Currents in Vineyard Haven Harbor
The basics:
Think of the moon-produced tidal current coming in from the ocean at Newport. It divides into a stream to the left into Long Island Sound and stream to the right toward Boston. As the Boston Stream gets to Buzzards Bay, some if it flows around Cuttyhunk into Vineyard Sound. The portion going north in Buzzards Bay tries to get through the canal but is forced to rush through the holes in the Elizabeth Islands (Canapitsit, Robinson's, Quick's and Woods) into Vineyard Sound, thus reinforcing the current there. Thus the “flood” is a strong current running east past West Chop. Approximately six hours later, the reverse occurs and there is an “ebb” current running west.
The effect on Vineyard Haven:
The current flooding past West Chop cannot turn the corner toward Vineyard Haven and continues toward East Chop where it is able to turn and run into the harbor along the East Chop shore. This happens about 1.5 hours after the current starts to flood in the sound off West Chop (counterintuitively, the water continues to flow out around East Chop during this 1.5 - 2 hour period). It continues to the Lagoon Pond breakwater at Eastville where some gets around in to the Lagoon, but most makes a right turn and either flows into the inner harbor circling back along the West Chop Shore, or is deflected by the Eastville breakwater and flows out toward West Chop.
When the ebb starts, water pours out of the lagoon and runs out along the East Chop shore. It also runs through the harbor and out the West Chop shore virtually all the time. Look at the floating line to the Vineyard Haven Yacht Club's swim raft and you will notice it is almost always bowed north toward West Chop.
The racing considerations:
When the current is flowing along the East Chop shore, into the harbor and also when it is flooding out, there are back-eddies on the shore and about 100 yards out. They vary and can not always be seen on the surface. Sometimes tacking close to shore has a really helpful effect when heading into a foul current, but generally staying outside of the main stream of current is wise. With the tide flooding in on the East Chop shore, there is a noticeable current going out of the harbor at Buoy A (N6), and as noted above, it is almost always going out at Buoy B (N4).
The current in the sound reaches 3 knots. Tacking out into the flood is a major benefit if headed East, whereas a boat headed West would try to stay inside the current line which is generally just inside the line of the chops. (The line between B {N4} and C {C23a}.) The exception here would be a lee-bow current lifting you to windward.
Caution:
While these comments are basically accurate, a protest that the current during a race was not as described will not be allowed, nor will a protest that one of the general suggestions did not work out.
