Yeah - brain error there, Nick. You'll notice i gave up trying to be smart and went back to FM vs Ct/Sigma curve. Optimum Ct/Sigma is 0.125 regardless of bladespan.
Have just confirmed this by looking at Fig 1.13 (P28) in Prouty, which plots above for different Sigmas (Convert ordinate using Ct/Sigma = <Cl>/6 ). FM varies, but peak is always at Ct/Sigma ~0.125. Peak FM value increases with increasing Sigma, so it looks like Dave has a point about span improving efficiency.
Mart
Last edited by Graviman; 3rd Nov 2006 at 18:16.