|Wing Area:||175 sq. in.|
|Weight as Tested:||8.8 oz (see text)|
|Wing Loading:||7.2 oz/sq. ft.|
|Servos:||Two Micro Servos|
|Receiver:||Three+ Channel Micro|
|Battery:||2 cell 400 to 1000 lipo|
|Prop:||APC 7x4 Electric|
Take a drive to your local municipal airport and what do you see? Typically you'll see all manners of light civilian aircraft doing touch and goes, sight-seeing, and training. Unfortunately in this regard, when it comes to R/C aircraft, typically the first light private aircraft modelled are the less popular (nowadays anyways) civilian birds like the Piper Cub. It is with this in mind that Acme Aircraft has released a unique light single in the way of their C-170 parkflyer. With a light wing loading and small size, the C-170 looked to be capable of small field operations without undue stress on the pilot. As the icing on the cake, the fact that the C-170 is a balsa kit allowed me to build something unique - a rare thing nowadays!
Not shown in the above photo is a small bag of miscellaneous hardware, which includes the following:
The C-170 kit came mostly complete but left a few things out in order to save costs a little and also leave some options open to the builder. In addition to the hardware and electronics listed below, I opted to add a full function lighting system as well as a thicker covering to give the plane a more "solid" look. More on that in the "Covering" section.
Following is a list of hardware required to finish the C-170 kit. Varations to these are, of course, at the builder's discretion.
As with any other electric aircraft, there were countless possible combinations that would work in the C-170. However, the intention of the C-170 was to be a lazy circuit flyer, so with that in mind I stuck with the motor/battery setup as recommended by Acme Aircraft. Additionally, the firewall was already designed with the Himax 2208 in mind so fit was to be a non-issue. Larger motors in a plane like this would do little more than add weight, both in the motor itself as well as in the required battery. Following is the list of required electronics with my specific choices.
Construction started, as per usual, with the tail feathers. The outlines were all laser cut and interlocking, with a perfect parts fit. Despite the fact that there were no part numbers on the individual pieces, the parts were all grouped together on the parts sheets rather than scattered around, and as such finding the specific pieces for each assembly was no challenge.
The fuselage construction was quite straight-forward and resulted in a dead-true fuselage. Construction techniques are what have become the norm for semi-scale parkflyers. Flat plate sides with lightening holes got glued together with formers and then stringers were added on the top and bottom to maintain a rounded profile.
Again the standard in parkflyer construction techniques, the wing involved interlocking the ribs into a main spar complimented by a lightweight balsa leading edge, trailing edge, and turbulators. Regardless of this, this wing, as any wing, is still best built up on a flat surface to avoid warps.
As I was looking for a scale, chrome covering scheme, I opted to cover the C-170 in chrome Solartrim . The covering itself is sticky backed and, while it will readily shrink with heat, heating up the chrome does cause it to fade and discolor slightly. As such, I opted to lay the solartrim on one small panel at a time, minimizing wrinkles and avoiding having to heat shrink the covering itself. Even though the covering is sticky-backed, I found it best to still stick down the edges with the tip of an iron.
Servos get mounted in a pre-cut tray which was built in during fuselage construction. Pushrod installation is dead simple as it only required music wire to run a direct line from the servo to the control through laser-cut holes in the formers. There was no guesswork there. The receiver pretty much was just laid in the fuselage ahead of the servos. The fuselage width made this no problem at all as there was volumes of empty space. In addition, the control board for the onboard lighting system was laid in this gap as well. Battery placement is accomplished by velcro on a small balsa battery shelf just under the front windscreen. Don't worry - even my big hands were able to reach in and readily change the battery around after a flight.
My antenna of choice was a base-loaded micro antenna which is no more than about six inches long. This was routed through a gap just where the trailing edge of the wing meets the body and left to dangle in the breeze. In a faster plane, this may have presented an issue but as it stood, there were no problems with interference or range (see "Flying").
Beyond the basic construction, numerous small details were completed prior to the test flight. Things like wing struts, landing gear legs, and the cowling intakes were covered in solartrim and applied. The balsa landing gear legs were installed with small chunks of scotch tape while the wing struts used music wire on one end and small magnets (not included) on the other. The cowling intakes came as part of the kit and were laser cut from 1/32 plywood.
Once all the details were in place, a final control check was done to ensure correct direction and throw. A CG check also took place, showing that I needed to shift my 2s 420 pack to the forward half of the battery tray. This was surely due to the heavier covering adding more weight behind the CG.
The first flight took place on a sunny but cool day in March. The snow had mostly melted and the air was just above freezing, leaving our chosen flying field, a ball diamond, with mud instead of solid gravel in most areas. The large tires of the C-170 would go into use!
The question of whether or not the chrome covering would present any control issues was next on the list. With the antenna routed outside the airframe, and range check was done, varying with power on and off. Any concerns proved unfounded as the range was as good as with other, non-chrome coverings.
Finally it was time to let the C-170 take to the air.
One final control check was performed (a good procedure regardless of whether it's flight #1 or 101) to ensure proper direction and throttle was applied. The tail came up almost immediately and the 170 was off the ground on its own in about 25 feet at 3/4 throttle, needing only about 1/4 right rudder to maintain tracking. Further takeoffs have shown that the C-170 can be off the ground as quickly as about 10 feet at full throttle but the best scale results have been with lower throttle settings and a long ground roll.
High speed? What high speed? That's not to say the C-170 couldn't go fast but it was just never meant to. Push the throttle ahead and the plane does indeed pick up a bit of speed with little to no trim changes but higher speed with this airframe has served no purpose. On the same note, the C-170 is capable of some aerobatics like loops and hammerheads but since they're not scale, I haven't found myself doing them much.
Low speed is where the C-170 excels. I found a nice cruise throttle setting around 1/2 stick (which equated to 3 oz thrust and 1.5A on the wattmeter). At this throttle, the C-170 could be flown around in nice lazy circuits, passing within mere feet of the pilot.
Ideally suited to the first-time builder, the C-170 could very well suit the first time pilot with the aid of an instructor. Alternatively, the C-170 would nicely suit the self-taught pilot as their second aircraft.
There are times when nothing beats getting out with an easy-flying plane for casual circuits. The C-170 fills this role perfectly. As an added bonus, quick construction and crisp scale lines add to the overall enjoyment.
Boy, I like my Multiplex ARFs, but that is a beauty. I'd almost be afraid to fly it.
... then here comes you, flying the whole video 5 ft. off the deck.
That is the advantage of the cold winter days: no wind. I fly all year too. Not so many little brats polluting my soccer fields.
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