stunthanger.com
Electric Stunt => Gettin all AMP'ed up! => Topic started by: Larry Cunningham on January 26, 2009, 01:13:43 PM
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Wow.
Robert Compton invited me yesterday morning to the sod farm, a flying site near
Santa Theresa NM, to watch his electric powered Desperado fly.
From the rave reviews Robert had been giving me, I was already set for a positive
experience. Robert has flown a lot of CL stunt for many years, and is an accomplished
flier and builder. So, when he told me he was completely blown away with this electric
power system, I believed him.
But nothing is quite as convincing as seeing it fly. Which I did; now I'm really sold, sure
that electric has definitely arrived not as simply a viable but a superior power system.
I like virtually everything about it.
What power - I released this ship and its thrust is impressive, certainly as strong as
any .40/.46 IC power I've seen. Robert was getting consistent 5.3 second laps, which
he feels comfortable with. There was a light breeze, and never any line tension problems.
In fact the lines never bowed noticeably anywhere. Quiet. Powerful. Very impressive.
I like the way the controller beeps and spools up, and also how it warns end of flight
(set to 5.5 minutes duration). I had expected the power to sag a little perhaps, but it
simply didn't. Amazing. Robert tells me he is running about 35% power, and when he
recharged it used under 70% of the battery charge (don't quote me on those figures).
Virtually ideal power delivery - that little APC prop is clearly more efficient than its
IC engine counterpart.
The ship Robert was flying is his own creation from some favorite parts, and had been an
IC engine ship. He had repaired its nose and converted to electric, fairly easily I would
estimate. I gave him a copy of Mike Palko's latest CLW model about electric construction,
I'm sure he'll incorporate some of Mike's information into his next build.
Also, Robert flew his RC helicopter - he's no slouch with it either.
Afterward, over a BBQ lunch, I was trying to summarize whatever disadvantages
there were to such an electric power system.
I thought perhaps initial cost, but as Robert pointed out, what does one spend for a
typical modern setup? Hmm. Also, you need two or three battery packs for backup
and quick turn around on flights, it took about 45 minutes to recharge. How long
do LiPo batteries last? Apparently life is hundreds of cycles when properly cared for.
(It looks like there is downward pressure on the prices of the pieces.)
Hmm.. What happens in a crash? Is it bye bye for motor and/or other components?
Can the batteries short and catch fire? Well, that's a $64K question. But we can't
really expect to build models to crash, i.e. stand up to crashes if we care how they
perform. Perhaps some disadvantage here, but note ruined my Fox .40 and ST .51,
with bent crankshafts in crashes, so where's any guarantee?
I need not enumerate all the advantages, but it seems to me that the most important
one for any CL stunt competitor me is the incredible consistency of the run. As Robert
said, it won't matter if he is in New Mexico, Florida, Arizona, orTexas.. Altitude no
longer has anything to do with it. No farting with fuel, venturis, plugs, fuel tanks, pipe
header length, no need to carry an assortment of $50 CF props to get the power system
trim just right. I love the idea of a prop that costs under $4, and just WORKS. No castor
oil to wipe off, no smells in the car, no need for fuel proofing anything.
Well, as you can see, I'm pretty hopped up on it. Time for me to get some outline drawings
in CAD.
L.
"Beauty more than bitterness makes the heart break." -Sara Teasdale
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YEP!
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A couple of other notes, just thinking about the crash issues. And
construction issues - Robert said his next model would have removable
wings, and room in the center of the fuselage for the battery. And
he also noted that the battery pack could be oriented in any manner.
There is plenty of wire to move the battery, timer, and speed controller
aft a bit.. These might better survive most crashes there, and the battery
mass is likely better located nearer the CG as well. Yes, the motor is
going to be vulnerable, but I'm hearing that the Chinese knockoff of
the motor he is using is going to be less expensive; if it works as well..
I'm starting to think in terms of a new fuselage structure, with removable
wing feature, and perhaps a lift off fuselage top, to access the battery
package. Other wondering about connectors for field charging, even
programming, in ship.. ? Hmmm.. my own modular stunt ship ideas from
the distant past start to surface.
More interesting things to think about.
Wow. Again.
L.
"My boy says he can eat fifty eggs, he can eat fifty eggs." -Dragline, from Cool Hand Luke
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Larry,
What is Roberts set up? Motor, batteries, timer, prop, how much used in a typical pattern, launch RPM, etc. Sounds like you are hopped up! Glad to see you are excited.
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(snip)
But nothing is quite as convincing as seeing it fly. Which I did; now I'm really sold, sure
that electric has definitely arrived not as simply a viable but a superior power system.
I like virtually everything about it.
(snip)
Roger that. I had that "ah hah" moment last summer, realizing that while e-power continues to get BETTER, it is already the power of choice for just about everything we build. While my experience is still limited, the ease of set-up has been quite a pleasant surprise.
Just finished up the 3rd new E-bird for 2009. If it don't stop snowing and start thawing I might have 2-3 more! n~
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Roger that. I had that "ah hah" moment last summer, realizing that while e-power continues to get BETTER, it is already the power of choice for just about everything we build. While my experience is still limited, the ease of set-up has been quite a pleasant surprise.
Just finished up the 3rd new E-bird for 2009. If it don't stop snowing and start thawing I might have 2-3 more! n~
Dennis,
Pictures and details. pleeeease! #^
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Hello Larry,
Yes, the powerrplant module idea sure is tempting.
Dean P.
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On the plane Larry saw, it's the typical AXI 2826/10 with a Phoenix 45, Ztron v.3, APC 12-6e, Thunder Power 4 cell 25c 3850 pack. Only pulling about 2100 out per 5:30 flight.
I think the RPM is 8600, but as been perfect from the first flight, have not checked it. Plane weighs 54 oz and is 635 sq in.
Robert Compton
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Thank you Robert. Pretty close to what we've seen here on similar airplanes.