Small-Field Flying
Paul Bradley 32238 Spinnaker Run, Magnolia TX 77354 E-mail: [email protected]
“That's too big for my small field.” How many times have you looked at a model and said to yourself, “I would like one of those but it is too large for my small-field site”?
There are numerous models sized for .40 glow power or larger engines that look appealing. Unfortunately, they don’t normally come in a size that is commonly used for small-field flying.
Sam Will, of Phoenix, Arizona, has developed two printed-balsa all-sheet models that are enlarged versions of my reproduction drawings. I converted the rubber-powered free-flight Frank Macy American Junior Hornet to RC; Sam has created larger all-sheet versions based on my reproduction drawings and printed them on balsa.
Chris Poole, who lives at high elevation in Colorado, ran into the small-field problem with the Tower Hobbies Uproar. The kit produced a model with the features he wanted, but it was not suitable for his small field. Being an inventive 16-year-old, Chris did not let the unavailability of a kit for the size he desired stop him from having a small-field version of the Uproar.
Chris developed plans for the aircraft at reduced dimensions. Power comes from a direct-drive Mabuchi 280 electric motor turning a 5-inch Gunther prop (the same type used on the Zagi). A two-cell 720 mAh Li-Poly battery pack supplies the power. The airplane has full-house controls using three HS-55 servos coupled to a JR Electron 6 receiver. With a wingspan of 24 inches, Chris reports the model is a great flier. Hats off to Chris for rescaling and scratch-building to achieve his result.
More commonly, modelers scale designs down for small-field venues. Many classic early designs tended to be large and are good sources to scale down. Less common but equally valuable is scaling very small micro-RC designs up to sizes suitable for outdoor small-field flying. Some micro designs are elegant but require indoor sites; enlarging them can make them usable at individual flying sites.
Following this idea, I received photos from Sam Will. Sam has fond memories of the old all-sheet balsa Top Flite Jigtime models. When he saw the reproduction drawing packages of those classic designs on my website (www.parmodels.com), he jumped in.
Sam found an Epson 960 ink-jet printer that could handle printing on balsa. He turned out a set of the rubber-powered free-flight reproduction models and, as an RC flier, adapted the Jigtime models to radio control.
The Jigtime models make nice micro RC airplanes in their original size. Sam wanted a larger model for his flying site. His printer handles balsa up to 3/32 inch thick, so he doubled the model size. He printed parts on 1/16-inch balsa. One is based on the Jigtime Luscombe and the other is a blowup of the Carl Goldberg Cessna 180. Both are electric-powered: the Luscombe uses a geared 6-volt Speed 400, and the Cessna has a brushless installation. The Luscombe has a 42-inch wingspan and the Cessna a 46-inch span. I understand the Epson 960 is no longer produced, but I hope similar printers are available. Nice work, Sam.
Jim Walker’s Hornet was great then and now. A while back I shared a project of mine converting a reproduction Jim Walker 404 Interceptor folding-wing glider to RC. That was a fun project and has provided much small-field flying enjoyment.
Frank Macy, the maker of the 404 Interceptor reproductions, also offers another classic Jim Walker 1950s model: the rubber-powered free-flight AJ Hornet. My brother Ralph and I had many AJ Hornets as kids; thanks to those ready-to-fly models we experienced airplanes that flew well and helped keep us in the hobby.
Given my fondness for the AJ Hornet, it was only a matter of time before my reproduction received an electric motor and radio gear. The photos tell the story.
Component choices for the conversion began with a suitable micro receiver. I used the RFFS-100 from Dynamic Web Enterprises; another good choice is the JMP receiver (see sources). Both weigh roughly 2 grams and include a built-in 1.5-amp speed control. To operate rudder and elevator I chose Bob Selman standard-size magnetic actuators. I used a Mabuchi N-20 motor coupled to a Bob Selman 4:2:1 gear drive—the gear drive Bob sells for the N-20 is well suited to a project such as the AJ Hornet conversion. The propeller is the same 5-inch Gunther unit Chris Poole used on his scaled-down Uproar.
In its free-flight (rubber-motor) configuration the AJ Hornet weighs 18 grams. The electric RC version weighs 41 grams. You might expect the added weight to hurt performance, but it did not: the RC Hornet is an excellent small-field flyer.
I elected to use two Li-Poly cells in series. This provides plenty of power to punch through wind and perform simple aerobatics. The chosen battery capacity is 190 mAh, giving flights in excess of 20 minutes. Note: the RFFS-100 and JMP receivers are designed to run on a single Li-Poly cell; Bob Selman also sells a two-cell adapter if you prefer to use two cells.
After flying the RC Hornet, I considered using it as an air-tow tug for the 404 Interceptor. At first I thought there might not be enough power to tow the Interceptor, especially with the RC weight increase. The more I thought about it, the more I felt compelled to try. My initial attempts show the little RC Hornet has plenty of power for towing. I need to tune the towing geometry to improve Interceptor stability while towed, but this looks to be a great backyard-flying project.
The RC Hornet and similar models are ideal for small-field venues such as a large backyard. I like to fly mine from the back porch on calm evenings and do ROGs (rise-off-ground launches). Life is good in the small-field-flying world.
Float-Flying Revisited
Early in this column’s life I wrote about float-flying. Some nice bodies of water can be used by our small-field models when equipped with floats. Bill Stodgell of Jefferson City, Missouri, pointed out one aspect of float-flying with small electric models that I had missed.
With electric power, you can test a model’s water characteristics in a backyard swimming pool. Even if you plan to fly off an open body of water, a pool is handy to fine-tune float setup. One photo shows Bill testing his float-equipped SR Batteries Bantam biplane in a family member’s swimming pool.
After reading the March 2004 MA article that included the Electric Flash construction article, Bill adapted that float design to his Bantam. After building and installing the floats, he fine-tuned them in a pool. This is a great example of the advantages of smaller size and clean electric power for float-equipped models.
This brings me to the close of this edition. As always, don’t be bashful about sharing your latest small-field-flyer project. Please send a picture or two of your models so we can all enjoy them. — PB
Sources:
- AJ Hornet:
Frank Macy 1501 SW Baker St. #53 McMinnville, OR 97128 (503) 435-1916 [email protected]
- RFFS-100 receiver:
Dynamic Web Enterprises 159 Little Robin Rd. Amherst, NY 14228 (866) FLY-MICRO www.smallrc.com
- Magnetic actuators, JMP receiver, N-20 motor/gear drive, two-cell receiver adapter:
Bob Selman Designs 9054 Gum Rd. Carthage, MO 64836 (417) 358-9521 (after 6 p.m. CST) www.bsdmicrorc.com
Transcribed from original scans by AI. Minor OCR errors may remain.
