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The much celebrated 66% efficiency of the 1903 propellers not confirmed by wind tunnel tests[/h] In a March 6, 1903 claimed note, with calculations regarding the efficiency of their propellers, (see
http://www.localhangar.com/cgi-bin/c...age&PAGEID=116 ) the Wright brothers simply applied a known elementary relation:
Efficiency_propeller=Thrust * Plane_speed / Power_available, 66%=90lbf*24mph/8.73HP
They simply needed a 90lbf propeller at 24mph considering a 8.73HP engine was available and they calculated that their propeller should be at least 66% efficient otherwise the required 90lbf thrust to keep the plane aloft would not have been reached. Their calculations show just how great the performance of the propeller should have been not how great it really was.
This efficiency was never obtained by the people from Wright Experience project. The site
http://archive.today/0pne0 says that many tests were effectuated and efficiencies between 75% and 82% were obtained which in not 66%. They also say they reconstructed, with the help of computers, the propellers using badly damaged parts of the original. However, in their reconstructions, they made some assumptions that could have alter the efficiency. In conclusion that 66% efficiency is not confirmed. When a team wants to replicate the results or predictions of some inventors the team has to obtain exactly the same results not much better!
In the article "The Wright Brothers' Aeroplane, O. and W. Wright, The Century Magazine, September 1908, pag. 648-649,
http://www.loc.gov/resource/mwright.05001574/#seq-5 ", WB themselves wrote:
"Our first propellers, built entirely from calculations, gave in useful work 66 per cent. of the power expended. This was about one third more than had been secured by Maxim or Langley."
The text is clear, the two brother calculated and then obtained a 66% efficiency. This is their unconfirmed claim.
An advanced high efficiency propeller, made by Lucien Chauviere, can be seen in L'Aerophile from May 15, 1908, pag. 182 (see
http://gallica.bnf.fr/ark:/12148/bpt...=helice.langEN ). It is above the propellers presented by WB on Aug. 8, 1908 and clearly made before WB's propellers became known. Definitely, Europeans or other inventors did not learn from the Wright Brothers how to make efficient propellers. The opposite seems to be true.
The Wright brothers did not talk about their propellers, did not publish information about them, did not fill for a patent, did not show anything before Aug. 8 1908.
That day they appeared with propellers already built in France in 1907 and claimed they had invented them in 1903!