Discussion:
Glow to electric conversion
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H
2013-05-25 10:51:23 UTC
Permalink
I have been searching and reading all I can about how to choose motor
size for a plane that has been specified for a certain size glow
engine. Although the information I have been able to find is both
consistent and informative, there is one thing that does not add up:

Let's look at a .40 size trainer as an example. It weighs around 5-6
pounds. From what I have read, a power loading of 75-100 W/pound is
recommended for trainers. This means I would need 375-600 Watts of
power for this plane.

It is standard practice to put a .46 on .40 size plane, even for a
trainer. The OS .46 LA is rated at 1.18HP, or about 880 Watts. The OS
.46 AX is rated at 1.63 HP, or over 1200 Watts.

Why does an electric only need half (or even a third) of the power
you'd have used with a glow engine?
m***@htcomp.net
2013-05-26 22:55:35 UTC
Permalink
Post by H
I have been searching and reading all I can about how to choose motor
size for a plane that has been specified for a certain size glow
engine. Although the information I have been able to find is both
Let's look at a .40 size trainer as an example. It weighs around 5-6
pounds. From what I have read, a power loading of 75-100 W/pound is
recommended for trainers. This means I would need 375-600 Watts of
power for this plane.
It is standard practice to put a .46 on .40 size plane, even for a
trainer. The OS .46 LA is rated at 1.18HP, or about 880 Watts. The OS
.46 AX is rated at 1.63 HP, or over 1200 Watts.
Why does an electric only need half (or even a third) of the power
you'd have used with a glow engine?
I think you are right. I can't imagine having a less power for a trainer. You need the power to get out of rookie trouble. Though, a .46 AX on a trainer will make it snap roll nicely. I say go bigger on the electric.
mk
Charley38
2013-05-30 03:34:27 UTC
Permalink
First off, a glow .46 is overkill for a .40 size trainer. It's just
that there aren't too many .40 engines available anymore.

secondly, you're talking about max power output on the glow engine. One
doesn't run the engine wide open all the time. Usually it's about 1/2
throttle.

Anyway you're quoting "rules of thumb." Rules of thumb vary along with
thumb sizes. ;>)

CR
Post by H
I have been searching and reading all I can about how to choose motor
size for a plane that has been specified for a certain size glow
engine. Although the information I have been able to find is both
Let's look at a .40 size trainer as an example. It weighs around 5-6
pounds. From what I have read, a power loading of 75-100 W/pound is
recommended for trainers. This means I would need 375-600 Watts of
power for this plane.
It is standard practice to put a .46 on .40 size plane, even for a
trainer. The OS .46 LA is rated at 1.18HP, or about 880 Watts. The OS
.46 AX is rated at 1.63 HP, or over 1200 Watts.
Why does an electric only need half (or even a third) of the power
you'd have used with a glow engine?
chetaget
2013-06-13 15:08:26 UTC
Permalink
Post by Charley38
First off, a glow .46 is overkill for a .40 size trainer. It's just
that there aren't too many .40 engines available anymore.
secondly, you're talking about max power output on the glow engine.
One doesn't run the engine wide open all the time. Usually it's about
1/2 throttle.
Anyway you're quoting "rules of thumb." Rules of thumb vary along with
thumb sizes. ;>)
CR
Post by H
I have been searching and reading all I can about how to choose motor
size for a plane that has been specified for a certain size glow
engine. Although the information I have been able to find is both
Let's look at a .40 size trainer as an example. It weighs around 5-6
pounds. From what I have read, a power loading of 75-100 W/pound is
recommended for trainers. This means I would need 375-600 Watts of
power for this plane.
It is standard practice to put a .46 on .40 size plane, even for a
trainer. The OS .46 LA is rated at 1.18HP, or about 880 Watts. The OS
.46 AX is rated at 1.63 HP, or over 1200 Watts.
Why does an electric only need half (or even a third) of the power
you'd have used with a glow engine?
Could the increase in efficiency with the electric system be part of
the reason for needing less power ?
Jay Songbird
2013-09-19 21:06:06 UTC
Permalink
"H" wrote in message news:***@4ax.com...

I have been searching and reading all I can about how to choose motor
size for a plane that has been specified for a certain size glow
engine. Although the information I have been able to find is both
consistent and informative, there is one thing that does not add up:

Let's look at a .40 size trainer as an example. It weighs around 5-6
pounds. From what I have read, a power loading of 75-100 W/pound is
recommended for trainers. This means I would need 375-600 Watts of
power for this plane.

It is standard practice to put a .46 on .40 size plane, even for a
trainer. The OS .46 LA is rated at 1.18HP, or about 880 Watts. The OS
.46 AX is rated at 1.63 HP, or over 1200 Watts.

Why does an electric only need half (or even a third) of the power
you'd have used with a glow engine?

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Try here. Lots of good guys.

http://www.rcgroups.com/aircraft-electric-airplanes-4/
A***@optonline.net
2014-04-09 19:10:51 UTC
Permalink
The HP ratings of glow engines are based on RPMs that are not typically seen in RC flying. So the numbers you quote in HP is an over inflated marketing number.

Generally trying to equate glow engines with electric motors is a waste of time. Using the watts/pound approach is much more effective.

I find most glow pilots are going to want at least 100 watts/pound for their planes. If you are the "too much is about right" type than make 150 watts/pound your baseline.

But you only need about 75 watts/pound to fly the plane in most cases, but we tend to over power our models. A full scale J3 cub has about 55 watts/pound equivalent power and it flies just fine. But most RC pilots would want more than J3 cub scale type flight performance.

Here is a FREE on-line e-book that you may find useful.

EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT
www.wattflyer.com/forums/showthread.php?t=31368
http://www.rcuniverse.com/forum/m_7100376/tm.htm
Post by H
I have been searching and reading all I can about how to choose motor
size for a plane that has been specified for a certain size glow
engine. Although the information I have been able to find is both
Let's look at a .40 size trainer as an example. It weighs around 5-6
pounds. From what I have read, a power loading of 75-100 W/pound is
recommended for trainers. This means I would need 375-600 Watts of
power for this plane.
It is standard practice to put a .46 on .40 size plane, even for a
trainer. The OS .46 LA is rated at 1.18HP, or about 880 Watts. The OS
.46 AX is rated at 1.63 HP, or over 1200 Watts.
Why does an electric only need half (or even a third) of the power
you'd have used with a glow engine?
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