The voltage generated as output for a given rpm is a linear function of the number of turns of wire you have in the coil. Adding more turns reduces the cut in speed, and effects the matching of the blades power curve to the alternators output power curve. The current carried in the wire, and the voltage drop from (delta V = I * R) is a function of the resistance in the coil of wire. Thicker wire has lower resistance, and for a given voltage across it, more current will pass through the wire. Also a result is that since the thicker wire has less resistance, for a given current, there is less heat generated in the coil (Power = square of current multiplied by the resistance). Flux or some others can probably explain this much more clearly, but basically by tampering with the thickness of the wire in the cable, and the number of turns, you are changing the operational parameters of the machine. That being said, there is a bit of wiggle room with these things, and other parameters that can be adjusted to help compensate for some types of changes. Still for a first turbine, I for one would recommend following the specifications as closely as possible if you want to duplicate the performance. Rich