Park View: Stevens AeroModel RingRat
Bob Aberle
An electric-powered CL model for everybody
Electric power has been with us for many years and continues to grow as various technologies (motors, batteries, ESCs, etc.) continue to improve. Until approximately six years ago, electric power was primarily associated with radio-controlled model aircraft. Today we are seeing it used in more applications, such as free flight (FF) and control line (CL).
The lead photo in the article I wrote titled "Advantages of Electric Power" (published in the July MA) shows me hand-launching a 300-square-inch FF model. As a U.S. CL Aerobatics team member in 2006, Bob Hunt (MA’s editor emeritus) flew the first electric-powered model entered in a World Championship. So the message is clear: the use of electric power is expanding. The question modelers might have is how they can get involved with an electric-powered CL model. I’ll answer that question in detail.
Flying electric CL has a couple of advantages, one of which is that flight is limited to line length. Therefore, parking lots, school fields, and other small open areas can be used. Another benefit is that electric power is quiet, so you can fly almost any time of the day without upsetting the neighbors.
With these advantages in mind, Bill Stevens of Stevens AeroModel introduced a series of three small electric CL designs. He has produced a variety of excellent kits throughout the years, including trainers, sport fliers, aerobatic 3-D models, scale racers, micro airplanes, and FF aircraft.
Bill’s specialty is laser-cut parts kits that require assembling, painting, and/or covering. He also sells all of the support equipment for these designs, including motors, batteries, ESCs, cements, covering materials, etc.
The electric CL aircraft that Bill added to his product line are:
- the basic trainer named the RingRat (item CL-100),
- a larger RingRat (item CL-250) intended as an introduction into CL Aerobatics, and
- the SCRAM!: an electric Combat model.
The Kit
The basic RingRat is a good starting point for CL. The concept is that there are two kinds of fliers who would be interested in this airplane. The first is an experienced aeromodeler who wants to get a child interested in model aviation. The second is an old-time modeler who flew CL years ago but has been an RC pilot for many years and now wants to get back to his roots.
In either situation, the little RingRat offers a quick and inexpensive way to participate in CL—and now with electric power.
The RingRat kit is total simplicity. It consists of eight sheets of laser-cut balsa and plywood parts; everything fits perfectly and easily. It also includes essentially all necessary hardware, including the bellcrank, control horn, control rod, wheels, landing gear, tail skid, and more. The 26-page assembly manual contains many photos with detailed captions. Full-size plans are neither supplied nor required.
Assembly involves a built-up wing with laser-cut ribs and spars. The fuselage is a profile type made from 3/16-inch balsa. The tail surfaces are all sheet balsa. I built the entire aircraft frame using medium CA glue and accelerator.
The wing was covered with yellow Solite (Solarfilm). I sprayed the fuselage and tail surfaces with a coat of Rust-Oleum Painter’s Touch sandable primer, followed by a spray coat of Krylon Short Cuts. Sun Yellow (item SCSC036) matched the Solite perfectly.
I estimate that the total assembly and finishing time on my RingRat was less than two days. The only slight problem I had was not providing clearance holes for the two leadout wires; those holes are needed on the inboard wingtip. I simply corrected the problem by drilling two 1/16-inch-diameter holes and then inserting the supplied tubing.
I rate the assembly process as easy. Having a reasonably experienced modeler as a coach would be helpful, but it is not essential.
All of the necessary power-system components must be purchased separately. You can buy the equipment you want to use or purchase all of it from Stevens AeroModel.
My model is powered by:
- an SA Sport BL-300 brushless outrunner motor, 1,400 kV (runs at approximately 34 watts input) — $17.95,
- an SA Sport 10-amp brushless ESC — $16.99,
- a Thunder Power two-cell, 325 mAh 45C Li-Poly battery (item THP3252SP45) — $16.99,
- a GWS 7 x 3.5 propeller, and
- an E-flite Control Line Motor Timer (item EFLA172) — $10.99 (designed by Bob Wilder, a noted indoor modeler).
The combination of the kit and these extra items totaled nearly $115. That price does not include covering, adhesive, or paint.
Installing the electric power equipment is easy. All of the components have connectors, so no soldering is necessary. Four wood screws attach the motor to the plywood firewall. The ESC, battery, and motor timer are affixed to the profile fuselage with hook-and-loop fastener.
To start and stop the motor you need that all-important motor timer. It lets you adjust the motor speed from idle to full power by rotating one knob with a screwdriver. A push-button switch on the timer allows you to set the motor-run duration in one-minute increments. Instructions supplied with the motor timer spell out everything.
The power system I selected worked flawlessly during the many test flights that were made for this article.
Other items to consider:
- a control handle and a pair of 35-foot Dacron lines (Stevens AeroModel sells a Sig 1/2A handle and lines, item SIGSH544, for $7.99),
- a battery charger that can handle two Li-Poly cells (make sure the charger mates with the balanced-mode connector on your battery — in my case it was a Thunder Power connector).
Final Touches
I set elevator control travel at a minimum since the RingRat is a trainer. This particular model is not meant to do loops. I measured the elevator control throw on my model as 1/2 inch up and 3/8 inch down, with respect to the neutral (level) position.
The total weight of the RingRat with the specified battery pack was 6.0 ounces. I measured the balance point at 1 1/2 inches back from the wing leading edge.
Flying
My friends and I have flown this RingRat several dozen times. We have made every flight off of a low-cut grass field.
On several occasions the model went straight into the ground; the only damage in each case was a broken propeller. The message was to take plenty of propellers to the field and plenty of O-rings to hold the propeller to the prop-saver adapter.
We basically use full power, which is close to 34 watts of input at a 6-ounce total weight. That works out to a power loading of about 90 watts per pound, so the airplane takes off in a hurry. Several experienced modelers who learned to fly years ago with CL models had no problem flying the RingRat.
At first we set one-minute motor runs on the timer. Then we worked up to two and three minutes. That's nearing the time limit for this size of battery. Three minutes with a fast model such as this on 35-foot lines is enough.
I let several 10- to 12-year-olds fly the RingRat. One thing we learned for sure is that it does not like a lot of wind. Approximately 5 mph is comfortable. At 10 mph we had our hands full—especially the younger fliers.
We employed several battery packs. One was always on charge while we flew with another, which permitted almost continuous flying. No one got bored with this activity.
All of the test pilots eventually performed wingovers (in low winds). As I mentioned, loops cannot be done with this model unless elevator control throw is increased and the CG (balance point) is shifted aft somewhat. Moving on to the next-size RingRat would be a better way to advance.
This is one rugged airplane. The grass field helped, but we did not hold back in the learning process and it held together perfectly (except for the propellers).
The RingRat is a perfect electric CL trainer. It's easy to build, is inexpensive, and flies exceptionally well.
Keep in mind that this series of models was made small intentionally, so that short control lines could be used. This keeps the necessary field size to a minimum and even allows you to fly it indoors in facilities with the proper ceiling clearance.
If you catch on with this size of model, be aware that many larger electric CL ARFs are being advertised these days. This is getting serious.
MA
Bob Aberle [email protected]
Manufacturer
Stevens AeroModel Box 15347 Colorado Springs, CO 80935 (719) 387-4187 www.stevensaero.com
Transcribed from original scans by AI. Minor OCR errors may remain.
