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Old Nov 27, 2012, 04:22 PM
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Joined Nov 2012
3 Posts
Help!
Great Planes Piper J-3 Cub .40 to electric

Building a Great Planes Piper J-3 Cub .40 size and want to try electric power. The kit's paperwork only refers to regular power and the manufacturer did not respond to my questions, so I am concerned that this kit is not so suitable for electric, although the hobby shop says it should work. I am looking at an EFlite Power 60 Outrunner with probably an 80 amp Pro Switch-mode BEC EC5, but would really like to hear from someone who has experience with this. Other suggestions, plus prop and battery ideas would be welcome! Though not a complete beginner, I am far from being an expert and haven't flown anything since diesel engines and dope were the norm, so I have some catching up to do! I do want to eventually add floats as we are surrounded by water, so I need enough power to do this, but not too much to make the plane harder to fly or get into heat problems by running it at less throttle.
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Old Nov 27, 2012, 08:17 PM
Registered User
Canada, ON, Barrie
Joined Jul 2012
6 Posts
I almost did the sam ething and asked Jeff at Head Up RC.

Here is his reply:..

Here is what I suggest if you really want to use your 3 cell 2200 Lipos:
Emax GT4020 700KV
Hifei 60A ESC OR HURC 60A OPTO ESC and a 3A UBEC (or receiver battery pack).
APC 11x5.5E prop
Two of your 3 cell 2200 30C batteries connected in series with a Series Battery Harness.
Adjustable Motor Mount or Nylon Spacers and bolts
This set up provides about 7 lbs of thrust, but your flight time will be relatively short, and you should avoid running much wide open throttle, as it would be hard on your batteries.
For longer flight times, you could buy two larger 3 cell batteries, or one 22.2v 4200 35C battery.


If you're willing to buy a 4 cell battery, then this set up would work:
Emax GT3526/05 motor
Hifei 60A ESC OR HURC 60A OPTO ESC and a 3A UBEC (or receiver battery pack).
APC 11x7E prop (about 5 lbs of thrust)
APC 12x6E prop (about 6 lbs of thrust)
14.8v 4200 35C Lipo battery
Adjustable Motor Mount or Nylon Spacers and bolts
Best regards,
Jeff
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Old Nov 28, 2012, 12:06 PM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
12,788 Posts
Hi Ed
Have a look around both hereabouts and in the scale forum - the Cub is a popular electrocution subject in many variants and the kit you have. If you built doped covering models, you must have some wooden airframe experience that'll come back quick.

Snag here - Great Planes do good aerodynamics and kits, but are uncertain of the term 'weight' - their models come out hefty at best.

Good idea 1 - if you are set on an electric powered conversion, read up on and figure out how to deal with your new motor and 'fuel tank' (battery!) before starting on building.

Good idea 2 - don't cheapskate on your motor, ESC and battery. You will need substantial power for float-flying. buying cheap junk and flogging it hard could end up with a total loss of your model.

Idle thought. Sig's 1/6th J3 is a way better kit and has the scale cabin access hatch, which makes a great battery hatch. I've had Sig's 1/6th and 1/5th kits with e-power and both were great fliers. Unfortunately, my drivetrains were both out of history so not of much use now

Good luck with your project.

Dereck
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Old Nov 28, 2012, 10:51 PM
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USA, TX, Houston
Joined Mar 2010
35 Posts
J-3 electric conversion

I will gladly send you some pics of my Piper ( wingspan 72") converted to electric
I used a power 60 motor with a 100A Esc, both from E-bay for $ 59.00 shipped! About a year ago, though, might have gone up a bit.
This plane flies perfectly. In the words of an instructor at our local club, " A cub is not supposed to do a knife edge. This one does!"
A bit tricky getting the motor mounted to fit comfortably inside the cowl, but very doable, thanks to Ace Hardware.
Regards,
Ivan.
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Old Nov 30, 2012, 10:28 AM
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Joined Nov 2012
3 Posts
Thanks

Thank you all for your helpful replies. Not sure if the hobby shop carries the Sig or if they will take my Great Planes kit back but will look at both. Not worried about stunt flying and it sounds like the consensus is the 60 motor will be powerful enough even with floats but should up the controller to 100 amps. How about batteries? Thanks to all!
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Old Nov 30, 2012, 07:28 PM
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ib42. Love to see your pictures!
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