It doesn't work too well for currents. In places like the Cape Cod Canal, Hell Gate, and
Wood's Hole the current ramps up to over half strength in the first hour.

Marc wrote:
ratio of tidal rise over time.

Rule of Twelfths
Shape assumed to be sinusoidal
Rise in 1/12ths
1 in first hour
2 in second
3 in third
3 in fourth
2 in fifth
1 in sixth

sometimes used as a rule of thumb for tidal current as well




On Tue, 2 Sep 2003 11:21:19 -0400, "Simple Simon"
wrote:

Since Booby is too ignorant to answer the following question,
I'll throw it out to the group as a whole.

What is the rule of 12ths and how would you use it?


S.Simon - a Captain who's serious about sailing