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Written by Chris Mulcahy
RC Helicopters
As seen in the September 2018 issue of
Model Aviation.

This month, I chatted with Matt Botos from Synergy R/C Helicopters about nitro helicopters and some of the new and exciting products he’s been working on!

Chris Mulcahy: There was a time when nitro-powered helicopters were the only choice to fly. With the development of LiPo batteries and brushless motors, it sometimes appears that nitro has all but faded away. If you go to any fun-fly, however, you will see that nitro is very much alive and thriving. What do you think the appeal is?

Matt Botos: There are a few things that come to mind when I think about the appeal of nitro.

First is the power-to-weight ratio. A nitro-powered helicopter might have less power than electric, but it doesn’t have the burden of heavy LiPo batteries. The power closely matches the weight. A nitro helicopter has a confidence-inspiring feeling primarily because its power level is much lower than electric.

Next is the flight time. The average flight time for electric power is approximately 4 minutes, unless you have a low head-speed configuration, which might give you upward of 10 minutes. The average flight time for a 700-class nitro heli is approximately 7 minutes. Even after your nitro flight is finished, it’s quick and easy to refuel and go at it again.

Finally is the sound, smell, and smoke of a nitro-fueled, internal combustion engine. Nitro has been around for a long time and it’s not going to die anytime soon.

Matt Botos with the new Synergy N556.

CM: For those who are thinking about trying nitro helis, can you explain your break-in procedure for a new engine? What are the important steps to ensure that an engine is good, strong, and has a long life?

MB: There are approximately 100 opinions on nitro engine break-in procedures, but there are only a few important things to remember.

First, never overload or overheat a new motor. If you have to, reduce the collective pitch to 8° to prevent loading.

Next, start tuning your needles on the first flight immediately after you verify that your factory settings are rich. Your engine will not break in properly if you are running too rich.

Components of an internal combustion engine will expand with heat, so you need to ensure that your motor is close to operating temperature for a proper break-in.

CM: Tuning can make or break an engine. What are some tips you can offer for tuning an engine? How do you know when it’s time to start tuning?

MB: Proper tuning is not something that comes overnight. It involves sight, sound, and the feel of the helicopter.

Many pilots will have to go through a trial-and-error period to determine how much power these engines can produce without destroying the motor. The trial-and-error period will also teach you what a lean or rich motor sounds like, as well as how hot the motor is in both conditions.

The amount of smoke that a nitro motor is producing is also a key indicator of how it is performing. Start tuning immediately after you verify that the factory settings are rich.

A Synergy N556 gets ready for a flight.

CM: Night flying with nitro helis is extremely popular. Can you explain why nitro engines seem to have more power under the floodlights?

MB: With any internal combustion engine, we always try to provide the engine with the densest air possible. Why? The denser the air, the more fuel we can add to that air, which in turn makes a bigger boom! Night air is generally cooler than daytime air, which means night air will be denser.

Remember, when you have more air, you need more fuel! If the temperature fluctuation between day and night flying is large, you will usually need to richen your high-end needle between three and four clicks and the midrange between one and two clicks.

CM: If we’re not planning to fly a nitro engine for a while, what steps should we take before storing it?

MB: If you don’t plan to fly your nitro helicopter for more than two weeks, do a few things to keep your motor in good shape.

Nitro fuel contains a large percentage of methanol, which attracts water. This is also known as hygroscopic. Water will corrode your engine bearings. The best thing you can do to prevent bearing corrosion is to remove any trace amounts of fuel. There are many effective methods for accomplishing this, but here is what I do for my engines.

• On your last flight before storage, run the fuel tank dry or pinch the fuel line until the motor stops.
• Remove the motor backplate and pour in your choice of anticorrosion fluid. I use one capful of automatic transmission fluid.
• Manually rotate the motor to ensure ample coverage of the fluid over the rear bearing.
• Drain the excess fluid into a pan or on a shop towel.
• Reinstall the backplate.
• Close the carburetor barrel.
• Rotate the motor crankcase until you are at the top of the compression stroke. This helps seal off the bearings in your crankcase from outside air.
• Plug your muffler.

A Synergy N7 sports a new ProTune 105 muffler.

CM: Synergy R/C Helicopters carries two nitro helicopters, the N7 and the N5c. What prompted you to develop the N556? Can you tell me about some of its features?

MB: I designed the N5 around 2008. At that time, nitro helicopters and flybars still dominated the helicopter scene. Shortly after the release of the N5, flybarless systems became popular, which meant that I needed to adapt the N5’s mechanical control system to accept the demands of an electronic flybarless system.

Many years passed and every helicopter I designed after the N5 was designed specifically for flybarless control systems.

In 2018, I am finally getting around to designing a 600-class nitro helicopter that 100% caters to flybarless electronics. While designing the N556, I analyzed every part for potential weight reduction.

The fuel tank is centrally located so that the center of gravity does not change during flight. I simplified the cyclic control system by mounting the servos in a direct-drive orientation. The rotorhead was redesigned for a more rigid feeling and weight reduction.

My canopy designer, Rob Cherry, gave the N556 a stunning wraparound canopy and fresh paint scheme. Rob has also begun helping me design other components within the helicopter.

CM: There is a new name in the muffler world: ProTune! Can you tell me about how you got started with mufflers, and some of the process behind developing them?

MB: I watched the decline of nitro helicopters for many years. With that decline, I saw many companies close their doors, which left large gaps in the number of products available.

In approximately 2015, I began to witness the resurgence of nitro helicopters. I decided that it was time to start filling the gaps with products to ensure that new nitro hobbyists would have success and enjoy nitro.

Prototyping the ProTune 105 was not easy. I first designed the new pipe in Solidworks and sent it off to my factory. After several modifications, I was finally happy with the result. I would love to tell you more about the details, but the things I learned during this process were time-consuming and expensive.

CM: What’s next from Synergy R/C Helicopters, Rail Blades, and ProTune?

MB: You can count on more new model helicopters, the best rotor blades I can offer, and more great developments from ProTune.

-Chris Mulcahy


Synergy R/C Helicopters

ProTune RC

Rail Blades

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