by Keith Quigg
For most aviation enthusiasts, biplanes portray an evergreen era of nostalgia when ever they’re mentioned or seen airborne. Even the very latest slick and slippery Pitts Python can trace its ancestry back to the original 1945 Curtis Pitts S1 biplane.
Just The Facts:
AIRCRAFT: Bucker BU133B Jungmeister
MANUFACTURER: Seagull Models
AIRFRAME LENGTH: 147cm
AIRFRAME WEIGHT: 6.2kg
POWER RANGE: 0.9cu.in 2 stroke, 1.2cu.in 4 stroke, 20-22cc petrol
CATEGORY: ARF Scale
RADIO CHOICE: Minimum 6 channel
PILOT STANDARD: Intermediate
WHAT GEAR WE USED
Hitec Aurora 9x 2.4gHz transmitter
Hitec 9 channel Optima receiver
Hitec HS-645MG servos on all control surfaces
BATTERIES: Dual LiFe 2100mAh battery packs for receiver & ignition module
WHAT WE LIKED
• Something a little different & eye catching
• Handy size with good presence in the air
• Wing brace system for transportation
• Ease of assembly
• Plenty of room in the engine cowl
• Easy access for batteries if using electric power
The immediate attraction of the Seagull Models Bucker Jungmeister is that it is just that little bit different. It has an aerobatic thoroughbred but not in the familiar form of the Extras, Yaks or Edges, plus, maybe even a little air of aristocracy?
I was keen to add a biplane of sorts to my fleet, so the Bucker’s arrival meant the workbench was again cleared for a new project. The original Bucker Jungmeister first flew in 1935 and was a further development of the Jungmann biplane. It boasted a top speed of around 220kph, a creditable 119kw from the Siemens-Halske radial engine with a service ceiling of just under 15,000 feet.
Seagull Models’ example depicts the 1936 rendition of the Bucker 133B made famous by Alex Papana and carried the notable registration of YR-PAX. Alex competed and won the US Aerobatic Championship in 1938, 1940 and 1941. The vibrant red and silver checker scheme blends into the overall cream finish of the airframe nicely. I liked this model right from when I received it. Some years back (quite a few actually) I had a smaller Bucker Jungmeister marketed by the Pilot Corporation which as I recall, was powered by an OS 25. The word lively comes to mind when I think of that particular model!
As we pretty much come to expect these days, the kit arrived very well packed and all the internal parts were in first class condition. Overseas manufacturers really to a great job in packaging. I had a quick read through the assembly manual before starting the job and everything looked very straight forward. The only real difference from other scale models was the fact that some rigging would be required between the struts of the wing sections.
Working from the manual, the individual elevator and single rudder surfaces are installed using a few drops of cyanoacrylate on each hinge. Control horns (made from printed circuit board type material) are epoxied into place. I suggest installing the control horns for the ailerons similarly while you have the epoxy mixed up. Before installing each horn, I drilled two small holes in the base that slides inside the control surface to provide a more secure joint and allowing the epoxy to form a type of pin through it.
Moving up into the fuselage area and I installed a set of Hitec HS-645MG servos for the dual elevators and single rudder. I used these excellent Hitec servos all round for this model and I believe they represent great value for money for larger aircraft and a good choice when using petrol power. At six volts, they will provide around 10kg/cm of torque which is more than ample for this size aircraft. The metal gears also provide substantial protection against the vibrations of petrol powered engines.
In anticipation of the need for nose weight, I installed the two LiFe battery packs, (one for the Hitec receiver and one for the ignition module) placing the ignition module as far forward as possible in the forward fuselage followed by the fuel tank. There is no shortage of room for this equipment and should you choose to install electric power, the large hatch will allow easy access for your battery packs.
I was installing a 21cc petrol twin for this project and that was right within the suggested power range for the aircraft. Given the fact that there is a very large cowl up front, you will have no problems installing your preferred power plant in the Bucker. Just don’t go overboard with larger than needed engines – this is a scale biplane and does not need it.
The engine mounting is straightforward enough, but the attachment points for the large cowl (six in total) will need your attention. As they come out of the box, they will fail in a short space of time as did mine while I was trial fitting the cowl. You can either provide more support for the existing structure or replace it completely. I choose the latter and simply installed some Dubro PVC mounting points made for the job. At this point you will also need to cut the outlets for your exhaust.
In a departure from the supplied manual, I choose not to fit the wheel guards or wheels from the kit. Photos of the original aircraft show that the guards were not fitted and I also wanted to install a set of four inch Dubro pump up tyres. These tyres offer a little more bump absorption when operating off not so perfect surfaces and the occasional hard landing, plus they look good too! Talking about the scale look and the original aircraft did not have the red accents on the engine cowl either, although they really do look good on the model. If you’re really fussy it’s a simple case of a light sanding then a spray with silver paint if you wanted to preserve the original look.
Back to the rear of the plane now and after removing the covering from the horizontal stabiliser, it was epoxied to the fuselage along with the vertical stabiliser. The pushrods are then slid into the outer rods in the fuselage and the elevators and rudder can be attached to their respective control horns. Final step here is to trim the pushrods for fitment to the servo arms. I opted for a “z” type crimp to secure the pushrod to the servo. I prefer this over plastic keepers, especially in petrol powered aircraft.
The top and bottom ailerons on the wings come hinged from the factory, so all that is needed here is to install your servos in each lower wing half. The upper ailerons are connected by a sturdy pushrod attached with a metal clevis on each surface.
Once the wing panels are slid into place (there are two sturdy aluminium wing rods for the top and bottom wings) you can begin the rigging process. This has been simplified by Seagull using a similar method to a pull-pull rudder system. The metal cable is crimped to the clevises through a turnbuckle. One end is attached and you then take up the tension (not too much) before crimping the opposite end.
A little time consuming but not difficult and something not common in many ARF kits. Good fun.
Seagull include a handy ply wing brace which will hold the top and bottom wings together when you remove them from the fuselage. This makes for a very quick and easy set up at the field as you only need to connect your servo leads and insert four wing bolts to secure the wings. The wing rigging wires stay in place.
Final radio installation was a breeze in the Bucker with plenty of room for everything as mentioned. The Optima 9 channel receiver was placed on the side of the inner fuselage as I wanted it to be easily accessible to be able to experiment a little with the Hitec telemetry system in the near future. After mounting it to some high density foam, I secured the receiver on a balsa plate with some Velcro.
As usual, I set up the control surface throw as suggested in the manual and added around 30% expo. The balance point is shown at 180mm from the leading edge of the upper wing which seemed about right. I needed to add around 150g of lead weight to get this. Of course, your choice of engine plays a big part in determining the additional weight needed. With the twin cylinder I’d used, it gave me a few precious extra grams where it was needed.
This was my first model setup using my new Hitec Aurora 9X transmitter and I could not help but be very impressed with it. The transmitter is light and all the controls fall easily to hand and the large touch screen at the lower half of the radio is very easy to read. A simple programming interface along with all the mixing and servo fine tuning you will need, it represents very good value for money. A high quality 9 channel 2.4 GHz radio with 4096 resolution, a full range 9 channel receiver for less than $450 is pretty hard to find these days. Well worth adding to your shopping list if you are in the market.
The day had come for the Buckers’ first flight and I had gathered at the VARMS facility in Melbourne early in the morning. The day had started OK, but the winds were picking up and a menacing rain cloud was moving in faster than an Airborne Magazine deadline, so it was time to get moving.
Set up at the field was minimal as the Bucker easily fits into my trailer in one piece so it was a matter of a quick engine run, a range check and final control check. Controls were set to low rates for the ailerons, full rate for the rudder and elevator. The new RCGF flat twin came to life quickly, settled in to a very acceptable idle and ran very smoothly – testament the characteristics of modern twin cylinder petrol engines.
The wind had now settled into a decent crosswind, but nothing of concern so the Bucker was assisted onto the runway and lined up along the centreline. One last check of the controls and the throttle was eased forward. In no time the Bucker had picked up its tail and was tracking true along the strip with minimal rudder input and a little left aileron to counteract the crosswind. At just over half throttle it was airborne, climbing out nicely over the edge of the strip and I started a left turn to remain within the field airspace boundaries.
Despite a bit of a buffeting from the winds, the Bucker was flying well but it was evident it still needed a little more weight in the nose. The amount of control throw felt about right for the ailerons and elevator and given the slightly tail heavy condition, I was glad I’d dialled in sufficient exponential for the test flight. Continuing with the flight and a few basic manoeuvres along with reduced throttle to explore the slow flight conditions prior to landing. Biplanes with large round cowls, along with the extra struts and rigging carry a lot of drag, so make certain you take a bit of time to get used to slow speed flight.
A few passes along the strip for the photo shoot and the wind was not getting any lighter, so it was time to think about the landing. Just under half throttle and re-trimmed in the circuit brought the biplane down to a suitable pace for the downwind and base leg with the wind doing its best to upset the approach. Holding a little power on the final leg and the Bucker settled in for a mains first landing just past the half way mark. A quick check over the engine mounts, rigging and controls to make sure nothing had come lose and I was more than happy with the first test flight. I subsequently added another 200g of weight to the front, making the Bucker a much happier machine in the sky the next day.
The Seagull Models BU133 Jungmeister is model that is a little out of the ordinary and once you address the few minor blemishes that are present in the kit, you have an excellent flying scale model to present at the next flying day.
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