Each week, we offer you a question about the boat license. To validate your knowledge or to discover unexplored areas. This week, we are tackling a question about tides.
The tidal current
In the Atlantic, at the edge of the coast, the current is linked to the tide. It reverses when the tide rises or falls. But the informed boaters know that the cycle of the tide is not linear. It follows a progressive curve. Thus, at the beginning of the tide, whether it is rising or falling, the change in water height is small. It is only in the middle of the tide, that it is the most important. To finish, at the end of the cycle, by a weak change.
Apply the twelfths rule
It is common to say that the water level evolves according to the twelfths rule .
- Hour 1 1/12th
- Hour 2 2/12th
- Hour 3 3/12
- Hour 4 3/12
- Hour 5 2/12
- Hour 6 1/12th
We can see that at mid-tide, hour 3 and 4, the sea will go down, or up, of 2 x 3/12th. It is at this period that the current will be the strongest.
