stunthanger.com
Electric Stunt => Gettin all AMP'ed up! => Topic started by: Jim Thomerson on May 17, 2007, 02:54:52 PM
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I've seen learned expositions on how the CG of an IC powered stunter shifts rearward as fuel is used up. Supposedly the pattern is set up with the more difficult maneuvers toward the end to allow the flier to take advantage of the more rearward CG and thus more maneuverable airplane. I presume you electric guys want the same effect. Do the batteries get enough lighter as they lose electrons? Or do you have to have some mechanical way of gradually moving them back? I haven't seen any discussion of this matter. LL~ S?P
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My electric seems to hit more bugs than my I.C. airplanes so the electric plane actually weighs more at the end of the flight CG more forward.
linheart
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I'm not sure if this is a serious question or not, but I don't see any advantage to burning fuel to change the CG. I think everyone will tell you no CG change is an advantage!! Some have gone as far as to design the tank location as close to the CG as possible. Fly an electric airplane and see how consistant it is. If you were kidding, you got me. :-[
Mike
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Jim,
Of course the batteries get lighter as the flight progresses. By this I refer to
E=mc2. where "c" is the speed of light, ~(3*108) m/s.
For example, my Super Clown uses ~1800 mAhr's of current at an average battery voltage ~10.5V during the flight. This equates to an energy usage of 18.9 Watt-hrs, or 68000 Joules of energy.
So the decrease in mass would be (solving for m in the equation) 68000 J/(3*108)2 or about 1 nanogram.
I was wondering why the plane felt so sensitive in the cloverleaf! H^^
No electrons were created or destroyed for this post.
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1% serious, 99% kidding. Thanks Alan.
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Good answer Alan!!! ;D
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Actually, batteries dont' work that way. All of the electrons stay in the system, they just move from one place to another- from the anode to the cathode of the battery, and into and out of the lithium ions trapped in the anode to the lithium carbonate trapped in the cathode. The lithium ions complete the circuit by moving through the polymer from the anode to the cathode.
http://www.agmbatteries.com/chemistry.asp
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Phil,
I don't know if you are refering to my post, but as I say at the end, no electrons were created or destroyed! That's conservation of charge! So you are agreeing with me, and I with you.
Actually, and I am serious, the mass change is due to the fact that energy does weigh something!
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Orient the battery such that, during discharge, the electrons move from the front of the battery to the rear of the battery.
Stark simplicity!! H^^
Jim
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Alan, E=mc2 describes what happens when mass is converted to energy. A battery does not convert any mass. Shades of cold fusion! In a battery chemical potential energy is turned into electricity with no loss of mass, not even a nanogram.
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Phil is right.
(EDIT to remove the boring parts)
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A chemist colleague once told me that every change of energy in a chemical reaction involves a change in mass. Isn't a charged electron heavier than a discharged electron? Isn't it a matter that electrons leave the battery heavy and return light, to pick up more mass before making another circuit?
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E=mc2 describes what happens when mass is converted to energy. A battery does not convert any mass.
That equation says that both sides are equivalent. Means any change of energy means change of mass. Does not matter if it is nuclear weapon, chemical reaction or just spring compression.