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Written by George Kaplan
Captures the lines and looks of a full-scale C-47
Product review
As seen in the January 2018 issue of
Model Aviation.



Bonus Video



Specifications

Model type: Semiscale ARF
Skill level: Intermediate/advanced pilots
Wingspan: 70.8 inches
Airfoil: Semisymmetrical
Length: 47.2 inches
Weight: 7 pounds
Power system: Two .25 two-stroke (glow) or electric equivalent
Radio: Spektrum AR6600T receiver; a mix of mini servos; several Y harnesses; and servo extensions
Price: $289.95; $119.95 for optional retracts


Test-Model Details

Power system: Two Cobra C-2820-10 motors and matching 60-amp ESCs; Master Airscrew 9 x 7 x 3 counter-rotating propellers
Flying weight: 8.25 pounds
Flight duration: 9 minutes


Pluses

• Captures the lines and look of a full-scale C-47.
• Laser-cut balsa and plywood construction make up the entire airframe.
• The self-adhesive covering is preprinted with panel lines and hatches.
• Fiberglass cowlings and vacuum-formed nacelles, dummy engines, and tail fairings are painted to match the covering.
• Includes all pushrod and control linkage hardware.
• Fixed main gear hardware is included. Optional main gear electric retracts are available separately.
• Large battery/radio access hatch (held in place by strong magnets) is built into the cockpit area.


Minuses

• Limited electric motor options are available to swing propellers clear of the fuselage.
• VQ’s optional electric retracts require modifications to the internal framework of both nacelles.
• Wing attachment bolts were too short.
• Recommended 7-pound weight does not include retractable gear weight.
• The manual is well illustrated, but leaves out information in several of the steps, requiring the builder to figure things out.
Out of the box, the VQ Warbirds C-47 main airframe components are all built from laser-cut balsa and plywood construction. The model is rigid and well put together. Covering the airframe’s balsa sheeting is a preprinted, self-adhesive covering in the colors and striping that the U.S. Army Air Corps used on D-Day.




In a growing world of foam models, it’s refreshing to review a built-up balsa and plywood kit. Everything you see here is part of the kit, including the stock, nonretractable landing gear.


Also incorporated into the printing are panel and hatch lines to add scale realism. I’m happy to see that the covering has a matte finish because a glossy or shiny surface is never the way to go on most warbirds.

The nacelles, dummy radial engines, and tail fairing pieces are vacuum-formed plastic, and the cowls are fiberglass. They are prepainted and nicely match the covering. The hardware for the control linkages, fixed gear, tail wheel bracket, wheels, and an instruction manual round out the kit.

The manual’s steps are nicely illustrated, but I found it to be lacking during several steps of the build, requiring me to guess how to get things done. You’ll learn more about that as we go along.



Assembly

If you’d like to refer to the instruction manual as I go along, you can download a copy at the link in the “Sources” section.

Assembly starts with the wing—more specifically, installing the main gear into the wing’s center section. Depending on the type of landing gear you choose, the steps vary. VQ supplied a set of optional electric retracts along with the kit, so I set aside the standard fixed-gear parts and bolted on the retract units. The existing rails had to be modified to clear the bulges in the sides of the retract case. A few minutes with a sanding disc attached to my Dremel tool did the trick.

The framework of each nacelle is attached next. CA glue is called for in the manual, but I chose 30-minute epoxy to hold them in place. I also removed a bit of the covering around all of these joints. This is not mentioned in the manual, but I prefer a wood-to-wood bond.

After the nacelle’s framework was in place, things got tricky. Without further modifications, the main gear’s forks cannot fully retract because they hit the sides of the retract bay. I again used my Dremel tool to remove a significant amount of structure from both sides to allow the retracts to work freely.

I left the retracts powered up so I could remove a little wood at a time, check the clearance by operating them, and then remove more as needed. I was able to sand away enough for good clearance without affecting the strength of the wing and the nacelle’s structure.




VQ’s electric retracts were provided with this model. Installing them requires some modification to the mounting rails, and several small modifications to the nacelle’s framework.


All of this work showed another problem in the bottom part of the firewall that would interfere with the wheel when it was fully retracted. I reluctantly trimmed a bit of the bottom portion of the firewall as needed to allow the wheels to fully retract.

With the motors and retractable gear installed, there was no room to mount the required 60-amp ESC so that it would fit in the nacelle and/or cowling without modification. Everything was fighting for the same space!

The only solution I could find was to modify the nacelle’s framework by cutting part of it away. By removing a bit of the plywood on the upper half of the firewall supports, I could use that space above the tire to horizontally mount the ESC.




Figuring out how to pack everything needed for the electric conversion into the C-47’s cowl required some imagination and a bit of modification, especially when it came to mounting the ESC.


It was a tight fit and left little room between the ESC and the nacelle covering, but it was the only available option. To support the ESC, I used a bit of the trimmed-off wood to make upper and lower supports through which the ESC could slide. Note that I also used a bit of glue to reinforce the remaining firewall to the firewall support joints and hopefully make up for the wood that was cut away.

I used small twist ties and electrical tape to tuck all of the wiring in place. The wires had to be routed out of the back of the nacelle, through the wing, and to the middle of the center section. That was easier said than done.

I found that the factory-provided access holes were too small. Enlarging them significantly provided enough room in which to allow the power leads through. Another hole had to be cut for the retract and ESC control wires. When I was satisfied with the fit, I installed two mini servos to work the inner flaps.

All of these wires have to exit at the center of the wing. The only precut holes in the center of the wing are a few lightening holes. Because they were in line with the routing of the wires, I opened those and fed the wires through. Later, when attaching the wing to the fuselage, I found that these holes were exactly over the plate in the fuselage into which the wing bolts are threaded. I enlarged the holes in the wing slightly to make sure the wiring wouldn’t be pinched during assembly.

After I finally figured this out, the nacelle covers were installed, as were the cowlings. The bottom nacelle covers and the bottom of the cowls had to be trimmed to allow clearance for the wheels.

When the work on the center section was completed, a couple of thoughts came to mind. First, I believe this C-47 was originally designed as a glow-powered aircraft, with no retracts. This makes sense because there would be room for a small tank and a servo in each nacelle. Converting the aircraft to electric power is easy without retracts because there is still plenty of room, but by adding electric retracts, there’s no room for a tank.

The outer wing panels were assembled next. Both required two servos each for the outer flaps and ailerons. When they were completed, the wing panels were attached to the center section and supported by a center wing tube and two small, anti-rotation dowels. A single screw holds each panel in place. The company mounted this screw to the top of the wing rather than the bottom where it would be less noticeable, but that’s the way it’s designed.

The assembled wing now presents even more wiring to run through to the center section and this is where I found a trick. Included with the kit are two large sheets of VQ Warbirds covering material. Knowing that I had this extra material, I decided to cut away a bit of the covering on the bottom side of the wing, exposing one of the larger lightening holes so I could fish the wiring through. When all of the wires were in the right spot, I used some of the excess covering and patched the holes.

All that was left to complete was installing the included control horns and metal pushrods for each of the ailerons and flaps. The wing alone weighs 5.5 pounds with all of the wiring involved, four flap servos, two aileron servos, two ESCs, and two retracts. All have extensions of various lengths that run from the exit holes in the center section. They need to be wired to a Y harness for a single connection to the receiver. In the case of the flaps, three Y harnesses are needed. Factor in the left and right power leads and that’s quite a lot of wiring!

When selecting the motor and propeller combination, keep in mind that clearance between the motor’s shaft and the fuselage is 9 inches at the most, and that’s exactly what a .25-size glow engine would have.

Innov8tive Designs offered to supply a pair of its Cobra C-2820-10 motors and matching ESCs. Allow me to share some of the email that Innovative sent me to figure out the problem. The company did its homework!

“The real C-47 Skytrain had a typical loaded weight of 26,000 pounds, with a maximum gross weight of 31,000 pounds. The two Pratt & Whitney R-1830 engines made 1,200 hp (895,000 watts) of power each. This gave the aircraft a typical full-throttle power loading of 69 watts per pound at 26,000 pounds, and a maximum gross power loading of 57.7 watts per pound at 31,000 pounds.

“For a plane like this, 75 watts per pound would give you ‘Scale’ performance, but we typically like to have better than a 5° climb angle on our models, so 100 watts per pound would give good sport flying performance and 125 watts per pound would give stellar performance, even from a grass field.

“With that information, a pair of motors that will deliver between 350 and 400 watts each, running from a three-cell battery with an MAS 9 x 7 x 3 prop would be required. Looking to our Cobra brand, the C-2820-10, 1,170 Kv motors would work, and provide the following full-throttle performance numbers:

“Volts - 11.1
“Amps - 31.6
“Watts - 351
“Rpm - 10,200
“Thrust - 58 ounces
“Pitch speed - 68 mph

“Two of these motors together would get you 702 watts of power and a total of 116 ounces or 7.25 pounds of static thrust.”

Work on the fuselage was straightforward. At the rear, the stabilizer was attached then the vertical fin. Two pairs of small, laser-cut braces were included to help support the vertical fin and keep it in perfect alignment. It’s a nice touch!

The rudder and elevator servos are mounted in a tray near the C-47’s nose. Preinstalled tubes allow the pushrods to easily run through the fuselage and exit in the right spots. Two pushrods are needed for each elevator half, and a pair is needed for the rudder and tail wheel. These can be operated by a single servo using the included bolt-on Y system.

Vacuum-formed tail fairings need to be trimmed slightly, then the top fairing is glued into place and bottom fairing attached with screws to allow access to the tail wheel steering assembly.

Attaching the wing to the fuselage showed that the supplied wing bolts were too short. I replaced them with wing bolts from my own stock that were roughly 1/2 inch longer.

The completed C-47 comes in well above the manual’s recommended weight, which doesn’t take into account the retracts. My review model weighs 8.25 pounds using two 3S 2,200 mAh LiPo batteries in the cockpit area. To my surprise, it balanced perfectly, but let me throw one note in here.

There’s no recommended battery size called out in the manual, but the VQ website mentions 4,500 mAh. Unless you modify the bracing on the front of the battery hatch, you are limited in the thickness of batteries you can install. All of my 2,200 mAh batteries will just fit. Using two (one per motor) gives me 4,400 mAh. Larger batteries will throw off the center of gravity slightly and there’s not much room to move them fore or aft.

I mounted some hook-and-loop tape (not included) to hold the batteries in place. There are also slots cut in the plywood shelf that will allow you to wrap a piece around the batteries for an even more secure mounting option.




A large hatch built into the cabin area allows access to install the radio and change the LiPo batteries.


This brings up one other thing and that’s clearance between the rudder and elevator servos, the pushrods, the LiPo batteries, and all of that wiring. Take some time to make sure nothing is rubbing or interfering because there’s a lot going on in a small space.


Flying

Taxiing through short grass proved to be no problem, and soon the model was lined up on the runway. With a nod to my photographer, I throttled up, and soon the C-47 was off the ground with plenty of power to quickly climb to an altitude that was a few mistakes high. After a couple laps around the field at half throttle, I was able to trim out some of the roll and a fair amount of climb.

I kept up the speed during the first photo passes because you never know what a scale warbird will do at slower speeds. After all of the photos were taken, it was time to get a sense of how the C-47 would fly. It can easily be flown at half throttle and it is comfortable and quite controllable.

Flap tests were next, so I slowed the C-47 down. I found no ballooning at half flaps, but there was some when going to full flaps. The model will slow down nicely and still give plenty of control—perfect for landing. If you go too slow, it will tip stall (especially in the turns). It’s not violent, but it will get your attention.

After roughly 5 or 6 minutes, I decided to end the maiden flight and had no problem landing with half flaps. The batteries showed roughly 50% power remaining, so I reset my timer for 9 minutes and set up for more flights.

Aerobatics are something you’d never associate with a full-scale C-47, and the same is true with this model. With plenty of power, it will loop fairly well. Rolls are ugly, but can be done. Anything more than that and you’ll realize that what you should be doing are smooth passes, large turns, chandelles, 360° descending circles, and similar maneuvers.

The calculations that Innov8tive Designs provided were spot on. Even with the heavier-than-expected outcome, the company’s Cobra motors and ESCs are perfect matches to the VQ C-47. The aircraft won’t go vertical or hover, nor should it, but there’s plenty of power when you need it!


Conclusion

In the air, the VQ Warbirds C-47 Skytrain looks great and it sounds fantastic with the twin Cobra motors whirring along. It’s a nice-flying model when flown in a scalelike manner. It doesn’t have an aerobatic design, but simple loops and rolls are possible.

If you’re looking for a scale electric twin, give the C-47 a look. This conversion to electric power and electric retracts was quite a journey. Electric power by itself is a relatively simple conversion, but adding the electric retracts requires some ingenuity. If you want to use glow engines, skip the retracts and you should be good to go.




Shot from a low angle, it’s apparent that the VQ Warbirds C-47 faithfully replicates the full-scale Douglas C-47 used in the D-Day invasion.


—George Kaplan
flyingkaplan@yahoo.com


Manufacturer/Distributor:

VQ Warbirds
info@vqwarbirds.com
www.vqwarbirds.com

Sources:

Innov8tive Designs
(734) 452-5788
www.innov8tivedesigns.com

Instruction manual
https://vqwarbirds.com/product/vq-c-47-skytrain-d-day-edition-70-8-epgp-...






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