richard dewey rvyc / uvic swiftsure.org web site race info currents during race rdewey@uvic.ca

Richard DeweyRVYC / UVic

Swiftsure.org Web Site Race Info Currents During Race

rdewey@uvic.ca

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 Deweyrdewey@uvic.ca