Electric for large Planes

I plan to start a 1/4 scale Stearman (Boeing Kadet) this Fall or Winter.  I intend to model the plane flown by Johnny Vasey in the 1949 National
Acrobatic Championships.  I will use the Barron plans for the basic plane.
My question is the practicality of using electric power for this airplane.  To make it even more complicated as I live at 9,750 feet (2972 meters) which requires significantly more power.
Is there a conversion formula for Electric Versus Gas?  How about relative expense?  Certainly not having to clean up the plane after flights is a plus, but a negative is the time to recharge batteries.
Any thoughts?
JakeInHartsel
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Electric is no problem. A bonus is you can drive a much bigger prop , because the rpms are lower,5- 7000 for a big motor. Flight time 10 mins ish, but the killer is battery recharge.Lipos are loads of money... Can be an expensive path to go down.
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On Wed, 21 May 2008 23:28:16 +0100, TT_Man wrote:

I have flown small electrics up here and in general all I had to do was go to a higher pitch prop.
Expense is another issue that I will have to think about.
Jake
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On Thu, 22 May 2008 19:39:08 -0500, Glenn Jacobs

The man who won the top class in the pattern nationals last year, Jason Shulman, did so with his electric backup setup. His YS "spun the prop" on takeoff and he got a zero for that flight.
I've seen articles on electric systems for the big aerobatic birds--IMAC/TOC stuff.
You **CAN** do it. It is **being** done.
To be competitive, you need several sets of batteries and a couple of good charging systems.
A while back, I figured it would take $3,000 to $4,000 to get set up for pattern (11-pound planes). I don't know how reliable those numbers are today. I haven't followed the market. I'm basically a duffer. I like to watch the big dogs fly and I am amazed at what they do, both technologically and on the sticks.
Good luck with your research. Let us know what you decide and how it all turns out.
                Marty
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| I plan to start a 1/4 scale Stearman (Boeing Kadet) this Fall or Winter. I | intend to model the plane flown by Johnny Vasey in the 1949 National | Acrobatic Championships. I will use the Barron plans for the basic plane. | | My question is the practicality of using electric power for this airplane. To | make it even more complicated as I live at 9,750 feet (2972 meters) which | requires significantly more power. | | Is there a conversion formula for Electric Versus Gas? How about relative | expense? Certainly not having to clean up the plane after flights is a plus, | but a negative is the time to recharge batteries. | | Any thoughts? | | JakeInHartsel
I have flown a Goldberg Electra sailplane at 9,000 + and was suprised how well it flew. It flew faster in relation to the ground but otherwise no different than at 3,500 feet. The electric motor does not lose power in higher elevations as does glow or gas engines, which is a plus. A guy in our local club uses battery packs that cost almost $300.00 a piece and he has three of them for his aerobatic plane. The balancing charger he uses is expensive too.
You might contact Hobby Lobby as they seem to be going more to electrics now. http://www.hobby-lobby.com /
Every one I know here in the Texas panhandle uses the maximum (or over) recommended engine size because of the power loss with altitude on glow engines
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Glenn Jacobs wrote:

Sign up and ask here. http://www.rcgroups.com/power-systems-13 / about a hundred experts, no just one and a half..
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On Thu, 22 May 2008 01:32:27 +0100, The Natural Philosopher wrote:

Thank you I will.
Jake
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Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

Some of the hobby sites can provide the information you need (Horizon, Hobby Lobby, etc) as far as motor, ESC and batteries. If you are willing to do some research on the motor to find an equivalent motor (or more powerful one), Hobby City
http://www.hobbycity.com/hobbycity/store/uh_index.asp
has some very reasonable prices on these items. I have used them on many occasions for my electrical stuff. The only downside is that it is going to take about 3 - 4 weeks to get the stuff (direct from Hong Kong).
FWIW - Turnigy makes a pretty bulletproof ESC and the Turnigy and HXT motors have a good reputation for power and durability. I am using several of their 4s 4400 lipos (2nd year on them) and so far have not had any problems with them (I do balance them while charging) I have converted about 1/2 of my 40 size planes over to electric.
Hope this is of some help
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">

SNIP I though they had a shipping warehouse in the USA now..... I just ordered some stuff ( from the UK) and it looks like it is being shipped from the States...
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On Wed, 21 May 2008 20:57:50 -0400, Ted Campanelli wrote:

Thanks Ted, I will have to balance cost in the process, maybe costs will come down some by the time I have it ready to fly.
Jake
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Most of what Hobby City sells is "domestic" quality, meaning it's made for the chinese market. It is not of the same standards and quality of the products sold in the US which is 'export' or 'international' quality. Some of their products are probably just fine for smaller airplanes, etc. but I would be careful with something as big and expensive as a 1/4 scale stearman.

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Jim wrote:

What a load of unadulrerated rubbish you do talk.
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Glenn Jacobs wrote:

What's the size of the model? Wingspan, wing area, all up weight sans power system? All this data needed in order to answer effectively.
CR
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On Wed, 21 May 2008 22:19:14 -0500, Charles & Peggy Robinson wrote:

Wing span is about 8 feet and of course it is a biplane and relpatively dirty aerodynamically. I don't have a good handle on weight or wing area as I am rebuilding my shop area and can not easily lay my hands on the plans.
I am really just doing some preliminary planning now and trying to determine if it is a practical idea at all. Which it sounds like it is except possibly from an expense standpoint. Who know when it is ready to fly prices may ba a bit less.
Jake
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Glenn Jacobs wrote:

Its surely possible.
Is this a prop hanging Pitts or Ultimate, or a WWI scale plane tho?

Have a look at www.maxamps.com for 100A capable packs and cells at realistic prices.
Have a look at www.neumotors.com for big ticket motors and so on.
Built lightly, 10lb is a realistic target weight, and that would need not much more than a kilowatt for pretty agressive performance, or maybe 2kW for prop hanging. If you build it like a gasser tho, to take gasser vibration stresses, it could weigh in a lot heavier than that.

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On Fri, 23 May 2008 08:45:38 +0100, The Natural Philosopher wrote:

A WW2 Trainer
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Glenn Jacobs wrote:

Well shoot for about 60 efficient brushless watts per lb AUW then and you will have a sensible flight envelope.I've gor a tiger moth that is well overpowered on that figure..but it is smaller and flies slower. If you sort of think in terms of around a KW capable components..so something like a 6s pack at 20V running at around 50A peak..50A speed controller and at that sort of level a switching BEC or sperate receiver/servo pack..
So you are probably looking at a 6s or 2 3s 5000mAh packs or so, a 50A SC and a motor that can handle the best part of a kilowatt..theres a lot more now than there used to be. www.maxamps.com or www.cheapbatterypacks.com sell no nonsense stuff that will do 10C delivery reliably, and I wouldn't attempt to squeeze more out. Besides being conservative means you can throttle back and get 40 minute flights..
I've been testing out some of the smaller Turngy's from United hobbies, they go well
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct !01&Product_Name=TR_50-65B_350kv_Brushless_Outrunner_(Eq:_4030_AXi)
looks suitable, but I dunno on the bigger sizes..or you can play safe and get an AXI - 4130 series is probably about the right size..
Looks like an AXI 4130/12 on 6s and 18x12 is not far of the sort of power you need.
http://www.modelmotors.cz/index.php?pagea&productA30&serie &line=GOLD
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Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

I think you will find the prices at Hobby City to be about 60% of what you will pay from a "brand name" manufacturer or in the US. Remember, MUCH of the electrical stuff is made in other countries and just "rebranded". I do know that Turnigy "rebrands" a lot of their stuff for sale in the US.
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Contact Vision Hobbies in Phoenix. They fly a big stearman on the Storm 6374 motor with great success. They may even have some videos of it on their website at www.visionhobbies.com

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Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

I would investigate the A123 batteries. They are heavier than lipos, but they can be "quick" charged (if I remember correctly) in about 15 minutes.
It is practical and feasable to do the plane as an electric. The only "problem" I can see is the battery expense. I suggest checking out the lipos (and also the motors and ESC) at Hobby City
http://www.hobbycity.com/hobbycity/store/uh_index.asp
Their prices are NOTICEABLY less than stateside. In 3 years I have had no problems with their 4s lipos and their motors and ESC (Turnigy and HXT) are at least equal to what is available here. I do not push my lipos and I charge them at 1C. For the difference in battery cost you can get 2 battery sets for the price of 1 battery set here.
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