If you're seeking to build some thing that moves a serious amount associated with air, picking up a 120mm ducted fan is usually usually the point where things start getting really interesting. There's an enormous leap in performance whenever you move from the smaller 70mm or even 90mm units straight into this territory. This isn't just about the dimensions of the housing; it's about the particular sheer amount of thrust you can generate as well as the way these types of larger units alter the flight characteristics of a size jet.
Most hobbyists which end up looking at a 120mm ducted fan are fed up with the particular high-pitched "mosquito" whine of smaller electric jets and desire something that noises a bit more authentic. Only at that level, you're getting into the big leagues, usually competing with turbine-powered models in terms of speed plus presence, but with no the complexity plus cost of actual jet fuel systems.
Why Phase Up to the 120mm Class?
The particular biggest reason to go with a 120mm ducted fan is pretty obvious: thrust. We're referring to units that can easily push away 7kg to 10kg of force, or even more depending on your motor and battery setup. When you have that much strength on tap, you can fly very much larger airframes. We're not talking regarding small foamies any more; we're talking about large-scale composite jets that have real "heft" in the air.
There's also the performance factor. While it requires a lot associated with juice to spin a huge fan, larger blades are generally more efficient in converting electrical energy into moving air than tiny types spinning at astronomical RPMs. A 120mm ducted fan allows you to move a large column of air in a somewhat lower velocity compared to a tiny fan trying in order to scream its method to the exact same thrust level. This leads to a much more realistic "whoosh" sound that mimics a real turbofan engine.
Selecting the Right Motor and ESC
You can't just throw any electric motor into a 120mm ducted fan and hope regarding the best. These types of units are weighty, and the rpm necessary to spin those blades is substantial. Most guys within the hobby stick with high-quality inrunner motors because these people can handle the high temperature and the high RPMs better within the tight confines of the fan shroud.
You'll generally see these supporters paired with 12S or even 14S LiPo setups. If you attempt to operate a 120mm ducted fan on a 6S battery, you're going to become disappointed—it'll likely pull a lot of amps that you'll puff your batteries in the single flight. Likely to a higher ac electricity (12S+) keeps the amperage at a reasonable level whilst giving you the particular wattage you need to actually get a heavy plane off the terrain.
Don't skimp on the Electronic Speed Controller (ESC) either. A 120mm ducted fan can easily draw 120 to 160 amps during a vertical climb. You want an TECHNOLOGY OF ESC that's rated with regard to at least 160A or 200A just to possess some breathing room. High-quality ESCs also have better thermal management, that is crucial because presently there isn't exactly a lot of natural airflow inside the jet fuselage except if you design the ducting perfectly.
The Importance associated with Ducting Design
Speaking of ducting, this is where a lot of people mess up their particular first big EDF build. A 120mm ducted fan is just as great as the air it may breathe. If your intake is too small, the fan will "starve, " creating the vacuum effect that kills your thrust and makes the motor run hot. If the intake is too huge or poorly designed, you obtain turbulent atmosphere that ruins the efficiency.
The particular exhaust side (the thrust tube) is usually just as critical. Most experts suggest a "pinch" or even a reduction in diameter on the very finish from the tube—usually about 85% to 90% from the fan's diameter. This increases the particular efflux velocity, which helps with top-end speed. If a person leave the tailpipe too wide, you'll have great static thrust (it'll take off quickly), but the plane will feel sluggish once it's moving. It's a bit of a balancing act, yet getting the ducting right for your 120mm ducted fan is what separates the "dog" of the plane from a "rocket. "
Electric batteries: The Heavy Raising
When you choose in order to run a 120mm ducted fan , your own battery budget will take a hit. Since you're most likely managing a 12S setup, you're basically taping two large 6S packs together within series. These aren't your average 2200mAh packs, either. You're taking a look at 5000mAh in order to 8000mAh packs along with high C-ratings.
Weight reduction becomes a real challenge right here. These batteries are heavy, and where you place them in the fuselage will dictate your own Center of The law of gravity (CG). It's luring to purchase the biggest batteries possible for longer flight times, yet if the plane turns into a "lead sled, " it won't fly well. Many people discover that 5-6 minutes of mixed-throttle flying may be the nice spot for the 120mm ducted fan setup.
Sound plus Realism
One of the best things about a modern multi-blade 120mm ducted fan is the sound. Back in the particular day, EDFs sounded like hair dryers—very high-pitched and kind of annoying. Contemporary fans, especially individuals with 10 to 12 blades made of carbon-fiber-reinforced polymer or high strength reinforced plastics, generate a low-frequency roar.
If you choose a high-speed pass along with a 120mm ducted fan , you get that "jet turbine" roar that in fact sounds like air being ripped apart. It's incredibly rewarding. If you're a scale enthusiast, this is actually the main reason to go big. There's just no way a smaller fan can move enough surroundings to create that specific acoustic profile.
Maintenance and Safety
It's worth mentioning that a 120mm ducted fan isn't a toy. Whenever that fan is definitely spinning at 30, 000+ RPM, generally there is an enormous amount of kinetic energy involved. You need to make sure your fan is perfectly well balanced. Even a small vibration at those speeds can cause the fan in order to disintegrate, which usually leads to the overall destruction of your own airframe (and possibly a trip towards the ER if you're standing too close).
Always check for loose screws and make sure the particular motor is securely mounted inside the particular shroud. Since the 120mm ducted fan generates therefore much suction, it's also a literal vacuum cleaner. It may suck up unfastened grass, pebbles, or even even your personal shirt if you're not careful during ground testing. Often keep the area within front of the intakes clear.
Heat Management
Heat is the enemy of any high-power electric setup. After a flight, you'll notice the electric motor within the 120mm ducted fan will be quite hot in order to the touch. This particular is normal, although you should avoid "hot loading"—which is basically landing and instantly taking off once again with a fresh battery power without letting the particular motor cool straight down. Giving the internals five or ten minutes to breathe will significantly prolong the life of your motor bearings and magnets.
Is really a 120mm Ducted Fan Right for A person?
If you're moving up from park flyers, the 120mm ducted fan might be a bit of a shock to the system. It's more expensive, the particular batteries take lengthier to charge, plus the planes are much faster plus heavier. But when you've mastered 90mm jets and need that extra level of "wow" aspect at the traveling by air field, it's the logical next stage.
There's a certain presence that a large EDF jet has. Whenever you're taxiing away a jet furnished with a 120mm ducted fan , people quit what they're carrying out to watch. It feels just like a "real" airplane. The power-to-weight ratios we are able to accomplish today mean you aren't just limited to flying circles; you can do big, graceful aerobatics, massive loops, and high-speed vertical climbs that just aren't possible with smaller sized units.
Within the end, it's in regards to the thrill of the build and the reward of that first takeoff. Viewing a 15-pound aircraft lift off the tarmac powered simply by only a 120mm ducted fan and a bunch of LiPos is a fairly great feeling. It's a lot of work and requires a bit of an investment, but for most of us in the pastime, the performance and the sound are worth every any amount of money.