BladeSolidity:

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   Blade solidity.

   Solidity of 0.1 is typical. Since solidity is n*c/d you can get
   a solidity > 1.

   Type BladeSolidity for a demo

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   Form:
   s = BladeSolidity( n, c, d )
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   ------
   Inputs
   ------
   n          (1,1)  Number of blades
   c          (1,1)  Chordwidth
   d          (1,1)  Diameter

   -------
   Outputs
   -------
   s          (1,1)  Solidity

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   Reference: http://club.cycom.co.uk/vertAxis.html
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