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 Ever since I can remember I have imagined having a scale looking, big, Cessna
to shoot touch and go's in the calm, still air at the end of a warm summer
day. I have flown many variations of Cessna's since I began flying models
in 1969 but none have lived up to the fantasy so carefully constructed
in my mind. Sometimes they would look great but wouldn't fly very well
or they would land real nice but look like a trainer.
A few months ago I got the opportunity to convert a Hangar 9 Cessna 182
to electric power. When I received the "ARF kit" I was amazed
at the scale detail and how much work the manufacturer had already done.
There was very little work required to finish the plane, just throw some
5-minute epoxy and a screwdriver in the box and shake it; a few minutes
later a finished 182 pops out. It's almost that easy. Everything is covered
and painted and there are lots of scale details that make this model an
accurate representation of the real thing. There is a tinted windscreen
and a scale interior with seats and the control surfaces are even corrugated
like the real one. I am frequently asked if the fuselage is fiberglass
but it is actually balsa and UltraCote. So far the dream is intact.
For those of you that are starting to get into electrics you learn that
there are two manufacturers that have established the state of the art
in electric propulsion, Hacker
Brushless motors and Thunder
Power batteries. They work together to provide unbelievable power
and endurance. Thunder Power batteries are a Lithium ion-Polymer hybrid
that are specially manufactured and matched to give the maximum power
for the most flight time. Hacker has used these batteries to refine their
motors to make use of the enormous power available and survive the extended
flight times given by those batteries. The result is that when you go
to an electric event and see an airplane with outstanding performance,
it usually has a Hacker motor and Thunder power batteries.
I called the folks at Hacker and they recommended a Hacker C-50 12XL
with 6.7:1 reduction turning an APC 18 X 12 and said to try two Thunder
Power 5S4P's in series. After a while you learn what all that means but
let's just say that they nailed it.
The conversion couldn't have been simpler. I used the standard Hacker
motor mount with a 1/8-inch shim for proper spinner clearance. I located
the batteries externally first to find the proper CG.
The only thing I had to do then was to cut two holes in the firewall
and make a ledge with a stop in front so that batteries wouldn't slide
forward. I used Velcro at the rear of the batteries inside the cockpit
and install the batteries from the top hatch before each flight. The modifications
were very simple and were done in an evening.
Normally there is a large hole in the bottom of the cowl to clear the
engine but in this case I made a cowl flap air exit to keep the motor
cool.
There is excess clearance in the holes in the firewall to provide airflow
for the batteries. The result is that the motor and batteries remain cool
even during the most rigorous flights.
Flight results were nothing short of stunning. I never dreamed that an
electric airplane could have that much power and speed. The takeoff roll
was short and the climb was amazing! I could get to 500 feet by the time
I turned downwind. A little more than scale performance but it sure is
fun.
The most rewarding thing about the project is how realistic the airplane
looks while flying. I recently got my private pilot license and can say
that it even has the same flight characteristics as the real one. I have
flown it in several demonstrations and it's always impressive even to
old TOC guys like me. I finally got to fly it for my own enjoyment without
the obligatory loops and rolls and just did touch and go's… for a
half an hour!! On electric power!!! The dream is alive.
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| Find the center of gravity by first placing the batteries on the
outside. |
Create ledges with a front stops for the batteries to sit in. |
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| Use strips of Velcro to secure the batteries inside the cockpit. |
Put a flap over the hole at the bottom of the cowl. |
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| Use the top hatch as an access point to install the batteries before
each flight. |
The 1/8 inch plywood shim used to get proper spinner-cowl spacing. |
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