Author: Bob Aberle
Edition: Model Aviation - 2009/03
Page Numbers: 83,84,86
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Frequently Asked Questions - 2009/03

Getting started with turbine power for model jets

Please write in with your questions, since that is the only way we can keep this column format going. When referring to published Q/As (for follow-ups), provide the number as a reference. References to addresses and Web sites are placed in a group, separate from the text, at the end of this column under "Sources."

Q390

"I've been fascinated watching videos of RC model aircraft powered by real jet turbine engines. I did some checking a while back and heard that getting started with jet turbine power could be very expensive; I was hearing figures of over $10,000. But I'm seeing more and more jets in recent times and I'm wondering if the prices have come down.

Also could you tell me what might be the easiest way to get started with jet turbine power?"

A390: The August 2008 issue of MA contained six features dedicated to jet modeling, including an article about the basics of the modern turbine. I don't yet own or fly a turbine model, so I talked with several experienced modelers who do.

Larry Davidson (Model Aviation Hall of Famer, Moneta, Virginia) recently pursued turbine power. Because his schedule didn't allow building a large 10–12 lb turbine model from scratch, he found a turbine distributor/supplier, Troy Built Models (Sarasota, Florida), and the MF Models Shockjet ARF. The Shockjet was designed for modelers who want to fly jets but lack the time to build a big aircraft.

Cost:

  • Turbine engine (recommended JF-50 Super Bee 50): about $2,500.
  • MF Models Shockjet ARF: lists for $500 but is often offered at a special price when purchased with the turbine.
  • Combined start-up (Shockjet + turbine + required gear): roughly $3,500 — not the $10,000 figure sometimes quoted.

Shockjet specifications:

  • Wingspan: 80 inches
  • Length: 73 inches
  • Dry weight: ~13 pounds
  • Recommended turbine thrust: 14 pounds (JF-50 Super Bee 50)

Troy Built Models' Web site has helpful subcategories: photos/videos, features, full specifications, and a PDF of the 10-page supporting manual. Even as an ARF, installing the turbine, a large 64-ounce fuel tank, and the radio/servos takes considerable effort.

Radio, servos and cabling:

  • Larry used a JR X9303 2.4 GHz spread-spectrum radio.
  • In this application you will typically need a total of eight servos and many servo extension cables.

Fuel and consumables:

  • Basic fuel: K1 kerosene (available at many gas stations) or Jet A (available at some airports).
  • Use rubber stoppers for the fuel tank that are compatible with gas, diesel, and kerosene — do not use stoppers intended for glow-fuel operation.
  • Turbine oil is available at many local airports.
  • Propane is required for starting the turbine.

Safety and AMA requirements:

  • A fire extinguisher is mandatory per AMA safety regulations.
  • The AMA requires each new turbine pilot to obtain a Turbine Waiver. The waiver must be signed off by an AMA Contest Director (CD) or a Hall of Fame member and another turbine waiver holder after you demonstrate that you can fly a turbine-powered model.
  • To help locate the waiver and safety documents, see the "Sources" list below: look for the "Acrobat Documents" section and scroll to the turbine section (510). PDF 510-A is the safety regulations for model turbines; 510-D is the fixed-wing turbine waiver application.

Support and builders:

  • Bill Hatcher of Troy Built Models and Eric Clapp of Jet Central Turbines were both cited as helpful contacts when problems arose. Eric can be reached via the email listed under Sources.
  • If you want to build your own turbine trainer, Nick Ziroli Sr. offers plans (the "Turbinator") and a short kit; his design resembles a military jet trainer and is available via his site (see Sources).

Summary: These models aren't for everyone and they still entail a significant outlay, but getting into turbine-powered model jets is no longer the $10,000 proposition it was a few years ago. The Shockjet + a recommended turbine represents a much more accessible entry point.

Q391

"I remember reading in your FAQ column back in 2006 about Don Bousquet's successes with digital aerial photography. As I recall Don used a very simple set up with an auxiliary RC servo pressing on the camera shutter switch. I would think by now the control mechanism for a camera might have been improved or handled electronically. Have you heard of anything?"

A391: Don Bousquet and his son Nate have built a successful aerial photography business using simple, reliable methods. Their system — an auxiliary servo pressing the camera shutter — has produced well over 100,000 pictures and remains effective for their work, particularly for low-cost real estate photography.

That said, there are commercial electronic camera-interface solutions. One example is the URBI R/C Camera Interface from Singapore Hobby Supplies. From their description:

  • URBI R/C lets you use an off-the-shelf digital camera for remote-controlled aerial photography.
  • It is compatible with common R/C systems (Futaba, JR, Hitec, etc.).
  • No wiring or soldering is required; it connects to the R/C receiver and controls the digital camera via the USB connector.
  • It uses a standard servo-style connector and draws much less power than a normal servo.

Price (at the time of writing): about $179.90. See Sources for contact and ordering information.

Q392

"I happen to like the Deans Ultra type connectors but have found them so hard to separate. In fact I actually pulled a wire off one of those connector terminals while trying to separate it. Any suggestions?"

A392: Deans Ultra connectors are a popular choice for main battery connections but can be difficult to separate when new. Suggestions and solutions:

  • Use a length of nylon fishing line to help get a better grip when separating connectors. Do not pull on the wires.
  • Duralite Flight Systems introduced "PIK Extensions": Deans Ultra and Multiplex connectors modified with an extra grip on both male and female halves.
  • These come with 16-gauge wire pre-soldered to the connector in lengths of 6, 12, 18, 24, and 36 inches.
  • You still need to splice the cable end to the battery leads coming from your ESC.
  • It would be useful if heavier-gauge (No. 12 or 14) options become available.

MA

Sources

Transcribed from original scans by AI. Minor OCR errors may remain.