Small-Field Flying
Paul Bradley 32238 Spinnaker Run, Magnolia TX 77354 E-mail: [email protected]
Michael Burdette's Peanut-Scale Sopwith Triplane
What do you get when you combine an interest in Free Flight (FF) with small-field Radio Control (RC)? Michael Burdette of Pleasant Hope, Missouri, has a great answer. Starting with Peanut Scale plans for a Sopwith Triplane and a ruler, he developed a gorgeous scale small-field flyer.
In case you are unfamiliar with the term "Peanut Scale," it is a category of rubber-powered scale FF models with a wingspan limit of 13 inches. Michael doubled the plan size to yield a model with a 26-inch wingspan, then performed an equipment transplant from a Lite Stik to arrive at the finished model.
Construction and finish:
- All-balsa structure with light plywood reinforcements where needed.
- Covered with clear-doped craft tissue.
- Markings hand-cut from colored tissue.
Equipment and specs:
- GWS DX-A motor package (from the Lite Stik)
- Seven-cell, 270 mAh NiMH battery pack
- GWS speed control
- Hitec Feather receiver
- Two Cirrus CS-10 servos
- All-up flying weight: about 9.5 ounces
Michael reports the model flies well indoors or outdoors. With the many Peanut Scale plans available, it would be nice to see other designs transformed into small-field flyers.
Lithium-Polymer Batteries
Electric power is very popular for small-field models, and battery technology is moving quickly. Lithium-polymer (LiPo) cells have generated excitement because they offer significantly higher power density than older chemistries. The downside historically has been current-delivery limits, but cells capable of higher continuous current are becoming available.
Joel Maxwell and J&N Performance Electric have begun offering a dual-cell LiPo pack from DynaPac along with an appropriate charger. The pack specs:
- Voltage: 7.6 V (2 cells)
- Capacity: 640 mAh
- Weight: 33 grams
- Current: 2 A continuous, peaks to 3 A
These lightweight, relatively high-current packs open the door to many small-field subjects by providing a compact high-power-density energy source. (The contact information for J&N is listed in the source listing at the end of the column.)
DJ Aerotech Roadkill Series
DJ Aerotech's profile "Roadkill" kits remain popular with small-field and indoor flyers. The Roadkill line originally emphasized World War II subjects; Don Stackhouse and Joe Hahn have added World War I and classic civilian aircraft to the lineup.
These profile models make excellent small-field flyers—especially when paired with lightweight LiPo batteries. The lighter weight and greater power density of newer cells bring Roadkill models to life.
My Rascal 18 Project — The Final Installment
In previous columns I described a project combining nostalgia and modern micro RC gear: a replica of the old Top Flite Rascal 18, converted to an electric RC small-field flyer. The project has reached a successful conclusion—the electric-powered Rascal 18 now flies gracefully around my backyard.
Construction and equipment:
- Motor: Mabuchi M20 with a homemade 4.2:1 gear drive (thanks to my brother Ralph)
- Receiver: RFFS-100 (Dynamic Web Enterprises)
- Actuators: Bob Selman units
- Battery: single-cell 190 mAh lithium-polymer
- All-up flying weight: 30 grams
One unique feature is Ralph's motor mounting method: the propeller-shaft support plugs into a slightly tapered hole in a dowel glued to the nose block. This allows the motor to be easily inserted or removed. Watching the Rascal float around the yard has produced many smiles.
Rascal 18 Recollections (Ed Mate)
I received a great note from Ed Mate in response to the January 2003 column in which I first mentioned the Rascal 18 project. In his youth he was part of the Rascal 18 development team. His recollections:
"Your Rascal 18 Jigtime story really struck a chord. In 1950 I was studying architecture and needed a summer job to help with college tuition. The magnet of model airplanes was stronger than that of what I was studying, so when my classmates went to work for architects for the summer I decided I wanted to work for the great Carl Goldberg. His company at the time was American Hobby Specialties. Reading this sign on the door I walked in and asked to see the master. Soon Carl appeared and I nearly begged him for a summer job. I was 18 years old.
"He handed me a notepad and a pencil and pointed at the Rascal 18 prototype on a display table in the general office area. He told me he would be back and that I should make a perspective sketch of the Rascal. He would decide when he saw the sketch. Thank God for the gift he gave me of drawing ability. After a slight correction (which Carl always did) I passed.
"He explained that I would work on his dream of a beginner's model airplane that would be guaranteed to fly. That it would be called Jigtime because the parts would be so designed that they would only fit one way, the right way.
"He said we had to design a total of four models. He already had picked the Stinson Sentinel and the Piper Vagabond for two of the remaining three. He asked me to think about what the other airplane should be. But right now we were to go all the way with the Rascal to produce a test model for testing with teenagers. It would go on the market alone for this purpose.
"Bill Ehrlich and myself would take hand-cut parts, assemble the new Jigtime prototype, and then do the most critical drafting operation, the die drawings that would be rubber cemented and shellacked to 3/8 inch plywood so a jigsaw genius could split a saw cut with our .005 lines for razorblade stock. Thus we had our Jigtime parts dies. Later we would add rubber stamp material to print the color pattern to the balsa as it was die cut. The wing had a separate operation to form the airfoil section curve into it—the only non-flat part in the kit.
"We had it ready for the market in about three to four weeks. But first we would test it with Boy Scout groups. Not too good. The kids were not paying any attention to the..."
(Note: the original source ends this recollection mid-sentence.)
Notes on Trainer Design (Stikum example)
A related section discusses a trainer design (Stikum) and the design philosophy behind it:
- Early goal: use readily available seven- or eight-cell packs in the 1,700–3,000 mAh range for cost, availability, and swap ease.
- Motor choice: a proven geared Astro 05—selected for serviceability, availability of replacement parts, and robust gears (long-term cost-effective despite higher initial cost).
- Durability features:
- Wing and tail surfaces rubber-banded on to give and reduce breakage.
- Wing dowels oriented so the wing pops off more easily on frontal impact.
- Battery mounted with Velcro so it can come free on impact, preventing severe nose-in damage.
- Sermos (disconnect) connectors used so wiring separates on impact.
For the author's Rascal 18 project, the motor plugs into a dowel-mounted support for easy removal—an example of practical, serviceable engineering applied to small-field models.
Closing
Small-field flying continues to benefit from developments in lightweight construction, profile kits, and especially battery technology. Converting classic designs and Peanut Scale plans into small-field RC is both feasible and rewarding, and new LiPo packs and compact micro components make more subjects flyable than ever.
Transcribed from original scans by AI. Minor OCR errors may remain.
