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Thread: Three bridge fiasco 2023

  1. #11
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    My favorite method is having both boat speed and SOG on the seahood displays. That and looking around tells me how the current is affecting me. It still gets confusing when you're going backwards, which seems to happen in this race!

  2. #12
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    A year or so ago I met Richard Reitmeyer somewhere. I forget where. After a race? Before a race? Then he showed up at an SSS race deck, then at Richmond Yacht Club for dinner. That Richard: He likes boats. Seems he doesn't have one at the moment, so he has agreed to serve on the Singlehanded Sailing Society Race Committee with whoever else shows up.

    Last week, when I posted about SF Bay currents and tides, Richard sent this information to me via email. And now I'm sharing it with you. If I had not mentioned Richard I would have seemed smart. But it's not from me. It's from Richard. I'm still waiting for my little book.

    Suggested resources and ideas about SF Bay currents for your consideration. Use at your own risk. Not for navigation. Past performance is no guarantee of future results. If symptoms persist, see your doctor. Etc.

    * Allen Edwards, the man behind L-36.com, is probably best known for his work on creating and publicising soft shackle techniques, but he also has easy-to-use tide maps. See https://l-36.com/sf_current_new2.php?menu=9

    * At a whole bunch of specific locations, NOAA has tide prediction coefficients (viz the table of them at the back of the book). The next step up from that is to generate harmonic coefficients and do all the math NOAA would do -- but present it in a friendly chart. David Flater did that in the 1990s with a program called XTide, and even better it's still hosted out of the biology department of the University of South Carolina. XTide has coefficients from NOAA and even coefficients back-calculated from people's submitted data. See http://tbone.biol.sc.edu/tide/ and pick a site like "Red Rock .1 E, San Francisco Bay, California Current" and then fiddle with the options at the bottom of the page. It will do graphs if the site's not too busy, but the tabular form is less impacted by server load and also more compact to put on a cheat sheet if you're doing a lot of locations. You will want the "Current" locations and, if possible, locations in bold type.

    * Those are predictions. Predictions are not reality, and so it's also nice to look at what is actually happening. The only place that takes measurements and then shows them vs their predictions is NOAA Ports. There's not many data collection stations, and they're down a lot of the time, but it's the only realtime data availble. You'll see 18 hours of lookback and 6 hours of lookahead in the summary for SF bay at https://tidesandcurrents.noaa.gov/po...de=allcurrents and you can 24 hours of lookahead (and often get wind too) at individual buoy locations like https://tidesandcurrents.noaa.gov/po...mode=composite. If you'll trust "beta" features, you can get predictions in advance at https://beta.tidesandcurrents.noaa.g...hresholdvalue= --- so that's perhaps the most trustworthy data you'll get for 3BF currents near Southampton Shoal.

    * The NOAA has an interesting way of bouncing high-frequency radar off the surface of the water and then inferring what the surface currents are doing from the wave patterns. This used to be combined with 48 hours of forward-looking predictions from a big computational fluid dynamic model, forced to fit the latest observations. Sadly, that's been broken for a while at https://tidesandcurrents.noaa.gov/hfradar/ but fingers crossed it comes back at some point. But you can use the following for seeing "what happened yesterday?": https://tidesandcurrents.noaa.gov/of...rrents_nowcast -- which is still a CFD model. Or https://cordc.ucsd.edu/projects/mapp...1km_h&ol=&cp=1 for something closer to the raw data.

    * Competitive racing can be pretty expensive, but World Sailing is trying to level the playing field by combatting apps or sites that could cause damage to a boat's chocolate candy capacity. You can use them before you start racing, but after the prep signal it might be best to turn them off and look at the sites above. See Rule 41 "A boat shall not receive help from any outside source, except ... c) help in the form of information freely available to all boats;" and World Sailing Case 120, specifically:

    Information for which a fee has been paid or that is not easily obtained by all boats in a race is not “freely available.” Examples are information supplied only to those boats that have paid a subscription or other fee, and information whose source is obscure.

    Good luck out there!

  3. #13
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    Quote Originally Posted by BobJ View Post
    My favorite method is having both boat speed and SOG on the seahood displays. That and looking around tells me how the current is affecting me. It still gets confusing when you're going backwards, which seems to happen in this race!
    Boat Speed on a knotmeter versus GPS SOG is a good comparison for telling what is going on with current if the knotmeter is clean and calibrated. But beware of tidal charts, harmonic current predictions, NOAA surface radar, and other hi-tech predictors. Actual current direction and timing can be wildly different from predictions, especially in the winter with river runoff.

    The best current predictor is to use your eyes. Blue water is seawater flood, brown is fresh water ebb. Look at the bow wakes on buoys. Are other boats in your vicinity "making or losing trees." Wind against tide creates chop. Wind with the tide makes smooth water. Oh, sorry, practicality takes the fun out of theorizing in advance, which is what 3BF is about. Carry on.
    Last edited by sleddog; 12-23-2022 at 01:52 PM.

  4. #14
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    Quote Originally Posted by sleddog View Post
    Oh, sorry, practicality takes the fun out of theorizing in advance, which is what 3BF is about. Carry on.
    Yep.

    But one year, Dirk Husselman beat all the other 3BF singlehanders by a country mile. After the race he shared his secret for deciding which way to go around the course. "I always go the same way around. I figured I'd get lucky eventually" (or words to that effect).

  5. #15
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    I like Skip's approach. Sometimes the tide is strong enough that the water " boils" and looks like there is no wind, but it's current.where often there is plenty of wind. Water color tells it all as well. I like using the visual, when it's available.

  6. #16
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    Quote Originally Posted by Philpott View Post
    * Competitive racing can be pretty expensive, but World Sailing is trying to level the playing field by combatting apps or sites that could cause damage to a boat's chocolate candy capacity. You can use them before you start racing, but after the prep signal it might be best to turn them off and look at the sites above. See Rule 41 "A boat shall not receive help from any outside source, except ... c) help in the form of information freely available to all boats;" and World Sailing Case 120, specifically:

    Information for which a fee has been paid or that is not easily obtained by all boats in a race is not “freely available.” Examples are information supplied only to those boats that have paid a subscription or other fee, and information whose source is obscure.
    Richard is right of course, but one wonders how level the playing field is when you can use a $35,000 instrument system but you can't use an $8 app, especially when the instrument system has wi-fi to keep its files updated, including the tide and current overlay for the chartplotter. The times, they are a-changin'...

    But no worries, Loomis has no instruments and the iPhone will stay in a baggie.
    .
    Last edited by BobJ; 12-24-2022 at 03:33 PM.

  7. #17
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    Over 10 years ago I wrote a web page that can do the hard starting math (time and distance) for the 3BF for you. It still works! Just select your PHRF and stare at the screen.

    It runs entirely on your phone, I swear no data is harvested, but you must give your web browser permission to see your phone location. The startline points are pretty approximate as I haven't surveyed anything recently. The line calculation extends the line to infinity so it is easy to test before the race and sight the actual line vs. the prediction. If you test it while walking around at home (a good idea) keep in mind the distance shown is to this infinite line approx N-S not the GGYC. The start times match up with last year's PHRF table and many years previous, so I assume it will be good this year too.

    I'll see you out there, I'll be crewing for my dad on his F-27 Seabird as usual.

    https://www.holdentechnology.com/mike/3BF_2014.html

    You should definitely try it before race day to see how good your phone GPS is (just walk around outside).

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  8. #18
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    Jan 2010
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    Thank you, Mike Holden! You are THE BEST! I have already forwarded your FIASCOMETER to my crew, who has been given responsibility to manage this wonderful technology. He will test it by walking around his yard in Oxford Mississippi. I'll let you know how well your HoldenTechnology.com works from so far away. Oh, this is so fun!

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