106 seamanship secrets
Max EbbMax Flood Max FloodMax Ebb6 hrsSlack Slack Slack Slack Slack6 hrs 6 hrs 6 hrsA typical day of tidal currents at a U.S. East Coast location where each fl ood and ebb lasts 6 hours.
From the National Ocean Service’s 2008 tidal current tables for the Atlantic Coast of North
America, we learn that the aft ernoon maximum current in Boston Harbor will be an ebb at
1611 (Daylight Savings Time) on August 2, and that current speed is 1.4 knots. Slack water at
Boston occurs at 1204 and 1834.
Another Method to Use Tidal Current TablesNow let’s fi nd something about the tidal currents at Neponset on the aft ernoon of August 2, 2008.
In the table of diff erences in the back pages of the tidal current tables, we fi nd that slack (Minimum
before Flood) at Neponset is 25 minutes earlier than in Boston Harbor on August 2, 2008. Th e
following slack (Minimum before Ebb) is 45 minutes later than in Boston Harbor. Maximum
fl ood current is 32 minutes earlier than Boston and maximum ebb current is 35 minutes later
than Boston. Th e speed ratio columns show maximum ebb and fl ood currents are both 0.4 times
as strong as in Boston Harbor.