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Jun 02, 2017, 01:19 AM
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Percentage weight penalty convering from I/C to electric


Has anyone done any comparison of weight penalty regarding power systems when converting from I/C to electric?

Tony
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Jun 02, 2017, 04:04 AM
jofro
You can work out %, as an example in one of my conversion from IC to E-power.
102" "HERC" powered by 2x OS 52FS on inner and 2x OS32FS on outer. (APC13x6 and APC12x6) AUW cca. 8kg. Static pull/thrust 6.5kg. Flight time cca. 5-6 min.
Converted to E-power 4x4S/2800mA packs spinning APC 13x6, AUW 8.2kg. Static pull 8.4kg. Flight time cca. 4-5 min.
Final conclusion, plug it in and off you go and very quiet.
Jun 02, 2017, 05:14 AM
AMA 537620
ChillPhatCat's Avatar
There is no blanket percentage penalty in converting from one to the other. Sometimes they come out lighter, sometimes heavier. Often times you lose run time but that's just a compromise on weight. My one conversion came out lighter but I lost half the run time... might break even if I did go for the full capacity to allow ten minutes of flying. But there are way too many variables to give a real definite answer.
Jun 02, 2017, 05:25 AM
A man with too many toys
With modern electronics and LiPo batteries many times it comes out less weight and has better performance but the flight times will be shorter. You can weight it down with batteries to get more flight time. Electric Power is very flexible and you can build it any way you want. That;s why it's so popular.
Jun 02, 2017, 06:26 AM
Registered User
flypaper 2's Avatar
I converted many of my !/4 scale planes from gas to electric. I found I could swing a bigger prop because watts to watts, the gasser was limited to the fact that it had to run at a higher RPM to get the same HP as electric. Bigger prop at lower RPM is more efficient at the same watt output.

Gord.
Jun 02, 2017, 06:34 AM
AndyKunz's Avatar
I have a build thread where the final electric version came out 50% lighter than​ the nitro version.

Andy
And RC electric lighter than FF nitro
a
Jun 02, 2017, 06:47 AM
aka: A.Roger Wilfong
gnofliwr's Avatar
In my experience, if you're just converting an existing nitro plane, the weights come out close. However if you're building a nitro plane as an electric, it usually comes out lighter. Without the vibration of the IC motor, you don't need as much bracing and over build - 1/8" sheeting can change to 3/32", 1/8" liteply doublers become 1/32" real ply (and are stronger), etc.

- Roger
Jun 02, 2017, 07:46 AM
AMA 537620
ChillPhatCat's Avatar
The Super Sportster EP (48") is a great example of what you can do with an airframe originally designed for Nitro... the EP version is a re-imagined Super Sportster 20, a plane that originally came out to 3.5 - 4 lbs on nitro, but extensive work was done to lighten the airframe for E-power, taking out unnecessary plywood and adding lightening holes.

My SS EP weighs 2.44 lbs, has unlimited vertical and runs 8-10 mins with throttle management. The SS 20 would have run about 10-15 mins with throttle management and probably would be around 0.9:1 thrust to weight.
Jun 02, 2017, 08:59 AM
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Clive66's Avatar
I converted three of my old nitro planes to electric (Goldberg Eagle 2 - SIG Kadet Senior & Balsa USA Enforcer)

The all up flying weight on all three, ended up almost exactly the same as before,
Jun 02, 2017, 09:59 AM
Registered User
flypaper 2's Avatar
Same here , but I did have to put the batts under the motor to get the CG right.

Gord.
Jun 02, 2017, 12:35 PM
A man with too many toys
After the introduction of LiPo batteries and bruchless motors I think that most conversions will weigh less.
Jun 02, 2017, 01:21 PM
Registered User
Clive66's Avatar
The thing with a conversion, is if the components in the nose, end up weighing less than before & there isn't a practical way of shifting the LIPO battery enough to compensate, you will need to add "dead" weight to the nose to get the CG correct.
All three of my conversions required no added "dead" weight at all, front or rear to maintain the CG.
The LIPO batteries in my Eagle 2 & Enforcer conversions, ended up in the same location as the fuel tanks were before (the Kadet Senior LIPO ended up back some from the fuel tank location)
As I said before, the weights of those planes ended up the same as before the conversions.

Oh, & a decent size LIPO that will provide enough run time on any of my conversions, weighs considerably more than a tank of fuel did.
Last edited by Clive66; Jun 02, 2017 at 01:30 PM.
Jun 02, 2017, 03:30 PM
Registered User
All of my conversions have come out slightly less weight than when they were glow-powered, and only one of them, a plan-built Blackburn 1912, has needed nose ballast. Admittedly, flight durations are usually (not always) shorter than with glow, but that just gives me more opportunities to practice my landings. Performance in all cases is improved over the glow version.
Jun 02, 2017, 04:28 PM
Registered User
Quote:
Originally Posted by abenn
All of my conversions have come out slightly less weight than when they were glow-powered, and only one of them, a plan-built Blackburn 1912, has needed nose ballast. Admittedly, flight durations are usually (not always) shorter than with glow, but that just gives me more opportunities to practice my landings. Performance in all cases is improved over the glow version.
That has pretty much been my experience as well. The shorter flight duration is easily handled by designing the system such that battery changes are quick and easy. I find that most people are not particularly interested in flying >10 minutes without a break anyway. If you are needing the ultimate in flight duration, electric may not be for you. But for most people it works extremely well. And in those cases it will usually be a bit lighter.


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