large electrics
 

anyone building big electric planes? i'm thinking about 60" ws and bigger. any info to get me started is appreciated

large electrics
 

Check out the Great Planes Electra-cub. It's in that category.

large electrics
 

There's quite a few people flying larger planes on electric power. Check out the "Glow to Electric Conversion" area.

Jason

large electrics
 

I build and fly 60" to 82" electrics. Warplanes mostly. You need to get a brushless motor for these. I like Maxcim motors and Jeti Phasor motors(their largest one) Maxcim motors can be geared for larger props Jeti does not recommend gearing thier motors and they are a lot cheaper. I use 10-24 sub-c 2100 cells with "Solderless Power Tubes" from Model Electronics Corp" (MEC) I suggest you get a $40 computer program called Electricalc or Motocalc. These are usefull tools to guide you in choosing cells and props and even airframes. They give APROXIMATE expected results from different combinations of all up weight/props/motors/cells/cell count/gear ratios / top speeds/ stall speeds and more.

large electrics
 

my sport-e-stick kit almost fits there (56" span), but I fly 80 and 88 inch span electrics also.

funtana
Hacker C50 acro on 30 roundcells or 9S4P lipo, 80 inch span, 22X12 prop , roughly 11 lbs

http://www.rccraze.com/funtana1.mpg

E3D-XL
Hacker C50 acro on 6S4P lipo , 24X12 prop
88 inch span, 9-ish lbs, originally flown on 20 roundcells
http://www.rcgroups.com/articles/ezo...aerobatics.mpg

http://www.rcgroups.com/articles/ezo...3dXL_Hover.mpg

large electrics
 

Not quite 60" (more like 48") but at more than four pounds ready-to-fly, she's quite heavy for her size (probably should have been 60" :^)

Here's an electric GeeBee that flies great with an AXI 2820/10 on ten cells, an 11x6 Graupner prop, and a Jeti Advance 40-3P programmable speed control.

She flies like a banshee...

large electrics
 

David Theunissen keeps a database of large electric models on his website.

http://www.flyelectric.ukgateway.net/largesum.htm

large electrics
 

thanks for all the responses guys, i've got alot more to think about now :)

large electrics
 

Ck out Sparky Paul he does a lot of med to big. CU

http://www.angelfire.com/indie/aerostuff/

RE: large electrics
 

If you want large and relaxed flying, try a glider or motor glider. I have built and fly two of the same model. My planes are an old motor glider design called a "Butterfly." I fly then on 10 cells, AXI 2820-10. They weigh 4+ lbs. One of them is as designed with a typical double dihedral wing design. The other I built with only a single dihedral, with ailerons & flaps. Good luck

RE: large electrics
 

Building a slow flying camera plane to take aerial pictures. Here is what I have so far?

Plane Specs:

90" Span
1123 square inches (a Cub wing)
10 pounds flying weight (or less, estimated)
intended for slow flying camera plane (basic trainer performance envelope), no aerobatics.


Motor:
option 1: AXI 4120-14 external rotor brushless motor

option 2: AXI 4120-18 external rotor brushless motor


Controller: JEC703OP Jeti 70-3P Opto Controller


Battery Option 1:
14 cells - 2 x 7 Cell CP-2400SCR NiCad pack (Sanyo)

Battery Option 2:
16 cells - 16 Cell 3000 mAh NiMh (Sanyo)


All options above have already been purchased (plus spare batteries and chargers $$$). I would like to use Option 1: motor + Option 1: battery - together on this plane.

I would like to build a 2nd plane for the Option 2: motor + battery, but could combine in different arrangements to suit flight regime:

Take off, fly no higher than 500 AGL, and have about 10 minute flight times. I hope to fly at 1/2 throttle or less to maintain altitude for photography.

Is this setup going to work? or do I go back to the drawing board (and credit card)?

Thanks!

RE: large electrics
 

Usually, to power a large, slow, electric airplane as you discribe it is recommended to use a geared motor and swing a large prop. I do not know if your motors are suited to gearing. If they are, gearboxes are what I recommend investigating,

RE: large electrics
 

Hi Bruce, I am using the 4120/18 with a 13x8 'master' undercambered wooden (electric) prop with 16x2400 cells and it is reasonably powrfull but I would rely on this set up as I have tried it out on the 18 and 20 cells if you need more power. I find the lower cell count better because of the large props allowed up to a 14x6 (wooden).
Don't forget that you need a 12% min wing thickness to allow easier slow flight.
I had to lengthen the udercart to allow the fitting of my 14x6 prop and get clearence as well. Don't use a fully symett section as they don't lift well at low speed. e-mail me for a secret section which I use on all of my 6-7ft Scale jobs and makes heavy planes behave as if they are lightweights, cheers Robin Andrew, Birmingham, England

RE: large electrics
 

What do you mean by large ?

Something like this :
http://www.rc-network.de/magazin/art...ch-03_194w.jpg

It's a 6m ( 236 in. ! ) span model of a Klemm 35, with a big torcman outrunner motor, and 2 30cell packs in parallel, batteries alone are about 6 kg ( 211 oz. )

This model was shown at this years Aspach E-flight meeting. Aspach is THE e-flight meeting in Germany.

For anybody who is interested, a bunch of pictures from that meeting can be seen here :[link=http://www.wherzog.de/aspach2003/]Aspach[/link]

Michael

RE: large electrics
 

liversalts

This plane is using the 90" cub wing from a Great Planes kit.

The following is from Motorcalc (I hope it is reasonable):

MotOpinion - Cubster 14x10
100ft above Sea Level, 30.00inHg, 70°F (Florida)

Motor: Model Motors AXI AC4120/14; 650rpm/V; 2A no-load; 0.041 Ohms
Battery: Sanyo CP-2400SCR; 14 cells; 2300mAh @ 1.2V; 0.0053 Ohms/cell
Speed Control: Castle Creations Phoenix 80; 0.001 Ohms; High rate
Drive System: APC 14x8 Electric; 14x8 (Pconst=1.08; Tconst=1) direct drive
Airframe: Cubster - Camera Plane; 1132sq.in; 162.1oz; 20.6oz/sq.ft; Cd=0.081; Cl=0.72; Clopt=0.83; Clmax=1.47
Stats: 58 W/lb in; 44 W/lb out; 19mph stall; 26mph opt @ 57% (16:56, 102°F); 28mph level @ 60% (15:27, 104°F); 713ft/min @ 18.2°; -249ft/min @ -6.3°

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (41.8A) falls between the motor's maximum efficiency current (21.4A) and its current at theoretical maximum output (115.7A), thus making effective use of the motor.
The voltage (13.6V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.

Aerodynamic Notes:

The static pitch speed (54mph) is within the range of approximately 2.5 to 3 times the model's stall speed (19mph), which is considered ideal for good performance.
With a wing loading of 20.6oz/sq.ft, a model of this size will have trainer-like flying characteristics. It would make an ideal trainer, for use in calm to light wind conditions.
The static thrust (91.5oz) to weight (162.1oz) ratio is 0.56:1, which will result in short take-off runs, and no difficulty taking off from grass surfaces (assuming sufficiently large wheels).
At the best lift-to-drag ratio airspeed, the excess-thrust (51.4oz) to weight (162.1oz) ratio is 0.32:1, which will give strong climbs and rapid acceleration. This model will most likely readily loop from level flight, and have sufficient in-flight thrust for many aerobatic maneuvers.

General Notes:

This analysis is based on calculations that take motor heating effects into account.


Motor Model Motors AXI AC4120/14
Motor Constant (rpm/V) 650
No Load Current (A) 2
Armature Resistance (Ohms) 0.041
Battery Sanyo CP-2400SCR
Series Cell Count 14
Parallel Cell Count 1
Cell Capacity (mAh) 2300
Pack Capacity (mAh) 2300
Cell Voltage (V) 1.2
Pack Voltage (V) 16.8
Cell Resistance (Ohms) 0.0053
Pack Resistance (Ohms) 0.0742
Speed Control (ESC) Castle Creations Phoenix 80
Resistance (Ohms) 0.001
Maximum Current (A) 80
Number of ESCs 1
Drive System APC 14x8 Electric
Gear Ratio 1.00:1
Propeller (in x in) 14x8
Series Motors 1
Parallel Motors 1
Number of Propellers 1
Blades per Propeller 2
Airframe Cubster - Camera Plane
Wing Span (in) 90
Wing Area (sq.in) 1132
Total Weight (oz) 162.1
Static Predictions
Current (A) 43.2
Motor Voltage (V) 13.6
Input Power (W) 585.1
Input Power Loading (W/lb) 57.7
Power Loss (W) 134.7
Motor/Gearbox Output (W) 450.3
Output Power Loading (W/lb) 44.5
Motor/Gearbox Efficiency (%) 77.0
Shaft Efficiency (%) 62.1
Motor RPM 7111
Propeller RPM 7111
Static Thrust (oz) 91.5
Pitch Speed (mph) 53.9
Run Time (min:sec) 3:12
Flight Predictions
Stall Speed (mph) 19
Optimal Flight Speed (mph) 26
Throttle for Optimal (%) 57
Duration at Optimal (m:s) 16:56
Motor Temp at Optimal (°F) 102
Hands-off Speed (mph) 28
Throttle for Hands-off (%) 60
Duration Hands-off (m:s) 15:27
Motor Temp Hands-off (°F) 104
Best Rate of Climb (ft/min) 713
Rate of Sink (ft/min) -249

RE: large electrics
 

;)
I built a Pieienpol Aircamper , extended the 80" wing to 86" plus drooping wingtips, 5" wheels. Axi 4120/18 Motor direct drive 15/8 Pro. 16 cell 3000mAh Sub C cells, covered with Solartex. The Pane has Copilot, and carries 2 video cameras,(one for check on the insstruments like compass , Altimeter and Wattmeter, the other looks outside)
The Video equipment has 800mW transmitter Audio/video and supplied be 10 Nimhi 2100mAh batteries. Total wight 13.68 lbs. Flight time about 9 minutes.
The Pane flies very stable, not arobatic. beautiful video pictures, no vibration. It climbs very good Over 1050 Feet AGL. It is so stable that we had it land itself, with only a little rudder input.
We tried smaller props, and they don't work nearly as good. 15/8 seems to be just right. I can monitor the Amps and Watts during flight, and it uses abaut 550 plus Watts on takeoff. Level flight is susstained with 300Watts. Sometimes we use 757 Watts on takeoff. but now we fly more conservative.

RE: large electrics
 

nice quote shupack !

RE: large electrics
 

I have a Pietenpol 88" wingspan with AXI 4120-18 and 16 cell NIMHI 3000maH batteries, but I am not flying it any more, because it has only about 5 minutes duration. It is a camera plane, with 2 cameras, One for looking around the other looking at the instruments, like Amp/Watt meter, compass, altitude.
I will buy LiPo batteries for it, because I have another plane with them, and I get between 25 - 35 minutes flight time, depending on wind condition.
I am using TMM controller, but I don't want to buy from Northeast Sailplanes (bad company) any more, I would like to find another source for these controllers, because I think they are safer on start-up.
Greetings, Rudolf.

RE: large electrics
 

I put a Mega 22/45/3E in a Sig 4 star 40 using 16 rx2400's(2x8), jeti opto 70A controller swinging an apc 10.5x6E prop..
Did not change anything except made a hatch from cockpit to firewall and cowled in the top of motor area. It worked very very well, convinced my-wet fuel- mentor to seriously start thinking e-flight. He said it was the sweetest 4* he's ever seen .

Jarvis

RE: large electrics
 

Just to be different from what everyone is saying... ;) You don't NEED a brushless system for a model of this size. There are some VERY nice brushed motors made by Plettenberg in Germany. He also happens to make the Graupner "Ultra" series of motors. These big brushed motors are very fine quality and can be every bit as efficient as the average brushless motor of equivalent power capacity. Personally, I have experience with the Graupner Ultra-3300 series of motors. I have used the 10, 7 and 5-turn versions on a 2:1 Kruse gearbox, swinging props from 16-20" diameter. Batteries ranged from 18-36 cells, Sanyo CP-2400. This was for a competition and NiCd was specified in the rules... otherwise I would have used GP3300 NiMH cells. The brushed controllers for this power level (60A) are also smaller, lighter and less expensive than those for the equivalent brushless.


Don't get me wrong... I love brushless power, but it's not the only option.

-David

RE: large electrics
 

I fly Big Old Timers:
80"+ inch Powerhouse uses an Astro 40 with Superbox.
72"+ inch Buzzard Bombshell On An Astro 25 with astro regular gearbox.

Currently finishing a Sr Cadet that I converted to taildragger. It flies with the regular wing and will fly with another wing that has just a little diehedral and large flaps. Using the new big AXI motor.
Also fly a Sig Senorita with the AXI 2820/10 and it flies great.

RE: large electrics
 

Brushless may not be the only option, but when you look at the cost of brushed vs. brushless once you get out of the realm of cheap can motors, it's not all that much different. On top of that, you have brushes to replace, and a commutator that needs occasional turning and will eventually wear out, rendering the motor worthless. Yes, you can probably have the commutator replaced on many of the fancier brushed motors, but that can't be done by the average modeler, and costs money. In contrast, brushless motors are essentially maintenance-free.

RE: large electrics
 

What you say is correct... no arguments.

The only thing I'd say is that it really isn't that hard to replace brushes (a couple springs), and the entire armature can be replaced, if need be, for about $75 on the motor I mentioned. That requires the removal of 4 screws... probably not beyond the capabilities of most modelers.

High power ESCs are relatively cheap for brushed motors... and quite expensive for brushless. Compare the 140A Jeti brushed (~$110) to the Aveox SH-96 120A ($329.99). Castle Creations' PH-80 (80A) ESC has a 20-cell limit, Aveox can take 30. The JETI brushed controllers can take 30 cells.

The way I see it, it's easier to do a big model (lots of W) with a conventional brushed motor. For medium size, it's a tossup. You're right.

-David

RE: large electrics
 

I have flown a specially built Sig LT-40 with an Astro 25G and 16-18 cells. If you can locate a used Astroflight motor either here or the Ezone, then go for it. Either the 25G or 40G will be a good place to start and you can use conventional esc's. I have a number of brushed motors that I have experimented with including Kyosho Magnetic Mayhems, Trinity Chameleon, as well as the speed 480 size. Used correctly they can be very useful for flying evena larger plane than you might think. People are flying Sig Senioritas with the Magnetic Mayhem, Master Airscrew gearbox at 3.5:1 ratio and 10 cells. I also use brushless motors on my Magic 3D and in my (currently being converted) Great Planes 40 size cub, as well as a converted Goldberg Tiger 2. IN the larger sport planes, unless you are using the outrunner motors you should use a gearbox or beltdrive. Tom Hunt (Model air Tech) makes some great belt drives in various ratios. My cub is fitted with one mated to a Mega 2230-3 motor. Battery power will be 16 cells swinging an APCE 14X12 prop. Ecalc says 77 watts per pound , although I can't remember the thrust calcs they are more than adequate for the plane.
If you go to "The Future is Electric"(The Ampeer) website, they have a list of plane ratings which include power systems being used. Very helpful when starting out.
Good luck with your project. jollyroger

RE: large electrics
 

Here is an update on what I'm currently thinking of putting into production at some point over the next year or two.
It is a Pattern/3D Hybrid that is designed to use the AXI 4130/20 motor for peak performance.
It has an approx. wingspan 0f 80" and should weight around 5 pounds, which includes retracts.
One design feature to note is the use of double hinged flaperons, that more accurately change wing camber, for greater control surface torque and efficiency. The inboard part of the aileron is also enlarged to take advantage of prop-blast when hovering, etc.

Here is what MotoCalc has to say about its predicted performance using 20 Sanyo RC2000 cells: