1/20 Nichimo Cessna 172

Skyhawk Scene "First Solo"

 by George R. Mustafa

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  IPMS USA Nationals 2006

 

INTRODUCTION

 

The 1/20 scale Nichimo Cessna Skyhawk 172 is not a new model. This model dates back to the 1970’s and was reissued about five years ago. I bought this one then. The model depicts a C-172 of the 1970’s. Despite the fact that Nichimo does not make any reference as to the year model of the plane, my research points to a C-172 circa 1970’s. Taking that into account I decided to slightly modify the plane to be early 1970’s model. Nichimo went to great lengths to detail this plane, even in the time when recessed panel lines and rivets were not the norm. Nichimo did a great job with these kinds of details. Inside and out the model is a jewel. Hence, I decided to do a small scene, reminiscent of the old days at flight training, called First Solo, where I depict a flight instructor about to remove the right wheel chuck from the Cessna for a young student pilot to go on his first solo flight. (Any good memories from your first solo?)

 

 

HISTORY

 

The venerable Cessna 172 Skyhawk is a four-seat, single-engine, high-wing airplane. Probably the most popular flight training & private aircraft in the world, the first production models were delivered in 1957, and it is still in production in 2006; more than 35,000 have been built. The Skyhawk is ever-present throughout the Americas , Europe and parts of Asia ; it is the aircraft most people visualize when they hear the words "small plane." More people probably know the name Piper Cub, but the Skyhawk's shape is far more familiar.


The 172 was a direct descendant of the Cessna 170, which used conventional (tail dragger) landing gear instead of tricycle gear. Early 172’s looked almost identical to the 170, with the same straight aft fuselage and tall gear legs, but later versions incorporated revised landing gear, a lowered rear deck, and an aft window which added rear visibility. The final structural development, in the mid-1960’s, was the sweptback tail still used today. The airframe has remained almost unchanged since then, with updates to avionics and engines including (most recently) the Garmin G1000 glass cockpit. Skyhawk production ended in the mid-1980’s, but was resumed in 1996 with the 160 hp 172S and 180 hp 172SP.


The older Skyhawks shipped with a 145 horsepower engine; later planes shipped with engines up to 180 horsepower, though 150 or 160 hp is more common. Cessna produced a retractable-gear version of the 172 named the Cutlass 172RG and also produced versions on floats. The 172RG also had a variable pitch, constant speed propeller and more powerful stock engine. The normal cruising speed for a fixed-gear 172 ranges from about 105 to 125 knots, depending on the engine and vintage.


The Skyhawk is part of a large family of high-wing, tricycle-gear, single-engine Cessna planes, ranging from the two-seater 150/152 (no longer in production) to the more powerful 182 Skylane, the six-seat 206 Stationair, and the fourteen-seat turboprop 208 Caravan, along with several other models no longer produced.

 

 

THE MODEL

 

The model comes with a beautifully detailed interior to include a very good instrument panel. Of course, in order to make this model really accurate, I scratch built and added other details in the cockpit, as shown in the images below. Likewise, the engine is another jewel. In itself the engine is a model all of its own. It comes with metal baffles (disks) to assemble the cylinders and a lot of details shown in the images below. Sadly, the scene I’m portraying does not include an open cowling, and because of some “defects and fit issues of the plastic itself”, I had to permanently enclose the beautiful engine. Nichimo includes parts (but not the electric motor) for motorizing the engine and adding the landing light (a bulb is included, but I used a white LED). I went further than that and motorized and fully illuminated the Cessna with micro LED’s. Additionally, I included a series of electronic circuits (called Audio-animatronics) to control the on-off function of all these gadgets with a preset timer, (these circuits were kits themselves). The whole thing, including the sound module, runs for approximately 20 seconds and then resets until the momentarily push button is once more depressed.

 

This model won First Place in the Civil, Sport, Racing Aviation Category (158) at the IPMS Nationals 2006 in Kansas City, Mo

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Building the Cessna was no easy task. Nichimo, for some obscure reason, did not design this model with locator pins for matching the parts, which translates into hard work in matching and aligning parts correctly before gluing in place!  When modifying a model like this one to include electric motor and illumination, the simple assembly task turns into an engineering project. Like I mentioned above, I also included several electronic circuits to control everything, so it was a matter of going back to my basic electronics days. In the end it paid well.

As briefly as I can explain it, I added micro LED's for navigation lights and a 3mm white LED for the landing light. I used a mini red LED for the beacon light, with a 555 chip based flashing circuit.  I routed the wiring through the main landing gear legs and wheels ending in two pins which are the power contacts. Notice that I separated the electric motor circuit from the illumination circuit, hence ended up with two contact points. I did this to reduce the load on one circuit and to be able to control de electric motor RPM using a motor controller circuit.

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Modifications to an already good model included close to 40 scratch built items. Starting with the interior, I added photo-realistic instruments to the instrument panel by obtaining actual images of the instruments, and reduced to scale. After printing them on glossy paper in my Color Laser printer, I simply punch them out using a punch set. Additionally I also added the throttle and mixture levers, push to talk switches in each control wheel, (known as yokes), with their correspondent coiled cables. I replaced the yokes horizontal control tubes with aluminum tubes. Since I wanted to portray an old 1970's Skyhawk, still in use today, I also added a Garming GPS unit atop the instrument panel dash. I also added other interior details such as the door handles, window locks, seatbelt hook atop each door frame all made out of flattened solder, and the two windshield mounted air vents, with the right one portraying the outside temperature indicator, like in the real plane. I added all the safety belts using a medical brand tape and solder fashioned buckles. I used the Nichimo supplied pilot figure, which looks like a young man, hence the idea of a first solo. To keep in touch with the real thing I scratch built the pilot's headset, to look like my very own David Clark headset with cables and boom microphone. Additionally I added sunglasses to the pilot and the flight instructor all done with Tamiya two part putty. I used a Tamiya 1/20 scale mechanic figure for the flight instructor. The interior was painted with a combination of acrylics and enamel paints. Outside I added scratch built items such as the door stoppers and hitches under the wings, the under wing  fuel collection and drain points, various antennas, and a Garmin GPS antenna atop the wing, and the metal tie downs under each wing pylon and tail, among other details. I added all the weight I could inside the limited areas in the fuselage, but at no avail the bird still ended up tail heavy, so I had to fashion a hold down bolt in the nose wheel which when installed held the model in the right place.

Furthermore, I modified and completely wired the engine as per Cessna specs, only to have to permanently enclose it due to a serious flaw of the cowling and the airframe, (the model came like that from Nichimo). However, the engine is a jewel all by itself. I built the carburetor and the air filter linkages, added the sparkplug wires connected to both magnetos, all the ignition, starter and generator wiring, as well as other electrical wiring. I modified the flywheel to also turn with the propeller (like the real thing).

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On the other hand, assembling this model without locator pins was a challenge. I matched the parts and used clothes pins, flat clips and good old tape to ensure a square fit before gluing. After the assembly was done, I dry-fitted the wing assembly which goes atop the fuselage, to ensure the brass contacts for the wingtip navigation lights would work correctly, and the proper dihedral and symmetry of the wings themselves to be correct. The worst case is that you show up to a competition and the model wings are not symmetric! Instead of gluing the wings in place, I drilled three small holes, one under each antenna location, to hold the wings in place. Later, when the model was finished the two rearmost antennas and the new GPS antenna would cover the micro bolts I used. After the assembly was completes I covered the small gap between the lower side of the wings and the fuselage with a shaped piece of lead foil. This replicates the actual wing to fuselage covering fairing in the real 172. The same was done with the edge of the wings and windshield, which had a very noticeable gap.

The model was painted in two sections, fuselage and wings. I used Tamiya white primer (fine), sanded down with micro-mesh (3200 to 6000 grit). It was at primer time that I discovered that many rivet holes came filled up from the factory (Nichimo's defect), for which I had to re-bore each and everyone of them. I ended up re-boring all the rivets in the upper and lower wing (about 800 of them!) and most of the lower and upper fuselage, (another 300 of them!). After spending a couple of days re-boring rivet holes then I painted it gloss enamel white, exposing all the painted surfaces to the sun for a period of time.  After the paint was cured I polished the entire model with micro-mesh (3200 to 12000 grit) and the white surfaces really got crystallized! After that I masked and painted the green trim, which was also polished to perfection. The final color was the gold. I masked the plane and used Aclad II Gold, which I also polished. Right after that I used the Novus Polishing compound to really make that bird shine! Furthermore, since the model had all those beautifully recessed lines and rivets, it cried out loud for some weathering. Using a water based Tempera paint, I mixed light to medium gray tones, (the usual goo mix using dish washing detergent) and applied liberally to the entire model. Once dried I just cleaned away the excess, leaving just the right shade of grays in the recessed areas, highlighting the rivets and panel lines, without over doing to ridicule. In the end, it came out very good, and was so acclaimed by the Head Judge at the IPMS annual convention in Kansas City, Mo last August.

The model brought a set of white vinyl letters and numbers, in the right font and angle to create an registration number the modeler would like. In the interest of time (which was running short for me to have the model ready for the 2006 Nationals), I decided to use these letters and numbers. In the end they look good. I created some additional stenciling in my computer and made home-brewed decals for the Cessna logos and lettering.

ELECTRONICS

The whole scene uses several circuits to run the "show" as I call it. Following the tradition established by the late Walt Disney, and his invention of "audio-animatronics", my model incorporates light, action and sound, truly, audio-animatronics. First, the model incorporates internally all the LED lights, flashing circuit and electric motor. Then, through both landing gears the contact points are met by two connectors in the base which goes to the circuits located in an external control box. The circuits work as follows; a 12 volt (uses 8 AA batteries) timer circuit with three separate relays controlling the electric motor speed control circuit which uses 4 AA batteries (6 volts), the LED circuit which uses 2 AA batteries (3 volts), and the sound module which uses 4 AA batteries (6 volts). All this run by the timer with a single push and release button that runs the show for 20 seconds and turns off by itself. The time limitation was due to the sound module which had only 20 seconds recording capacity. I created a mix of the Cessna engine sound from startup, and tower and Pilot conversation for the sound module. Except for the flashing circuit that I fashioned myself, the other circuits mentioned are all electronic kits readily available in the market.

The whole scene rests atop a runway (tarmac) made from artists painting board, scribed and detailed, and all that set into a plastic 16x20 picture frame. I did not use the glass that came with the frame because I had to drill holes for the circuit connectors and the nose wheel hold down bolt. Instead I used double board, reinforced below by strips of wood glued together. Two 1/4 female connectors were located in the rear frame to accommodate the two separate circuits for the lights and action. I used a "clouds" backdrop obtained from a model train shop which served to add a true "diorama" sense to the model and to hide the control box and speakers.

Finally

 

Inside and out, this model required over 450 hours of hard work to complete, and I am certain it is a refreshing, somewhat different model than what we are all used to see in shows and contests. It is my most sincere expectation that this model will be a memory jogger for all those pilots-modelers that will have the chance to take a close look at the kind of aircraft we all have flown at any given point in our pilot’s career.

 

For additional information I may be contacted at mustafa56@msn.com

 

Happy modeling,

 

George

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Photos and text © by George R. Mustafa