|Wing Area:||813 sq. in.|
|Weight:||6.5 to 7 lbs|
|Wing Loading:||19.5 oz/sq. ft.|
|Servos:||Cirrus C601 (7)|
|Transmitter:||Airtronics RDS 8000|
|Receiver:||Airtronics FHSS 92824 2.4 GHz|
|Battery:||4.8 v 1000 mAh NiMH|
|Motor:||SK .50 - $59.00|
The Waco UPF-7 is a grand contribution to flying history. The U designated the large W-670 engine, the P was the style of wing, and the F designated the type and series which differentiated itself in many ways. The single-seat made it more of a racing plane than the typical trainer. In some cases, the front seat would remain, but the windshield was removable. A variety of highly refined renditions featured the single seat.
The single-seat in Kangke's production is very unique; not because of the design, but for the attention it brings to the great Jimmie Franklin who flew his 1937 modified UPF-7 at air shows across America until his death in 2005. Flying the Masters of Disaster air show, Jimmie's General Electric J-85 jet powered Waco awed crowds with aerobatics and wing walking. His jet powered JMF-7 Waco produced 3000 pounds of thrust, and in combination with the with the big 500 horsepower Pratt & Whitney R-985 produced over 2000 total horsepower and 4500 pounds of thrust (the AUW was 3330 pounds).
The Super Kraft Waco UPF-7 does replicate the performance of Jimmie Franklin's Waco. The fully symmetrical wings with four ailerons can produce a nearly 360 degree per second roll rate. The large tail gives the Waco great control. The wing loading of only 19.8 ounces per square foot combined with the SK .50 engine makes for an eight pound biplane with excellent performance.
It is an extremely well built ARF, and when I completed the build, I enjoyed just admiring it. While I do still enjoy how it looks, the flight characteristics make this a flight line favorite.
Kangke's single seat version is beautifully built in 1/7th scale in the popular yellow and blue colors. Mine arrived in perfect condition and was something I was looking forward to building over the winter.
I could not wait to start this project. It is not a difficult build, but one that requires some attention. The instructions were well written and full of helpful photographs.
The ailerons are hinged but need to CA'd to complete the process. A rigid and straight wing joiner is used on both wings. The joiners are also used in the packaging to secure the ailerons.
They wings were a perfect fit with no warping or out of square joints. I used string that I could tighten to draw the two halves together.
The wings receive four servos, and both the upper and lower will need 12" extensions and a "Y" connector.
The fuselage is very detailed. There are 10 to 12 blind nuts already installed. It is a good idea to work over a foam pad to protect the finish, and do not damage the lite-ply ring that will eventually support the cowling.
The tail is very big and lends itself to stable flight. This kit uses stiff steel control threaded linkages in place of guide wires. They work well and are adjustable so you can square the tail. Under the tail there is a spring loaded tail wheel that is very scalelike.
Squaring the tail with the fuselage is easier done before the wings are attached. The vertical stabilizer passes through the horizontal stabilizer, and the guide wires finish the tail.
SK engines are manufactured exclusively for Kangke USA. The come pre-lubed from the factory and ready to run. The SK 50 is a non-ringed ABC constructed Schnuerle ported engine with bearings at both ends of the crankshaft. All SK engines are serviceable in the US through a designated repair center, and all parts are available in the US through Kangke USA.
The SK engine was no trouble to break-in. I ran a few tanks through it at a rich mixture and then worked to set the high speed and idle. I did have to adjust the low speed jet to get a good idle.
The firewall is not drilled, so I had to make some measurements to get the engine centered in the middle of the cowling and far enough forward to clear the it.
One would typically use a Pitts style muffler but none were available for the SK engine. Instead, I extended the exhaust stack with a block of aluminum so the muffler cleared the cowling.
The wing joining is a very detailed operation that requires attention. It begins by installing the bottom wing and putting the struts in place making sure that they are pointed forward.
Once both struts are in place, the cabane mounts install to the fuselage followed by the cabanes. The cabanes and struts are covered lite-ply.
The hardware loosely installsto the underside of the top wing. There are eight brackets.
Once you have the upper wing stable, bolt everything together. If something does not fit, it is likely you have something on backwards. Make sure all the bolts and nuts are tight!
I used a very trustworthy Airtronics 92824 2.4 GHz receiver and RDS 8000 transmitter. It is small and fit nicely under the control linkages of the elevator and rudder. There is limited space on the servo deck, and that location worked well. Because the wings will likely never come off, I did not need to be sure I had enough servo lead to move the wing. Once in place it was there to stay. The 1000 mAh NiMh 4.8 volt receiver pack fit along the side wall of the fuselage. I installed the switch along the left side away from the exhaust.
The decal installation is very easy. Also now is the time to add the wheel pants.
After the engine break-in I reinstalled the cowling, prop and nose cone. The red nose cone I used for break-in was replaced with a matching yellow cone.
Getting the CG right requires a CG stand. The CG is 4 to 4.5 inches behind the leading edge of the UPPER wing.
At first I was not sure the SK.50 engine was enough for the eight pound Waco, but it easily took off and flew with no problems. Other than the exhaust extension that I think added some resonance to the engine, the plane looked as good in the air as it does on the ground. In fact, it looked bigger in the air, and the bright yellow and blue trim was excellent visually.
I enjoyed flying the Waco and will continue to fly it more. I realize now I can extend my aileron and rudder throws to enhance the flying. It do not see this heavy bird as a 3D machine as built with the SK .50, but it can easily handle a bigger engine. Stability was great, and air tracking with minimal trimming was perfect. Slow and high-speed flight was dead-on.
The SK engine performed perfectly with plenty of power and reliable idle. I like the easy starting and setup. The extension I added required some effort, but allowed me to use the original muffler. A Pitts style muffler is best, but I really do not see anything that makes my method undesirable.
One of the unique features of the Waco is the spring loaded tail wheel and rudder. As you can see in the video, ground maneuvering was no problem. The takeoff roll was only about 40 feet, and the Waco moved down the runway with little need for offsetting with the rudder. Landings were no problem either. The glide slope is excellent, and I found flying to the end of the runway was easily followed by a gentle touch down. I also thought the ground stability was solid, and high-speed turns on roll out did not create much problem.
The as built version was very gentle - almost too gentle. The rolls, were big and wide, with the expectation being 360 degrees per second in a Waco. but to get this I would have to max out the throws. Loops and inverted flight were no problem, and inverted required little input. Knife edge seemed to be a combination of not enough air over the tail or not enough rudder movement: I continued to lose altitude, but very slowly. Throttle management helped or perhaps a slightly higher propeller pitch.
No, the Waco is not for beginners. It is more advanced, but not to the degree that it has to be flown by experts.
From the minute I received this kit I was impressed. The color and trim are outstanding, and the overall build went perfectly. In the end I had one heck of beautiful plane that flies well and looks fantastic. The great folks at KangkeUSA are easy to work with, and in conjunction with Super Kraft, produce some really well built kits.
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