Question
As a boat without speed sheets on to move forwards she initially drifts side-ways. Is this action considered a change of course under rule 16?

Answer
A boat moving from a stopped position to sailing in a direction would not be considered to be changing course, except when she went from having sailed backwards to sailing forwards or vice versa. (See Match Racing Call MR B 7).

In order for rule 16 to apply, there would need to be two boats and the right-of-way boat would need to be changing course.