[ExI] probably extremely simple physics problem

spike spike66 at att.net
Mon Aug 7 17:00:16 UTC 2017



From: extropy-chat [mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of William Flynn Wallace
Sent: Monday, August 07, 2017 9:39 AM
To: ExI chat list <extropy-chat at lists.extropy.org>
Subject: [ExI] probably extremely simple physics problem


Recall those Dutch windmills:  huge area on the sails.  Look at the current enormous wind machines for making electricity: so skinny.


It would seem to a simpleton like me, that the more area you had, the more wind you caught - but apparently not - or something.


What gives here?


bill w



The optimal solution was enabled by advanced material technology.  Billw, the critical number is not the area of the blades but rather the swept area.  Part of the reason is that having a wide chord, like the Dutch windmills, makes higher wind resistance, so they can’t turn as fast.  The modern skinny blade windmills really get kiting around there, much more efficient for swatting birds into the next county.


Note a sail plane, where gliding efficiency is everything: the wingspan is long and the chord is short: very efficient for glide ratio.  The fighter plane has short wingspan, long chord: inefficient glide ratio, better for high performance in what fighter planes do.  Cargo planes have the wider chord for increased lift capability, where speed isn’t critical.  Different missions.


The Dutch were using wind power to lift water, whereas the Yanks are using it to generate power: different missions.


Now that you mention it however, please offer your take on something that has long puzzled me: why didn’t the Dutch get to powered flight first?  They had way more understanding of aerodynamics than anyone because of their experience with the windmills.  They were early adopters of the German Nickolaus Otto’s marvelous internal combustion engine.  They had plenty of flat ground on which to build runways.  They were well along in the industrial revolution, factories and such.  They had worked out the notion of rigid cantilevered structures such the windmill blades.  I am amazed the yanks would get powered flight off the ground first, with the French in close pursuit.  I would have thought the Dutch would be the first to fly, followed by the Germans with the Yanks third and the French well back there.



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