Giant scale J3 conversion
 

Hello RC people. I am just finishing a Great Planes J3 Cub, and I want to convert it to electric. Ithink that a RimFire 60 size motor, and an 60-80 amp ESC will do the job. My question is about which battery to choose. Ineed a 22.2v LiPo, somewhere in the 3500-5000mah range. I've been looking at Thunder Power, FlightPower, and ProTek. I need the cheapest one there is. Would you give me some advice on how to choose. I've been flying for about 2 years now, but this is my first glow to electric conversion. Any help is appreciated.


Thanks, Matoran629</p>

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"From a kit you came, and to a kit you shall return"</p>

RE: Giant scale J3 conversion
 

Hi, if your Cub is an 81" ARF from GP, then you are going to overpower it. I fly an 81 GP ARF with an AXi 2826-12 motor, 13 X 7 prop and 3400 14.4 battery. It does every maneuver in the book and is perfectly matched power for weight. Norm

RE: Giant scale J3 conversion
 

I don`t know the size of your Cub, there are so many Cubs out there...
But if it is a 2-meter as Norm said I agree a .60 equivalent setup is a bit of overkill. But myself I would have used a setup in the .50-range aiming for capability of 1000 - 1200Watt at WOT. Which isn`t needed at all, but every part are running cold. In addition you get good flighttime!

This mean: a good outrunner, kV in the 450-550 range and 5S5000 LiPo-batteries. An ESC at least 60A. Then choose a propeller which only give a max load of 800 Watt for the first flights, I would guess this is more than enough. Then your setup could be wild or steady by just choosing an other propeller.

I don`t know Rimfire motors, but have read some bad things on them. I prefer high-end motors, but I am demanding http://www.rcuniverse.com/forum/js/f...ular_smile.gif
When it comes to batteries and ESC I have had good luck with some cheapies. Turnigy ESCs from Hobbycity, and the new Zippy Flightmax LiPoes are working OK and are extreme cheap! Buy yourself 2 Zippy 5S5000 and you would propably get 2 flights of 20-25 minutes each at the field. A 2-meter Cub won`t care of the weight of the batteries.

RE: Giant scale J3 conversion
 

<span style="font-family: Comic Sans MS;"><span style="font-size: larger;">Your Cub is suppose to be 8.5 lbs on glow. For me I would go with nothing less than a 4S set up. This will give you good power and with the right motor we are possibly turning a nice 14x7 prop. Motor I am thinking of something like the AXI 4120/14 or one of the Chinese 4260 of about 650KV. Battery size I will say go with no less than a 3,700 mAh pack.

But what joo recommends is nice ... a 5S 4,900 mAh pack (this will help ge the nose heavier). For motors you can look at the DualSky 4260-6, Hyperion 4025, AXI 4120/18 all are around the KV that joo says. :)

The ESCs from Turnigy work great and they have a built in UBEC so you can just use the ESC to power your servos.

Caveat: think carefully before you purchase the packs, what will you use them in when you move on. For me I am using Rhino 20C 5S 4,900 packs as when used in a 10S set up they are perfect for 180 sized planes and on its own it will haul a 40 sized plane out of sight!</span></span>

RE: Giant scale J3 conversion
 

Okay, sounds good. What do you guys think of the EFlite Power series of motors?  I read the 60 amp ESC manual, and they say a 5-6 cell pack should do the job. Thanks again.<div>
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</div><div><span style="white-space:pre"> </span>Matoran629
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</div><div><span style="white-space:pre"> </span>"From a kit you came, and to a kit you shall return"
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RE: Giant scale J3 conversion
 

<span style="font-size: larger;"><span style="font-family: Comic Sans MS;">Mato ... I have never tried them but always read good things. However, the Turnigy motors are cheap and work very well for planes such as Cubs where you are not pushing the limit. I do like the DualSky ones too, they are nice. But again, sometimes we should spoil ourselves. Hehehehe ...</span></span>

RE: Giant scale J3 conversion
 

Okay folks. Looks like I'm going with the E-Flite Power 46, 60 amp Pro ESC, and either a TP 5 cell LiPo, or a ProTek 5C LiPo in the 3600 to 5000mAh range. If this won't work, please tell me soon. Also visit my page.<div></div><div><span style="white-space:pre"> </span>matoran629</div>

RE: Giant scale J3 conversion
 

You're in the ball park, make sure you set the landing gear and wheels for tail dragger geometry, Norm

RE: Giant scale J3 conversion
 

Also, I forgot to tell you that my J3 has a 77 inch wing. It's the 40 size kit from GP<div>
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</div><div><span style="white-space:pre"> </span>mator629
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RE: Giant scale J3 conversion
 

You're still okay, as kits weight a bit more than the ARFs so the power is right on, Norm

RE: Giant scale J3 conversion
 

<span style="font-family: Comic Sans MS;"><span style="font-size: larger;">Mato ... me thinks the Power 46 will be screaming with a 5S set up. I doubt you can go more than a 12x8 at all as the KV is 'best' suited for a 4S set up with a larger prop. Not that you cannot use a 5S set up but you need to really prop down and even with a 12x8 you will be pulling around 50A on WOT I suspect. One thing for sure, you will have a lot of power.

Also please purchase a WATTMETER ... this is your best friend for EP. It will ensure that you know how many amps you are pulling with what batt and what prop. Get one and you will not regret it at all. Enjoy your conversion!

Oh ... welcome to the Dark Side!!!
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RE: Giant scale J3 conversion
 

The prop range is from 10x7-13x7, so I don't know

RE: Giant scale J3 conversion
 

So I should go with a 4 cell setup??? I thought that the ESC said 5.<div>
</div><div>I'll have to take a look</div><div>
</div><div><span style="white-space:pre"> </span>mato
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RE: Giant scale J3 conversion
 

Okay, it's 3-7 cells for the ESC. I should go then with the 4 cell setup.<div>
</div><div><span style="white-space:pre"> </span>Thanks, mato
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RE: Giant scale J3 conversion
 

If I go with 4 cells, what prop should I get?<div>
</div><div><span style="white-space:pre"> </span>Thanks, Mato
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RE: Giant scale J3 conversion
 

would someone please reply?

RE: Giant scale J3 conversion
 

I will make the first flight on my J-3 today, June 20, 2009. The power system is a RimFire .46 size brushless outrunner, a E-Flite 60 Amp Pro ESC, and a MaxAmps 4200 mAh 14.8V lipo battery. I might put pics on later<div>
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</div><div><span style="white-space:pre"> </span>Mato
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