ORIGINAL: britbrat
Actually, anhedral destabilizes straight-winged aircraft at high angles of attack. It shifts the center of pressure forward, thus having the effect of moving the C-of-G aft & increasing the nose-up trim force. Conversely, dihedral shifts the AC rearward, reducing nose-up trim forces.
I did not know this. Isn't it also true that geometric anhedral partially inhibits spanwise flow, increasing effeciency to a point?
edit: the part I didn't know was that anhedral moves CP forward.