a wrote in
:

On Sep 6, 3:51*am, Bertie the Bunyip wrote:
a wrote in
news:e5fb9dcd-6bd8-42e3-9a50-f6370d188424
@x35g2000hsb.googlegroups.com:

On Sep 5, 6:46*pm, Leviterande Leviterande.
wrote:
Now woludnt a shorter prop with a bigger chord(and q-tips) move
more a
ir
and thus creating equal thrust as a longer propeller with thinner
chor
d?

when I tried the patented fan it was pretty quiet *however.

How did you try the patented fan?

AS for longer chords? Probably not. Think of the *most efficient
wing
s
for airplanes -- the ones that provide the best lift/drag. They are
long and slender. The same principles hold for props. You can be
sure if wide chords were better they'd be showing up on
experimental aircraft, and they are not.

They do actually, and they can be very efficient indeed.

http://www.youtube.com/watch?v=Nxz1UF67EQI

There's also been the Dyke Delta, and the facetmobile, of course.

Bertie

I don't think you'd find these as 'efficient' as conventionally shaped
aircraft, else we'd be seeing competition gliders shaped this way.
Those airplane shapes would have very light wing loading of course,
but huge wetted areas -- think drag.


Yeah, I understand al of that, but the word efficient is one that is
often bandied as some sort of standard, but is just as misunderstood.

While I know you mean aerodynamic efficiency in it's purest form, the
mission is the yardstick by which you must measure the success of an
airplane. Gliders are good at what they do, but they're as much a
compromise as any other type of airplane. Low aspect ration machines
have a few enormous advantages, not the least of which is a huge speed
range and relatively low drag at low alpha. Span loading is more
relevant than area loading in many ways and application, depending on
what you're trying to get the wing to do at any given momen, and a low
span loading, as in a glider, has to be paid for with drag just like
any other aerodynamic benifit. Simply put, the longer the span, the more
air you're moving around. Now, for some applications, this is more
efficient, since by agitating a greater volume air in a less agressive
fashion than a little air, you may, and may is the operative word here,
create less drag in your flight situation.

. As for using that concept for prop blade shape, , where efficiency
is defined in the conventional engineering sense as power out divided
by power in, long and thin blades seem to win over short and fat.

Depends on the application and what you're asking the blade to do.
Length brings its own problem here again, but in spades, since tip
speeds, particulalry at high cruise speeds, becomes a problem.
There simply are no pat answers in aerodynamics. "Monoplanes are more
efficient than biplanes" for instnace, is an oft touted example. Simply
not true in every aspect. It depends on what you're asking the airplane
to do. Of course, particualrexamples may be plucked from the air to
prove almost any POV here. You could look at two types of aircraft and
compare their performance with a single yardstick, such as fuel burn,
but that doesn't make one more efficient than another as whole. just on
fuel burn. If the fuel efficient one can't get out of the 800 foot strip
it's parked in and the other one can, then the one that can is the more
efficient machine for it's mission. That's not to say some airplanes
aren't just plain inefficient, but it is a bit ridiculous to say that
just because there's a popular mission and most airplanes tend to gel in
that corner of design that those types of aircraft are ultimatley the
most efficient things in the sky.



Bertie