Sunday, October 22, 2017
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Curtis Youngblood Rave ENV

A best of breed 3D machine!

The Rave ENV is the first 90-size helicopter designed and released by Curtis Youngblood himself. People who have been in this hobby for a few years should all recognize the Curtis brand. In the last twenty years, he has won F3C World Championships and 3D competitions around the world countless times and he helped pioneer switchless 3D flying 20 years ago.

Prior to the ENV, Curtis helped design the Futura in collaboration with Robbe in Germany, and he collaborated in the development of the original JR Vibe, working with JR in Japan. The ENV is his first 90-size nitro helicopter released by his own company: CJ Youngblood Enterprises, Inc. (CYE). CYE is a thriving business; it focuses only on helicopters and related products. This line includes the famous Muscle Pipe designed by Curtis, as well as rotorblades, gyros, and helicopters.

The electric flybarless version tested by the author is the same model that Nick Maxwell used to win the 2010 3D Masters competition at Venlo, Holland.

ENV ORIGIN

The name ENV for the new helicopter stands for Electric Nitro Variant. The customer has a choice of buying any one of the four versions: electric powered, nitro engine powered, flybar equipped, or flybarless. The price is $799 regardless of which version. And, it is possible to buy additional parts to convert from one version to another.

The version I chose to build is the electric powered flybarless version. This is the version that Nick Maxwell used to win the 2010 3D Master competition in Venlo, Holland. With a flybarless helicopter, it is a must to use an electronic stability augmentation system (SAS). The Total G from CYE is an electronic box that combines many functions into one unit. This includes a stability augmentation system (SAS) for flybarless flying and a builtin engine governor for nitro engines. JR/Spektrum satellite receivers can plug directly into the Total G. The Total G permits connecting a 2-cell LiPo battery directly to the Total G to power high voltage servos, such as JR 8717HV. I really like these features because they simplify wire connections.

Aluminum anti-rotation scissor assembly.

The reason I chose the flybarless version is because when properly set up, a flybarless helicopter equipped with an electronic blackbox can be even more stable than a flybarred helicopter yet at the same time a lot more responsive to cyclic commands at any rotor rpm. The amazing fact is the Total G or any good SAS, can keep the cyclic control response nearly constant regardless of variation in rotor rpm. The ENV is fun to fly and it can perform all of the 3D maneuvers in an extremely agile fashion. This relatively large model at 10 pounds feels light and nimble running on a 12S LiPo battery system.

SAS BENEFITS

Even as rotor speed drops as the battery gets weak, the model can still flip, tumble and roll at nearly the same fast rate. The SAS makes the control system become a rate command system, so the helicopter roll rate or pitch rate becomes proportional to the amount of your cyclic stick input. This means the SAS will put in whatever necessary amount of swashplate input to give the helicopter rolling or pitching rate proportional to your stick input, regardless of rotor rpm. Without the Total G, the stationary flip rate would be sluggish when rpm drops. With the Total G, the stationary flip is amazingly quick, even when the rotor speed drops to only 1,400 rpm. This is also true in autorotation; when rotorspeed bleeds off due to poor collective management, the cyclic response is still authoritative. This is something, also, that the pilot has to become accustomed to.

Front view of the ENV mechanics. Wide distance between the sideframes enhances structure strength

Removing the flybar also eliminates roughly 10 percent of the aerodynamic drag. The Total G only weighs one ounce, so it is lighter than all the parts removed from the rotorhead. For experienced pilots who want to try something different, then a flybarless ENV with an electronic stabilization system is a fun project to try. The 3D becomes very crisp and axial rolls are true. No wonder many experienced 3D pilots are trying flybarless flying. You will also be amazed by the artificially enhanced stability.

Since this SAS is not an autopilot, it can be used in 3D competitions, such as the 3D Masters and XFC. In a sense, it does provide an advantage over your competitors because it can make your flybarless helicopter even more stable than a flybarred helicopter; yet, when you move the sticks, your new flybarless helicopter will respond instantly. As I personally witnessed, the flight by Nick Maxwell with his electric flybarless ENV at the 3D Masters definitively demonstrated the extra edge a flybarless helicopter can have over a flybarred model when properly tuned.

Tail rotor pitch control on the ENV tail gearbox.

HIGH VOLTAGE SERVOS

There is also a strong advantage in using the new high voltage servos. Running a 2S 7.4 volt LiPo battery pack with the Total G, driving the servos directly, gives a really fast servo response. They provide instant torque the moment a cyclic command is entered. It also simplifies installation because that eliminates the need for a large switching battery eliminating circuit (BEC) to convert the 7.4V to 5 or 6V. Therefore, I recommend using a 12S battery for powering the electric motor, and a separate 2S LiPo to power the Total G, receiver and high voltage servos.

Another setup solution running standard digital servos uses a Castle Creations 20 amp switching power supply. That is plugged in to the flight motor battery pack, and the Castle unit reduces the voltage down to 6V. This method also works well and eliminates the need for a separate 2S LiPo battery.

Carbon sideframes braced with molded plastic spacers and bearing blocks offer a light but cost effective, strong design.

TOTAL G WITH FLYBAR

If you do not have a flybarless helicopter, the Total G can be used as a stand alone heading lock tail rotor gyro by disabling the two other axes. The Total G has a built-in mixer for eCCPM. This means it is possible to use it with a standard 6-channel airplane radio to control an eCCPM helicopter. In fact, the Total G does not want you to use the eCCPM software in your transmitter! In case you chose to build a glow engine version ENV, the Total G also includes a built-in engine governor. The Total G may cost almost $500, but it is a total solution.

BUILDING THE ENV

The ENV model is relatively simple to build. It will take a few evenings to construct the mechanics. Everything fits and there were no missing parts. The design is elegant, simple, and light. The frames are made from carbon graphite. The two side frames are spaced far apart to provide strong torsional rigidity. The aluminum tail boom is clamped firmly between two heavy duty plastic blocks. The radio tray on the front, and the landing gear spacer and bearings blocks are also molded from plastic. They are robust and help keep the kit affordable at a price of $799. On many high end Japanese models, beautiful CNC aluminum spacers are used, but that can raise the price to well over $1,000. The ENV rotor head, swashplate and control bellcranks are metal pieces and very well manufactured, and this is what counts. The molded gears run true and smooth.

The Total G is an electronic box that combines many functions into one, which includes a stability augmentation system (SAS) for flybarless flying and a built-in engine rpm governor for nitro engines. JR/Spektrum satellite receivers can plug directly into the Total G which helps eliminate a main receiver and reduces the wire count.

MANUAL

The instruction manual of the ENV is absolutely outstanding and you can see it at www.curtisyoungblood. com. Brian, one of the CYE team, did an outstanding job using SolidWorks CAD graphics to create many of the drawings shown in the manual and he also put together the instruction manual. The manual is a full color book, and it is a pleasure to read. I appreciate that the ENV package included a printed manual instead of a CD.

The ENV, especially the flybarless version, has very few parts and its assembly is straightforward, but note that this is a high performance model and is not intended for beginners.

FIVE HORSEPOWER!

Running on a 12S LiPo battery at 44.4V, and drawing up to 80 amps means that the motor is putting out 3500 watts of power! Since 746 watts equal one horsepower, the motor is putting out almost five horsepower! That is more than an OS .91 glow engine. This is why an electric ENV can nearly always beat a nitro version ENV in drag racing and in rapid acceleration. The advantage of a glow powered ENV is that it requires no charging and will give you 10 minutes of steady power down to the last drop of fuel. The electric version provides five minutes of all out 3D or 8 – 10 minutes of leisure flying (running a 12S, 5,000mAh LiPo). With either ENV variant, you will not go wrong.

A good electric helicopter needs a powerful electric motor. The Scorpion 4035 series with 500 KV is a good choice. When ordering this motor from Innov8tive Designs, make sure to ask them to replace the standard motor shaft with an extended shaft.

ROTOR BLADES

Choosing the correct rotor blades is important when flying flybarless helicopters. CYE makes a version of their carbon blade just for flybarless flying. These special blades have more weight near the leading edge of the airfoil to enhance stability. If you are flying flybarless, be sure to order the blades for flybarless flying. That said, because the Total G works so well, the ENV will still fly fine with standard rotor blades.

MOTOR & ESC

To ensure success, pick the correct motor, electronic speed controller (ESC), battery and charger to best match the helicopter. CYE offers its own Next-D motor which is produced for CYE by Scorpion. I am flying with a Scorpion 4035 series 500Kv brushless motor. Scorpion motors are distributed in the USA by Innov8tive Designs. The standard 4035 also fits many other large 90-size electric helicopters. To use the 4035 motor, Innov8tive recommends replacing the motor shaft with an extended shaft. The ENV kit does not include any pinion. When using a motor with a Kv between 500 and 560, it is necessary to use a motor pinion between 14 to 12 teeth. If you have any questions, please call CYE and their staff, world experts, will be very helpful.

At the IRCHA Jamboree, I saw Curtis himself helping a pilot set up a complete ENV the mechanics and the radio. Ten minutes of his help can help answer that question you have been struggling with for hours! I have known Curtis for over 20 years, and he is always a gentleman and packs a wealth of knowledge. I have owned every machine he has designed or competed with, from the GMP Competitor back in 1983, to the Robbe Futura, JR Vigor, and now the ENV. His models have that unique feel “ they have F3C smoothness, but can also be set up for edgy 3D “ which is the combination I love.

ESC POINTERS

When it comes to large electric helicopters running on 10 to 12-cell LiPo battery, there are only a handful of ESCs that can handle the large power requirements. The Castle Creations Ice series is a good choice and Kontronik Power Jive 120+ HV from Germany is also an excellent choice. Castle Creations and CYE say an Ice 120 amps ESC is sufficient, and that is what I used. The Ice 120 can handle continuous 3D for five minutes without overheating or having any issues at all. The Ice 120 with its green heat sink is only two inches long and weighs about three ounces.

LIPO BATTERIES

To get the full performance out of the ENV, use the best quality LiPo. With a 12S 5,000mAh battery, it is possible to get five minutes of maximum performance 3D. The 45C Thunder Power battery I am using provides the current needed without any damage to the cells. Even after a hard 3D flight, the 12S battery did not get hot. It was surprising during recharging the charger said almost 5000mAh was consumed in the previous flight. This means the Thunder Power 45C cells truly do have a useful capacity of at least 5,000mAh. It is not a good practice to drain the battery of all of its capacitythat can reduce battery longevity. I did not intentionally fly that long. There was no indication the battery was getting weak at alla testament to the quality of Thunder Power batteries. Recently, Thunder Power introduced new 65C LiPos!

What does 45C and 65C mean? 45C means the battery is designed to safely handle current drawn from the battery continuously at 45 times its rated storage capacity. For example, the 5,000mAh battery is a 5 amp-hour capacity battery. 45C means 45 x 5 will allow this battery to safely discharge at 225 amps continuously. 65C means it can handle 65 x 5 or 325 amps. There is no way our motor can draw that much juice. If it drew 325 amps, the battery capacity, roughly speaking, would only allow about a minute of flight.

Moreover, the ESC is only rated at 120 amps. Therefore, a Thunder Power 45C pack can easily handle any outrageous 3D flying you are capable of. My Thunder Power 45C pack is never hot after a flight and has been charged over 30 times with no sign of weakening. Then why get a newer 65C? Owing to new manufacturing technology, Thunder Power can produce a 65C battery at a lower cost than a 45C pack a year ago. We are seeing LiPo batteries become more and more affordable, more reliable and more rugged. The weight of the 65C is only very slightly heavier than a 45C, and about 15 percent heavier than a 25C. If weight is not a concern, a 25C Thunder Power battery would be more than sufficient.

CHARGING

Thunder Power recommends their TP610C AC-DC charger or their TP610C DC charger. Not too many companies in the world offer a 12S charger with a built-in 12S balancing port. Therefore, I used two TP610C AC-DC chargers to charge and balance the two 6S packs separately. Just released is a new TP820CD dual port charger that can charge two 8S pack at the same time. This new charger can either charge the two 8S packs as separate packs, or you can connect the two 8S packs together and charge them in series! This means you could use the new TP820CD charger to charge two 6S packs in series in one shot.

AIRBORNE

The RAVE ENV offers the best 3D flight performance available. It is among the few best of breed helicopters at the very top of the ladder. And you would expect nothing but the highest flight performance given that it is designed by the world famous 3D pioneer and world champion pilot, Curtis Youngblood. There is no need to say more. To see this heli in action, please visit Find.helipilotonline.com/061126. Colin Bell has now also joined the CYE teamsee videos of him flying the ENV as well. 2011 will be a very interesting year and be sure to watch out for these and other top pilots flying the ENV.

SPECS

HELICOPTER: Rave ENV flybarless electric

MANUF. & DIST.: Curtis Youngblood Enterprises

TYPE: 90-size glow engine or electric helicopter

FOR: Intermediate to advanced pilots

FLYING WEIGHT: 10.5 lb.

MAIN GEAR: 130 tooth

PINION GEAR FOR ELECTRIC MOTOR: 12 to 16 tooth

TAIL ROTOR RATIO: 4.54:1

BLADES: 690 “ 710 mm

ROTOR SPAN: 60-1/4 “ 61-3/4

TAIL ROTOR SPAN: 11-1/2 in.

RADIO: Heli radio required, electronic stabilization system such as Total G is necessary for flybarless version

MOTOR: Scorpion 4035-500

MAIN ROTOR HOVER RPM: 1,600 hover and 1,950 in idle-up

BATTERY: Thunder Power 45C LiPo

CHARGER: Two Thunder Power TP610C AC-DC chargers

DURATION: 5-10 minutes, depending on flying style

COMPONENTS NEEDED TO COMPLETE: Radio, SAS, main rotor blades

PRICE: $799

SUMMARY: Superb quality, excellent engineering and a good combination of aluminum, carbon and plastic components that yields a top performing 3D machine.

CONCLUSION

The RAVE offers flawless performance and can handle any 3D maneuvers that you can fly. If Nick Maxwell cannot break it in the air, then it™s unlikely you will! However, it is also a very smooth flying machine that is great for everyday enjoyment.

Links

Castle Creations, www.castlecreations.com , (913) 390-6939

CJ Youngblood Enterprises, Inc., www.curtisyoungblood.com , (979) 828-4269

Innov8tive Designs, www.innov8tivedesigns.com , (760) 468-8838

Thunder Power RC, www.thunderpowerrc.com , (702) 228-8883