FinFactors:

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   Compute the hull and fin efficiency factors for an airship.
   Zero dihedral is assumed.
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   Form:
   [etaK, etaF] = FinFactors( J1, Sf, Sfh, vol )
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   Inputs
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   J1          (1)       One of Munk's integrals; see AirshipIntegrals.m
   Sf          (1)       Fin reference aera
   Sfh         (1)       Combined fin & hull cross-sectional area
   vol         (1)       Hull volume

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   Outputs
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   etaK        (1)       Hull efficiency factor (effect of fins on the hull)
   etaF        (1)       Fin efficiency factor  (effect of hull on the fins)

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   Reference: Khoury, Gillett, "Airship Technology", p.53
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   Copyright 2003 Princeton Satellite Systems, Inc.
   All rights reserved.
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