Sizing Electrical power system for my big plane - RC Groups
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Nov 19, 2007, 03:28 PM
nakman8's Avatar

Sizing Electrical power system for my big plane

I'm putting together a CG Staudacher S-300GS.
Big plane ! 60" wing. Flying weight is 6.5-7.5 lbs.
Calls for .45 t0 .61 2-stroke.
The kit is so old it doesn't even mention electric.
Need recommendation on power system size.
Not looking for vertical climb capabilities,just a
good all around flyer.

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Nov 19, 2007, 04:09 PM
Registered User
Dr Kiwi's Avatar
You'd need maybe 75W/lb, so 500W or so. That would require 50A on 3s (and very good packs to deliver that), so it would be better to go for 4s/5s.

This might do you well:

A Phoenix 45A ESC, and some 4s 4000 packs would fit the bill.

Edit: Another look at your plane ------and a .61 motor - wow! that's well over 1000W - do you you really need that much?

If so then this motor (.46 equivalent) might suit:

Heck if you adhere to the .61 glow you might even need the 1100W Dualsky!

At that point you are up to 80A ESC's and monster 5s packs.
Last edited by Dr Kiwi; Nov 19, 2007 at 04:17 PM.
Nov 20, 2007, 07:04 AM
volare est vivere
ray foley's Avatar
Hi there from Toledo

For a 7 lb +/- airplane, 100 watts per pound will give great mild pattern performance. So equip the plane for 700 watts or so (1HP =746Watts). Most .46 equivalent electrics will be good for that much power. A .61 equivalent will be a lot more powerful but I say go for it if the family money tree can tolerate it. Unlimited vertical is so cool and the looks from the stunned slimer pilots, priceless.

ciao -rjf
Nov 20, 2007, 07:33 AM
Registered User
Ken Myers's Avatar
You might find this article useful:

700 watts in or so for a 7 pound plane provides fun.

For some specific suggestions, look in the Glow Conversion thread area ( ) for "60 size" warbirds. There are many of them there right now.
Last edited by Ken Myers; Nov 20, 2007 at 07:35 AM. Reason: spelling/typing
Nov 20, 2007, 08:43 AM
Registered User
Hyperion 4020-10, 13x10 APC E prop and 5s 3700-ish LiPo. Needs an 80A ESC, will put in 1300W and a pitch speed of around 200 kph, which should make it vanish in no time. Or for a slightly milder effect, prop down a bit or use a 4020-12 or -14. Your model is a bit lighter than the Lancair I have the -10 in, so you should be well into unlimited vertical; the Lancair slows a bit on an upline, enough to notice the speed drop, but will go vertical as far as is reasonable with a 1.5m plane.
Nov 20, 2007, 08:46 AM
Registered User
you'll want a fairly comfortable 600 watts (90ish watts per lb will see you very happy)... a scorpion 3026 motor would be ideal ... or if you're going to anyway have balance issues with tail-heavyness - then plump for a scorpion 3032 and reap the benefits of greater efficiency...

I suspect that that airframe will need a bit of weight in the nose so that's good news for you as it means budget efficiency (big outrunner)

the kit motors are cheap and the ready to run motors are very reasonable...

gobrushless and innov8tive have them ...

I'd go with 4s at least - should get a resonable deal on an ESC (Hyperion, Scorpion, Castle etc)

(BTW, don't be bowled over by Scorpions power handling claims when compared to other brand outrunners of similar mass - the fact that they can pump 1000 watts through a 190g motor isn't as it usually would be, an indicator of tremendous efficiency, but rather of a motor that is reasonably efficient and has been built to withstand massive heating.) They are of course good motors... but they won't give you more than your comparable Hacker, Axi, Hyperion etc.

Remember, this is a glo airframe - designed to withstand the rigors and vibration of glo engined flight. You don't need this heft and structural massiveness for electric flight... With a little effort you can knock 20 to 25% of the weight out of it with absolutely no adverse effects on structural strength... but with major gains in flight envelope and also thus requiring a much smaller, cheaper power system (come down a size in motor, battery and ESC)

big bird
Nov 20, 2007, 08:51 AM
Registered User
I should say... the 4020 series are somewhat overkill for this job. But if you want to make some glow guys think twice, a good choice.
Nov 23, 2007, 03:40 PM
nakman8's Avatar
Has anyone seen a good combo package today that I could use for my 7.5lbs
plane? I have been looking myself all morning but haven't made a purchase yet.
Can I use an outrunner?? The Rimfire on TH looks pretty good.
Pleas LMK if you find something I might be able to get a good deal on.

Nov 23, 2007, 04:30 PM
Registered User
What sort of packs do you already have? That will make quite a big difference.

If 5S lipo of around 3500 to 4000 mAh is around, then:
Hyperion 4020-14, Hyperion Titan 80 ESC, APC 13x8e

That WILL perform on something that required a .60-ish four stroke. Draws upwards of 65A, so the pack needs to be able to handle that.
Nov 23, 2007, 06:26 PM
Registered User
the rimfire motors are only so so... you can get better bang for your buck ...
Nov 23, 2007, 06:30 PM
nakman8's Avatar
Ok.Did you see any motors out there today that might work and had a good
turkey day price?


Originally Posted by big bird
the rimfire motors are only so so... you can get better bang for your buck ...
Nov 23, 2007, 06:42 PM
nakman8's Avatar

kit motors

Having trouble finding the kit motors referred to by big bird.
could someone point me in the right direction please.

Nov 23, 2007, 07:13 PM
Registered User has them

just be warned that with Scorpion, the power figures are power in, not power out - they will perform no better than Hacker or Hyperion, prolly a shade less well. They are good value IMO
Nov 23, 2007, 08:30 PM
Innov8tive's Avatar
big bird,

Just to set the record straight, the Scorpion motors do perform as well, and in most cases, better than the motors offered from Hacker or Hyperion. The Scorpion Factory has done a LOT of testing to ensure that their products are as good or better than anything else out there. When you consider the fact that they are also made from higher grade materials, are better packaged, and sell for less money than the other brands, they are a truly remarkable value!

Lucien Miller

Innov8tive Designs
Nov 24, 2007, 06:07 AM
Registered User
Sorry if i caused any offence. I'm a big fan of Scorpion motors - I think they are very well made and represent very good value for money. Perhaps the best value available - that's why I'm comfortable with recommending them.

I think it's important to point out however that the very high power handling figures posted for them could be a little misleading for the more innocent motor buyer.

The fact that the 3026 Scorpion (a 189g outrunner for those who mightn't know) has a power handling figure of 1000 watts suggests that it might be extremely efficient.

In fact, it is a very efficient motor, but I would wager not significantly more or less so than a Hyperion/Hacker in this weight class

The fact that it can "handle" 1000 watts testifies more to the robustness of the materials used to make it rather than to its efficiency at converting electrical to mechanical power. I would wager that it is not doing anything productive with the last 400 watts of that 1000 watt figure, other than heating the sky.

Bear in mind that 1000 watts also requires a 1000 watt capable battery - which is a big weight to shlep about if a lot of it is being used to heat the air rather than to turn a prop.

I'm not trying to be down on Scorpion motors. I have the 3026 earmarked for a project of mine (in a 600 to 650 peak watts application ). I believe it to be a wise investment and a high quality product.

To focus on the positives, the massive heat handling ability means that the motor should be just about indestructible from over powering. The very high quality and low price puts them in a unique position in the market...

but for the inexperienced motor buyer, the high power handling figures should be understood more in terms of extraordinary heat handling ability rather than extraordinary motor efficiency - meaning that if they are looking for the power of a 1000 watt motor they might want to go up a size or two

Hope this clarifies my position.

big bird
Last edited by big bird; Nov 24, 2007 at 09:28 AM.

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