There are some small versions of a wind generator
which has a vertical axis and comes in several configurations, simple cups or more complex structure which has a technical name I have forgotten. As I understand it these generators may be slow to get going, and not produce much.
The vertical axis idea seems to have a lot of potential on a boat; the axis could be quite long.
Does anyone have practical experience, or used one on a boat; or has someone some enlightening knowledge to impart?