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1/4 Scale Balsa USA J-3 Cub

Old 02-16-2009, 09:17 PM
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EDFFanatic
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Default 1/4 Scale Balsa USA J-3 Cub

Hi, I really need help on this. I went to the flying field yesterday. A friend of mine pulled out a 1/4 scale Balsa USA J-3 Cub and gave it to me. The fuse is pretty much framed out. One wing panel is done. I've got all the rest that came with the kit. Also included are the ABS fake motor and cowling parts. I also got bent landing gear and scale Cub wheels.
Right now, all I have are two MaxAmps 5000mAh and two MaxAmps 4000mAh 3-cell lipo battery packs that could be used with this airplane, if it even cn be converted to electric power.
Is this airplane a candidate for conversion to electric, and if so, what would you recommend to power something that will probably end up weighing 15-17 pounds. The fuse you see weighs 39 ounces.
I will appreciate your opinions and suggestions. Caley
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Old 02-28-2009, 08:27 PM
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jollyroger
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Default RE: 1/4 Scale Balsa USA J-3 Cub

Caley, First of all you cannot use the two different packs together. You must use battery packs with the same current ratings in order to avoid a potentially dangerous overdischarge. So I would recommend the 5000 size packs and then add 2-4 extra cells for the required output power.
Next is to determine how much power you really need for this plane. The real J 3 Cub flies with the equivelant of about 50 watts /Lb. using a Continental 65 HP engine. So now we can determine that a motor with a rating of around 1600-1800 watts would be more than suffecient for this plane given the power loss due to the efficiency of the motor. Some motors are more efficient than others. Outrunners are not as efficient as the inrunner types but you will need a gearbox for an inrunner to be able to swing the large prop needed for that plane. Which brings us to the outrunners. Since no gearbox is needed, you can decide what size and especially how much money you have to spend as these motors now come from manufacturers from all over the world, especially China. These motor sare inexpensive when compared to the Axis, Hackers, Plettenbergs and are not as accurately wound, neither is the materials used as good. There are some exceptions: Hyperion Motors from Japan are very well made, have good efficiency and are not as expensive as the motors made in Germany, Cech Republic.
Another brand now coming on is the Scorpion Motor. Although this motor is made in China, its designer is German and strives to obtain and use the very best materials including high temp wire and magnets.
For this plane, one of the larger Axis in the 50** series, a Hacker A60 series, Hyperion in the 50 series will work. I used Ecalc to estimate a motor for this plane and came up with a Hacker A60-12M on 8-10 cells. Just remember that this plane flies on the wing and doesn't need the power of a 3D or warbird. Around 70-85 watts /Lb will be sufficient. I would have to check back with my Ecalc records to see exactly what I came up with but I do believe an 18" prop was used.
The Axis are not the best in efficiency they lag behind the Hackers, Pletts and Hyperions. Quite a few people are using the less expensive motors from Chinese manufacturers but, you get what you pay for. Quality control is not the best, especially when it comes to windings as two motors of the same size and specs will measure different KV and winding resistance. Still a lot of people use these motors with some satisfaction they spent less money and get adequate performance.
http://www.allerc.com/
http://modelmotors.cz/index.php?id=en&nc=domu
www.Aero-Model Inc.com (Hacker motors)
Some other brands such as Turnigy are popular as they are not as expensive as those mentioned above. Plettenbergs are by far the most expensive but they are the best built and most efficient of the outrunner types.http://www.icare-rc.com/. You will spend a lot more money for these.
Don't forget to use the appropriate size speed control and either seperate Rxcr pack or switch mode BEC unit for your receiver and servos.
Kepp us posted with your progress.
cheers
Old 02-28-2009, 08:49 PM
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Default RE: 1/4 Scale Balsa USA J-3 Cub

Roger, I am well aware of mixing different capacities will create big problems. I was talking about two 3-cell packs of either 5000mAh or two 3-cell packs of 4000mAh hooked in series, but didn't mean I would mix 4000 and 5000.
As it is, I did a cost analysis for electric conversion, and found it cost prohibitive. So I am gasifying the airplane. I dislike glow power with a passion. Just too messy. With the gas version using a 26cc engine, I can swing intitially during engine breakin a 16x8 prop, and then move up to an 18 inch prop. Can't remember what the gentleman said the pitch was, but he said it would fly slower and more scale like with the larger prop, and be very close to the correct diameter of a scale prop.
Thanks for your concern. But I just cannot afford over $1000, which is mostly batteries. Caley

EDITED: If anyone else is going to electrify a BUSA J-3 Cub, go ahead and use this thread. I am on another now that is for gas power.
Old 03-12-2009, 12:53 PM
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Willit Run 353
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Default RE: 1/4 Scale Balsa USA J-3 Cub

Hi

Does any body produce a 1:2 J3 cub. If not i guess i will have to upsacle a Balsa USA one
Old 03-13-2009, 03:14 PM
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Darrell B.
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Default RE: 1/4 Scale Balsa USA J-3 Cub

Caley,
Your cub will be approximatly the same size as the Hanger 9 cub. I know that there are several power systems that will fit it. If you order your components from Hobby City, you should be able to come in for less than $300 for your entire system. If you were to want an extra battery, you would want to add about another $100 depending on which capacity you choose. A friend of mine built his 94" cub and only has $200 in his power system. Good luck on this project.
Darrell B.
Old 07-11-2010, 11:23 PM
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Default RE: 1/4 Scale Balsa USA J-3 Cub

I saw a monster power 160 fly a hangar nine 1/4 182 on 8 cells. It was scale. The 182 had been crashed are repaired a couple times and was a heavy pig and the guy that did it put lead in the nose in lieu of putting the batteries farther forward. 6 cells would be pretty anemic. I don't think you could get enough amps out of the packs to make good power. I would pick up a 3rd pack and try for 9cells on the monster power motor if your on the cheap. I have seen several 110 rascals on hacker a50 and I have an a60 on 12s- That is a monster.. If you get the batteries forward, keep it light I think it would be ok with the monster power 160. I am putting one on a morrisey bravo that was built really light and it will be fine. you can get them from hobby partz for under 50bucks...I have seen several run and they seem ok- ok enough that i have two of them on the bench..

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