Editor's note: This article originally appeared in the Northland Flyer's newsletter, a club located in Kansas City Missouri. My thanks to William and his club for letting us reprint this excellent article.
I have always wanted an electric model. When I was young I used to dream about mounting electric motors into my plastic scale models. Then I would fly them around my room by remote control. I even went as far as mounting a small slot car motor into a Comet kit and powered it with a AA cell. The launch from the roof of my parents house was enough to convince me to wait about 20 years before trying something like that again. The spanking alone, for being up on the roof without permission, was enough to keep me from sitting down for a week!
So I waited 20 years or so while other people, gurus with fat wallets and great internal drive pushed forth the electric field. People who walk down the Mixer isle at K-mart with the same look in their eye that you or I have when looking at a new Saito 3 cylinder 4 cycle.
Remote Control hobbies changed as well. In those 20 years some amazing things have happened. Servos have decreased in size and increased in power and precision. Entry level servos that were selling for 30 bucks, now cost 10. Micro servos that were unheard of, now cost under $25 AND are more powerful than my entry level servos were. Batteries have also shrunk while having their capacities increase. The normal flight pack when I started flying RC in 78 was 400 mah, now a slightly smaller pack has 600 mah in it. Receivers have shrunk too while rejecting noise like nobody's business. In 1978, we considered it a lucky if we made it through the day without getting hit by someone using a CB and a slider. I have yet to take a radio hit since rejoining RC some 5 years ago.
***WARNING, SHAMELESS PLUGS BELOW***
Finally last winter, a group of devious modelers on Modelnet, a CompuServe forum, got me started thinking about my old dream again. Yes, the Internet is another new thing in the last 20 years. My CompuServe buddies told me to get on the Eflight mailing list. Eflight and the Ezone are services provided by Jim Bourke. They are absolutely free save the price of your own Internet hookup. Jim runs them out of the goodness of his heart and they are the regular haunts of most of the Electric Guru's. Greg Gimlick and Larry Marshall, contributing editors to RC Magazines frequent Jim's services along with several manufacturer's like Astro Flight, Aveox, MaxCim and others. If you have an electric question, this is the place to get it answered.
I asked my new friends to recommend a good electric setup. I told them to keep in mind that I wanted a plane that didn't cost an arm and a leg so as to scare off the average modeler. Something with a little zing to impress the Wet boys. Immediately came back a list of powered gliders! GLIDERS! I again posted saying I wanted something with a little Zing and had one of my on-line acquaintances convince them that I could handle just about anything. Well anything save walking and chewing gum at the same time. Still don't have that one figured out. Armed with the knowledge that I new how to fly, I received a list of sport planes. Top on their recommendations was the Electro Streak by Great Planes.
This simple plane builds like an Andrews kit. It is light, strong and goes together quick. A week after I got the kit, I was ready to cover it. If you can fly an Ugly Stick, you can fly the Electro Streak. The fuselage is minimalist at best and is more of a slope soaring style. Just large enough to get a 10 cell pack in with built up tail feathers. The wing is a thin semi symmetrical section, and it combined with the fuselage makes for one slippery ship. The boys at Eflight had advised me to make some minor changes for that Zing factor I had asked for.
I moved the servos and receiver from under the wing, to inverted behind it. I made a small hatch to provide access to the gear. This was to make way for a 10 cell pack that dominates the area under the wing that was designed for a 6 or 7 cell pack. There is a motor that comes with the kit and I have read that it works fine as designed, but for that Zing I was told to buy an Astro Flight Cobalt 15. Through an ordering mistake, I got a FAI version of the motor. This motor is a Rossi compared to a Thunder Tiger. It sucks more juice from the pack while providing that power. As a result I have truly spectacular flights of reduced duration. With the performance this model has, I can live with that!
"So what does it compare too powerwise?" is the first question everyone usually asks about electric motors. That really is a moot question. After all when you started flying wet, did you ask what a 40 compared too? If you did, were you satisfied when they told you it was about 2/3 the power of a 60? Internal combustion engines work differently than electric motors. Put more prop on a gas motor and it will heat up, slow down and probably die. Put a bigger prop on an electric and it will suck more juice to spin the prop at a RPM determined by the voltage of your battery pack. How does this motor compare? It will spin an 8x4 prop at over 16,000 RPM. The motor is wound to spin at 2295 RPM/Volt. With a 10 cell pack that means the motor would like to spin around 28,687 when it unloads. Of course as you're sucking electrons' outta the pack at around 40 amps, the voltage of the pack will tend to drop a bit. Listening to it in the air however you can tell it is spinning close to 20g's. Try getting that outta a Wet .15? No Way, more like a 40 with a small prop.
Should you go about building one, what do you need to do? Think light, is the first recommendation. It is also the most important one. Batteries are inherently heavy, so any structure that is not necessary is added dead weight. Most of the plywood and doublers of the average sport airplane is just sitting there trying to keep the airplane from shaking apart as the Internal combustion engine hooked to the nose detonates a small charge thirteen thousand times a minute. Electric power is smooth and therefore does not need all that extra weight. The E'streak is designed with this in mind. Follow the kit instructions and be careful with the glue and you will be happy with the results. This plane won't shake itself apart. I didn't use CYA to glass the center section of the wing like in the instructions though. I think that a properly laid cloth with epoxy is lighter and produces a smoother surface. Besides I used the CYA method once and could not get the wrinkles out of the cloth. One surprise was the aileron control rods. These exit through the fuselage sides and go to the aileron control horns straight from the servos. This eliminates the torque rods and saves weight. The holes in the fuse also provide cooling air exits. The other surprise was the motor installation. With electric planes motor installation is simple. On the Streak, two pieces of light ply are cut with holes for the motor in them. You mount two screws through the front mount screwing it to the motor. The back mount slips through the motor and glues into the forward compartment. This is even easier than the clamp mounts for a glow engine.
Remember when I said to build lightly? Well so far so good for my building experience, but now it was covering time. I picked Pearl Red and Yellow to cover with. I don't think Ultra Coat makes any heavier colors than these, a fact I was made aware of when I stumbled across a covering weight table. If I would have used something like transparent Monokote I could have shaved 2 or 3 ounces off the airframe weight. Probably could have shaved another 1.5 if I would have used Lite Span. But no, I used the Pearl colors, the heaviest covering known to mankind, save a bad paint job or my Mother in Laws gravy. Still, I had been told to shoot for 50 ounces battery included and I ended up with 47. I was blessed with a kit that had light wood in it and thanks to some free flight building, I know how NOT to soak everything in the glue. Did I mention to be careful not to use too much glue? Just follow the instructions and you will be happy with the results.
Do you worry about hand launches? Not with this setup.
The Electro Streak almost rips itself from your hands and if built straight will only need a little trimming. Mine needed a couple clicks of right trim. And as for landings, well,
Oh it's not all roses, I've burned a fuse out at an in-opportune time, and had to repair the damage. But hey, NO FUEL SOAKING TO DEAL WITH! It wasn't the planes fault either. With this setup I am drawing close to 40 amps on the full pack, and I had been using a 30 amp fuse. So much to learn!
Duration is less than most wet designs where you can usually stick a bigger tank in. I have stretched a flight to over 8 minutes, and it still had a couple of full out passes. It did include plenty of loops and rolls. This was with 1700 mah cells, 2000 mah cells are now available for about 2 dollars more a cell. Hope it goes down a bit before I order them in the fall.
So where do we go from here? I have my eyes set on one of two projects. A Senior Kadet ala Herm Perez of Eflight. Herm uses an Astro Flight 40g motor on 18, 1700 mah cells that spins a Master Airscrew 15x12 which has been cut down to 13 inches. This provides 15 minute flights with touch n go's during the days. 23 minute flights in calm evening air. Using an Astro Flight 15g it gets 28 minutes. This sounds like an ideal night flyer to me.
Another option is the cool P-38 designed by Jim Ryan. You have probably seen this model in Model Airplane News. It runs on two speed 400 motors and 16 600 mah cells. Jim's plane is a semi scale hotrod but is as he describes "Every Mans Twin".
Remember with electrics, either both motors are turning, or they are not. No more one engine out problems. The speed 400 motors only cost 12 bucks each too. Talk about cheap power. Jim is getting ready to produce this as a foam winged and laser cut kit. I can see both of these planes in my immediate future. The question is, which one first? Ah such a sweet dilemma.
Give serious thought to electric for your next airplane. I'm no expert, but I have many folks on-line that can give us help. You can contact them too. If you are a CompuServe member, go to Modelnet. For extensive help might I suggest going out on the net to the Ezone at www.ezonemag.com. Here you will find all the electric experts and all the help you will ever need.
You know, if I can swing the Kadet for my Birthday, I could be the first member to fly Electric at night at our field before the end of summer.
Hmmmmm, another record?
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