GREAT PLANES SUPER STEARMAN 1.20 ARF
by Dick Slutz
Aircraft Type: Classic Biplane
Mfg. By: Great Planes Model Mfg. Co., Inc., P.O. Box 9021, Champaign, Illinois 61822, (800) 682-8948, www.greatplanes.com
Expected Street Price: $379.99
Available From: Both Mfg. & Retail
Wingspan: 71.5 Inches
Wing Chord: 11 Inches
Total Wing Area:
1466 Sq. In.
Fuselage Length: 57 Inches
Stabilizer Span: 29 Inches
Total Stab Area: 290 Sq. In.
Mfg. Rec. Engine: 1.20 4-stroke
Rec. Fuel Tank Size: 24 Oz. (Supplied with Kit)
Rec. No. of Channels: 4
Rec. Control Functions: Rud., Elev., Throt., Ail.
Basic Materials Used In Construction:
Fuselage: Balsa, Ply, Fiberglass, Plastic
Wing: Balsa & Ply
Tail Surfaces: Balsa
Building Instructions on Plan Sheets: NA
Instruction Manual: Yes (40 pages)
Const. Photos/Illus.: Yes
Radio Used: JR 8103, 5 Hitec 605BB Servos
Engine Used: Zenoah G-26
Fuel Tank Used: 24 Oz. (Supplied with Kit)
Weight, Ready to Fly: 242 Oz. (15 Lbs. 2 Oz.)
Wing Loading: 23 Oz./Sq. Ft. (approx. equiv. to 28 Oz./Sq. Ft. in a Monoplane)
WE LIKED THE: Instruction manual is excellent, profusely illustrated; everything fit perfectly; plane flies very well.
WE DIDN'T LIKE THE: Wrinkled covering, very hard to remove wrinkles from wing, and the wrinkles return after a period of time.
Be there a model builder with soul so dead, who to himself has not said, "I wish I had a model of a Stearman."
Well Great Planes has fulfilled those wishes with a beautiful rendition of an air show style Stearman. Having seen the pre-introduction photos of this model, my first stop at the Toledo Show was to the Great Planes display to see the Stearman. I was not disappointed.
The Stearman "Kaydet" was designed around 1925, and it was destined to become the Army Air Forces principal Primary trainer before and during WWII. The Boeing Company acquired Stearman in 1938 and manufactured the majority of the 10,000 or so produced. The Military designation for the "Stearman" was PT-13, PT-17, or PT-18 depending on the engine used. After the war, many of the ex-military Stearmans were converted to airshow use and, of course, the airshow pilots wanted more performance.
The resulting Super Stearman, as modeled by this kit, is usually powered by a 450 h.p. Pratt and Whitney radial, has wheel pants, top ailerons and flying and landing wires. There is even a Stearman with a jet engine mounted under the fuselage. There are five paragraphs of inter-esting facts and historical notes about the full-scale Stearman scattered through the instruction book. Very nice touch!
My kit arrived in a box 47" x 15-l/4" x 12", with no external or internal damage. The outside of the box has 14 detailed photos of the model which can be used to detail the "ship" after final assembly. All parts in the box are plastic wrapped and there are numerous cardboard separators in the box to prevent component movement and subsequent damage. The heavier items, such as landing gear, cabane struts and "N" struts are all taped to the bottom and did not move. Removing the plastic bags revealed an absolutely beautiful job of decorating the model with all stripes carefully aligned, and flawless paint on the cowl, wheel pants, and the wing struts. Unfortunately, the MonoKote covering was severely wrinkled at the corners of all four ailerons, the area just above the wing seats on the fuselage, and the corners of the stabilizer and fin. It was moderately wrinkled everywhere.
The kit includes this neat plywood weight box to hold the 18 oz. of nose weight required to balance the Stearman when using a 1.20 4-stroke engine.
The author elected to use a heavier gas engine in place of the 1.20 and the added weight. This plywood plate was fabricated to act as a spacer/mount for the Zenoah G-26.
The construction of the landing gear assembly, "N" struts, and cabane struts is, in my experience, a "first." They are all encapsulated in fiberglass fairings of the proper shape, not just flat pieces of metal or wire. The landing gear legs and cuffs fit the fuselage curvature perfectly (more about this later). The paint on all the glass parts is also flawless. Those of you who have built biplanes and had to make the cabane struts or "N" struts know what a tedious task it is to make them look right. The struts and particularly the landing gear fairings and cabanes that come with this Stearman are outstanding!
The supplied American hardware is so complete that I did not have to purchase any odds and ends to complete the model. The instruction manual is 40 pages of American English profusely illustrated with 164 photos, numerous line drawings, and builders' tips. As usual, Great Planes has done an excellent job with the instruction book. Read it twice before beginning assembly!! Assembly begins by making a decision whether to use two or four servos in the wings. I chose to only use two wing servos. To facilitate this option, the kit comes with two aileron connector links which are lengths of plastic-coated wood, airfoil shaped, with a 4-40 stud sticking out of each end.
The G-26 installation is simple and neat. The kill switch and choke rod exit through the cooling area at the rear of the cowl.
There is plenty of room for the radio components in the cavernous fuselage.
By following the steps, as outlined in the manual, assembly proceeds in an orderly and logical sequence. Great Planes warns that when using the recommended O.S. 1.20 4-stroke, 18 oz. of weight in the nose is required, and as part of the kit, they supply a laser-cut plywood box that mounts on top of the engine to hold the weight in place. Now I'm sure the 1.20 4-stroke would work very well in the Super Stearman, but that 18 oz. of dead weight gave me the opportunity to use a Zenoah G-26 instead. The G-26 puts out about the same power as the O.S. 1.20-FS but weighs 21 oz. more which eliminates the dead weight necessary to balance the airplane while providing all the benefits of gas power instead of glow. The firewall on the Stearman is very well engineered and appears more than strong enough to support a gas engine. Adapting the G-26 is simply a matter of mounting a 3/4" plywood adapter plate to the existing firewall using the factory-installed blind nuts and bolts. The 3/4" dimension of the plywood is dictated by the 6-l/4" distance to the front edge of the cowl as per the instructions. The throttle linkage and fuel lines are no problem due to the spacious interior of the fuselage. Servos are installed as per the instruction manual, and the receiver and battery pack are approximately 1" further back, but still mounted as per instructions. With all components installed, my Stearman balanced right on the recommended Center of Gravity, which is located 5-l/2" back from the leading edge of the top wing.
There are 14 blind nuts that are factory installed under the covering to facilitate mounting the wings and their location is clearly spelled out in the instruction book. All 14 attaching screws install easily with the cabanes and "N" struts lining up perfectly. The wing retaining bolts at the trailing edge of the lower wing and the nylon front alignment pins also fit with no modification or enlargement needed.
The dummy engine is provided in the kit. Only the spark plug and exhaust pipes of the G-26 protrude through the cowl. Cooling has not been a problem.
The fact that the empennage is a built-up structure covered with MonoKote indicates the effort Great Planes made to reduce the amount of nose weight needed. The landing gear struts and upper fairing cuffs fit the fuselage so perfectly that there is no space between the fairing and the fuselage structure, a beautiful piece of work.
I am an average flier operating off a grass field and my landings are not always grease jobs. Having said that, I felt that a small amount of clearance between the landing gear fairings and the fuselage side would prevent damage to the fuselage when the landing gear flexed on a less than perfect touchdown. To accomplish this required a 1/4" piece of plywood drilled to match the holes in the landing gear and installed between the aluminum gear and the factory-installed block with the blind nuts. This only makes a gap of approximately 3/32" due to the compound curves of the fuselage and landing gear fairing. The resultant space is hardly noticeable.
The plastic parts, windscreens and turtledeck all have well-defined cut marks, making trimming to shape easy.
Another unique idea is a carrying handle built from laser-cut plywood that bolts to the cabane struts and doubles as a stable platform when working on the model, upside down. The kit includes a decal sheet with two instrument panels and hundreds of simulated rivets, which really make the model come alive. I modified the technique used to install the simulated flying wires to allow them to be removed from the fuselage when maintenance is being performed. Start by drilling the hole in the fuselage as per the instruction manual but instead of gluing the elastic thread in the hole, install Du-Bro Rigging Couplers, Part #201 (2-56) or #618 (4-40) in the eight holes. These are the threaded studs with a hole at 90 degrees to the thread used in pull-pull control cable hook-up. A pin can be bent through the hole or a fishing leader clip-on used, with the elastic thread tied to the bent pin or fishing leader clip. When it becomes necessary to remove the wing, dis-connect the elastic thread at the fuselage connection. It is not necessary to cut the elastic thread.
As mentioned before, the covering had many wrinkles when the kit was unpacked. I left all the wrinkles as they were when the model was unpacked. This was an attempt to let the airframe acclimate to the humidity in a normally heated house on the East Coast. After two weeks, during which the model was assembled, the wrinkled areas had not changed (time to chase wrinkles). All four ailerons had severe wrinkles at the inboard corners at the trailing edge which required extreme heat to remove. This is how I know the color of the covering on the model and the MonoKote available from hobby shops is an exact match. The wrinkled areas at the stabilizer, rudder and fin tips did not require as much heat. There were several long wrinkles in the area just above the fuselage to wing juncture that did respond to gentle heat from the tip of the sealing iron. Even after approximately two months in the East Coast environment of high and low heat and humidity, minor wrinkles frequently reappear and then promptly flee when approached with a hot iron.
With the factory-supplied pilots, simulated rivets, beautifully shaped "N" struts, cabanes, headrest, wind screens, the landing gear fairings, and wheel pants installed, this is one gorgeous Stearman replica.
I set the C.G. and control travels in accordance with the instructions. My preference is to fly with high rates but using 25% exponential to simulate low rates for the first half of the stick movement -- saves a lot of switch flipping. My Stearman weighs 15 lbs. 2 oz. ready to fly.
Now to the good stuff: For most ARF modelers, assembling or building the model is the means to an end. Let's go flying. (FYI: the completely assembled model fits into my Honda Odyssey Mini-Van. No field assembly required.)
Sydney Clement, test pilot extra-ordinaire, agreed to test-fly the Stearman so I could take the necessary photos. I always develop a severe case of knee knocking and shaking hands on test flights. Syd is a perfectionist and triple checks everything.
The Zenoah G-26 on a 16 x 8 APC propeller tached out at 8,500 rpm's and sounded happy. The JR 8103 radio with high-tech 605 BB - 72 oz. torque servos, range-checked perfectly.
The time has come to stop talking about it and go fly this beauty. The take-off was uneventful with a small amount of right rudder to hold the ship on the centerline, the tail lifted and we were flying! Syd held the climb-out angle shallow, until flight pattern altitude was attained. The only trim necessary was a slight amount of down elevator. A little later I asked Syd how the plane climbed, in answer to my question he pointed the nose up and the engine stopped! Holy Cow! Just minutes into the first flight on a kit review model and the first landing is dead stick.
The dead-stick landing was uneventful except for having to listen to Syd berate me for doing something wrong. The engine would not restart - so back to the workbench. Disassembly revealed that both the carb fuel line and the fill/vent line had come off the tubes in the tank. No matter how good an engine is, it won't run without fuel. I normally use Tygon gas fuel lines, but when I installed this fuel tank I attempted to use a different type tubing from my local lawnmower shop. The new tubing became very slippery when wet with fuel and slid off the brass tubing inside the tank.
After assuring Syd that this time the engine would keep running no matter what he did, another uneventful take-off ensued. A couple clicks of down trim and the plane flew hands-off at approximately three-quarter throttle. After a number of low passes for photos, it was time to turn Syd loose! Loops are large and round, rolls are axial with no tail wiggle, stall turns are beautiful, wing overs are awesome, four point rolls, inverted flight and spins, all the maneuvers a Stearman is expected to do are done with grace and style. Intentionally, Syd put the Stearman into a flat spin, after a couple of turns I begged him to stop (he did), my stomach could not stand the stress. The approach and landing was typical of what you expect from a high drag biplane: The Stearman requires approximately 1/4 open throttle to maintain good airspeed on landing approaches, cutting throttle to full idle just prior to touchdown. Three point landings look best but wheel landings are also accomplished with no problem.
I (an experienced pilot of average skill) have now flown the Stearman numerous times with no mishaps. The model is easy to fly with no unpleasant quirks, and is only of moderate speed at full throttle.
The image the model presents both on the ground and in the air is simply wonderful! I heartily recommend this kit to any modeler with moderate experience at both flying and ARF assembly. The engineering and thought that Great Planes lavished upon this model is outstanding.
Remember, real airplanes have two wings and round engines.
Photos by Dick Slutz. Reprinted with permission.
November, 2004 R/C Modeler Magazine
Editor: Patricia Crews