Jim Fruit’s Cessna Bobcat
by Fred Cronenwett
clscale7@gmail.com
Jim Fruit builds models that look like miniature versions of the full-scale aircraft. His Rearwin Speedster was on the June 2015 cover of Model Aviation and he won the High Static award at the Nats with that model. He has completed a new model—an electric-powered Cessna Bobcat.
The best way to get a better static score is to take a three-view drawing and enlarge it to the size you want to build, instead of using plans or building from a kit. Enlarging the three-view that you show the judges will eliminate many of the outline errors that appear in some of the plans from which we often build.
Jim started with the Wylam Plans Cessna Bobcat three-view to build the 62-inch wingspan model. The full-scale Bobcat has flaps and retractable landing gear, so these were duplicated on the model. A pilot’s realism score will be higher if the model has flaps and retracts like the full-scale aircraft.
With two or more motors, you can use the multiengine option in competition. Flaps count as one option and are easy to add, but learning how to fly with flaps can take some practice.
Retracts count as two options; they are not as easy as you might think, but they are well worth the effort. When you use the newer E-flite electric retracts that plug into the receiver, the air valve, air tank, and tubing with the pneumatic retracts are eliminated. Jim used E-flite .46-size 85° retracts.
The flaps are controlled with a single servo that plugs directly into the receiver. The electric motors have an ESC that also plugs directly into the receiver, which makes setting up the model easier than setting one up with mechanical pushrods.
One of the more difficult things to figure out with electric power is what motor to use so that you have enough power. Himax HC3522-0990 motors and 54-amp Castle Creations Thunderbird ESCs are used to power this model. This combination results in approximately 106 watts per pound, which is a great power loading. Jim uses Clancy Arnold’s U/Tronics down-the-line electronic controls to control the throttles, flaps, and retracts with insulated lines. The model is painted with Behr latex house paint and has a Rust-Oleum clear satin over that. The model weighs 7½ pounds, making the wing loading 24 ounces per square foot of wing area.
Ronnie Tribe’s B-17
This model comes from the United Kingdom. Ronnie Tribe scratch-built a B-17 from his own plans to compete in the 2015 British Nationals. With a 54-inch wingspan and weighing 6½ pounds, you would be surprised to find out how many features he has put into the model. The construction is typical balsa, but he fiberglassed the aircraft and painted it with Tamiya Acrylic paint, which is typically used on plastic models. The model is powered with four Turnigy 1,400 Kv outrunner motors
using 40-amp speed controllers. When you build an aircraft of this size, the amount of space in the cowl can limit where you can put all of the parts. The speed controllers for the outboard motors are in the outboard nacelles, while the inboard motors have the speed controls in the fuselage. Even with a 54-inch wingspan, the cowl is smaller than you might think. The single 2,200 mAh 4S LiPo battery is located in the fuselage and powers all four motors. Because of the current draw, Ronnie chose a 65C battery. The motors turn 6 x 4 three-blade propellers. He can even have the motors tick over slowly, simulating startup and shutdown, by using a variable resistor. The model also has a sound system that offers machine gun sounds when the top and bottom turrets are rotating. After taking off, the Turnigy landing gear retracts. Ronnie’s website has pictures of his B-17 and other models that he has built and flown. The website also covers electronics, retracts, and a variety of interesting Control Line (CL)-related topics.
Contest Listing for 2016
With the Nats behind us, we are getting into the last part of the contest season. If you have qualified for the National Association of Scale Aeromodelers (NASA) Scale Classic, you will soon be getting ready for that contest. The NASA Scale Classic will be held in Waynesburg, Pennsylvania, on September 23-25. The Dayton Buzzin’ Buzzards CL Scale and Broken Arrow CL Stunt and Scale contests remain as qualifiers for the Scale Classic if you don’t already have an invitation. Remember that Fun Scale and ½A Scale do not need invitations to compete. Be sure to verify all contest dates and information with the AMA Sanctioned Event Calendar before making travel plans.
- Dayton Buzzin’ Buzzards CL Scale Contest, August 13-14, Dayton OH
- Treetown Modelaires Midwest Regionals, September 4, Aurora IL
- Broken Arrow CL Stunt and Scale Contest, September 17-18, Valley Park MO
- NASA Scale Classic, September 23-25, Waynesburg PA
- Carrier Plus Scale, October 29, Phoenix AZ
- 1cc Multi-Engine Scale Contest, October (date TBD), Tucson AZ
I always welcome contest reports, upcoming contest flyers, pictures, and any projects you are building and flying. When sending me pictures for publication, send high-resolution versions.
Land softly!
Control Line Flying
Ronnie Tribe
www.control-line-flying.com
SOURCES:
E-flite
(800) 338-4639
www.e-fliterc.com
AMA Event Calendar
www.modelaircraft.org/events/calendar.aspx
