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View Diary: Fokker D.VII – so dangerous, it was mentioned in the Armistice Agreement (74 comments)

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  •  The biggest difference between a ship screw (8+ / 0-)

    and a propeller is that water is incompressible.  Thus, a propeller in water pushes the craft forward.  Because a propeller in water is in an incompressible medium, a very low aspect ratio is required for boat props.  An airplane propeller has a very high aspect ratio.  That is, the ratio of span (length) to chord (width).

    An airscrew propeller has to deal with a highly compressible medium that obeys the laws of gas flow rather than water.  An airplane propeller mostly pulls the machine forward, rather than pushes it.  

    Recent tests on the Wright brother's propeller show that their twist formula and airfoil profile approach optimum performance, and the quality of their workmanship was impeccable.  Even a modern computer aided design could not improve on their props, after all variables were factored in, including shaft horsepower and forward speed (relative wind).

    The general who wins the battle makes many calculations in his temple before the battle is fought. The general who loses makes but few calculations beforehand. - Sun Tzu

    by Otteray Scribe on Fri Jan 11, 2013 at 06:04:29 PM PST

    [ Parent ]

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