Dave, seriously good effort!
Maybe keeping the pitch of the NACA 0012 at 8º explains why the power is varying as it does - higher speed means more drag. Normally the wider chord would operate at less pitch, at the same RRPM in hover as cruise (except in S76A). I imagine figure of merit suffers for wider chord blade with camber, operating below optimum pitch.
Nick, thanks for explaining this.
Couldn't find diagram in Keys (looked pretty hard), so am referring to
Prouty "Helicopter Performance Stability & Control"
Figure 1.12 - Figure of Merit vs Average Lift Coeff <Cl>
(Where <Cl> = 6* Ct/Sigma).
Originally Posted by Nick Lappos
...note that the Ct/sigma wants to be about .125 or more at peak FM. Since most high speed helos want to have hover Ct/sigma at about 0.07 to .08, that means they throw away a significant rotor efficiency potential (about 7% thrust at equal power.)
For maximum ideal twist:
Peak FM of 0.8 gives <Cl> of 0.76, or Ct/Sigma of 0.127
Hover Ct/Sigma of 0.075, or <Cl> of 0.45, gives FM 0.7.
So hovering wide chord blade rotor operating at 88% of what the "skinny blade" ideal could achieve.
Seeing Dave's data leave's me more confused, but i'll wait until Ct/Sigma = 0.12 data.
Mart