[NSRCA-discussion] E Stuff

Sat Jan 21 09:30:34 AKST 2006

After Orland and I went through a steep learning curve at the beginning last year, the whole set-up became VERY reliable.  Hacker geared motors, Hacker controllers, 22/12 props and Kokam 3200 20c batteries.  As it turned out, the airplanes were pulling around 65 amps at full throttle and the batteries were not happy for longevity much over 10c.  I sort of re-grouped when all three sets of batteries called it a day after about 25 cycles ea. set--decided that I'd wait until the technology caught up.  The old Jag('68 2+2)(2m will just fit) we've been madly restoring is about under control and I'm about to get back in the fray--so I'll be casting around for a battery set-up.  Castle Creations(local) sent me a controller to try and I may whip something up for that.  Unfortunately, both the airplanes I've got are a little heavy that anything over the 3200s will put 'em over the limit.  I may not sweat that for now as I'm probably not going to hit any big-time contests this year.  As I've said before--everything seems pretty reliable at this point--except battery life.  Weight certainly affects amp draw which affects battery life--so if we have to live with existing technology--then that is the first place to look.  I could be wrong, but I have the feeling some folks have about 5 sets(or more) and one or two are in transit to and from the manufacturers supporting them during the heavy contest season.  If you've got deep pockets(or are sponsored)--that's cool--for the rest of us; either the batteries have got to come along, or we build lighter, change our flying approach--or all of the above to extend battery life.  I am NOT bashing Kokam--they are great folks and they were learning right along with us. I'll be talking to them first.  I may chat with Tanic since they are local.   We'll see.

Richard 
  ----- Original Message ----- 
  From: Earl Haury 
  To: Discussion List, NSRCA 
  Sent: Saturday, January 21, 2006 11:02 AM
  Subject: [NSRCA-discussion] E Stuff

  The E info on the list has been scant. Probably some are reluctant to hype / criticize products because of their involvement with suppliers. Some of us are just blindly exploring options, gathering data / information, and forming opinions without experience to back up our conclusions. Certainly information offered by those with experience is very welcome and appreciated. Those who are qualified experts in the various fields that can correct / clarify information gained through the school of hard knocks are not only welcome, but I suspect somewhat obligated to protect the rest of us. As this entire topic expands there will be conflicting opinions which in themselves provide info - that's what this list is for and no one should take offense that some prefer other views.

  After teasing the E guys at the Nats I recognized that the E powered airplanes flew better (I'll admit to being obstinate - but not totally dumb). There were also differences that seemed related more to E equipment choices than differences in pilot skills. The info published by Jason, Frack, Adam, Chad, and others (in RCU forums) provided an insight to the various equipment choices (and passionate defense of same in some cases). Interestingly, a lot of the discussions revolve around equipment type rather than the effect on flight characteristics.

  So - I set about trying to determine if E flies better and why. So far the answer is yes and I'm not sure. While differences in dynamics can be identified, it's hard to quantify the effects. For example, the lighter / slower rotating E prop generates a lower gyroscopic precession force during looping maneuvers than glow - this also suggests the lower rotating mass of a geared motor might be better. The lighter motor (compared to glow engine) up front can result in a lower pitch moment of inertia if the tail is light enough to allow the battery mass to be close to the CG. Airplane smoothness in rough air is markedly better with E. (I did most of my comparisons with twin Partners - one glow and one E - at about the same flight weight.)  This may be an effect of the large diameter prop or lack of vibration effect on the servos. As others have noted, thrust application is very good with E as the slower prop is efficient and the motor is instantly responsive and very linear. E can be flown slower than or as fast as glow, the airplane is more stable with E when slow  - again probably the large prop effect. Overall, it's easier to fly well with E but E won't fix sloppy flying.

  As with most things in model aviation - there are learning curves. Some suppliers are better than others, some equipment is better than others, some choices will be revisited after experience is gained. The hardest thing to get used to is the metrification of cost - kilo dollars. Not that E is that much more expensive than glow - just that very little from glow is useable with E. That means one must acquire motors, controllers, batteries, chargers, power supplies, meters, connectors, wire, props, etc. pretty much from scratch.

  If there's interest in this becoming a thread I'll discuss the reasons for some of my choices of equipment and the data I've generated / will generate with the full understanding that I might be operating under false assumptions and some of this stuff will change - I'm still learning.

  Earl

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