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  #21  
Old 05-31-2012
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Re: Advice on SF Bay summer sailing

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Originally Posted by puddinlegs View Post
No, the surf inside has nothing to do with the south tower demon. The STD is more about swirling winds, etc as you leave the lee of the south tower coming back into the Bay. Typically you're under spinnaker tooling along thinking life is good and you're close to being home, then WHAM!!!! About 30 seconds or so of a large puff that knocks the unaware and complacent on their ear. Been there, done that as have many many others. Latitude 38 has had a number of great pictures over the years of the south tower doing its thing to boaters.
Ahhh, think I met him a couple of weekends ago. There was one near Richmond too, where the Windex was saying we were on port tack, but the sails were backwinded as if they wanted to be on starboard.
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  #22  
Old 05-31-2012
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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.
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  #23  
Old 06-01-2012
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Re: Advice on SF Bay summer sailing

The thing to remember is to be vigilant. There is nothing the same about the wind and water they're dynamic. In the morning the breeze usually comes out of the North and then moves around to the West as the day kicks in anywhere from 5 to about 18 MPH. Around 1:30 you best be already reefed back. That's when the breeze can turn to wind (Wind is technically about 32 MPH). I have seen it pick up to 40. Of course the weather reports can give you clues but don't rely on them. I have ignored them plenty of times and had a wonderful sail when all the believers stayed home because of promises of rain.
Better to hug the North shore going out, beware of breakers (and surfers) on the South shore going in or out. The ships are annoyingly quick and most dangerous, the ferries and pukes can be as well so count on giving way regardless of law in some circumstances.
On mellow days stay in the gap toward the mouth where the real breeze is. On rough ones, avoid it. Richardson bay gets you out of the wind for an anchor or lunch. 'Cyclone alley' (by Sausalito water treatment plant) can slow you up as the breeze comes at you on all points. This can make getting back to the gap a pain.
It seems odd that green sailors and many wind-boarders like to hang out beneath the bridge so avoid that when crowded. Be advised of a rock to the West by NW of Alcatraz.

I have never seen a better sail than SF bay. Sailed it often with the MMBA over the years. Maybe I will again and see you out there.
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  #24  
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Re: Advice on SF Bay summer sailing

I had no idea that the currents would persist long after high or low tide. Are there many accidents happening due to sailors being pushed into bridges, islands, and rocks? What are your thought processes as you near one of these areas? How do you judge the effect of the current visually?

I guess I had better hang out S of the bay bridge for a while. It's hard to see all the boats out in the slot and not think "THAT! is where all the fun is! I'm going out there." I won't be getting near the golden gate anytime soon. This Sunday I'll be out practicing reefing and heaving to.

About wind forecasts... I've found and book marked most of the web based pages and installed just about every sailing/wind app on my phone and tablet.... I understand they all pull data from the same general set of computer models. I'm confused about how much trust I can put in what they're telling me. My surprise that day was in part because sailflow was calling for 9-12 and in reality it was more like 25. As a newbie I would have not gone out if I'd known wind would be like that. Now... I'm glad I did because it was a good lesson and helped get me over my fear of higher winds.

What about the various models? WRAMS 2km, WRAMS 8km, NAM 12km, and GFS 0.5... it appears that most sites and apps are using NAM 12km or GFS 0.5. But when you compare them to WRAMs... the predicted speed difference is huge.... and I'm wondering is there is a particular model that you trust more? why?
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  #25  
Old 06-02-2012
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Re: Advice on SF Bay summer sailing

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Originally Posted by jblumhorst View Post
Watch the currents -- learn to read the chart in the back of the tide book. On a day with big tides, the currents around Treasure Island can wreck you in dozens of places on the Bay. For example, the towers on the Bay Bridge or the rocks at the east end of Treasure Island. Currents are a big deal here, and an important part of local knowlege.

Fair winds,
Judy B
Sailing windy SF Bay
Could you tell me more about the rocks at the east side of Treasure Island? I can see what look like some abandoned piers on the chart (the structures sticking out with dotted lines). Are those what you are referring to, or something else? I do give those a wide berth. The chart gives no indication of how far under the water those are, btw.
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  #26  
Old 06-02-2012
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Re: Advice on SF Bay summer sailing

The rock is on the SF Bay chart.
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  #27  
Old 06-02-2012
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Re: Advice on SF Bay summer sailing

Quote:
Originally Posted by MarkSF View Post

Quote:
Originally Posted by jblumhorst View Post
...
Watch the currents -- learn to read the chart in the back of the tide book. On a day with big tides, the currents around Treasure Island can wreck you in dozens of places on the Bay. For example, the towers on the Bay Bridge or the rocks at the east end of Treasure Island. Currents are a big deal here, and an important part of local knowlege.
...
Fair winds,
Judy B
Sailing windy SF Bay
Could you tell me more about the rocks at the east side of Treasure Island? I can see what look like some abandoned piers on the chart (the structures sticking out with dotted lines). Are those what you are referring to, or something else? I do give those a wide berth. The chart gives no indication of how far under the water those are, btw.
Quote:
Originally Posted by puddinlegs View Post
The rock is on the SF Bay chart.
I'm looking at the sfbay chart and I see a submerged rock on the west side of Treasure Island, but not the east. What coords do you see/know of one at?

Do you mean the shoal at 039 49.7391 N 122 21.4354 W? I suppose that might be a rock, but even at the lowest tide it would be well under the keel of any boat I am likely to sail.


Last edited by groggy; 06-02-2012 at 06:10 PM.
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  #28  
Old 06-02-2012
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Re: Advice on SF Bay summer sailing

I agree, I looked carefully at the chart and the only submerged rock is on the west side and is 26ft below MLLW.
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  #29  
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Re: Advice on SF Bay summer sailing

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Originally Posted by crstophr View Post
I had no idea that the currents would persist long after high or low tide. Are there many accidents happening due to sailors being pushed into bridges, islands, and rocks? What are your thought processes as you near one of these areas? How do you judge the effect of the current visually?
You can see current on anything that's 'fixed' like a buoy, etc... Seeing current; a great example is the SF city front. There's usually a very clear tide line about 100 yards off the shore. Sometimes the color of the water is even different. A quick rule of thumb is when current is with wind, the water will be flatter. When it's against the wind, it will be rough. One of the reasons the slot has the reputation it does is because you often have a very strong ebb tide against a strong westerly breeze tbrough under the Golden Gate. This is when the washing machine is in full effect. If I remember, the tide usually turns on the shore before out in the middle of the Bay. Your eye can also tell you if you're being pushed left or right from your heading. If you have COG and your true course, you'll also know you're being pushed when these numbers are different. There's more, but that's a start.
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