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?

Dan