RADIO CONTROL JETS
Jim Hiller, 6090 Downs Rd., Champion OH 44481
THE INFLUX OF Almost Ready-to-Fly (ARF) models is hitting jet modeling more all the time. Cermark, DL Aeromodeles, and ElectroDynamics have joined up to bring us a new Sport Scale jet—an ARF version of the Aermacchi MB-339 DL Aeromodeles kit. The kit version has been available for quite a few years and has proven to be a solid, good-flying model with ducted-fan power and with turbine power.
The Cermark Aermacchi MB-339 is sized for .91-size ducted-fan units or 12- to 17-pound-thrust turbines. It has a 67-inch wingspan with tip tanks installed, and is only 64 inches long. Bare weight of the airframe, without systems, is approximately seven pounds. This should result in a model that weighs 14-17 pounds, depending on the power system and optional systems. The kit includes a double-walled, stainless-steel tailpipe.
The airframe consists of a molded fiberglass fuselage with built-up-construction wings, stabilizers, and fin. These parts are fiberglass-covered, and they come prepainted. The Italian colors of the Frecce Tricolori aerobatic team are used for this ARF model.
The prototype ARF kits are flying on RAM 500 and RAM 750 turbines, proving the capability of this airframe to handle the 17-pound-thrust turbines. The fuel tanks are not included, but this should not be a problem. The RAM 750 model is flying with two standard 12-ounce saddle tanks and a main 48-ounce tank, all available from the hobby shop. No expensive, specially fitted tanks are required to get this model into the air.
The model built from the DL Aeromodeles kit has been flown at Superman with ducted-fan power, then later that same day with turbine power. I have been assured that this feature—the ability to swap between ducted-fan and turbine power—can be used with the ARF kit, but the modeler will have to develop his or her own techniques to accomplish the task quickly.
Additional information about the Sport Scale ARF Aermacchi MB-339 is currently available on the DL Aeromodeles and ElectroDynamics Web sites at www.dlaero.com and www.electrodynan.com respectively. This model is priced at $998 with introduction scheduled for March 2002.
I have become an advocate—as have many other jet modelers—of switching to small whip antennas on my turbine-powered models. Many modelers are flying with antennas such as the Deans unit with great success. I flew all my ducted-fan and turbine models last year with a Deans antenna without any problems.
The advantage of these whip antennas lies in their size. The long wire antenna that comes standard on our receivers is difficult to place in a turbine model without degrading range to an unacceptable degree. The extensive use of carbon fiber, the large array of servo loads, and the stainless-steel turbine tailpipe have an adverse effect on range when the antenna wire is routed near them.
These short whip antennas eliminate the problem by allowing us to mount them outside the airframe or up in the nose, ahead of the nose gear—a traditionally empty and nonstructural area that is usually molded from fiberglass cloth.
I was unable to route a standard wire antenna inside my Crown aviation, Inc. (CAD Racer) without degrading the radio’s range to less than half of normal. The simple installation of a Deans whip antenna allowed me to stuff it up into the model’s nose.
A ground-check of this installation resulted in a loss of only 10% of the best range I could attain with the wire antenna when it was outside and in front of the airframe. I learned that the standard antenna wire, when hid outside the airframe but along the length of the fuselage, had a 25% range reduction. The extensive use of carbon-fiber reinforcements in this CA kit really affected my radio.
Jet-A Fuel and Long-Term Storage: Kerosene can support the growth of algae, which ruins the fuel. This can, and does, happen to many modelers when they store last summer’s Jet-A for use the next flying season.
Inhibitors can be added to block algae growth, but they are not necessarily used. I checked with my local airport, and people there knew of the problem, but they do not add inhibitors to their Jet-A fuel.
This is a case of education for us. If you store your Jet-A fuel, look inside the can for a greenish or black residue inside the bottle; this is algae growth.
Joe Amisler reported that he is continuing to run his kit-built ID Enterprise Wren 54 turbine. He had a conservative start with his running this turbine because he questioned his balancing technique with the rotating assembly.
Now he has some time on the engine, some adjustments to the start sequence, and faith in his balancing of the rotating assembly. He reports that the Wren 54 is running well, producing full rated thrust and full rpm with no problems.
The Wren 54 turbine kit is well done and can be built by the modeler. I am sure Joe will tell you that it is not just a bolt-together-and-go endeavor, but it is definitely a project that a modeler can complete.
Joe can’t wait to get the Wren 54 into the air in his fer-real DL Aeromodeles’ Aermacchi MB-339—not the ARF; it’s the one he built from the kit a while back.
The cockpit detail in many sport jet models is often so complicated and so detailed that in many pro-scale models the one thing that really sets one model and another apart is the instrument panel. Complicated, three-dimensional, and close-fit requirements make a good instrument panel.
Most panels consist of at least two layers: the instrument panel itself and the instrument faces behind that. Additional layers such as the glass face, spacers, and instrument needles can be included to provide even greater three-dimensional depth, depending on the level of detail one wants to go into. It just takes additional time and effort.
I start my instrument-panel construction with the instrument faces. The detail work must be crisp, clean, and include colors other than black and white; many full-scale instrument faces include yellow, green, and red accents. The artificial horizon can be quite colorful, with blue, gray, black, and white details.
The instrument faces are easy to create and reproduce. I create a quality picture or print of the instrument face I want to reproduce. Use a copying machine to transfer the image onto transparency film like that used for overhead projectors. I suggest using a mirroring step, that is, printing on the back side of the shiny, protective plastic so the printed side is forward. This way, the plastic will be the face’s outer surface and will protect the printed surface.
Some instrument faces need the instrument glass to be domed or have thickness. You can add the dome by using a clear epoxy or a clear acrylic “doming” product.
The white lines of the instrument faces will be left clear by the copying process, allowing color to be painted on the back side of the transparency. The black ink will hide the paint so only the clear areas will allow the color to show through to the front face. In this way you can add color to your instrument faces in a quick, simple manner.
In an alternative method, slightly more time-consuming but provides a sharper image, draw your instrument faces on your computer. I have used Microsoft PowerPoint and Autodesk
Transcribed from original scans by AI. Minor OCR errors may remain.
