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Glow-to-electric conversion guidance

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Old 08-23-2006, 08:04 AM
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JustErik
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Default Glow-to-electric conversion guidance

Hello,

I’m preparing to get my first electric powered bird in the air and would appreciate some ideas on how best to proceed. The plane is a plans built home brew designed by a fellow club member several years ago. It’s a 1/2A powered 2-channel bird with a flat-bottomed, high-mounted wing. Span is 40 inches, chord is 7.25 inches, yielding almost exactly 2 square feet of wing area. All up with a Black Widow .049, two HS-55s, and 4 AAA receiver batteries, it weighed about 16 ounces. The bare airframe weighs 8.7 ounces. It’s stick built and very sturdy, so I’m confident it will handle the extra weight of the conversion. I know there are lots of options out there and my head is swimming in them, which is why I’m here asking for help.

I’m guess a 2 or 3 cell lipo pack in the vicinity of 1,000 mah would provide a reasonable flight time, but I’m lost on motor selection. Should I go with a conventional motor, motor/gearbox combo, or one of the outrunner models? How do these compare in terms of power, service life and flight duration? What about an ESC? How many amps would a motor this size draw? 10 to 20 is my best guess, but that could be way off. I’m looking for very specific recommendations as well as the reasoning behind them.

I’ve done a lot of reading, but it seems the more I read, the more options I find….which is probably a good thing, but for an electric rookie like me, it’s been somewhat frustrating. Thanks in advance for any thoughts you may have.

Edited to add: This plane is a relaxing, slow flying bird and does not need screaming performance. I'd be very happy with enough power for a strong climb out and a flight duration of 10 to 15 minutes.


Regards,

Erik
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Old 08-23-2006, 08:48 AM
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Default RE: Glow-to-electric conversion guidance

Erik:
THEY (the experts) say it takes about 50 watts per pound to fly a airplane, that is just normal putt around. To do aerobatics THEY say around 75-80 watts per pound to do vertical stuff you need 100+ per pound. I have converted 1/2 A planes and used speed 400 motors and the planes weight is around 16 to 22 ounces. Watts(power)==volts X amps . Most 400 motors draw around 10-12 amps so if you use a pack that will put out 8-9v under load you have a pretty good flier. Most of todays motor manufacture will give you the watts that the motor is capable of so you can match them up that way. I personally like the outrunner type of motors of today (no gear boxes) and still pull pretty good size props. There are a lot of these 75 to 100 watt motors available today so the choice is wide open and they are getting really cheap and the ESC are coming down in price also. Thats the way I would go today...
Good Luck
Bob
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Old 08-23-2006, 10:55 AM
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Default RE: Glow-to-electric conversion guidance

Bob,

Thank you very much for taking the time to reply. I too am leaning toward an outrunner. Here is a [link=http://www.fmadirect.com/Detail.htm?item=2114&section=66]link to a package deal[/link] that I found at FMA that seems like a viable solution. It's very reasonably priced, includes an ESC and appears to have more than adequate powr. What do you think?

Erik
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Old 08-23-2006, 01:56 PM
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Default RE: Glow-to-electric conversion guidance

Hi Eric,

I received a copy of this question. Since your bird weighs a pound a Hacker 20 motor will do fine with a 30A ESC. Power with a 900 -1000mAh 11.1V packs. As far as gearing or stright power this is your call. The motor without gearing will take the plane stright up.

Hope this helps you.

Bern
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Old 08-23-2006, 08:46 PM
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Default RE: Glow-to-electric conversion guidance

Erik:
That looks like a very good unit. All plug and play, no soldering or anything, and FMA is a old and reputable company. Fred the owner is a modeler himself or used to be maybe doesnt have enough time now since his company has grown so much. I would go with a 1500ma lipo or even a 2200 if you can afford it and it will fit into you plane. I have learned in the last 4 seasons that I have used lipos that bigger is better, it doesnt put a strain on them if you have a reserve of output capability you dont work them as hard and they last longer. FMA used to have Kokam batteries but I heard they dont sell them anymore, dont know who they are tied into now. Best of luck on your project, Im sure it will be succesful with the power unit your looking at and thats a damm good price I think for a matched outfit, Let us know how it works out!!!!!!!!! BTW what plane are you converting??
Good Luck
Bob
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