Discussion List (Batteries)

[Rcmaster199 at aol.com]

There are two mutually exclusive factors at work:  ARFs and prefabs  and the 
need for light, strong airframes. I understand all the reasons why ARF's  and 
prefabs are here to stay and I even agree with some of them. What I don't  
agree with is taking someone else's idea of how heavy something should be to  
work, and make it one's own. There's alot of room for improvement in that  area
 
In my view, a lighter but just as whale-like, 2m electric platform  will 
require expert building from the ground up. I challenge my pattern brethren  to 
start redeveloping those forgotten skills again. It's exactly what's needed  for 
electric at its present state of development. Prefab is great but if you  
really want to save a pound or more, learn to build it from scratch and learn to  
take the vibration absorbing fat out. 
 
And if you must, at least challenge the kit makers to come up with lighter  
solutions to the landing gear mounts. Nat and I have written a bit about that  
before. That isn't difficult at all and it will save about a half pound by  
itself on any plane that doesn't have a built in mount in the fuse.
 
1/16",  3/32" and 1/8" molded balsa isn't that hard a technique  to master 
and offers terrific strength for the weight. I'm not talking about  that goofey 
planking that some have passed on as molded, but reall molded  balsa-wood. 
Stunt guys use it all the time
 
MattK
 
In a message dated 11/18/2005 1:18:53 PM Eastern Standard Time,  
chochhalter at direcway.com writes:

 
In regards to the  airframe, I am agreeing with you in a sense that the 
planes will e-volve (grin) to be able to compliment the electric  setups.  Right 
now we are adapting  current IC airframes.  The  advantages of “braking” with 
the controllers and larger props may see another  swing in basic design 
concepts.   Look at Nats Voodoo express, now that may be  the extreme end of design 
compared to the airframes we see now and what we  evolve to but who knows, 
could a redesigned curare with slim fuse make a come  back???    
Can’t wait to see  what comes next. 
Chuck 
-----Original  Message-----
From:  discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On 
Behalf Of Richard  Strickland
Sent: Friday,  November 18, 2005 11:58 AM
To: discussion at nsrca.org
Subject: Re: Discussion List  (Batteries) 
 
Gray,  Dean,
 

 
While my experience wasn't the  greatest--it really wasn't all that bad once 
we had the bugs worked out.   BTW, it was a Hacker system like Jason's.
 
One of the issues was to determine  how cool the batteries needed to be 
before putting them back on charge;  another was to make sure you were not over or 
under charging.  Another  was to make sure they were balanced.  But for me it 
came down to weight  and longevity.  Contrary to where your information is 
coming  from, my understanding is that modeling IS driving this battery  segment 
along with the military.  I'm reasonably confident there will be  significant 
breakthroughs like that nano-tech unit(Toshiba or some other  heavy-hitter 
like that) posted earlier this year that will impact the  market fairly shortly.  
The 3200s were under-sized, but 4000s would be  also.  The motors would peak 
out at 67-69 amps on application of full  throttle and back down to the 63-65 
range.  This system worked well, but  we were too close to the edge to lose 
any capacity and complete an  FAI flight.  Temps started with a 40-50 degree 
rise when we  started using them in the upper 70s and 80s and the same and a 
little more as  ambient got warmer.  They got too hot.  We also tend to fly  out.
 

 
Realistically, if to get decent  mileage out of these things and have to stay 
close to 10C; then you've got to  have at least 6000s+ and keep the weight 
down.  I know zip about  batteries, except how to design conveyor systems for 
them, but they almost  need to act like a capacitor--very high charge, discharge 
rates, and unlimited  cycles with no damage.  I can't imagine there aren't 
MANY folks  working on that concept.
 

 
Of course there are other  alternatives--lighter and/or smaller airframes, 
different motor, ESC, prop  combinations--but if you want unlimited vertical 
with 11 lbs--then your're  going to draw 55-70 amps.
 

 
Richard

 







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