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Ready to try the electric route

Old 08-30-2005, 01:16 AM
  #1  
shardin
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Default Ready to try the electric route

Well all you e-heads, I need advise on converting to electric. I am planning a build of the Sky Shark Stuka

1/9th Scale
Wingspan: 60 inches
Wing Area: 576 Sq. In.
Flying Weight: 6 to 8 lbs.
Engine Size: .45 to .61 2-stroke, .60 - .72 4-stroke

I plan on using a AXI 4120/14 brushless outrunner with a Jeti 70A controller and 2, 4 cell 2000 mAh 14.8 V Li-poly batteries. (info courtesy of Hobby Lobby)

I have build and flown glo, but I am not that familier with electric. I become sold on e-power at a recent local warbirds fly-in. I was trying to maiden a TF 1/7 scale P-47 with a Super Tigre 0.75 glo engine. I spent the whole day fussing with the engine trying to get it running as it should. This was after several hours of break-in on and off the bench. While I am sweating over the engine, I keep seeing a 60 size Corsair making repeated flight. Guess what....electric power....
After this experience I began investigation into electric power. At first I was planning a Sky Shark TBM Avernger, i liked the looks and it would have been a good companion to my -47.

1/9th Scale
Wingspan: 72" inches
Wing Area: 906 Sq. In.
Flying Weight: 9 to 13 lbs.
Engine Size: .60 to .80 2-stroke, .60 - .90 4-stroke

But, then i priced the power for this size plane!!! Over $1,200! After that I knew I needed to scale back my thinking, my wife had the same idea, on my first electric.

I would really appreciate any feedback on the power that has been sugested for the Stuka and any other tips that you might have learned. I am a real rookie and need all the advise I can get.

I am posting some pictures of my P-47, even though it's glo powered, just so you know I can build a plane
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Old 08-30-2005, 02:05 AM
  #2  
2dogrc
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I really like you plane! I would say you are a good builder! This forum should have many helpers!
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Old 08-30-2005, 02:32 PM
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Originally Posted by shardin
Well all you e-heads, I need advise on converting to electric. I am planning a build of the Sky Shark Stuka

1/9th Scale
Wingspan: 60 inches
Wing Area: 576 Sq. In.
Flying Weight: 6 to 8 lbs.
Engine Size: .45 to .61 2-stroke, .60 - .72 4-stroke

I plan on using a AXI 4120/14 brushless outrunner with a Jeti 70A controller and 2, 4 cell 2000 mAh 14.8 V Li-poly batteries. (info courtesy of Hobby Lobby)


But, then i priced the power for this size plane!!! Over $1,200! After that I knew I needed to scale back my thinking, my wife had the same idea, on my first electric.
You provided a lot of info, but left some out. Needed is what prop (or approximate range) you intend to use, and the calculated watts (out) of this set-up. Also, do you intend to series the 2 packs, or parallel them? If it were me, I would probably parallel them, or better yet: use a single pack witha higher mAh capacity. I am using 3S 4400mAh packs which I purchased on ebay for about $80 each. A 4S pack of simlar capacity can probably be had for about $120. I am certain that this is considerably less than the pack(s) at Hobby Lobby. Hobby Lobby has traditionally had higher battery prices. Good deals on motors and speed controls, not not so good with batteries. Also, on the speed controller: I am using (and recommend) the Jeti 40P, which is rated for 40 amps, up to 6 Li-Poly. Cost less than the 70 series, and should do the job. I would think you would be looking for a maximum current draw (static) of no more than 35 amps. With a 4 S pack, this equates to about 500 watts in, which should be plenty for your Stuka. My converted (to electric) H-9 Corsair weighs 8 1/2 lbs, and flies very comfortably with about 600 watts in.

Here is a link to a motor/ battery/ prop calculator, which should be useful in determining correct set-up:
http://brantuas.com/ezcalc/dma1.asp
According to it, (static) current to motor is 35 amps if swinging an APC 13 x 7, using 4S 3200 Li-Poly. Thrust is 85 oz, or better than 5 lbs, which should be plenty for a fairly streamlined warbird such as yours.

So, in summary: I think your motor choice is good, shop around for a 4S battery pack in the 4400 to 6000 range, and the Jeti 40P will do the job.

Here is a pic of my AXI 4130/16, 6S 4400 Li-Poly with DynaTrust 14 x 8 powered H-9 Corsair. This setup provides over 12 minutes of dependable, scale flight with reserve. Cost of my setup: about $150 for motor, $115 for the 40P with program card, and about $160 for the two (2) 3S 4400 mAh packs with are in series. Add price of prop, and it's still less than half of the Hobby Lobby set-up. As for charger: the AstroFlight 109 is the only way to go, designed and manufactured by the INVENTOR of electric powered R/C flight.
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Old 08-30-2005, 03:09 PM
  #4  
Geoff_Gino
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Hi CorsairJock

Good looking airplane!!

Too late she cried You should have been here last week. Placed my order at Hobby Lobby and came out at $819-00, but that did include $118-00 shipping to South Africa.
Purchased the following:-

AST 109 charger (Glad to hear you like it)
2 Kokam 3 cell 3.2Amp batteries (going to connect in series)
UBEC
Jeti 77 Amp ESC
Axi motor mount
15x8 3 blade prop and adaptor
Axi 4130/16 motor (locally in S.A.)

Calculations give me 710 watt/lb, I think I'll weigh in at about 10 lbs, so I am VERY pleased to hear that your 600 watts is giving you 12 minutes with spare in the air.

Can't wait to get airborne, should be next week some time

Geoff
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Old 08-30-2005, 05:22 PM
  #5  
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10 lb is ok but rather limit for the 4130/16, try to be in the 8 to 9 lbs range.
All my H9 planes (8lbs) have the same motor on 6S
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Old 08-31-2005, 07:11 AM
  #6  
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Hi Luc

Weighed the plane without the electrics and it came in at 2,6 Kgs (5,7 lbs).
Not totally sure what the final weight is going to be as I am still waiting for the electrics to arrive. I studied Greg Covey's review on his F4U and he did recommend the 2 3S packs in series, which does make sense as I will be saving some weight with smaller pack. (if the electrics weigh 2,3 lbs or less I should be OK). Time will tell

Geoff
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Old 08-31-2005, 07:22 AM
  #7  
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my lightest setup is 6S1P TP 2100 15C prolites (new cells not yet released for sale, I got from Charlie I saw before the world championships): only 290g!! (here is a pic of a 3S pack I made).
another light setup is TP 6S2P 1320 prolite: 360g
A third one is 6S1P tronic 2100 15C: 380g
these setups don't give long flight durations (5 minutes flights, but that's ok) but are very light.
here are 3 pics:
TP 2100 15C prolite (3S pack with balancing plug) on my scale
TP 3S2P 1320 prolite (hooked in // with 3 plugs for perfect balancing)
Tronic 3S 2100 with the TP205 balancer plugged
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Old 08-31-2005, 07:31 AM
  #8  
Geoff_Gino
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Hi Luc

Going for a little more airtime and Greg did assure me via PM that my setup will be OK - will just have to watch the weight, besides not much option as my parcel is finally in South Africa and I should have by Friday (I hope). Think I'll weigh the electrics before I even assemble them.
Thanks for sharing, I'll let you know how it goes.

Geoff
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Old 08-31-2005, 01:29 PM
  #9  
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Geoff: I am wondering about your prop choice. According to Chuck Gadd's Electric Motor Calculator, peak effiency (about 85%) for this motor occurs with about a 25 amp (to motor) current draw, when using the batteries you are getting. IMO, max draw (static) should ideally be about 125% of max effiency current, allowing it to be most efficient when it is 'un-loaded' (airborne), thus, about 31 amps. In testing that I have done, I obtained that current (31 amps from battery) when using a Master Airscrew 3 blade 14 x 7. The prop you are suggesting: a 3 blade 15 x 8 will no doubt draw a significantly higher current, thereby reducing efficiency and flight times. You will of course have more power, but I question the need if the model will end up in the 8 lb range.

It appears that you are not alone tho, in what appears to me to be over-propping these motors (AXI 4130/16). From reading what others are doing, there seems to be a lot of people installing (watt I consider) over-size props, drawing over 40 amps with 6 cell (Li-Poly). There also seems to be a few encountering problems with these motors, as in magnets becoming dislodged/ over-heating: I wonder if these incidents are somehow related to the over-size props?

And then there is the batteries: altho many Li-Po batteries are rated 10C, 12C, and higher these days, experience has shown me that they are much happier if limited to somewhere closer to 5C constant. They will provide more mAh if current draw is not maxed out, and I believe they will last longer as well.
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Old 08-31-2005, 05:52 PM
  #10  
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I agree with you about the overprop. I tried the axi 4130/16 on a 16*10 apc E, and really could not see much difference in flight, despite a much higher amp draw. I know also that I threw a magnet out when I initially used this setup.
presently, I stay with a 15*10, which gives an amp draw in the ball park you mention (26 to 30A in flight), which gives a good motor performance. Yes, the axi 4130/16 does not like too many amps (the 5330 can climb much higher).
As far as batteries, as mentioned earlier, I am spoiled by using 15C (true 15C) batteries, in most of the cases.
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Old 09-01-2005, 07:34 AM
  #11  
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Hi Luc

Parcel came in yesterday and BOY am I excited especially since I weighed everything and it came in at 4 Kgs (8,18 lbs).

Hanger9 60" F4U Corsair
4 x JR 539 Servos
Hitec retract servo
JR Slimline 7 cannel Rx
2 x 3S 3,2 amp Kokams in series
Axi 4130/16 motor
Jeti 77 ESC
UBEC
15x8 Graupner 3 blade prop

Hope to maiden this week-end.

Geoff
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Old 09-01-2005, 03:40 PM
  #12  
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that is fast...
takes me around 40 hours to build these arfs.
good combo!!
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Old 09-02-2005, 06:44 AM
  #13  
Geoff_Gino
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Default Fast Build

Originally Posted by luc
that is fast...
takes me around 40 hours to build these arfs.
good combo!!
Hi Luc

Was that intended for me? I would love to be that fast. Plane, servo's and all the rest were complete, just need to put the electrics and I am fact still busy.

Geoff
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Old 09-02-2005, 05:41 PM
  #14  
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...I thought you started from scratch....
I built 3 H9 arfs..I don't even see the notice now, they all build alike...
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Old 09-03-2005, 08:44 PM
  #15  
shardin
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Default Back after much research!

Hi everybody, thanks for all of the feedback on the thread (I'm the one that started it). I have spent the previous week reasearching the information provided and have come up with the following....

Power for a Skyshark Ju-87 Stuka.
1/9th Scale
Wingspan: 60 inches
Wing Area: 576 Sq. In.
Flying Weight: 6 to 8 lbs.
Engine Size: .45 to .61 2-stroke, .60 - .72 4-stroke


DescriptionSourceQtyEachExtentionMotor AXI 4120/14Hobby Lobby1 $139.00 $139.00 Mount PM41002 RadialHobby Lobby1 $ 18.50 $ 18.50 Batteries 4S 14.8V 2200mAhCheap Battery Packs2 $ 87.95 $175.90 Parallel Module FMAC03PHobby Lobby1 $ 15.90 $ 15.90 Controller Jeti40Hobby Lobby1 $116.70 $116.70 Charger Astro 109Light Flight R/C1 $119.95 $119.95 Prop 12x6 APC electricTower1 $ 3.79 $ 3.79 $ - $ - Total $589.74 0Amperage calcualtions ,4200mAh (could not find 4,400mAh in calculator)Cells4# Parallel2Motor Amps27.93Motor RPM7,804Watts in367.36Watts out309.07Prop Static thrust61.8oz3.8625lbsProp pitch speed44.3MphFull throttle duration9.01min

Finding the correct batteries took some time and research and I never did get the calculator to accept a "custum" setting. It finally sunk in that I was looking for two packs to equal the 4,400mAh (2,200+2,200) and that I need 4 cells in series to reach the 14.8 volts. Well it is a learning experiance. So by using the provided feedback and some of the other threads on the site I was able to increase the battery capacity by 400mAh's and reduce the total cost by $109. (The last part makes the wife happy)

Please let me hear your feedback on the above selections and calculations
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Old 09-03-2005, 09:03 PM
  #16  
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Default Let's try those table again!

Sorry I tried to paste some Excel cells into the last post....didn't work so well Here's the data


Motor AXI 4120/14 Hobby Lobby $139.00
Mount PM41002 Radial Hobby Lobby$18.50
Batteries 4S 14.8V 2200mAh Cheap Battery Packs $175.90
Parallel Module FMAC03P Hobby Lobby $15.90
Controller Jeti40 Hobby Lobby $116.70
Charger Astro 109 Light Flight R/C $119.95
Prop 12x6 APC electric Tower $3.79
Total $589.74

Amperage calcualtions @ 4,200mAh (could not find 4,400mAh in calculator)
Cells 4
# Parallel 2
Motor Amps 27.93
Motor RPM 7,804
Watts in 367.36
Watts out 309.07
Prop Static thrust 61.8 oz 3.8625 lbs
Prop pitch speed 44.3 Mph
Full throttle duration 9.01 min
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Old 09-04-2005, 04:25 PM
  #17  
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for me, everything looks good.
I could have bought everything escept the astro 109 which I don't like (I would have preferred the ice or triton), but that's me....
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Old 09-05-2005, 07:47 AM
  #18  
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Hi All

How best to describe the feeling?

It is early morning at about 06:30 the sun is barely up all is quiet and a beautiful blue bird rises up into the clear blue sky. The culmination of 4 months of pleasure in building, 2 months in struggling to learn what was needed to know about e-flight.

AWESOME, FANTASTIC, RELIEF, ECSTACY are only a few words to describe what my emotions were. Oh and very many "butterflies".

Specs of the plane:
Hanger9 60" F4U Corsair
Standard JR 539 servo's
JR700 Slimline receiver
Hitec retract servo (95 oz)
JR 2610 Tx
TopFlight cockpit kit
Graupner 15x8 3 blade prop (being spun at 6980 rpm)
Axi 4130/16 brushless motor
Jeti 77 ESC
UBEC
2 3S Kokam 3,2 Amp cells in series
All Up Weight 4 Kg (8,18 lbs - 887,5 watss/lb)

In the pits.
CG had been set for 4,5" from the leading edge of the wing and was checked, all control surfaces were checked for correct direction and the radio was set to 70% for all controls except the throttle (obviously). Chris my instructor and pilot for the maiden made sure that everthing was secure, the motor was spooled up and his immediate comment was "What power this bird has".

Taxied out to the tar runway and it was all systems go. Chris had decided to run the motor up slowly to get a feel of the power and to our amazement the plane took itself off in about 15 metres and 60% throttle. AWESOME.

Minor down trim was needed for level flight and Chris then did a few rolls, loops, checked the retracts after this and all was FANTASTIC.

Spent 8 minutes in the air with a low pass about 10' high and the "bird" was true and level.

Landing.
Now the butterflies took over (don't know how Chris felt) and the gear was put down and the approach started.
Gently around to finals and with the precise control of the electric motor an even and controlled descent was made to look easy, touch down and the plane rolled out straight and true and the gear showed no sign of any problems at all. RELIEF.

Fill her up.
After cooling down for about 30 minutes put the battery (still in the plane) on charge and in 40 minutes it had taken 1,7 amps to get to full.

My turn (many butterflies again). Chris still had the radio and the take off was just as good and once up I took over and the shake in my hands was so obvious when I tried a loop that I immediately levelled out and continued with level ccts. Handed back to Chris and he brought her in. ECSTACY.

Second flight was 11 minutes and this time I put 2,3 amps back in which took about 50 minutes.
Checked the retracts and had to tighten one of the ball links (loctite going in there) with everything else perfect. The bird had flown.

Never again will I have a glocell engine in any of my planes, and when it came to the clean up I simply started the "fan" to dust her off.

My many thanks to all at WattFlyer for helping make this maiden perfect and to name but a few, Marc, Matt, Mike, Jim and of course Greg Covey.

Geoff

Last edited by Geoff_Gino; 09-07-2005 at 06:54 AM.
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Old 09-05-2005, 08:34 PM
  #19  
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A Big CONGRATS to you, Geoff, and yes I know the feeling. So many doubts when you first advance the throttle on an aircraft such as this: designed for glow power, converted to electric. Then it flies, and it flies beautifully and with authority, and all worries are gone. And, at the end of the day, no mess to clean up.
"I love it when a plan comes together"

Here is a pic taken on mine yesterday, by an obviously talented photographer.
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Old 09-06-2005, 06:37 AM
  #20  
Geoff_Gino
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Hi CorsairJock

GOOD looking plane.

Geoff
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Old 09-07-2005, 07:35 AM
  #21  
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Hi CorsairJock

Finally did the resize thing so that I can down load some pics. Here's one as a test.

Geoff


[IMG]C:\Documents and Settings\Geoff Ogden\My Documents\My Pictures\Resized\fill her up.jpg[/IMG]
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Old 09-07-2005, 07:36 AM
  #22  
Geoff_Gino
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Wow that didn't work. Any idea what I am doing wrong

Geoff
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Old 09-07-2005, 07:52 AM
  #23  
Geoff_Gino
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Hi CorsairJock

Try and try again.

Geoff

P.S. That's my instructor Chris

Last edited by Geoff_Gino; 01-31-2008 at 11:34 AM.
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Old 09-07-2005, 10:54 AM
  #24  
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nice opening hatch...looks like an open heart operation...
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Old 09-07-2005, 01:54 PM
  #25  
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Yes, I like the hatch also. As mine is, I must remove the wing to charge batteries, and I have no external means of connecting and disconnecting batteries, so the ESC has power available for long periods of time. NOTE: the WILL eventually drain the batteries, even if motor is not run, so disconnect batteries to speed control when not in use.
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