Join Date: Dec 2004
Location: Alameda, San Francisco Bay
Thanked 60 Times in 59 Posts
Rep Power: 13
Re: Advice on SF Bay summer sailing
The skipper of Yachtsea said that he couldn’t see the surfers initially as the height of the swells blocked his view. Had he known that waves were breaking there, he said he wouldn’t gone inside the South Tower.
A Quick Guide to Sailing the Bay in Summer:
“Be as far west as you want to be before 2PM” – Richard Spindler (Editor, Latitude 38)
Everything you have read so far will help you understand the Bay’s summer weather patterns. Your biggest consideration is your boat’s and your own capabilities. There are multiple races held every Saturday and it is a good idea to understand where thier “usual” turning marks are and to recognize boats who are racing (if you see a whole lot of boats close together, going in the same direction, chances are it’s a race). Nothing worse than being on Port and twenty or more J boats closing in on Starboard ("Frogger" anyone?). If you look out across the Bay and see boats either on the Marin or Oakland side and nothing in the middle – chances are it’s blowing nuclear in the “Slot”.
A Little info on tidal currents: Something like 90% of all the river water in California and Oregon south of Grant’s Pass drains through the Bay – That’s a lot of water! Thanks to PG&E, Irrigation, Salmon, Delta Smelt and the Sierra Club, the water flowing through the Delta is consistent throughout the summer and the current prediction models are pretty accurate (I use “Local Knowledge” and “Tide Tool”). This extra water flow makes the ebbs about two times stronger than the floods. These can easily flush a small boat out the Golden Gate. Become proficient at calculating current set and you will be OK.
We have two tide cycles a day on the Bay. The tidal currents are out of phase with the tides themselves. At the Golden Gate, there still will be major current even when it is a high or low tide for the following reasons: Assume that there is a rising tide at the Gate. The flood migrates up the Bay, into San Pablo, Suisun Bays and then into the Delta. When the Gate is at high tide, water is still rushing into the Bay in order to create the high tide further upstream. Sacramento and Stockton are about the only places I know of where slack current happens close to high or low tide. When the tide ebbs, an interesting phenomena happens. Part of the ebbing river water splits off and heads south joining the flood in the South Bay. That’s right, there are times in each cycle where one side of the Bay is flooding and the other is ebbing. Look for tide lines and the color of water. Brown is ebbing river water (except when it is flooding the South Bay) and clear, green is ocean water which flooding in from the Gate (which also floods into the South Bay). Yes, it is complicated. A fun field trip is a visit to the Corps of Engineers Bay Model in Sausalito. Even more fun is to hear one of Kame Richard’s tidal current lectures and demonstrations.
How do you sail in this stuff? Understand and pay attention to the current tables. Read the "signs" of current. The tide tables themselves are only interesting if you go into really skinny water. Generally speaking, the deeper the water, the more current you will experience. The San Francisco side of the Bay Bridge has lots more current than the Oakland side. There are no “boundary layers” on bridge piers or buoys. The current will take you right into them, or Alcatraz, Red Rock, Angel Is… Really work on identifying and calculating current set. Look for changes in color and tide lines. For maximum current relief, you need to be in 10 feet or less depth.
One of the other reasons that makes the South Tower such a joy is that the South Bay can be ebbing south of the Tower when it is flooding north of the Tower and vice versa. Also, the ridge in the Presidio forms an natural amphitheater which “pulls” some of air in from the Gate. Racers know that you can sometimes ride a lift if you are really close to the shore alongside Chrissy Field. This lift becomes a wind shift at the South Tower and is responsible for the “demon” If you are wanting to go outside the Gate, your best strategy is to sail over to “Hurricane Gulch” on the Marin side and short tack along the cliff on the north. Better wind and an eddy usually forms there. Returning, we like to be at center span on Starboard Board. This gives us a straight shot at the finish line at either GGYC or StFYC. Any closer to the South Tower and we have two gybes in that last mile.
Good luck and have fun sailing the Bay!
Last edited by GeorgeB; 05-31-2012 at 09:44 PM.