Author: Michael Ramsey
Edition: Model Aviation - 2010/03
Page Numbers: 52,53,54,55,56
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Plane Talk: Easytiger Models Stealth EDF Fleet - 2010/03

F-117 Pluses and Minuses

  • Pluses:
  • Plug-and-play advanced electric-ducted-fan model of a modern design.
  • Excellent parts fit.
  • Good finish and detail for EPS molded foam.
  • Servo-operated retracts, bomb-bay doors, nose-wheel steering.
  • Totally prewired with necessary extensions, reversed servos, ESC.
  • Shock-absorbing landing gear with tethered door covers.
  • Ready to fly in one evening.
  • Minuses:
  • Gear struts need thread lock to prevent failures.
  • Requires a 30C–40C battery to realize full performance.

Review

Introduction

Easytiger Models (ETM) calls many of its aircraft "Black Projects," for one obvious reason: those particular designs are painted black. It's sleek, hip, and cool, and it's easy to touch up and maintain. The company also mimics the high-tech impression that stealth aircraft make. Several ETM models are representations of stealthy jets; this review focuses primarily on the F-117, which we found to be the benchmark to date of the company's efforts.

ETM imports its models from a number of sources. A peek at the website reveals that the company sells more than electric jets and is pioneering in the realm of electric Giant Scale. The people at ETM are modelers, and they seem adept at handpicking good products because they test each one (instead of relying on factory hype). When factory instructions are insufficient, ETM will supplement, or in some cases (as with the SR-71), redo a manual.

Construction and Fit

The F-117 (and the F-35C or SR-71) is all foam, though not every ETM offering is. Call these models "foamies" if you will; this type of construction has benefits and disadvantages. Foam EDF aircraft are almost the lightest that can be found, which helps make them easier to fly. Light weight also means faster acceleration, so a burst of power can help recover from trouble.

However, lightweight models can be somewhat delicate. The EPS foam used on ETM aircraft is exceedingly stiff, but it will abrade on asphalt or damage on workshop edges. Repairs are simple; a can of flat-black spray paint is an excellent field repair item.

I was initially concerned about the absence of traditional reinforcements such as wing spars, but ETM wings have held up well. The parts that are not molded align with creatively designed sockets; these increase the gluing area and reduce joint failure. Glue is included, but ETM doesn't recommend it for assembly because of long cure times; five-minute epoxy works well, and parts fit so precisely that epoxy mostly squeezes out, keeping joints light.

The flat-black paint absorbs epoxy chemically (it practically bonds), so little joint preparation is necessary. Messy epoxy-packed joints can be cleaned with rubbing alcohol without damaging the finish. Foamie jets such as the F-117, F-35, and SR-71 can be built in one short evening using five-minute epoxy. All wiring is complete and finished so a basic (non-computer) radio would be sufficient.

Electronics and Radio

Each set of Y-harnesses used to link the twin elevator, aileron, and retract servos runs to the receiver compartment, where individual pre-labeled leads are ready to connect to the receiver of choice. A full-range receiver is best for any jet. I used the Graupner MX-16 radio; its XPS eight-channel receiver fits snugly into the radio compartment under the magnetically sealed canopy and has only one radial antenna.

Wired in series with the 50-amp ESC is a 7-amp BEC chosen for the nine-servo load. The F-117 comes with decent instructions in a full-color 14-page booklet. The photos tell most of the assembly story, but the control-linkage geometry is not fully detailed. I made sure the linkage ratio was near 1:1 and tested that 100% travel limits were reasonable.

All linkages are adjustable, and the included 9-gram micro servos are centered and glued to the molded sockets. One retract servo is a reverse type, which simplifies radio setup. My aircraft's retract-servo limits needed to be increased to 150% to ensure full travel. Screw-lock connectors make retract-pushrod adjustment easy. If retract servos "buzz," they'll draw current and may overload the BEC—so get the setup right.

Molded channels enclose all wiring to keep things neat and out of critical airstreams such as the intake ducting. Servos are glued in, but a small amount of leverage in the correct spot (opposite the direction of throw) will pop them out for service. The components are serviceable: if a servo dies, motor chokes, or ESC goes DOA, ETM has made sure parts are reparable or replaceable.

Landing Gear and Canopy

The F-117's retractable landing gear is notable. Formed wire struts are pressed into aluminum sockets within the mechanical retract; these sockets include a shock-absorbing spring. Gear doors use spring-loaded hinges to open automatically, with a string tied to each door that snags the retracting strut and pulls them shut. To ensure gear struts stay put, wick the joint with green thread lock or thin CA.

The nose gear uses two servos: one for retraction and another for steering. The steering servo is wired with the forward-pointing landing light. I like that the canopy latches with a magnet, but the glue let go on the first flight; I repaired it with epoxy.

Power and Batteries

My F-117 came a bit nose-heavy from the indicated balance point with a PowerEdge 4S 2200 mAh Li-Poly battery from RC Accessory. The battery's weight is average, but its output rating is high (30C). It fits with breathing room in the battery compartment; the factory-mounted security strap acts mainly as a stop.

The specified thrust is a bit less than flying weight. EDF models will never achieve rated performance without a good battery. Evan Chapkis started the PowerEdge line of Li-Poly batteries around the time my F-117 arrived; I ordered a test sample from RC Accessory. A high-performance battery in this high-draw application is the smartest accessory for the money. Every flight brought the PowerEdge pack back just slightly warmed (near 90°F). The 20C batteries I tested returned exceeding 100°F in other models.

Flight Impressions

Jets tend to fly with a slight nose-high attitude; the faster they fly, the lower the angle of attack. Knowing this helps when trimming for normal cruise. Because the F-117 rests on the ground with a close-to-zero deck angle, it needs to be hauled off the runway on takeoff—this can surprise a test pilot and produce a stall on first attempts. Once the model pops off, establish about a 25° climb and bring up the gear. Using 50% exponential on the steering control helped.

The retracts "bang" into the wheel wells; if your radio can slow the servo transition, that looks better but isn't required. Without a headwind, the F-117 needs 30–40 feet of runway; with a 10 mph breeze it can be airborne in about 20 feet. The elevator typically needs roughly 2° of up trim for cruise. Altitude is easy to gain, but climb ability is limited.

Stall testing showed a predictable left-wing drop followed by a shallow descending turn; recovery was instant with no violent tendencies noted. By design, the F-117 is a challenge to see in the air—especially in profile. Bank the wings occasionally to confirm flight path. Keep power on during slow flight and approaches; control surfaces need airflow to remain effective.

The bomb-drop feature sets the F-117 apart. Included dummy ordnances are lightweight foam and fling out of the bomb bays—fly low and slow, actuate the bomb doors near the runway to appreciate the effect. Add white or yellow tape if retrieving the bombs proves difficult.

At high speed the F-117 grooves and feels like a sport model. Any forward-flight maneuver that requires no rudder can be performed. At slow speed I noticed a tail wiggle—common on V-tail aircraft—but no loss of control authority was observed.

Landing and Handling

Landing is best done by establishing a higher angle-of-attack cruise with throttle near 50% and gear down. Use throttle to manage altitude as you guide the jet to the runway threshold. A full stall is not required for landing because the automatic nose-high attitude encourages main gear first contact. The shocks in the landing gear help the model stick to the runway.

In crosswinds, you can slip the F-117 down the centerline (hold the upwind wing down), but avoid crosswinds faster than about 10 mph. I miss having a flying rudder on foamie jets; point rolls would be better coordinated, and landing-approach headings could be managed more precisely. On the F-117 it wouldn't be difficult to rewire for V-tail mixing to improve this.

Conclusion

The F-117 demonstrates that ETM is listening to modelers and improving presentation, hardware, and manuals. The model is a forgiving, attractive foam jet that feeds the "jet bug" and teaches skills that translate to higher-performance models. The bomb-drop adds fun beyond flight performance. My experience with ETM has me hooked on jets.

Michael Ramsey [email protected]

F-117 Specifications and Details

  • Model type: Receiver-ready EDF RC
  • Skill level: Beginner builder, intermediate pilot
  • Wingspan: 31.5 inches
  • Wing area: 570 square inches
  • Length: 45.5 inches
  • Weight: 42.3 ounces
  • Wing loading: 10.7 ounces per square foot
  • Power (included): 70mm EDF with 2850 Kv outrunner, 50 amp ESC
  • Radio: Six channels (minimum), nine servos (included)
  • Construction: Molded EPS foam, plastic hardware, aluminum landing gear
  • Covering/finish: Durable paint finish with water-slide decals
  • Battery: 2200 mAh 4S PowerEdge Li-Poly
  • Motor output: 1,000 grams of thrust
  • Radio system: Graupner MX-16 transmitter, XPS eight-channel receiver
  • Flight duration: Five to eight minutes
  • Price: $259 (as tested)

Manufacturer / Distributor

Sources

Other Published Reviews

  • Model Airplane News: March 2010

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