Well, let me start with a lame observation, so that my humble pie tastes a little better: my assertion was that no sideslip or yaw is necessary for dihedral to give roll recovery. This, I think, is true. However, when I consulted my favorite aerodynamics reference, Model Aircraft Aerodynamics, by Martin Simons, I discovered that sideslip actually makes a bigger contribution than the "projected area" mechanism, at least for larger roll angles. According to Simons, when the roll input disappears ( aileron deflection, wind gust, etc. ), the dihedral results in a sideslip toward the lower wing, which raises the effective AoA of the lower wing, and lowers the AoA of the higher wing, which gives higher lift for the lower wing, which acts to correct the roll. Let this be a lesson to me!

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