Wednesday, March 14, 2018
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Gaui X7 3D Helicopter

Gaui X7 Competition 3D Helicopter

Competition Quality, Flybarless 3D Helicopter

When I first saw the prototype X7 at the 2011 3D Masters, I wasn’t sure what to think about it. At that time, the model was still being developed. Around May 2012, the X7 was launched worldwide and Gaui assembled an armada of thirty people strong and attended the 2012 3D Masters at Venlo, Netherlands. Gaui fielded six team pilots and even though none of the six pilots captured first place in neither the Masters Class nor the Expert Class, nevertheless the combined score of the six pilots was good enough to allow Gaui to capture the 3D Masters Constructor Trophy. With the impressive competition results and awesome freestyle demos during the 3D Masters, Team Gaui and their X7 debut grabbed the attention of everyone, including me. The X7 is out of this world and it is nothing like what Gaui has created before. The X7 is ultra sleek looking, the flight performance is fantastic and the quality is topnotch.

Author’s Opinion
The X7 has awesome 3D performance, sleek look, excellent quality parts, and a clear instruction manual. Gaui has come a long way in the last decade and really made an impression with the X7, which is their first ever competition quality 3D helicopter.

Need To Know
TYPE: Electric 3D helicopter
FOR: Intermediate to advanced pilots
PRICE: $899 for basic kit; $1,250 for the combo “A” kit

What We Used
MOTOR: Scorpion HKIII4035-450
ESC: Castle Phoenix ICE2 120A HV
FLIGHT BATTERY: Venom 50C 6S 5000mAh LiPo (2)
RECEIVER/GYRO: Spektrum AR7200 w/built-in Microbeast SAS
SERVOS: Hitec HS7940TH (4)

Gaui X7 Competition 3D Helicopter

FLYING WEIGHT: 10.8 lb. (4.9 kg)
LENGTH: 52.7 in. (1,340mm)
HEIGHT: 14.6 in. (370mm)
ROTOR SPAN: 63.4 in. (1,610mm) w/710mm blades
ROTOR DISK AREA: 3,155.2 sq. in. (using 710mm blades)
ROTOR DISK LOADING: 7.9 oz./sq. ft.
MAIN BLADES: Fun Key 690mm (included in combo “A” kit)
TAIL ROTOR DIAMETER: 10.3 in. (290mm) w/105mm tail blades
MOTOR: Scorpion HKIII4035-450
ESC: Castle Phoenix ICE2 120A HV
FLIGHT BATTERY: Venom 50C 6S 5000mAh LiPo (2)
RADIO: Spektrum DX8
RECEIVER/GYRO: Spektrum AR7200 w/built-in Microbeast SAS
SERVOS: Hitec HS7940TH (4)
MAIN ROTOR RPM AT HOVER: 1,600 to 1,800
MAIN ROTOR RPM IN IDLE UP: 2,000 to 2,200
DURATION: 6 minutes with 12S 5000mAh
RC club flying field
NEEDED TO COMPLETE: Radio system, 3-axis gyro, receiver battery or BEC, main rotor blades, motor, ESC, flight battery, combo “ A” kit comes with motor, main and tail blades

• Superb CNC machining for all metal parts
• Carbon parts are cut cleanly with no sharp edges
• Nicely painted canopy and very lightweight
• Extremely stable in hover and agile in 3D
• Ultra smooth tail rotor pitch control with the carbon tail control pushrod and guides

• Would be nice if two spare battery mounting plates were included
• Instruction does not show how far to mount the ball on the servo arm
• The X7 main rotor blade grip has a 14mm jaw opening which will require spaces with some aftermarket blades

Specific Specs
Material: Carbon
Type: Flat frame
Servo linkage type: Direct connect between servo and swashplate

Grips: Aluminum
Head block: Aluminum
Links: Steel pushrod
Swashplate: Aluminum
Control: 120 degree eCCPM

Drive system: Aluminum torque tube
Auto capable: Yes, driven autorotation
Tail slider type: Aluminum bellcrank grabs aluminum slider on bottom, bellcrank and aluminum pitch fork
Tail blade grips: Aluminum
Tail case: Aluminum
Boom material: Aluminum
Boom strut material: Carbon

Motor to main gear: 10:1 (100-T main gear, 10-T pinion)
Main to tail rotor gear: 4.71:1

Gaui X7 Competition 3D Helicopter

Inside the box, all of the parts to the X7 were carefully packed. This is also the only kit that I am aware, which even includes velvet material canopy socks. The X7 is very easy to construct. The instruction manual is extremely clear with excellent isometric drawings. The parts all fit together perfectly and as long as you follow the manual, you will be rewarded with a textbook build. During assembly, I discovered many well thought out engineering details. For example, underneath the motor mounting plate is an additional bearing block which can be used to anchor the tip of the 6mm motor shaft. This reduces the wear and tear of the bearing inside the outrunner motor.

The X7 has a torque tube drive tail rotor system. The front end of the torque tube is a steel bevel gear that rides on top of the molded black autorotation main gear. This is similar to those used on earlier Schulter machines, Miniature Aircraft Xcell 60, and JR Vibe. However, the X7 has added an extra bearing in front of the bevel pickup pinion gear to anchor it and to prevent it from jumping upward during extreme 3D. Without this anchoring bearing block, the bevel gear could jump up and chew up the plastic autorotation main gear. The three eCCPM servos are all mounted directly below the swashplate. This provides a very short and direct pushrod run to yield precise eCCPM control. Very high-quality servos should be used because for a flybarless helicopters, the blade aerodynamics and dynamic loads are fed directly from the blade pitch arm to the swashplate to the servos.

Gaui X7 Competition 3D Helicopter

I like the way the X7 uses two black plastic forks to constraint the rotor blade control pushrods. The little plastic forks are attached to the main rotor hub and they force the upper swashplate to rotate with the hub. Each plastic fork can independently swing up and down because they are mounted on two ball bearings. It is a clever and effective design.

The battery mounting scheme is quite interesting. It requires mounting each 6S 5000mAh LiPo battery to a carbon plate first using Velcro and a single Velcro tie strap, then the carbon plate is clipped onto two posts on the helicopter, finally the battery is secured using two more Velcro tie straps. The system works, and just requires getting use to. The advantage is the batteries have some fore/aft wiggle room to allow one to get the perfect center of gravity for the helicopter.

Gaui X7 Competition 3D Helicopter

I like the tail rotor pitch control pushrod assembly. It has three 2-inch long metal sleeves over the carbon pushrod. The metal sleeves then ride inside the three plastic guides on the tail boom. The end result is a very slop-free and precise control system. The tail rotor gearbox is machined from aluminum and the pitch control arms utilize metal construction. The whole presentation is clean and precise. Once again, the engineers did a thorough job and did not cut any corners. Gaui realized that if it wants to be a world class competitor, it must consider every detail carefully. The X7 is not a copy of any helicopter on the market and in terms of mechanical design, it gets an “A”.

Gaui X7 Competition 3D Helicopter
The X7 mechanics have a clean and elegant layout.

In The Air
Once you have flown it, you will not regret your purchase. The X7 is responsive and tracks like an arrow in fast forward flight. Yes, all of the 700-class electric helicopters on the market today fly very well, but I like the look of the canopy on the X7 and the forward mounting front landing gear strut. They make the X7 look fast even when sitting on the ground. The X7 is indeed fast. Powered by two 6S 5000mAh 50C LiPo from Venom, the X7 easily moves out at 80mph. A flybarless rotor head design reduces aerodynamic drag and provides instantaneous cyclic control response which is why all top 3D pilots in the world have switched to flybarless helicopters for 3D competitions.

I have my main rotor rpm set at about 1,950rpm in idle-up because I am using a 450Kv motor. At 1,950rpm the X7 is extremely smooth and it performs 3D very gracefully. With my 690mm length rotor blades, the X7 has tremendous lift, it will climb out of sight in about five seconds. My X7 flies like a very powerful 90-size nitro helicopter. I have flow 90-size nitro helicopters for over ten years and use them as a benchmark when testing large 700-class helicopters. Besides, almost all 90-size nitro helicopters use around 1,950rpm in idle-up. The electric X7 may have the same rotor speed, but it feels lighter and has quicker acceleration. That is the trademark of modern high-performance electric helicopters. Most large electric motors designed for 700-class helicopters can easily put out 3,000 to 4,000 watts of power. The more expensive limited edition motors can put out over 5,000 watts of power. About 750 watts equal to one horsepower; 3,000 watts is like having four horsepower under the hood. My X7 can easily perform tick-tocks, funnels, and rainbows with no dropping of the rotor speed. The Castle Creation’s 120A ICE2 ESC has a governor mode and I set it to give about 1,950rpm on my X7. I have also flown the X7 with the ICE2, set in non-governor mode, and then left the idle-up throttle curve 100-percent flat open which also provides approximately 1,950rpm in 3D.

Gaui X7 Competition 3D Helicopter

If you install a 500Kv motor, then the maximum rotor speed can go up to around 2,150rpm. To reach 2,200rpm, professional 3D competitors, such as Eitan Goldstein, use the Scorpion HK4525-520Kv Ultimate Edition motor and Bhumipatara “Poom” Uditananda uses Scorpion HK4530-540 Limited Edition. I carefully watched Eitan and Bhumipatara flying their X7s at the 3D Masters. Their rotor was screaming. They needed that fast rpm, not because they needed more cyclic control, but rather because they needed fast and explosive collective response. With any flybarless helicopter, the cyclic response can be set up as fast as you want by tweaking the electronic SAS. But to get explosively fast collective response, a fast rotor speed is needed. The combination of powerful and responsive collective and cyclic control allowed Eitan and Bhumipatara to perform ultra low smackdown 3D. During their freestyle demo at the 3D Masters, their X7 was always under five feet in altitude and the models looked as if they were always on the verge of smashing into the ground, but that is what smackdown 3D is all about. After watching them fly, I knew the X7 is capable of handling much more abuse than what I am dishing out to my machine.

Gaui X7 Competition 3D Helicopter

Pro Tips
• The instruction manual of the X7 is excellent. All the parts fit perfectly and the holes are drilled accurately. Follow the drawings and the instructions precisely and you are almost guaranteed to end up with a properly built and set up model. It was a pleasure to build this model.

• Follow the manufacturer’s advice and use a 450 to 500Kv motor because that provides the perfect rotor speed. A 470 to 480Kv motor would be a perfect choice if you want a reasonable hot, but not overly extreme, 3D machine. A 520 to 540Kv motor is perfect for aggressive 3D flying. Order a motor with a “long” 6mm motor shaft because the X7 has an extra bearing block mounted below the motor to permit anchoring the motor shaft. Scorpion, Kontronik’s and some other manufacturers sell motors with XL motor shafts.

• Get the highest quality digital servos with double ball bearings supporting the output shaft. Better yet, use high-voltage servos—then you can use a 2S 3000mAh LiPo battery to directly power the four servos, receiver and electronic SAS without having to worry about a BEC (battery eliminating circuit). The advantage of running a 2S LiPo directly is it can supply as much current as necessary and a 2S LiPo has a nominal voltage of 7.4 volt, so the receiver is unlikely to go into “brownout.” Most receivers and electronic SAS on the market allow the use of a 5 to 8 volt power source. Please double check your unit.

The Last Word
The Gaui X7 packs beauty, form and quality all in to one package. After years of exploring the RC helicopter market, Gaui has finally hit the big time with their X7 design.

CASTLE CREATIONS, (913) 390-6939
EMPIRE HOBBY, (480) 982-0909
HITEC, (858) 748-6948
INNOV8TIVE DESIGNS, (760) 468-8838
SPEKTRUM, (800) 338-4639
THUNDER TIGER, (800) 637-7660
VENOM, (800) 705-0620

Words: James Wang Photos: James Wang