Module 07 · The tidal stream
The heart of the plan: the stream read from the atlas as vectors, one triangle for a short leg and one for a long one, the time at each waypoint, the stream band and the crossing.
How the lesson starts
Sam's five legs from Dover to Boulogne-sur-Mer, steered as they are drawn, each heading the same as its track. The red dashes are where the boat really goes: the stream of the Dover Strait carries it off every leg, and it ends 6.5 miles from Boulogne.
This chapter is that difference: where the stream comes from, how much of it each leg gets, and the course that cancels it.
On the crossing leg the bow points at right angles to the traffic (Rule 10), and the line on the chart is where the stream carries you.
On an arrow, or between
The marker works it more finely — each arrow weighed by the inverse of its distance — and accepts any estimate within its margin. You are not asked for that sum.
What you practise inside
- With and without
- At a point
- A short leg
- A long leg
- The crossing
- The times
- Wind
- The stream band2 exercises
This is a preview. The lesson itself is interactive: you work through it step by step, and every answer is checked as you go.