Forgot one thing
Just to add one thing after reading Mad (Flt) scientists and Big Grecians post, i would have thought that the angle of bank and weight would be largely irrelevant as Vmca is a speed that will give directional control with a bank angle of 15 degrees. However if you reduce below Vmca in a 15 degree angle of bank then surely you'd also be below Vr and Vref and therefore directional control is the least of your worries.
If you're below Vmca in a turn, then you are going down, and going down rapidly.
Again, I'm more than happy to be shot down in flames if I am wrong.