richard dewey rvyc / uvic swiftsure.org web site race info currents during race [email protected]
TRANSCRIPT
Tidal Heights and CurrentsTidal currents “flood” in from the ocean on a rising
tide and “ebb” out to the ocean on a falling tide.
Surface Slope Drives Tidal CurrentsCurrents flow down-hill, from higher to lower
water.Racers needn’t worry too much about tidal
height, except when anchoring or rock hopping.Local current patterns are determined by the
channels, straits, and sounds in response to these ocean and basin “sieches”.
Mean flows in June: surface water exiting Salish Sea (¼-½ knot), some of this is in the tidal current table values. Weak (≈¼ knot) in 2015
Deep vs Shallow Tidal Currents
Deep water has more inertia, will ride “up-hill” to stop, reversals are lagged/delayed.
Shallow and boundary layer flows have more friction (turbulence), can be slower & will stop and reverse sooner.
Lateral convergence or vertical shoaling can result in accelerated flows.
Points of Sail in a CurrentAlthough the speed of the current is low
compared to the wind (hopefully), a few knots of current over time will make a difference.
Avoid currents on the windward quarter.Heading into a tide, try to keep the tide under
the leeward bow, (lee-bow).A current under the lee side always better than
on the windward side: apparent wind and lift.
Tidal Current StationTidal Height Station
Reading Tidal Height Tables
PDT=PST+1Victoria
(CHS)
Tidal Height: May 23 – 25, 2015
Tidal Current StationTidal Height Station
Reading Tidal Current TablesPDT=PST+1
Race Passage
1 knot = ~0.5m/s
+ flood- ebb
Tidal Currents: May 23 – 25, 2015
Foreman, et al, 2004
Tidal Currents: May 23 – 25, 2015
Good Luck!At Swiftsure.org
Race Info Currents During Race(please save PDF files, don’t print )
Richard [email protected]