The Great Planes Electrostreak [Archive]

William Crane

Apr 01, 1997, 01:00 AM

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<title>The Great Planes Electrostreak: A Review by William Crane</title>

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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. 

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<img src="http://static.rcgroups.com/articles/ezonemag/1997/../images/crane1.jpg" align="right" hspace="0" width="320" height="193">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. 

 

<img src="http://static.rcgroups.com/articles/ezonemag/1997/../images/crane5.jpg" width="320" height="168">

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. 

 

<img src="http://static.rcgroups.com/articles/ezonemag/1997/../images/crane2.jpg" align="left" hspace="0" vspace="3" width="253" height="282">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.

<img src="http://static.rcgroups.com/articles/ezonemag/1997/../images/crane4.jpg" width="320" height="175">

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,

<img src="http://static.rcgroups.com/articles/ezonemag/1997/../images/crane3.jpg" align="middle" width="176" height="300"> ------no problems.

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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