Tips & Advice

What is a Good “Contest Flying” Model?

I’m back, by popular demand, with a post about some good models for use in Precision Helicopter Aerobatics, aka FAI or Contest Flying. This is a second installment about contest flying that started with What is Contest Flying?

A common question in response to that post was: what is a good heli for contest flying? The current technology that goes into modern RC helicopters allows many options in setup for most of them. Some have more aerobatic potential than others, and some at the expense of stability. On the other hand, some have the versatility to be setup from one extreme to the other. The trick to setting up a contest model is in creating a model that will sit still in a windy hover, while at the same time be able to perform crisp, high speed aerobatics at the flip of a switch. While this post is not about contest setup per se, it will refer to some aspects of advanced model setup. These are items such as Delta, Flybar Ratio, Bell Ratio, Damper design, and spindle support. I will be discussing a few models that have proven to be great contest birds, and in so doing, will be detailing these features as they apply to those models. I will also illustrate the various setting positions as they apply to each model.

First, I will cover a couple 50s that can make great, entry level contest models for use in AMA class 1 or 2. These are the Kyosho Caliber 6, and the Hirobo EVO 50.

Kyosho Caliber 6

The current model in the Kyosho 50-size Caliber series has proven to be a reliable, stable model for practicing and performing precision aerobatics. The model has a belt-driven, two stage main transmission, belt driven tail, and high-quality plastic main frame. These features make for a smooth running, relatively quiet bird at lower main rotor RPMs. Fit a good quality Hatori and equivalent muffler, and you have a nice model with which to perform with. Both the YS50 or OS50 Hyper will provide ample power for great speed and tall verticals for an awesome presentation of the maneuvers.

The picture above shows the Caliber 6 Main Rotor head. You may note that the head mixer arms are a bit unique, and this design carries over directly from the flagship Kyosho model, the Caliber 90. Also note that there are two mixing options for the Bell Mixers to connect to the main grip pitch arms. These options set how much Bell input is mixed into the blade pitch. While there are no options for Delta or Flybar Ratio, the stock condition of this head is rather optimized for precision aerobatics, and the current geometry works as-is.

Above you see the new tail pitch mechanics of the Caliber 6, also brought down from the Caliber 90. This is also a unique design that has its roots in large scale, precision aerobatics airplanes - Pull-Pull rudder control. Rather than using cables, as in fixed wing rudder controls, the Caliber 6 uses two light control rods connected to a T lever and torque axle that drives the tail pitch plate. This setup allows the ability to tighten up the system and remove virtually all free play between the servo and tail control. The servo output shaft us balanced, just as in regular push/pull design elsewhere in helicopter control systems. The entire system allows for a bit tighter gain on the gyro, and more precise tail pitch control…important in precise hovering maneuvers and pirouettes.

Here you see the Caliber 6’s two stage, belt drive transmission. The auto-rotation “one-way” clutch bearing is housed in the first stage pulley, rather than the main gear hub. This means the one way is subjected to only a fraction of the load encountered in other designs, as the bearing has mechanical advantage by way of the gearing of the second stage. The first stage belt drive absorbs engine power pulses, and smoothes out transmission from the clutch to the main gear. This system also has very low gear noise, as the pinion is operating at a much reduced speed compared to traditional single stage transmissions.

These features, along with the Caliber 6’s standard push-pull controlled eCCPM controls, make the 6 a great model with which to practice and perform precision aerobatics. It’s stable, fast, and reliable. Also, for those who prefer the advantages of a mechanical collective mixing system, the 6 can be fitted with a mechanical mixing tray.

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Hirobo EVO 50

The next model I’ll discuss is the Hirobo EVO 50 series. These helicopters have been on the market for some time now, and have “evo"lved into a very capable precision aerobatics model, as well as a nimble 3D model. This model is also available with mechanical or electronic mixing options. The EVO 50 is another mostly plastic composite model, which lends for a smooth, quiet bird. The EVO 50 employs a traditional, single stage transmission and belt driven tail.

Above you see the EVO 50 main rotorhead. This design also uses a free-floating axle that supports the main blade grips. The Bell Mixer arms are supported by the flybar carrier (see-saw). There are no mixing options on either the arms, nor the carrier, so no options exist for changing flybar or Bell ratios. However, the existing geometry does lend well for a stable yet fast flying model. With a set of flybar weights, heavy-set paddles, and good blades, the EVO 50 is a formidable model for AMA class 1 or 2.

The main swashplate controls of the EVO 50 are all push/pull for slop reduction and servo balance. The rear fuel tank location also allows a more consistent balance throughout the entire flight. The low cost of the EVO 50, coupled with its long legacy of great support by MRC/Hirobo, make for a great long-term investment for contest flying. You can get EVO 50 parts just about anywhere, however you rarely need to buy many parts for a contest model. When I flew Hirobo X-Specs in competition, I never needed to replace anything except the odd bearing or ball links.

Next, I’ll discuss a couple 90 sized helicopters that are great for flying in competition or precision style without the price of a top-end FAI machine like an Eagle 3WC or Caliber 90. These are the Hirobo EVO 90 and the Blitz Avro 90.

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Hirobo Evo 90

The EVO 90 takes the 50 to a whole new level of performance, stability, and versatility. The new FFZ-III rotor head has a dozen possible setup combinations that allow the user to customize it to whatever feel and performance desired. The EVO 90 is also a mostly plastic-composite framed model. The transmission is the traditional, single stage pinion and main gear setup, with a multitude of gear ratios available.

Here you see the EVO 90’s main rotor head. The FFZ-III head is very similar to the one on the 50, but as you can see, there are numerous tuning options for Bell Mixer ratio and Flybar Ratio. The mixing arms mounted to the flybar carrier have three mounting positions on the carrier. This adjusts how much influence the flybar has on the blade pitch. The mixing arms themselves have 4 mixing options, based on how the connections are placed on the arms. These tuning options alone equate to 12 different head setups in one system. Add to the fact you can install various hardness dampers, and spacers on the blade grip pitch arms to adjust Delta, you can have dozens of setup combinations. You can also see that there are two options on the washout arms, for adjusting flybar paddle pitch rate.

The tail rotor and control system on the EVO 90 is legendary. The octagonal cross section of the boom tube makes for a super rigid design. The double supported pitch plate eliminates most of the system slop, and lasts a long time without wearing out. The power in this tail system is tremendous, capable of insane pirouette rates. At the same time, this system is incredibly precise, allowing tight gyro gains without wag at high forward speeds. This tail is also belt drive, so you can start to see a pattern here. Many, if not most, models that are applied to precision aerobatics use belt driven tails. Maintenance is essentially non-existent, and in the event of a crash, repair bills are lower. I flew a pair of X-Specs for over three years, and never had to touch a thing on their tails, including the belt.

The swashplate control on the EVO 90 is also mechanical; however a CCPM (known as SWM in Hirobo-ese) option is available. The standard mechanical setup is interaction free, and very precise. The plastic swashplate that’s standard will work for some time, but a high-quality, precision machined metal swashplate is available also. All controls are push/pull as well. The geometry in the system is very well balanced, and when setup properly, works very well with little slop.

Overall, the EVO 90 is probably the best bang for the buck when it comes to 90 sized models. It can use any 90 size engine on the market, with its multitude of available gear ratios. It will fly well with mid-grade servos such as Futaba 9252s or Hitec 6975s. The rotorhead now allows the use of up to 720mm blades without issue. The stock paddles with both weights installed are actually very well suited to precision aerobatics…in fact, I use them on my Caliber 90 contest model. The EVO 90 has proven itself in a number of contests worldwide.

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