When the requests for a biplane version started to pour in, Great Planes listened.

    The new Reactor Biplane has a 48" span, semi-symmetrical airfoil and can be powered with a 61 2-stroke, 70 - 91 4-stroke, or a RimFire 80 motor with a 60a ESC.

    It requires 7 mini servos, although there is a nice template included if you want to enlarge the rear mounts for standard-size servos and the wings can accept standard-size servos as well.

    It looks like Great Planes really did their homework on this one. Let's dig in!

    Name: Great Planes Reactor Bipe GP/EP Sport 3D ARF
    Price: $299.97
    Wingspan: 48" (1220mm)
    Wing Area: 1145 in² (73.9dm²)
    Length: 58.5" (1485 mm)
    Flying Weight (advertised): 7-7.5 lb (3170-3400 g)
    Flying Weight: (actual) 7 lb (3170 g)
    Wing Loading: 14-15 oz/ft² (43-46 g/dm²)
    Airfoil: Semi symmetrical
    Center of Gravity: 5.25" (133mm) from the leading edge of the middle of the top wing

    Radio Used:Futaba 6EX FASST
    Servos Used:Futaba S9650 (3) - Futaba S3102 Mini (4) - Futaba S9001(1)
    Engine Used:O.S. 61FX
    Channels Used: 4 total - Elevator, Aileron, Rudder, Throttle
    Prop Used: APC 14x4

    Control Throws:

    Items Needed To Complete

    • 4 Channel Radio (Minimum) w/ 7 mini servos, 1 standard servo for throttle if using glow engine (cutouts in fuselage for elevator and rudder servos can be enlarged to accept standard size servos)
    • Aileron Servo Extensions: Four 6" (152mm), One 12" (305mm) Three dual servo connectors
    • Elevator and Rudder Servo Extensions: Three 24" (609mm)
    • Engine: .61 cu in (10cc) 2-stroke OR .70-.91 cu in (11.5-15.0cc) 4-stroke OR Electric Motor: RimFire .80 (50-55-500kV) with Silver Series 60A ESC and 11.1V 3200mAh (3S) 20C LiPo Battery
    • Thin and Medium CA Glue
    • 30-min Epoxy
    • Various Standard Shop Tools

    The packaging was really outstanding. The box was good and sturdy, and I couldn't help but notice that the compartment under the wings was extremely organized.

    Construction was excellent and I was happy to see the fiberglass landing gear that I have become familiar with on some of the newer Great Planes ARFs. These gear are very strong and they look great!

    A few other things that stood out are that the covering has already been removed from the stab and servo openings and the ailerons are pre-hinged.


    For the most part, the manual was up to the usual excellent standards expected from Great Planes; however I did notice a few mistakes and omissions. Under "Aileron Servo Wires" in the "Radio/Servo Recommendations" section, they list servo wires by inches and millimeters, but the conversions are wrong (6" is not 300mm and 12" is not 600mm). Also the manual neglects to mention that a hole must be drilled in the fiberglass wing support for the servo wires.


    We start out by making sure the covering is well adhered, especially around the servo and stab openings.

    Now the three rear servos can be installed. Be sure to apply THIN CA to any screw holes throughout the entire build! This can get to be redundant at times, but it is necessary to ensure that these holes will hold up!

    Not only is the covering removed from the stab opening in the fuse, it has also been removed from the center of the stab (another time saver!). The stab is now epoxied in place and aligned.

    Once the epoxy had fully cured, I added the CA hinges with pins to center them.

    The elevators are slid onto the hinges, pins removed and (making sure that the control surfaces will move the required 2 1/2") Thin CA is applied to both top and bottom of each hinge.

    The rudder is attached in the same manner with the addition of using epoxy to hold the tail wheel bracket. With the control surfaces attached, they can now get control horns added.

    You must measure and cut the 4-40 pushrods to length and solder a clevis to the non-threaded end. I used long servo arms on all three servos.


    The landing gear is the newer type which I have seen on Great Planes models and I really like them. They are made of solid fiberglass, they are very strong, and they look great! They are also practically effortless to install.


    Mounting the engine begins by removing the excess from the engine mounts and then bolting the mounts to the firewall with 8-32 cap screws into the pre-installed blind nuts. The mount allows for some adjustment to accommodate a variety of engines.

    With the engine in place, I used my Great Planes Dead Center Tool to locate the holes, then I removed the mounts, drilled and tapped them.

    I am using an O.S. 61FX for power. I debated which way to mount the engine and how the muffler would work out and I decided to go with a side mount and Pitts muffler.

    OS 61FX Closer Look
    O.S. 61FX

    The state-of-the-art in sport/competition engines!

    • All FX engines come with remote needle valve - the feature most asked for!

    • A longer crankshaft provides more secure attachment for spinner, prop and nut

    • Dual ball bearing construction adds durability and longevity

    • Semi-square head shape creates more fin area to increase cooling capacity
    • Each engine comes with a high-performance carburetor and muffler with adjustable exhaust direction and built-in pressure tap

    • 61FX and 91FX feature a remote needle valve that can be positioned two ways, to help you avoid cowl modification and preserve your plane's scale lines; 61 FX remote needle can be mounted three ways
    • Bore: 0.945"
    • Stroke: 0.866"
    • Displacement: 0.607 cubic inch
    • Power Output: 1.90 @ 16,000 rpm
    • Practical RPM Range: 2,000-17,000 rpm
    • Weight: 19.4 oz
    • Sport Prop: 12x6, 12x7, 12x8, 13x6, 13x7
    O.S. 2-Year Warranty icon

    Download the manual in PDF format - Click here

    Two plywood rings are glued to the rear of the firewall before the tank is installed. To align the rings with the hole in the firewall, I rolled up a piece of waxed paper and inserted it through the rings. The tank is held in place by a rubber band which attaches itself to some hooks built into one of the fuse formers (Pretty cool!).

    Once the tank was in place, I got a little creative with the plumbing because I wanted to use one of the new DuBro fuelers, but I also wanted to mount it in the fuse so it would not hinder cowl removal.


    I made some cardboard templates to locate the holes that would be needed in the cowl, then I used tape to locate the mounting holes. After the holes were drilled, thin plywood "donuts" are glued behind the holes to reinforce them.

    It was a little tricky getting the cowl over the Pitts Muffler, but I found that I could unscrew the muffler, place the exhaust through the bottom of the cowl, attach the cowl and then bolt the muffler in place. It was a little more work, but it made for a nice, clean installation.


    The aileron servo installation is a bit unconventional in that they have you drill the servo blocks and mount the servos before gluing the blocks in place. They also supply a set of smaller blocks in case you are using mini servos like the S3102s that I am using.

    Now the servo leads can be pulled through the wing with the installed pull string and the hatches screwed in place - and as always, hardening the screw holes with thin CA.

    Since the ailerons are already hinged, all that's left is to add the control horn, measure, cut and solder a link to the pushrods and hook everything up (and of course, do this three more times for the other ailerons).

    Next, you need to insert blind nuts into the strut tabs and epoxy the tabs into the bottom wing - immediately followed by attaching the struts and fully seating them.

    Once the epoxy has set, you can add the wing bolt plate.

    Two alignment dowels are glued into the top wing which will fit into the fiberglass wing brace, but the manual made no mention of the fact that you will need to drill a hole in the wing brace for the servo wires.

    The wing brace gets epoxied into the fuse, then four more strut tabs are inserted into the top wing, and the top wing is installed (making sure the tabs are fully seated).


    A tray is supplied for the throttle servo (for those of us using glow power) and due to the high current draw of the servos, I used a heavy-duty switch and a 2000MAh, 5-cell battery pack.

    The rear of the compartment was a perfect fit for the battery and receiver. Velcro is supplied for securing them and I glued two pieces of pushrod tubing at 90 degree angles for the antennas.


    They give you a template for marking the CG on the underside of the top wing and there is a nifty little jig that you assemble for doing the final balancing.

    I found that I needed to screw the jig down to a long board to keep it from tipping once the weight of the plane was on it, but it worked well. What really surprised me was that the Reactor balanced perfectly without having to change a thing!

    Time to add a few decals and bring her out of the basement!

    I maidened the Reactor Bipe at the Paynsville RCer's "Blue Sky Fun Fly". I got there early, so I pretty much had the sky to myself for a while. She tracked extremely well as she rode down the runway and lifted off effortlessly. I literally did not need a single click of trim anywhere, so I immediately started putting it through a few gentle maneuvers. It handled them VERY well, but I thought the low rates were a bit too slow for my liking, so I decided to land and increase the throws a bit.

    As I landed, I couldn't help but notice how easy it was to land. I remember thinking, "Was that a fluke, or did it really land that nicely?"

    With the ailerons cranked up a bit I was really enjoying it now! Loops, Cuban 8's, Hammerheads, etc were all excellent. There was a slight pitch to the belly in a Knife Edge, but noting I couldn't handle. When it came time to land again, I paid particular attention - Wow! I did about 5 or 6 touch-and-goes just to enjoy the fun of landing this plane. You just throttle back, turn to final and it will start to sink. Now add a little power to cross the threshold, pull the power back, pull some up elevator to drop the tail and she settles into a perfect 3-point landing every time!

    Now I turned the transmitter over to Paul Hollermann who, along with his brother Ross took first place in Team Airplane at XFC this year. Paul flew a few laps to get the feel for it, then he flipped on the high-rates and wrung her out! 3D performance is excellent and the roll rate is absolutely crazy! Paul's only "less than stellar" comment was that he would prefer a little more power, so I'm thinking an OS 91 Surpass, or better yet, the new OS 110 Surpass would be killer!

    Just a few days later, my friend Josh Moen blew into town from Denver. Josh is another outstanding 3D pilot, so I met him at the field and let him have his way with the Reactor. Same thing - Excellent performer, but Josh also wished for a little more "oomph" in the power department.

    Check out the video to see her in action!

    Great Planes Reactor Bipe ARF
    Or, Download the Video (35meg)

    Wow, I really like this little bipe! It is so smooth that it will make an average pilot look great. On regular rates, this thing is an aerobatic wiz and on 3-D rates, it's crazy! It's rock-solid, tracks very well and landings are my favorite part!

    You have the option of using mini or standard size servos and if you're not looking to fly 3-D, you could even use good standard servos.

    It builds easily and has no bad habits in the air. I am slightly awed by its performance. I remember what I thought the first time I landed it; quietly, under my breath, I said, "wow", not "WOW!", just a nice quiet,


    Great Planes Model Distributors
    2904 Research Rd.
    Champaign IL 61826
    Phone: (217) 398-8970

    Futaba Radios
    Distributed through Great Planes Model Distributors
    2904 Research Rd.
    Champaign IL 61826
    Phone: (217) 398-8970
    Website: www.futaba-rc.com

    O.S. Engines
    Distributed through Great Planes Model Distributors
    2904 Research Rd.
    Champaign IL 61826
    Phone: (217) 398-8970
    Website: www.osengines.com

    Everything For The R/C Hobbyist
    Phone: 1-800-848-9411
    Website: www.dubro.com

    APC Props
    Distributed by:
    Landing Products
    1222 Harter; Woodland, CA, 95776
    Website: www.apcprop.com
    Email: apcprop@aol.com

    Comments on RCU Review: Great Planes Reactor Biplane .61 GP/EP

    Posted by: RTLIKESRC on 09/22/2009
    Hi Mike, I am thinking Christmas gift to myself. What a super bibe from what I have read and seen on the video. This is a must for my hanger, thanks for the review. Happy Flying1 Ron
    Posted by: summerwind on 10/11/2009
    glad to see you were the one to do this review Mike. always the best detailed notes presented and the flying of course is what sells.............how about a YS 1.10-s in this puppy? mike
    Posted by: orangepeal on 12/07/2009

    Posted by: orangepeal on 12/07/2009
    Oops. Speaking of xmas presents, I have given my wife a choice to surprise me with either this or the Great Planes Skybolt ARF, to fly with a .91 4 stroke. Any opinions as to how this compares to the Skybolt (which is not a 3D machine). As far as sport and pattern flight, how do they compare?
    Posted by: MinnFlyer on 12/07/2009
    Summerwind, I think a YS 110 would be dynamite!
    Posted by: MinnFlyer on 12/07/2009
    Both are excellent (I have both) I would be hard-pressed to pick which one I like better!
    Posted by: hellblastervolly on 01/02/2010
    Wow Summerwind we keep thinking the same, from the small Reactor to the Bipe, plus I have a YS 110 for this plane. lol
    Posted by: SigMan on 06/21/2010
    i love it ! great review !
    Posted by: ameyam on 10/17/2010
    I read through the manual and your review too. The ailerons accept both standard and mini size servos. Is that correct?
    Posted by: MinnFlyer on 10/17/2010
    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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