My own take on it is that the spar orientation should be
relative to the chord line of the selected airfoil. The
quirk in the deal is that some of the older airfoils were
referenced to a line along the bottom, which made some sense
with flat-bottomed airfoils like the USA35. However,
camber and cusp change the picture, plus the fact that all
modern airfoils and all analysis programs reference the
mean aerodynamic chord (I believe). In any case, the Riblett
is not a flat-bottomed airfoil and all of its published
characteristics are referenced to the chord.
I wish the world was simple again, like it used to be ;o)
Oscar Zuniga
Air Camper NX41CC
San Antonio, TX
mailto: taildrags@hotmail.com
website at http://www.flysquirrel.net
