Radio Control Aerobatics — Eric Henderson [[email protected]]
An in-depth look at The World Models Manufacturing Co.'s Groovy 50
Also included in this column:
- Congrats to the 2007 US F3A team
Introduction
In a previous column I wrote about airplanes you could use as precision aerobatics (Pattern) primers or as good vehicles with which to learn aerobatics. Now some ARFs are specifically called “Pattern” airplanes. Their names often include the label “F3A,” which is synonymous with Pattern.
The US has five RC aerobatics classes of increasing difficulty. The top level is AMA class 406, which is also referred to as FAI F3A Pattern.
Top-of-the-line Pattern airplanes tend to be just inside the 2-meter size limit. They use big glow engines in the 1.40–1.70 cu. in. range or large motor equivalents turning such propellers as those measuring 24 inches.
Smaller, more economical Pattern ARFs are available in the .45–.90 engine range, one of which is The World Models Manufacturing Co. Ltd. Groovy 50. This airplane will not break the bank, but it will do almost everything a 2-meter FAI airplane can do.
Specifications
- Wingspan: 54.5 inches
- Wing loading: 20.3 ounces per square foot
- Expected final weight: 5 pounds, 11 ounces
- Construction: balsa and plywood, precovered with fuelproof iron-on material
- Typical engine range: .45–.90; review example used O.S. .61 FX
- Servos required: 5 (two aileron, one elevator, one rudder, one throttle)
- Battery used in review: 4-cell, 1300 mAh NiMH
Assembly and Preparation
The wing comes in two parts and is held in place with a wing tube, as are many current 2-meter Pattern airplanes. Not many items were needed to complete the Groovy 50.
The instructions are a series of photos and basic directions; the builder is expected to have some RC model-airplane construction knowledge.
The engine installation took the most time. The model was designed for the YS .53 engine, which has been superseded by the more powerful YS .63. An O.S. .61 FX is also a good fit. I attached the O.S. .61 to the mount, offered the whole assembly to the firewall, and positioned it so the muffler lined up under the airplane. This hid most of the muffler and directed exhaust downward and away from the model. No special muffler was required; with the original baffle in place the sound is acceptable to Pattern ears.
The landing gear was predrilled and mainly a matter of assembly. The wheel pants were opened to give better wheel/tire clearance and were held in place with 2-56 bolts and blind nuts.
I glued the stabilizer in place with 30-minute epoxy and lined it up with the plug-on wings. I fitted the elevators before hinging the rudder to allow for more accurate throw and neutral alignment of the halves. All control surfaces used Mylar hinges; fitting them was quick. The fin was already part of the fuselage, making alignment largely automatic. The fin and stabilizer aligned correctly with the wings, important because the factory-fit wing tubes dictate the finished model’s success.
It took less than 30 minutes to complete the wing. The plug-on configuration removed much of the hard work. The aileron servos fit in the wing panels and needed no extension leads to reach the fuselage.
The receiver and battery were held in place with double-stick Velcro tape. The rearward placement of the rudder servo proved successful; the CG with an O.S. .61 and standard muffler on the front came out exactly as in the instructions.
The all-up finished weight of the Groovy 50 with an O.S. .61 FX was 5.0 pounds, 3.2 ounces—about 8 ounces lighter than the box specification.
Decals were difficult to apply until I used soapy water. I spray-painted the canopy on the inside because there was no need to add the weight of a pilot bust. The last step was to iron down all covering edges and wait for a good flying day.
Radio, Servos, and Setup
Any four-channel radio and a Y-lead will allow you to fly this airplane. However, a computer radio with channel-mixing options will let you eliminate any minor rudder-control coupling.
As a safety precaution I programmed the JR 10X fail-safe settings so the throttle goes to idle and a touch of up-elevator before the first flight. I reset it after the flight to match any primary control trims needed.
Range checks were completely satisfactory.
Break-In and First Flights
The first task at the field was to take pictures; the second was to break in the O.S. .61. It needed only a half tank of Coolpower 15% fuel to get sorted out. The break-in process drew many questions from onlookers, who were eager to see the airplane in the air.
The Groovy 50 tracked straight down the runway and lifted off easily at half throttle, requiring only a tiny bit of right aileron trim. Initial testing went so well that I attempted most of the FAI F3A P-07 schedule. Rolling maneuvers were easy.
Low-rate throws chosen from the manual were suitable for smooth Pattern flying. The airplane performed snaps in both down-line and up-line without switching to high rates. Throws used were:
- Elevator: 18 mm up and down
- Rudder: 45 mm left and right
- Aileron: 10 mm up and down
Handling and Performance
I performed inverted spins using only rudder and elevator; the model stopped rotating as soon as the controls were centered. It is capable of long and extremely slow rolls, which please spectators.
In knife-edge flight there was a minute roll toward the canopy during long knife edges. I dialed in 11% anti-roll mix to correct this; now knife-edge performance is excellent. The Groovy 50 also executed Avalanche-type snaps without problems.
Takeoffs were helped by using the ailerons as flaperons to lift out of long grass. Slight up aileron on both sides helps slow the airplane on landing. A total of 20° down flaps provides extremely short takeoff runs and reduces wear on the landing gear when using rough runways.
Landing is straightforward: line up on the runway, chop the throttle to low idle, and let the airplane touch down with a small flare.
Although this review evaluated the Groovy 50 as a Pattern airplane, it is an excellent sport model as well. It is predictable, flies smoothly in wind, and will help anyone develop aerobatic skills. It is a small Pattern airplane with a lot to offer—good for practice, competition, or just fun.
Aerobatics can often be out of reach for the average sport flier’s budget. The good news is the Groovy 50 meets regulations and is affordable.
Congratulations
Congratulations to Andrew Jesky, Jason Shulman, and Quique Somenzini for making the US FAI Aerobatics team. These fine young men will represent the United States at the 2007 F3A World Championships in Argentina in November.
Transcribed from original scans by AI. Minor OCR errors may remain.
