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Aerodynamics - does size matter?

Old 05-28-2014, 01:30 AM
  #26  
fhhuber
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Originally Posted by kyleservicetech View Post
LOL
Unless you're the TV show Mythbusters, where they launch a ping pong ball at 1100 MPH Wonder how far that ball would go through open air?

https://www.youtube.com/watch?v=msgfm4DHiyc

Not as far as a metal ball of the same weight launched at the same speed... (supersonic bullet)

Both would slow down below 750 mph very fast. The bullet might go a mile. the ping-pong ball I would bet not even 100 yards.
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Old 05-28-2014, 03:08 AM
  #27  
kyleservicetech
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Originally Posted by fhhuber View Post
Not as far as a metal ball of the same weight launched at the same speed... (supersonic bullet)

Both would slow down below 750 mph very fast. The bullet might go a mile. the ping-pong ball I would bet not even 100 yards.

Yeah, this is way off topic.

There was a reason they had the target so close to the ping pong gun barrel. Other parts of that show had the ping pong ball exiting at some 1200 MPH. That ball disintegrated a few feet from the barrel, after hitting the air. They didn't show how far the shattered ball traveled.

One of the shots showed the ping pong ball hitting a standard ping pong paddle. It cut a perfect circle right through the plywood paddle.

To get the gun to work, they had to pull a vacuum on the barrel end. Otherwise the ball stopped right in the middle of the barrel due to air pressure build up inside the barrel.
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Old 03-05-2015, 08:46 PM
  #28  
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Indeed most airfoils have very nasty stall characteristics if they are not designed for low Re flight. At a certain Re having a thicker wing is better at high angles of attack because it keeps the air attached longer, but in reality the length of the chord will change the Re so having a long, thin wing is better. When I was testing a NACA 0012 at just over 100,000 Re the wing stalled at a ridiculously low angle of attack, and when it did the L/D ratio was cut in half! Ouch! BTW, higher Re is not always better. Performance reaches a peak, usually in the 100,000 to 10,000,000 range before it decreases again. So bigger is better TO A POINT. Check out this graph for a ball's drag!http://www.grc.nasa.gov/WWW/k-12/air...ragsphere.html.

The best solution to your woes is boundary layer suction! lolololol!http://en.wikipedia.org/wiki/Boundary_layer_suction
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