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My Electric Adventures
By Tony Iannucelli
Twenty some years ago I wanted to try an electric model airplane. In those days we were sold geared “Cobalt” motors and heavy NiCad batteries as the answer to electric flight. Most airframes available were old timers and motor gliders, and they were true kits. There were no performance aircraft available as the weight of the power system would relegate higher wing loaded airframes to taxi practice. I had a nice electric “Playboy”, a kit by Bob Boucher, and I wish I had the plane today. Its limitation was that silly motor and battery. I did manage a few short flights, but they weren’t much more than takeoffs followed by immediately lining up for landings. It was a porker because of the battery. Fast forward to 2011.
What a difference. Brushless/lipo power has allowed and fostered model aircraft for the 21st century. In case you haven’t noticed, electric flight is catching on really fast and has been a large segment of the hobby for several years already. The model magazines are about half and half, electric and nitro/gas evenly distributed. Several guys at the field only fly electrics, and their aircraft are beautiful and fly very well. Several others mix and match nitro, gas, and electrics. I’m personally experimenting with the small EDF planes and 450 size electric helicopters, a couple of propeller-driven pusher “jets”, and the occasional larger Edge/Yak. But my small world of electrics is far from all fun and trouble free. Here’s why.
I’m a serious novice at it. Here are some of my problems, dating back a few years. I’m getting better with most of this now, but you may experience some of it if and when you decide to try electrics.
Let’s start with the motors. Only a few companies make any attempt to explain what a 28-15 designation means or 42-50-1100 or any other of the large number of combinations out there. I didn’t know what KV meant, or what an AMP draw was, or why “watts” are something to be concerned about, or why shaft diameter differences are a concern. The trusty voltmeter I used to check my old NiMH packs has been replaced by a “Wattmeter”. I still can’t define some of it. One is expected to know the difference between an “outrunner” and an “inrunner”. OK, that’s not so bad, I’ll grant you, but remember the first time you heard it? That’s the trouble in a nutshell – everything is “the first time you heard it”. If you don’t know, trust me, it comes at you fast, but it’s not that difficult to grasp. But there’s more trouble on the horizon after you learn the lingo...
Like what size prop to use. I have a 50 inch Great Planes Edge 540 that weighs a couple of pounds and uses a four cell lipo battery rated at 2650 milliamps. I use the 25-50 and 35-70 “C rated” batteries. Don’t ask me about those designations … I do know the higher the “C” the better, but still don’t know why, except that I think it means capacity, or duration, or both. Anyway, the motor is a 42-50-700, which means it is about the equivalent of a .30-.40 glow engine in terms of power – which lasts about 5-6 minutes per charge. That’s not very long compared to other power sources, which is yet another issue with me. But back to the propeller choice. I started with a 13-6 “electric wood”. The plane performed well, but the first half of transmitter stick travel seemed to provide all the throttle, and from half stick up to the max, not much additional power or rpms were evident. I followed the ESC directions, and think I set it up correctly. I also heated up one of my batteries and it “puffed” a little. Uh oh, too much prop? So I went to a 12-7, then a 12-6, and not much seemed to change. Performance seemed the same in all respects. Happily, the batteries ran a little cooler, ditto the motor, which was a good thing, and additionally I reduced flight times to five minutes. I used the Wattmeter and was well within the limits of the motor and ESC. But hit or miss is not a satisfying way to go for me. By the way, the ESC performed well at all settings, and it is a Turnigy 60 AMP, and it has what’s called a balance port. This feature allows the balance connector to be plugged into the ESC as well as the power lines, and the ESC manages the balancing of the cells and protects them from over-discharge. It shuts you down if one cell goes haywire or below 3 volts. It’s worked perfectly for a couple of years, but don’t ask me how or why. To sum it up, prop choices are still a work in progress for me. What about motor, ESC, and battery choices? Things get a little better with these...
I know many of you guys have a lot of knowledge on this stuff. Sadly, reading about it hasn’t helped too much. I end up walking away from my computer just muttering unintelligible cuss words and not learning any more than I knew 30 minutes earlier. But to help solve motor, ESC and battery choices, the ARF manufacturers provide that information on the kit boxes. Only rarely do they fail to suggest the ranges on these components. I honestly think they don’t mention props so they can sell more props, but the other information gets you there. I also have to say Troy, Frank, Carl, Jim and others have been helpful. I’m just dense when it comes to electrics beyond the simple stuff. I never was very good at the vocabulary of other languages, and believe me, this stuff is like another language. So the translators are the manufacturers and that is often helpful. What really helps is buying a little EDF that has the motor, fan, and ESC already installed. But having no choices is not always a perfect world. For example...
A couple of other things have recently occurred that may confuse you the way they did me. I got a couple of twin motored planes; an A-10 Warthog and a P-38. Both came with preinstalled motors and ESCs. That was part of the problem. In reading about the A-10 in articles written by current owners, it seems some have had issues with two BECs being wired incorrectly into the planes by the manufacturer. When using two ESCs some suggest the red wire has to be cut on one of the ESCs so that the receiver or ESC isn’t fried by too much juice being put into it. Nothing in the instructions mention that! A separate BEC is the answer when there are more than 4-5 servos in the aircraft. Ask me how I know...
Frank helped by suggesting I address the uneven throttle response on my Edge by using the throttle curve settings in the transmitter. I never thought of that option until he mentioned it. I don’t know if there is any effect on the motor, battery or ESC loading when I do that, but I’m about to find out. It works on the electric helicopters so there’s no reason why it won’t work on a plane.
The economics of electric flight, especially compared to prices just a few years ago, is cost effective compared to nitro and even gas operation, although the whole topic is still debatable. My argument comes with an equation:
Fun Factor = (cost) of the airframe + motor/engine + fuel supply
Definitions:
Fun factor – do I like owning this airframe, does it fly to my capabilities, am I proud of it at the field, is it good looking, is it easy to manage physically, etc.
Airframe – what is your out-of-pocket cost to get it flying
Motor/engine – cost, how durable is it, are parts necessary and/or available, is it easy to use and maintain.
Fuel supply -- batteries, or gasoline/oil mix, or nitro fuel – cost of the three choices, availability, ease of storage.
My equation may seem oversimplified, but economics play a part in everything most of us do. I’d have 100 airframes if it didn’t. I think electrics might now be leading the choices in all of the above factors. Here are some considerations.
Clearly most of the latest airframes are either offered as straight up electrics, or, electric power is an option and the parts and manuals are provided allowing conversion. Even large aircraft are included.
Engine and motor choices are available in a wide range of types and by a growing number of suppliers and manufacturers. Electrics take the lead here. The German and other European motors are still relatively expensive, but Hobby King and others offer the equivalent motors at a fraction of the cost and they perform very well. One can pay a lot more, and some guys’ personalities require buying “the best”, but I would argue for the average sport flier the Chinese brands are fine. I’ve never had a motor fail yet, and if one does fail, $20-25 replaces it. Gasoline and glow engines cost 5-10 times as much as an equivalent electric motor. A 60 size OS glow engine costs about $150+. A small (Chinese) 20cc gasoline engine about $250. The larger gasoline engines like the DA engines are $500 - $1,000 and more. It takes a long time for the fuel-saving effect of gas over nitro to equal out based on just engine cost. Advantage electric, next is glow, then gas.
Fuel cost is a close one. My 90 size glow engine will give me 10 flights on a gallon of 20% nitro fuel. Bigger engine, fewer flights. Storage of nitro fuel in the garage does not generate an odor and is no more dangerous than the gasoline in the tank of your car. A gasoline engine, considering the cost of the gas plus the oil mix, is less expensive to operate than nitro if the size of the engine is about equal. The engine itself is more costly, but a gallon of gasoline with the mixing oil included is currently about $4. And a gallon lasts a long time, so I’m told. Gas in the garage is worse than nitro fuel in my opinion. I can’t argue that one based on fact, I just think those fumes I smell are more dangerous than a sealed glow bottle or can. Battery cost for electrics win hands down in the category of fuel economy. The blue lipos from China cost between $10-20 delivered. If you “only” get 50 flights on a battery, that’s er…. 20-30 cents a flight! Not $2+ like the glow fuel, or even $1 like the gas; advantage electric. By the way, a guy can spend a lot more on batteries from the U.S. suppliers. I can’t say they are worth the difference in my limited experience.
To sum it up, there’s an awful lot I really don’t know, but like a lot of things in the R/C hobby, with time and patience the average modeler can figure it out. All part of the fun of the hobby I guess. A lot of guys are saying the future is electric, so take heed. By the way, if you see one of my electric planes trailing smoke while it’s in the air, keep in mind none of them have a smoke system built into them… and that it can only be a bad thing...
See you at the field. I’m the guy with the large selection of propellers and batteries -- scratching his head.
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