Bucker Jungmann (oz5505)

About this Plan

Bucker Jungmann. Radio control scale model biplane. This is the discontinued kit # K-51 from Carl Goldberg.

Direct submission to Outerzone.

Update 28/04/2018: added kit review from RCM&E, December 1996, thanks to RFJ.

Update 09/05/2018: added kit review, from Flying Models, January 1997, thanks to RFJ.

Update 08/04/2020: Added kit review from RCM September 1997, thanks to RFJ.

Quote: "RCM Product Review. BUCKER JUNGMANN from Carl Goldberg Models. By Mike Lee.

Biplanes have always held a special place in the hearts of pilots and spectators when it comes to flying aerobatics. Beginning with the barnstorming bipes of the 1920's to the modern Pitts, Eagles, and now the Bucker Jungmann. The Jungmann began life as a German military trainer for most, turning into a strong, aerobatic stunt bipe well after World War II. Today, modern examples of this classic design still fly, and the subject of this review is a modernized version of the Jungmann by Carl Goldberg Models.

The Bucker Jungmann model is a smaller version of Dave Patricks's Tournament of Champions design, yet it retains the out-standing aerobatic capabilities the larger version possessed. All primary building materials are lite ply, balsa, and a few vacuum formed plastic parts. These parts are all packed into a colorful box that measures 48 x 15 x 10 in, making it shipable by UPS. All parts are well packed and protected from damage by rough handling, and you can tell by the box that this is going to be a big bipe.

General design parameters of the Bucker Jungmann has a sym-metrical airfoil section on both wings, and both are a modified 'D' tube design. The fuselage is a cleverly designed box style, using almost all plywood in the construction, yet is quite light and strong. Tail feathers are built-up and sheeted for strength and lightness. Plastic parts include the canopy/cover, cowling, and the wheel pants. The plans are in two large sheets, full-sized, and accompanied by a detailed instruction manual with photos to assist.

The kit hardware package is quite complete, providing the modeler with darn near everything required to outfit the aircraft. It misses only 3 in tires and a 3 in spinner.

Construction: Assembly begins with the wings. Most parts are die-cut from balsa and ply. The balsa ribs are cleanly cut and separate easily from the sheeting. To assist in the wing assembly, alignment tabs are made a part of selected ribs, but I found they tend to fall off easily. Yes, they are supposed to fall off, but only after the wing is completed. I used a bit of masking tape to hold them in place until I was ready to remove them. The wings assemble flat on the building board, making life very easy for the modeler. Using the instruction manual, you can assemble the wings in a step by step fashion, checking off each point on the instructions with the printed check box. This is especially handy considering that both top and bottom wings are almost identical. Each wing is assembled in three distinct portions, and if you assemble the wing portions to the plans, which are excellent, then each portion will fit like gloves to each other.

Pay attention to the placement of the plywood pieces and how you glue them in place. Most of these are stress bearing parts, and a little attention here will go a long way towards the life of the aircraft. Servos are mounted to the inside of the lower wings, and the ribs are cut to allow a servo cable to easily thread through. Span-wise strength of the wing is enhanced with sheer webs at the spars. Stress bearing areas are all plywood reinforced. Sheeting of the wings along with capstrips finishes the wing assembly.

At the tail, we find a flat airfoil, horizon-tal stab, and elevator structure, constructed with geometric ribbing and then sheeted over. Once the sheeting is in place, the structure is quite strong. Make sure you do not warp these sections, as getting the warp removed later will be near impossible. The vertical fin and rudder are built the same way. Note that both the elevators and rudder are very large, indeed. This should be a hint at the effectiveness of these surfaces later on. Once the tail sections are completed, the fuselage construction begins. This item is a basic box type fuselage using die-cut lite ply almost exclusively. The die-cutting is very good here, and I found that I had to be careful to prevent parts from falling away from the die-cut sheets, or they would get mixed up. Thankfully, the instructions provide a die-cut sheet diagram, showing where the parts are located within each die-cut sheet.

At the fire wall, we find a double lami-nated former, with all other formers being single layer. It goes together alarmingly fast, leaving the impression that there has got to be something missing in the assembly. Not so, as the kit features a large, vacuum formed canopy and top nose section, spanning from the nose to the headrest of the cockpit. About the only difficult part of the fuselage assembly is installing the rear turtledeck, this being a single sheet of 1/32 plywood. The application of water to the plywood, allows you to make the bend without splitting the wood.

At this point, the fuselage looks like a plywood skeleton, to which we begin mounting the wings for alignment. I was amazed to find that the lower wing is held to the fuselage with only two 6-32 screws. The top wing is held to the main cabane struts with four 4-40 screws. Both wings are held in place outboard by 2-56 threaded rods with devises at the tips. For such a large aircraft, this seems like pretty small hardware. However, when you consider where the actual load bearing will occur, it makes sense that this is all the hardware you need to keep the plane in one piece. Once the wings are aligned, the tail feathers are mounted and the canopy/ forward cover is placed. The instructions say to paint the canopy/cover from the inside prior to mounting. My own common sense says that glue won't adhere to a painted surface very well. Also, the resulting finish of the canopy/cover will be a very high gloss, compared to the covering. So, I opted to paint the outside of the canopy/cover, allowing the glue to bite into the plastic directly. This worked very well for me, and the painted finish looked like a dead match for the film finish of the rest of the fuselage. In this case, I used 21st Century paints to make the match.

Covering/Finishing: All of the basic construction work was accomplished using Satellite City Hot Stuff Super T. This has been my adhesive of choice for over a decade because of the consistency of quality. I used some epoxy to paint the fire wall and to place reinforce-ment fiberglass cloth over the wing joints. From here, we applied the finishes to the airframe. 21st Century film covering was used over the entire airframe, except where we painted the canopy/cover. We found good results with the film, including being used as a color trim. The cowling and wheel pants we painted with 21st Century paints, which provided an exact match in color to the film covering. Inside the kit box, we found a can of Carl Goldberg Cowl Bond adhesive. This stuff is used to glue the vacuum formed cowling and wheel pants together at the seams for a strong, permanent bond. Like any other glue, be sure you don't overdo this, as the Cowl Bond will eat into the plastic when excess glue is used.

Radio: The radio I installed was the Futaba 8UAP system, which I consider a superb radio system for this application. On board the Jungmann, RCD Hitec servos and receiver provide the command and control functions. At the elevator, a single HS-705BB servo handles both elevator halves. With 133 oz of power to drive the pushrod, it will be hard to imagine a servo stall here. At the ailerons, an HS-605BB servo resides in each side of the lower wing, providing fast and accurate aileron response. The rudder also sports an HS-605BB, and the throttle has an HS-425 moving it. An RCD Hitec Supreme receiver does the decoder work, served by a 900 mAh battery. There is a canyon of room inside the Bucker, making installation of the radio a snap.

Engine: Powering the Bucker bipe is a Saito 150GK Golden Knight 4-stroke engine, mated to a Du-Bro isolated engine mount. This engine has gobs of power, and is listed as the upper engine requirement for this model. It is such a good looking engine that it's hard to have the cowling cover it up. Only the gold color valve covers poke through the cowl cheek. The use of this engine also forced me to place the cowling well beyond the recommended placement, due to the length of the engine. It still makes a good fit, just don't drill out the recom-mended mounting holes in the cowl. A McDaniel Model 403 remote plug adapter is used on the glow plug to prevent the necessity of putting a big hole in the cowl for the glow plug connector. Du-Bro super low bounce wheels round out the aircraft. Finished weight is just over nine pounds, with four ounces of lead in the tail to balance.

Flying: Our first day out was partly sunny with 5 mph winds and only 68°. Our Saito 150 fired right up and a quick check confirmed that she was ready to go. With the applica-tion of throttle, the Bucker Jungmann needed hardly a bump on the rudder to hold her straight, and went airborne in about 80'. Only a tad of trim was required to get her inline, and then we put her through the paces.

Elevator response is quite smooth and positive. Although the amount of recommended throw does not appear to be much, it is plenty for what we need to do. Ailerons are solid, leaving the bird right where you want it with crisp response. Rolling maneuvers handle well, and look axial, particularly when you consider this to be a bipe. Rudder response is radical, letting you know each time you apply rudder that you have a positive yaw movement. This is especially nice in the point rolls, knife-edge, and stall turns. As for the claim that the Bucker will perform a knife-edge loop, indeed, it really will perform a knife-edge loop with the Saito 150 up front. There is only a slight hint of roll coupling through the rudder, which was mixed out in the transmitter.

Snap rolls are positive, yet semi-slow in nature. You definitely know the aircraft is in a snap roll; it just occurs slower than you first anticipate. This makes it easy to get the plane to stop where you want when exiting the snap. Spins are easy, but will take about 1/2 turn to stop upon releasing the controls. Landing the big Bucker is not hard, as the plane slows down nicely. In fact, it has a very good glide. You will have to practice wheel landings before going to stalled landings, as the Bucker has a nasty bounce on anything but a greased, stall landing. Overall, this is a plane that any sport pilot can handle and a hot dogger will appreciate. With power like the Saito 150GK, you have an airshow type machine.

In summary, I am very pleased with the Bucker Jungmann bipe, both in the con-struction and in the flying ability. Although not as crisp flying as a pure pattern aircraft, it is as honest a flying aerobatics bird as there ever was, short of a pure pattern aircraft. Indeed, it will be a real contender in IMAC competition. She handles great and leaves me with a smile every flight. Other pilots who have also flown this plane, agree. I give it a two thumbs up rating!"

Update 3/1/2025: Added kit instructions, thanks to ChrisBohn.

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