Small-Field Flying
Paul Bradley | [email protected]
People and things at the Tri-County Barnstormers fly-in
Events limited my participation in the 2006 fly-in season, but one of the few I did enjoy was an annual event organized by the Tri-County Barnstormers of New Waverly, Texas. Held in early October, BEST (Best Electrics in Southeast Texas) is a great way to slip from the balmy days of the summer flying season into the fall and winter seasons. As in past years I spotted several models and modelers who would be of interest to the small-field-flying community.
I'll begin with a modeler who made an interesting statement about the state of the art to small-field flying. One of the photos is of Joe Ross holding his Cox Wings P-47. Nothing remarkable is apparent. The Cox Wings series has been with us for a while now and represents a nice resource for the small-field flier.
What you can't see in the photo is that Joe came to the event with the P-47 still in the box and unassembled. He set up next to me and I noticed that he was building the model at the field. In only a few hours he had all the equipment installed, and the little warbird was ready for its maiden flight. The first flight went off without a hitch and he enjoyed the model for the rest of the day.
Models such as the Cox Wings offerings combined with the current generation of small RC gear make it easy for someone with experience to go from a box of parts to a flying model airplane in a short time. Completely ready-to-fly models are available, but it is interesting to see that we have offerings that allow people with limited time to assemble a model that delivers plenty of flying enjoyment.
Another model that caught my eye was the Radical RC Micro Bipe built by Tres Wright. It has been available for a while, but it makes a statement for the small-field flier. This is a little airplane with a wingspan of 14 inches.
Despite its small size, the Micro Bipe is not small in performance. Powered with a direct-drive Feigao 12 mm, 4,000 rpm-per-volt motor, the model is a major performer. Tres used a GWS 3 x 3 propeller, a three-cell 620 mAh Li-Poly battery pack, two GWS Pico servos, and a Spektrum receiver. This little model is well suited for flying on windy days. Wind is often an issue for some of our small-field models but not for the Micro Bipe. It was a treat watching Tres fly his aircraft during some gusty conditions with little effect. Source information for the Radical RC Micro Bipe is at the end of this column.
More than models drew my attention at the fly-in. Keith Sparks showed me a neat item he had developed. You may recognize his name from his many published designs and his book Building with Foam. Keith showed me a neat, simple safety switch to use when charging Li-Poly battery packs. Li-Poly battery packs have a flexible outer structure. The batteries will swell before having a catastrophic failure during charging. Recognizing that characteristic, Keith designed the safety switch shown in the picture that shuts off the charger if a pack swells during a charge cycle. The concept involves placing the pack to be charged between two plywood plates. The distance between the plates is adjustable to allow for different battery-pack configurations. The top plate is hinged at one end.
If the pack swells during charging the hinged plate rotates. That action actuates a microswitch that shuts down the charger current and activates an alarm. A 9-volt battery supplies power to the alarm.
This is a neat and effective way to help prevent a major disaster should a Li-Poly pack develop a problem during charging. All you need are a few pieces of plywood and a few parts from your local RadioShack.
To make life as easy as possible for anyone interested in replicating Keith's safety switch, you can buy a set of laser-cut plywood parts from Manzano Laser Works. The source listing is at the end of the column.
Scale Airplanes for Small-Field Flying
Models based on full-scale airplanes have always been appealing to me. Seeing a miniature version of a full-scale airplane speaks to my love of aviation.
Building scale models has been part of the hobby since its inception, but they can be a challenge to fly well when they get smaller. We have learned what adjustments to make to the scale outlines to allow the resulting model to fly well. Things such as increased tail surfaces go a long way to help us enjoy a nice-flying model of our selected subject.
Knowledge such as this developed by the free-flight (FF) community has been passed along throughout the years. Because of model aviation's long heritage, we have many wonderful scale FF model-airplane designs at our disposal. A number of these are available in kit form.
This is a boon to one who likes scale models. There are not many scale model kits on the market specifically for the small-field RC modeler. These FF kits are ideal for our purposes and convert well to RC using current equipment. The FF designer knows all the tricks to make the model fly well, and when converted to RC the aircraft retains those good flying qualities and rewards the builder with a model that is well suited for flying in confined spaces.
I have an excellent FF kit that was converted to a small-field model. It comes from Lex Taylor from the Dallas, Texas, area. Lex chose the Herr (Sig) Pitts Special. This is a nice laser-cut kit with a 24-inch wingspan and a 216-square-inch area.
I provided a picture of the finished model for your review. Ready to fly, it weighs 10.5 ounces. Power is a Balsa Products—now BP Hobbies—2408-21 brushless motor turning a GWS 8 x 6 propeller and controlled by a Castle Creations Thunderbird-18 ESC. A two-cell 720 mAh Li-Poly battery provides the current.
Flight controls on the Pitts Special include rudder, elevator, and ailerons on the bottom wing. The receiver is a GWS R-4P, and Coverite Microlite is the finish. No deviations from the plans were made other than to make the control surfaces move. Wheels that weigh less than what came with the kit were used and a steerable tail wheel was added.
The Pitts Special flies well in a 100 x 105-foot gym with a curved but unobstructed 25-foot-high ceiling. According to Lex’s father, the airplane looks great in the air.
When you look at the FF offerings from Guillows, the Herr line now offered through Sig, Dumas, and the cottage-industry manufacturers, you find a cornucopia of wonderful scale models well suited to the role of small-field RC flying. Thanks to equipment available today for smaller RC models, we have the option of enjoying these fine kits in either format.
Evolution and Batteries
I have to confess to being a pack rat when it comes to model-airplane “stuff.” I have been in the game for a while and my pile of stuff, including many old model airplane magazines, reflects the number of years. During this time of the year when building is a common practice, I like to look through the old magazines. Sometimes a new project will be inspired and other times it is just interesting to see the evolution of the hobby.
One of my trips down memory lane involved the February 1962 American Modeler. I came across an offering for an electric-powered FF model called the Electra-Fly from Aristo-Craft. A copy of the photo in the magazine shows the model with Irv Polk and Cal Smith. Irv was the distributor and Cal was a well-known member of the model-aviation community.
Electric power has become more popular in recent years, but it is easy to forget that it has actually been around for a long time. What caught my eye with the Electra-Fly was the battery offered with the model. I have included a copy of the battery advertisement for your review.
It was a single-use, silver-chloride cell that was activated with a shot of salt water. The model required two cells. The resulting battery pack produced 2.5 amps at 2.5 volts and weighed slightly more than 1 ounce. It delivered full power for roughly 30 seconds and then died off. For the day the two-cell battery pack was lightweight.
The Electra-Fly appeared in 1962 and was successful because of a lightweight battery that could deliver enough current to fly the model. That seems to be the key for electric-powered models. Success has been dependent on batteries that are relatively lightweight and can deliver adequate current to develop enough motor power to fly our airplanes.
The passage of time has resulted in the development of battery technology. We now have rechargeable cells that are much lighter for a given capacity and can deliver enough current to allow model airplanes to fly vertically.
As an interesting contrast to the 1962 Electra-Fly, I have provided a photo of a current micro helicopter sold by RadioShack called the Pico Z and the 50 mAh Li-Poly battery used to power the system. This little helicopter uses infrared signals for control and can fly seven minutes on a single charge. Its flying weight is a scant 9 grams.
Battery technology has come a long way since 1962, as have electric motors and electronics technology, but the foundation of it all is the power source: our old friend the battery. We are limited without a good power source.
This brings me to the close of the column. With all of your new projects in progress, please don’t forget to send me a few pictures so we can enjoy your efforts. I can be reached via regular mail at 23238 Spinnaker Run, Magnolia TX 77354, or via the e-mail address in the column header.
Sources
- Li-Poly safety switch wood parts:
Manzano Laser Works 1 Hawks Rest Rd. Tijeras, NM 87059 (505) 286-2640 [email protected] www.manzanolaser.com
- Micro Bipe:
Radical RC 5339 Huberville Ave. Dayton, OH 45431 (937) 256-7277 [email protected] http://radicalrc.com
- Pitts Special and other Herr FF kits:
Sig Mfg. Box 520 Montezuma, IA 50171 (641) 623-5154 [email protected] www.sigmfg.com
Transcribed from original scans by AI. Minor OCR errors may remain.
