Propeller Efficiency

On Apr 16, 3:05*am, wrote:
On Apr 15, 3:53 am, WingFlaps wrote:





On Apr 15, 3:11 pm, wrote: On Apr 13, 8:20 pm, WingFlaps wrote:

Does anyone have any idea of the ratio between thrust power and churn
power?

Less than 80%. Look in Wiki for discussion of losses.

* * * Wiki isn't so accurate. The figure for max efficiency is in the
range of 85 to 87%, depending on AOA and a bunch of other stuff. The
Wright Brother's propeller on their Flyer had an efficiency of 83%
because they understood that it was a rotating airfoil rather than
some sort of paddlewheel.
* * * For prop math, see this: *http://www.epi-eng.com/propeller_tec..._propeller.htm

There's nothing like theoretical efficiency calculations to impress.
I'll say it again, real props struggle to achieve 80%. Now Dan, before
you jump down my throat, note that of these calculations in your ref.
did not include vortex tip losses and most don't even consider
friction and never compressibility (which is major problem *as the tip
goes near or supersonic). Basing efficiency purely on slip doesn't
work for real airscrews and the washout is nearly always _wrong_.

Cheers

*Those calculations are more than theoretical. We know, in foot-pounds
per minute, what an engine produces, and we can take that directly to
the acceleration of the airplane or its cruise speed versus drag, and
come up with an efficiency figure.

And the answer is TADA less than 80%....

Cheers

In article
,
Le Chaud Lapin wrote:

On Apr 16, 10:52*pm, Orval Fairbairn
wrote:
If the innovation offers improvement, then pilots buy it. Witness GPS,
glass cockpits.

Change for the sake of change, however, is just plain STUPID!

So...having an aircraft that is

0. smaller
1. quieter
2. lighter
3. more fuel-efficient
4. more comfortable
5. easier to control
6. more stable in adverse conditions

Would this fall into the "improvement" or "change for sake of change"
category?

-Le Chaud Lapin-

But your notional design falls into the category of "None of the Above,"
as it requires complex, stacked, expensive systems to work, as well as
an undefined means of propulsion.

There is a big difference between "starting with a clear head" and
starting with an empty head. You, sir, I fear, fall into the laqtter
category.

--
Remove _'s from email address to talk to me.

On Apr 16, 3:11*pm, wrote:
On Apr 15, 4:02 am, WingFlaps wrote:





On Apr 15, 3:11 pm, wrote:
The
Wright Brother's propeller on their Flyer had an efficiency of 83%
because they understood that it was a rotating airfoil rather than
some sort of paddlewheel.

83%? BS. Even if it had reached optimal speed it would have struggled
to get 70% (note the CFD calcs do not include surface roughness
losses):

http://www.fluent.com/about/news/new...i2_fall/a2.htm

It was lucky that Orville knew from tests a bit about about props (he
estimated 66% efficiency) or it might not have flown at all. That of
course was not such great insight on his part as the theory of
propellor design was well known from naval architecture.

* * * *Better see this: *http://www.memagazine.org/flight03/propwr/propwr.html

* * * *Wright estimated an efficiency of 66%. Later, more
sophisticated tests on the Flyer's prop design gave an efficiency of
82%.

* * * * A quote from the article:

* * * "These data show that the 1903 Wright propeller had a maximum
efficiency of 82 percent.
* * * "Based on Wilbur Wright's notes on the fourth flight of Dec. 17,
1903, the Flyer had an estimated forward speed of 31 mph during the
steady flight portion of its path and the propellers were turning at
379 rpm, which yields an advance ratio of 0.85. Hence, the 1903 Wright
propellers were operating at a mechanical efficiency of slightly over
75 percent during steady flight.
* * * *"This was a remarkable feat, considering the state of propeller
knowledge prior to World War I.
* * * "Since Wilbur estimated their propeller performance to be 66
percent in March of 1903, we found the results of our experimental
tests to be quite surprising. Using Wright bent-end propeller
reproductions as our reference test case (there are several well-
preserved sets in existence), we have subjected these propellers to
multiple wind tunnel tests. We recalibrated the instrumentation used
in the propeller tests and we subjected the bent-end geometry
propellers to a full Navier-Stokes equation computational fluid
dynamics analysis in order to affirm our test results. The bent-end
propellers had peak efficiencies of nearly 87 percent. The overall
comparisons between the numerical predictions and the test results
agreed. To our surprise, we learned that the Wrights' bent-end
propeller twist distribution (a variation of pitch angle with radius)
was in nearly exact agreement with modern computer-based designs over
the outer two-thirds of the propeller blade."

* * * *How's that?


Very romantic. You'd think that good propellors had never been built
before... The only uncertainty they had to deal with was the actual
RPM their engine would generate -they already knew the drag numbers
for the flyer by kite testing the design. BUT, as I said, the
optimal effiiency is almost never reached so less than 80% is the
correct ball park figure for props. I'm also suspicious that the CFD
calculation quoted in that article was a lot higher than that reported
by researchers I gave you the ref. for...

Cheers

On Apr 17, 12:31*am, "Morgans" wrote:
"Le Chaud Lapin" wrote!
You have proven none of your points below.

So...having an aircraft that is

0. smaller
What? *Pilots want bigger. *Biggest they can afford.

So basically, if a pilot has a choice between a C172 that is size of
a C172, and a C172 that is size of B-52, you're saying he'd want the
latter? [Assuming he could afford hangar fees.]

1. quieter
You have not shown that you can get quieter; first it has to fly with good
performance, and what you propose can not with the proposed power plant and
added weight and complexity.

What I have in mind is lighter than 60HP ICE.

2. lighter
Haven't you been listening? *Everything you propose adds weight.

But is lighter than that which it replaces.

3. more fuel-efficient
First it has to fly well. *Your fuel cell will not.

I never said anything about fuel cells [yet].

4. more comfortable
Not going to happen, unless you exceed your weight budget.

Computer-controlled auto-stabilization would probably do a bettter job
of maintaining comfort than pilot himself.

5. easier to control
Perhaps, until your fly by wire, unreliable system craps out. *What will it be
running, microsoft? *Gads! *How many backups will it have? *At least two, right?
That would be the minnimum number of acceptable backups.

Probably. If cost is cheap enough, 3, 4..whatever is necessary.

6. more stable in adverse conditions
Only you say so. *You want to make it shorter, and that will not be more stable.

Not an inherently true statement.

Try ballancing a bowling ball on your finger, then a 16 foot 2 x 4. *Which is
easier, or put differently, more stable.? *Hint-not the bowling ball. *Your fly
by wire has to be reliable, and that it will not be, and it has to have software
developed, and that will be too expensive to be done, and if you had the money
to do it, someone would probably die while developing it.

I don't see "too expensive" for software to be done, but as far as
dying, it is very likely that there will be serious injuries, but from
what I have seen, that is typical of this industry for new designs.

Go to engineering school, then come talk to us. *Then get some flying
experience. *You have neither. *You will never.

-Le Chaud Lapin-

Le Chaud Lapin wrote in
:

On Apr 17, 12:31*am, "Morgans" wrote:
"Le Chaud Lapin" wrote!
You have proven none of your points below.

So...having an aircraft that is

0. smaller
What? *Pilots want bigger. *Biggest they can afford.

So basically, if a pilot has a choice between a C172 that is size of
a C172, and a C172 that is size of B-52, you're saying he'd want the
latter? [Assuming he could afford hangar fees.]

1. quieter
You have not shown that you can get quieter; first it has to fly with
good

performance, and what you propose can not with the proposed power
plant an
d
added weight and complexity.

What I have in mind is lighter than 60HP ICE.

2. lighter
Haven't you been listening? *Everything you propose adds weight.

But is lighter than that which it replaces.

3. more fuel-efficient
First it has to fly well. *Your fuel cell will not.

I never said anything about fuel cells [yet].

4. more comfortable
Not going to happen, unless you exceed your weight budget.

Computer-controlled auto-stabilization would probably do a bettter job
of maintaining comfort than pilot himself.

5. easier to control
Perhaps, until your fly by wire, unreliable system craps out. *What
will
it be
running, microsoft? *Gads! *How many backups will it have? *At least
two, right?
That would be the minnimum number of acceptable backups.

Probably. If cost is cheap enough, 3, 4..whatever is necessary.

6. more stable in adverse conditions
Only you say so. *You want to make it shorter, and that will not be
more
stable.

Not an inherently true statement.

Try ballancing a bowling ball on your finger, then a 16 foot 2 x 4.
*Whi
ch is
easier, or put differently, more stable.? *Hint-not the bowling ball.
*Your fly
by wire has to be reliable, and that it will not be, and it has to
have so
ftware
developed, and that will be too expensive to be done, and if you had
the m
oney
to do it, someone would probably die while developing it.

I don't see "too expensive" for software to be done, but as far as
dying, it is very likely that there will be serious injuries, but from
what I have seen, that is typical of this industry for new designs.


Oh you so droll

Bertie

On Apr 17, 1:03 pm, Bertie the Bunyip wrote:
Le Chaud Lapin wrote :



On Apr 17, 12:31 am, "Morgans" wrote:
"Le Chaud Lapin" wrote!
You have proven none of your points below.

So...having an aircraft that is

0. smaller
What? Pilots want bigger. Biggest they can afford.

So basically, if a pilot has a choice between a C172 that is size of
a C172, and a C172 that is size of B-52, you're saying he'd want the
latter? [Assuming he could afford hangar fees.]

1. quieter
You have not shown that you can get quieter; first it has to fly with
good

performance, and what you propose can not with the proposed power
plant an
d
added weight and complexity.

What I have in mind is lighter than 60HP ICE.

2. lighter
Haven't you been listening? Everything you propose adds weight.

But is lighter than that which it replaces.

3. more fuel-efficient
First it has to fly well. Your fuel cell will not.

I never said anything about fuel cells [yet].

4. more comfortable
Not going to happen, unless you exceed your weight budget.

Computer-controlled auto-stabilization would probably do a bettter job
of maintaining comfort than pilot himself.

5. easier to control
Perhaps, until your fly by wire, unreliable system craps out. What
will
it be
running, microsoft? Gads! How many backups will it have? At least
two, right?
That would be the minnimum number of acceptable backups.

Probably. If cost is cheap enough, 3, 4..whatever is necessary.

6. more stable in adverse conditions
Only you say so. You want to make it shorter, and that will not be
more
stable.

Not an inherently true statement.

Try ballancing a bowling ball on your finger, then a 16 foot 2 x 4.
Whi
ch is
easier, or put differently, more stable.? Hint-not the bowling ball.
Your fly
by wire has to be reliable, and that it will not be, and it has to
have so
ftware
developed, and that will be too expensive to be done, and if you had
the m
oney
to do it, someone would probably die while developing it.

I don't see "too expensive" for software to be done, but as far as
dying, it is very likely that there will be serious injuries, but from
what I have seen, that is typical of this industry for new designs.

Oh you so droll

Bertie

He's a droll chode, er, Chaud, yeah. No, wait "chode" is accurate
after all.

wrote in
:

On Apr 17, 1:03 pm, Bertie the Bunyip wrote:
Le Chaud Lapin wrote
innews:8a7e9271-ef17-4f98-8a6a-ebe742c7fbf8
@a70g2000hsh.googlegroups.c
om:



On Apr 17, 12:31 am, "Morgans" wrote:
"Le Chaud Lapin" wrote!
You have proven none of your points below.

So...having an aircraft that is

0. smaller
What? Pilots want bigger. Biggest they can afford.

So basically, if a pilot has a choice between a C172 that is size
of a C172, and a C172 that is size of B-52, you're saying he'd want
the latter? [Assuming he could afford hangar fees.]

1. quieter
You have not shown that you can get quieter; first it has to fly
with good

performance, and what you propose can not with the proposed power
plant an
d
added weight and complexity.

What I have in mind is lighter than 60HP ICE.

2. lighter
Haven't you been listening? Everything you propose adds weight.

But is lighter than that which it replaces.

3. more fuel-efficient
First it has to fly well. Your fuel cell will not.

I never said anything about fuel cells [yet].

4. more comfortable
Not going to happen, unless you exceed your weight budget.

Computer-controlled auto-stabilization would probably do a bettter
job of maintaining comfort than pilot himself.

5. easier to control
Perhaps, until your fly by wire, unreliable system craps out.
What will
it be
running, microsoft? Gads! How many backups will it have? At
least
two, right?
That would be the minnimum number of acceptable backups.

Probably. If cost is cheap enough, 3, 4..whatever is necessary.

6. more stable in adverse conditions
Only you say so. You want to make it shorter, and that will not
be more
stable.

Not an inherently true statement.

Try ballancing a bowling ball on your finger, then a 16 foot 2 x
4.
Whi
ch is
easier, or put differently, more stable.? Hint-not the bowling
ball.
Your fly
by wire has to be reliable, and that it will not be, and it has to
have so
ftware
developed, and that will be too expensive to be done, and if you
had the m
oney
to do it, someone would probably die while developing it.

I don't see "too expensive" for software to be done, but as far as
dying, it is very likely that there will be serious injuries, but
from what I have seen, that is typical of this industry for new
designs.

Oh you so droll

Bertie

He's a droll chode, er, Chaud, yeah. No, wait "chode" is accurate
after all.


Groan!


Bertie

On Apr 16, 2:17 pm, Le Chaud Lapin wrote:

As I have said many times, the propulsion model I have in mind would
make significantly less noise than a prop. I doubt that any type of
headset would be necessary. It certainly would not make more noise
than an automobile engine.

It makes no noise at all, since it exists only as a figment
of the imagination. There are no noiseless propulsion systems.
Antigravity could be noiseless, but until the GUT theory is worked out
and understood there's no hope of creating antigravity.

Dan

On Apr 16, 4:23 pm, Le Chaud Lapin wrote:

That's what it means to advance in a field - move the old out of the
way to make room for the new, if it is deemed that the new is better
than the old.

The problem: what is the new? It doesn't exist.

Dan

"Nomen Nescio" wrote \

BTW, I bought a piece of equipt. in January, made in 2007, that uses
vacuum tubes.
Who do you think designed it?

That has my interest aroused. What pray tell was the equipment?
--
Jim in NC