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Old Jun 12, 2003, 04:01 AM
Houfek,Jim
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[EFLT] Watts/Weight

This message from "Houfek,Jim" <houfekj@oclc.org> brought to you by EFLIGHT!


Recent discussions regarding how many watts it takes to fly a 5 pound ship
reminded me that once upon a time someone had developed a table indicating
various weights and the watts necessary to fly them.....
Of course, the exact answer would depend on variables such as efficiency,
etc.......but there were 3 ranges given for each weight. For example (these
numbers are made up), for a weight of 3 pounds, the table would show
100-150-200 watts, where the first was for maintaining flight, the second
for mild aerobatics, and the third for competition aerobatics.
Does anyone know of such a table.......or alternatively, a formula that
could be applied like this ??

Thanks.....

Jim Houfek
Columbus, OH

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Old Jun 12, 2003, 04:01 AM
B12Boy@aol.com
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Re: [EFLT] Watts/Weight

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In a message dated 6/11/2003 2:13:06 PM Central Standard Time,
houfekj@oclc.org writes:


> Does anyone know of such a table.......or alternatively, a formula that
> could be applied like this ??
>
> Thanks.....
>


A table like this will always be vague and full of caveots.

In general, you'de need a side table correcting for average flight speed,
prop size, voltage used, ( more volts and less amps is more efficient and would
need less watts), ect ect ect.

It would get way to complicated and big to be very useful.

This is why we have motocalc. ; ) motocalc.com


Dean in Milwaukee


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Old Jun 12, 2003, 04:01 AM
Doug Ingraham
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Re: [EFLT] Watts/Weight

This message from Doug Ingraham <dpi@rapidnet.com> brought to you by EFLIGHT!

On Wed, 11 Jun 2003, Houfek,Jim wrote:

> Recent discussions regarding how many watts it takes to fly a 5 pound ship
> reminded me that once upon a time someone had developed a table indicating
> various weights and the watts necessary to fly them.....
> Of course, the exact answer would depend on variables such as efficiency,
> etc.......but there were 3 ranges given for each weight. For example (these
> numbers are made up), for a weight of 3 pounds, the table would show
> 100-150-200 watts, where the first was for maintaining flight, the second
> for mild aerobatics, and the third for competition aerobatics.
> Does anyone know of such a table.......or alternatively, a formula that
> could be applied like this ??


The general rule of thumb is 50 watts per pound. I have a small speed 400
glider that will hold altitude on 18.7 watts into the motor. At this
power level the S-400 is about 60% efficient so the power to the prop is
about 31 watts. The glider weighs 24 ounces so the power level to hold
altitude in still air is 20 watts per pound. At 100 watts per pound you
have a very aerobatic aircraft.

Of course if you have something that has an excessive wing loading it
might be difficult to manage but for typical models this rule of thumb
works out pretty well.


Doug Ingraham
Rapid City, SD USA




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Old Jun 13, 2003, 04:01 AM
FriarAHS@aol.com
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Re: [EFLT] Watts/Weight

This message from FriarAHS@aol.com brought to you by EFLIGHT!

Matt Orme's "Motor Selection" as found under "Articles" on the Aveox website
is comprehensible and is an easily applied "rule of thumb" concept.
Alan
(Alan H. Siegel, New York City)


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