[NSRCA-discussion] E Stuff

[vicenterc at comcast.net]

Unfurtunetely, I have to estimate the cost.  I did an estimate how much is the cost to run my 2c motor per flight.  At $15/gallon using 14 oz of fuel per fly the cost is $1.75 per flight.  This number is correct since I usually flight between 200-300 flights per year.  

The question is: what is the life of the batteries?  Base of the feedback I got at the Nats. the life flying F3A is around 60 flights.  Therefore, if I am correct the cost per fly is $11.  Assuming that I do 250 flights per year the cost of electric is $2,750/yr.  The equivalent cost of glow (2C) is $440/year.  With two kids in college my option is clear.  I am assuming that the cost of batteries is $640 but not sure now.  

Probably I am wrong in these numbers.  Clearly the cost of the batteries has to come down or the cycles have to go up to around 400 cycles to get equivalent cost to glow.  

Any information on this regard is welcome,

Vicente Bortone




-------------- Original message -------------- 
From: "Earl Haury" <ehaury at houston.rr.com> 

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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