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post #11 of Old 10-12-2007
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Location: Alameda, San Francisco Bay
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Alcatraz can be a real PITA, especially when used as a windward mark (stb rounding) and the tide is in flood. What happens is the west and south ends tend to be a lee shore wind wise as there this a persistent shift in that area due to the shape of the hills in the city. The island and seamount it sits on also deflects the tidal current in the area so the flood hits the north point (Alcatraz Shoal), splits and runs down both sides of the island. On the city side, it has a bad habit of sweeping you towards the island. The back side splits and flushes you straight out to the Olymic Circle and Berkeley. Coupled with the wind lifting to clear the island, you can find yourself in dirty (non-linear airflow) air just when you need the power to offset the current that can run as high as 2 and half kts. Cutting inside the buoy at the shoal is not advisable unless you want to make the cover of the BoatUS magazine like a powerboat did a few years back.

Our race strategy (coming out from the Berkeley Pier start line) is to sail up inside the “cone” then run up the tide line to the south end of the island (port tack). We will go to stb tack when we get headed right at the south edge or sooner if there is a lot of traffic. The water is really deep on this side and you can get real close without hitting anything on the bottom. We will then short tack the city side of the island and will over stand the “natural” layline to the buoy that marks the shoal. With the current set being as much as one third your boat speed and you’re crawling off a very rocky lee shore, you want to give yourself extra allowance as the current set doesn’t give you much margin of error.

On port roundings, we go up the cone, favoring the “slot” side. Again, you need to over-stand the layline on your last port tack as the current doesn’t really flow down the back side of the island but rather straight down the slot to Olympic Circle. So any type of current set will put you straight into the backside of the Island where there is one heck of a wind shadow.

Kinda hard to describe what happens at Alcatraz without the aid of a chart but I hope you can get the “drift”. Alcatraz is no common lee shore.
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