Steve Firth wrote:

If one is motoring in a calm on a flat millpond then there is an
apparent wind equal to the speed of the boat from dead ahead. Hoist a
sail and you can make no use of that wind, agreed. However that only
applies if you maintain the same course. Now do what any sensible bloke
would do and adjust your course to make use of the wind as well as the
motor. You now have wind in your sails and you still have an apparent
wind. If you look at the force triangle there is still a component from
the apparent wind.


But since you are creating this apparent wind yourself from your own
forward motion, it will come from dead ahead wherever you go. Changing
course will not bring the apparent wind aft so that you can use it.

Jeannette