TOP FLITE BEECHCRAFT BONANZA
PRODUCT TEST REPORT
by Dick Pettit

It's about time a major manufacturer introduced a high quality giant scale kit of a civilian aircraft besides a Cub! It's not that I don't like Cubs, but there are so many modeling subjects available on which to design a reasonably priced giant size kit. This particular model is the new Beechcraft Bonanza, modeled in 1/5 scale by Top Flite Models.

The prototype Beech Bonanza made its first test flights in late 1945, and the design was significant enough to be included on Fortune Magazine's 100 Best Designs List in 1959 (the only other aircraft on the list was the DC-3!). The Top Flite Bonanza can be built either in the familiar V35B V-tail design, or in the F33A straight tail version. Parts and instructions are included for both. The instructions say, "if you like the looks of the V tail, don't be intimidated. Actually the V tail is a little easier to build ... it has fewer parts!" I didn't plan to be intimidated, so I'm building the V-tail.

There are several other options in the Bonanza kit, including choice of fixed or retractable landing gear (even a choice of the style of retracts), flaps or no flaps, removable or fixed cockpit top, and optional lighting kit. The prototype Bonanza was flown with a SuperTigre .75 engine, which, according to the instructions, "provided excellent performance and more than enough power, even in gusty winds." I have a very powerful and smooth Saito 120 4C engine that may be more than enough power, but at slower engine speeds, the noise level will also be much lower. So that's what I plan to use in my Bonanza.

I called Robart Mfg. and ordered the sturdy retract kit with all the accessories. The lower cost retracts mentioned in the instructions would probably work well, but Top Flite says that they "may require periodic adjustments and maintenance". This sounds to me like the better, higher quality retracts are the ones you need for the best results.

The kit is packed well, with the large plastic cockpit top and cowl pieces on top, and all the sheet, strip, and die-cut wood parts neatly packaged below. All the various parts are bundled according to size, and the inventory sheet lists them in that order. The die-cut sheets are numbered, but the stamping is really hard to read. You may want to darken the part numbers with a pencil to locate them during construction. I found that all the required parts were included, and Top Flite even separated the retract/fixed gear parts and the V-tail/straight tail parts with different part numbers. The instruction manual, one of the best I have ever seen, by the way, has separate instruction steps for fixed gear and retracts, V-tail or straight tail, flaps or no flaps, choice of retracts installed, lighting kit, and optional accessories. Any builder that has completed several other kits could complete the Top Flite Beech Bonanza. With that in mind, let's get started.

First in line is the tail surfaces, either two or three pieces, depending on the version you're building. Top Flite actually instructs the builder to edge glue the sheeting pieces together before you begin building. It's about time someone did that! Actually, I skipped ahead and glued up the wing sheeting and the fuselage sides, allowing them to dry before sanding them flat. The stab and elevators, and the fine and rudder if you're building the F33A, are built up from balsa ribs and interlocking spars, with 1/16" balsa sheeting applied later. This results in very light but sturdy parts. I used a combination of carpenter's glue and Zap to complete the tail surfaces. Balsa block tips are added and shaped with a razor plane, and final sanding to the desired shape. There was a lot of small parts in the tail pieces and it took several hours to build and finish them.

Next come the wing panels, built from neatly die-cut balsa ribs, full top and bottom sheeting, hard balsa spars, and a cleverly designed shear web that is die-cut to the full length of each wing panel. First the landing gear mount ribs, depending on your choice of fixed or retracts, are assembled with plywood doublers. Holes are then drilled for servo leads and optional air and lighting lines. Then all the ribs are assembled over the plans using the spar web as an alignment aid. The ribs interlock the spar web, forming a strong and light assembly. The ribs and spar web are then fitted over the main spar where an "I-beam" is formed, once the other main spar is installed. Rear spar pieces, again die-cut balsa, are then installed at the back edge of all the ribs, forming the ailerons and optional flaps.

You may have noticed that I have not mentioned the word "glue" yet, and that's because you don't have to glue anything until all the ribs and spars are in place! This makes it convenient for last minute alignment and minor adjustments before you secure all the pieces with adhesive.

Once the ribs are glued, the leading edge is installed, and we're ready to sheet this side of the wing. I trimmed the sheeting to an approximate size and installed it using Elmer's Woodworkers Glue, with books and magazines on the sheeting to hold it in place while the glue dried. The sheeting is applied as a rear section and a forward piece, to allow minor positioning adjustments. When the first panel is dry, the other panel is built up to this same point. Next, aileron ribs, flap ribs, and landing gear mounts are added to both panels. I'm using the recommended Robart retract kit, and the gear mounting rails fit perfectly in the wing. They had to be notched and trimmed slightly to allow the retract units to fit, but only a slight amount. When the aileron and flap hinge blocks are glued in place, the panels are ready to be turned over and sheeted.

Before this, however, the wing center section is built from hard balsa ribs and plywood shear webs with hardwood spars, again in an interlocking fashion like the outer wing panels. Wing bolt and dowel blocks are added to the structure, and the whole thing is then glued together. Sheeting is then applied to one side, and the center section is done for now.

Four die-cut plywood dihedral braces are used to connect each outer wing panel to the center section, but they are only glued to the outer panel at this time. This allows the builder to finalize the landing gear installation, add servo and optional lighting wiring, and prepare the panels for sheeting on the remaining side. I ran the lighting kit wires through holes drilled in each rib before assembly, as detailed in the instructions. I also drilled holes for the air lines for my Robart retracts, and made sure the retract units fit well on the ply and hardwood gear mounts. The hoses can be run after sheeting the wings, as well as the servo wires.

Die-cut cradles are spot glued to the already sheeted side to keep the wing panel straight while the opposite side sheeting is added. When both outer panels are sheeted, the wing tips are added and shaped to match the clear plastic wing tip light lenses. Red and green lamps, along with blinking strobe lights, can be added to the wing, but I chose only the position lights.

The optional flaps are then ct free of the wing assembly, built up with balsa sticks and sheeting, and made ready for hinging. I chose not to install the flaps since they require more servos and a larger battery. I have flaps on a Top Flite Cessna 182, but they are now used only for display purposes. I'm not fond of cutting corners, but building flaps into a model that doesn't need them takes extra time, expense, and weight.

The ailerons are then cut out and shaped, and made ready for hinging. The aileron servos, along with flap servos if used, are mounted inside the wing panels using plywood hatch covers. Linkages are fabricated and will be installed after the Bonanza is covered. With both wing panels completed, they are joined to the center section, checking for the correct dihedral dimension.

Next comes the fuselage. A set of die-cut lite ply perimeter crutches are pinned in place over the top view of the plan sheet. Formers are then set in place over the crutch, with side stringers added to support the structure. A set of plywood doublers are then added to the sides over the wing area and at the nose. The balsa fuselage main side sheets I had prepared earlier were now added to the fuselage structure. It took some bending and forming, but both sides came out symmetrical. With the "hull" completed to this stage, it is removed from the board, and upper formers are added at the front and rear. Remember, there is a huge plastic cockpit top that requires no formers for support. The small area at the front and the entire rear deck is sheeted after installing the tail components. Several pages of separate instructions are supplied to guide you through either the V-tail or straight tail version. The rear sheeting gets a little thin after sanding, so take care not to sand all the way through.

The laminated firewall is attached at the correct offset for thrust, and supplied adjustable engine mount bolts in place. A set of hardwood rails, braced with plywood side pieces, are installed under the engine to mount the nose retracts or the fixed nose gear wire. In either case, good instructions are provided to get the job done. I installed the retractable nose gear and cut out some of the lower sheeting on the fuselage to allow the wheel to fit inside.

Nose wheel steering is done using a separate nose wheel steering servo, which brought up an interesting question. My Hitec/RCD Prism 7X transmitter has built-in V-tail mixing, using an internal mix of channel 2 (elevator) and channel 4 (rudder). Two servos are then connected to each of these channels at the receiver, later to be connected to each of the two movable tail surfaces. On a V-tail plane, both surfaces deflect up and down in the same direction when elevator input is given, and in different directions from each other when rudder input is given. This presents a major problem when it comes time to wire in the nose wheel steering servo. The rudder channel, when V-tail mix is selected, will also move when elevator input is used, making steering highly questionable.

Solution? Well, there are several ways to get around this problem. First, go out and get a new radio with both V-tail and a separate programmable mix. You can then mix rudder (before it gets internally mixed with elevator) with another unused channel as a master/slave configuration. I just bought this brand new radio, though, and I wasn't about to go out and buy another one right away.

The next option is to forget the V-tail mixing and connect the elevators as elevators only and use the rudder channel as steering. I didn't want to do this either. Finally, I discovered an auxiliary V-tail mixer circuit board from Precision Micro Electronics. This is connected between channels 2 and 4 to provide the V-tail mixing I wanted, along with the correct rudder output from the receiver for steering. It took a few minutes to wire all the connectors, but it worked flawlessly. The board is very small and light, it consumes practically no power, and is quite easy to install...especially if you get the one with the built in connectors.

With the wing panels joined, the wing is fitted to the fuselage after alignment to the centerline. I mounted the engine, a beautiful Saito 120 Golden Knight, to the included adjustable motor mount. I will have to put a tighter bend in the Saito muffler to exit straight out the bottom of the cowl. Next I mounted the Robart retracts in the wing and in the nose, along with all the necessary hoses, tanks, valves and connectors, and set the Bonanza up on its wheels. Completed to this stage, with all the servos, wheels, engine, fuel tank, and linkages, the Bonanza weighed 10.25 lbs. Still to be added was the covering, cowl and cockpit cover, a battery and receiver, and the interior kit. We're shooting for a 14 lb. airplane here and I think we'll make it in fine shape.

The front top and bottom are now sheeted, and a filler piece is added to the bottom of the wing to fill the gap to the fuselage. Once all the optional air lines, lighting wires, and servo extensions are installed in the wing, the center section can be sheeted and the wing final sanded. I found that the Robart accessory kit includes the tubing necessary to connect up all three gear cylinders and the fill valve, but not quite enough to mount the air tank at the rear of the cockpit as show on the plans. I have to head out to my local hobby dealer to pick up another supply of Robart tubing to complete the job. I contacted Bob Walker at Robart to tell them about the shortage, and he said that an extra 2' of tubing will be added to the Bonanza retract kit.

The plastic cowl parts, along with the plastic cockpit top and tail cone, were sent to Fiberglass Specialties for duplication in fiberglass. They are now available, and they fit exceptionally well as supplied. The builder must cut out the window holes and the necessary engine clearance holes on the cowl, but the glass parts are almost ready to prime and paint as supplied. Contact Steve at Fiberglass Specialties for prices and availability.

I selected a large roll of white MonoKote, and applied it to all the wooden surfaces after preparation with some fine sandpaper and a tack rag. The wing was easy to cover using four individual panel pieces and two center section pieces. The fuselage, with the attached V-tail, was also covered in sections. The removable cockpit top made the covering operation even easier. Once the base color was complete, a suitable trim scheme was drawn on a piece of paper, and the dark blue trim was cut out from pieces of Goldberg UltraCote Plus. The trim scheme was planned to hide or at least mask out the covering seams and the joints between the fuselage and the cockpit top. Some of the self stock decals provided in the Bonanza kit were applied in strategic locations, followed by panel lines drawn with a Top Flite Panel Line Pen. Flap outlines, door openings, hatches, and trim tabs were drawn using a small steel rule. To seal the panel lines, I sprayed several very light coats of Crystal Clear LustreKote on the MonoKote.

With all the major assemblies completed and covered, it was time to add the accessories. The Top Flite Lighting Kit wiring had already been threaded into the wing ribs during construction, so all I had to do was add the control unit, battery, and the fuselage lights. The wiring harness was cut to fit perfectly, and even includes a connector for the landing light on the cowl. I did notice that the simulated rotating beacon caused a bit of radio interference when the transmitter was turned off. I plan to use the lighting only during static displays, so that will not be a problem.

The Robart retract units fit perfectly, requiring only minor adjustments to the air lines. The control valve fits under the Bonanza dashboard, and is controlled by a servo that also operates the microswitch for the landing light. The adjustable control valve can be set to have the gear extend and retract at any desired speed, and this makes the retract action more scalelike.

The battery and fuel system were added, the wing was installed, and the CG location was checked according to that shown on the plan and written in the instruction manual. I had to move the battery to compensate for a nose heavy condition. Finally, I assembled and painted the Top Flite Scale Interior Kit and built it so that it could be installed or removed as a single unit. The lip on the cockpit top will sandwich it into position. The six seats and dashboard give the Bonanza a finished look, and the entire unit doesn't weigh more than 3 or 4 oz.

There appeared to be nothing left in the box, so I figured I was just about done building. I fired up the Saito 120 with a 16x8 APC prop, and there appeared to be an abundance of power available.

The completed Bonanza weighed 14.5 lbs., minus fuel and lighting battery. The wing loading was high, calculated at a little more than 30 oz.ft., but this was a rather large plane, so I had no problem with those numbers.

The Bonanza was taxied around in tall grass to check the ground handling and taxiing power, and all provide more than adequate.

The 4th of July was hot, humid, and windless. I took lots of photos (I wonder if I'll make the cover again), fueled up the Bonanza with some Powermaster 4C blend fuel, range checked the radio, checked and double-checked all the controls, pumped up the retract tank, and taxied back and forth a few times. Everything seemed to be in good working order, so I positioned my photographer, lined the Bonanza on the center line, advanced the throttle, and off we went.

The Bonanza rolled swiftly down the grass strip, and responded immediately when given a bit of up elevator. Yes, I said immediately and I meant it! The nose was pointed up at about a 70 angle, and I'd not applied any elevator! I pushed the nose down a bit to level it out, but it passed through level and entered a dive. I quickly pulled back on the elevator stick ... and off we went like a porpoise! Suddenly the Saito sounded a bit lean ... then more lean ... and then really lean! I reduced throttle to about half, which was still plenty to stay in the air, but not at such a blazing speed. Once I got the Bonanza leveled off, it seemed to be dragging its tail, but controllably. The elevator was very sensitive, so I switched to low rate ... well, I tried to switch to low rate, but found that it was already in low rate! Oh boy!

Here I was, on my first flight with a brand new airplane, with a lean running engine, an overly sensitive elevator, tail heavy flight tendencies, and all the while my "friend" is taking pictures!

I tried to make the best of it, and allowed the Bonanza to fly straight and level a while before performing a roll and a stall turn, both with excellent results. The rudder action of the V-tail seemed to be no different than that of a conventional plane with reduced rudder throw. I flipped the switch to bring up the gear, and they retracted very scale like. Another flip and down they came again (just checking, heh heh). The Bonanza seemed to be flying pretty well now, even at half power, by using only very gently elevator inputs. I made several low passes for the camera, but had to admire them myself, as the Bonanza looked really nice flying past low and slow.

Now for the real test. Take offs are optional, but landings are mandatory. I cut back the power and set up an approach, noting the Bonanza didn't want to come down much at all. I went around again, this time setting the power even lower and using some down trim to point the nose earthward. Still too high, so I got brave and set up a long, low approach, this time resulting in a nice angle to the field. The Bonanza crossed the end of the runway already at landing speed, and no more than 5' in the air. At about 2' off the runway, I pulled back for a nice flair, and the Bonanza stopped flying immediately ... and dropped. It hit a bit hard, but it was a landing of sorts.

With the first flight complete, there were a few adjustments to be made. Back at the shop, I checked out a couple of things, finding that I had misread the elevator throw. I had almost double what it should have been! This was easily changed, as was the indicated nose heaviness. The Bonanza was re-balanced about .75" ahead of the recommended starting point, by moving the battery up under the dashboard. The lean engine mixture was also readjusted.

I headed back to the field for more test flights. After my usual pre-flight checks, the Saito was fired up, throttle added, and the Bonanza again headed straight down the runway. This time, though, the elevator input gently lifted the nose, there was plenty of power with no leaning out, and the Bonanza flew in a straight line with its V-tail proud and tall. I then retracted the gear, and began the real test flights. Rolls were almost axial, a stall turn was beautiful, and a loop was large and round. Wait a minute! Bonanza's aren't designed to roll and loop! Nevertheless, the Top Flite Bonanza performed them flawlessly. Stall characteristics were straight ahead now, with no indication of falling off to either side. Low speed flight is rock steady and under complete control. Now, that's more like it!

However, the landing was coming up, so I tried the same approach as on the first flight. The Bonanza just hung in the air, seemingly floating instead of coming down. I must have attempted 10 landings, all of which were too high to hit the darn runway! Finally I got brave and kept a little power on, pointed the nose down, passed over the numbers at a brisk but controllable landing speed, and the Bonanza landed just fine when the power was cut. Perhaps the model needs some prop wash over the tail at all times. Otherwise, the surfaces don't respond all that well. I'll remember to keep some power on until the ground is within reach.

This test flying session went much better than the first, and I feel that the Top Flite Bonanza is an admirable model in the air and on the ground. The classic looks, especially the V-tail version, makes the Bonanza turn heads at any flying field. The kit builds quite easily and quickly, the quality of the plans, instructions, and materials is second to none, and the completed model is well worth the investment in both time and money. I attribute the weight of my Bonanza to the heavier Saito 120 engine, the fiberglass accessory parts, the heavier but sturdier retract system, and the lighting system. With a conventional .90 2C engine, no lighting, and the lighter retracts or none at all, I think the Bonanza could be built to weigh around 12 lbs. Still the calculate wing loading was no real measure of how well the Bonanza actually flies. It flies really well, and should make a great addition to the hangar of any giant scale modeler.