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Old 09-05-2008, 19:50   #1
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Timezones & Navigation/Logbook

Hello all, this is my first post, so please go gently on me.

My wife and I have decided to navigate the world, which leaves lots of open questions. Many of the smaller details bother me and I was hoping some of you experts can help me put some of my concerns at bay.

This specific question is for bluewater cruisers, but it may have merit for others.

The first such question I have is about timekeeping. I have been reading on people's blogs that they traveled X miles in 24 hours, but as you move between timezones how do you qualify what 24 hours is?

Do you all just leave one clock on UTC and then at 5 PM UTC every day you make a log entry so you can calculate distance and chart where you are at?

Or do you choose to keep the timezone you were in until you arrive at your destination? For instance if you left San Francisco for Hawaii, would you just leave your clock on Pacific time until you arrive?

How does all this work in regards to charts, tide tables, weather information? Are all of these in local or some kind of standardize timezone.

Thanks in advance, we are both excited to set sail in a few years after we find our sea legs.
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Old 09-05-2008, 20:18   #2
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In the Olden Days, they would reset the ship's clock every day to Local Noon, by taking a sun-sight. Sailing west, the noon-noon time will be longer than 24 hours, and sailing east it will be shorter. How much longer or shorter depends on speed and latitude.

What I have done when sailing from California to Hawaii and back is to fix the ship's time to California time. We do have to shift the watch schedule as we travel because of the changing sunrise and sunset times.

This may not be the best way to do things, though. I believe that most people do adjust the clock when they cross a timezone, and I may try it that way when we do our next Hawaii trip this summer.

My actual ship's clock stays on UTC. Printed tidetables are in local time. Weathercharts are in UTC.
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Old 10-05-2008, 03:12   #3
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Good question that - one more thing that never occured to me

I have not done the distances that many others have which would involve serious changes in Time Zone (not done the saili into the sunset!)..........but quite used to moving between Jersey and nearby Europe (mainly France) who are always on a different time by an hour......what I do (and copied from my Father since I was a kid - doesn't make it "right", just that it works for us) is to keep the boat on "Home" time for ease of Navigation purposes (if it ain't ever changed, no need to forget ), done by not changing the ships clock (apart from GMT to BST / daylight saving in Spring and Autumn), but personal time pieces watches / alarm Clock! get changed to local time when we arrive.......and this seems to work fine........but then again our local Navigation aids (Tidal Stream Atlas and Tide book) are also in local time which probably helps explain why this works well.

However I would mention that neither of us has gone down the road of all singing and dancing integrated electronic navigation (old style GPS that gives a heading to follow and a position in numbers that get plotted on a chart)......so I dunno whether "the boat" would always need to be on current time for more modern Nav gear?
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Old 10-05-2008, 06:20   #4
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Aaron,

24 hours is still 24 hours, regardless of what time zone you're in or how many time zones you've changed. If it's really necessary for you to track your 24-hourly distance-made-good, then I suggest you pick a UTC reference for those calculations, like noon Zulu. You can always leave your GPS set in UTC, but I recommend changing all the other clocks on board and shifting watches, meal times etc at appropriate intervals. Even on a fast boat this won't be more frequent than every two or three days. The gradual change allows your body's internal clock to adjust, so you won't be "jet-lagged" on arrival at your destination.

Kevin
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Old 10-05-2008, 08:38   #5
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Typically one takes 3 sun shots a day Morning Twilight, Noon, and Evening Twilight. As one progresses east or west about, local apparent noon changes at a rate of 1 hour per 15 degrees (=360*/24). How quickly ones local apparent noon changes depends upon how far north or south of the equator one is, how quickly ones yacht is traveling and on what course. If one were on the Equator and traveling dead west at 7.5 knts, ones geographic position would advance 180 miles in 24 hours (absolute time). However, having moved westerly, ones local apparent noon would have advanced 12 minutes on Greenwich time. Accordingly, the time of ones "noon Lat" may be more, or less, than 24 hours on Greenwich.

Cheers,

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Old 10-05-2008, 09:04   #6
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Old 10-05-2008, 11:16   #7
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Quote:
Originally Posted by Lodesman View Post
Aaron,

24 hours is still 24 hours, regardless of what time zone you're in or how many time zones you've changed. If it's really necessary for you to track your 24-hourly distance-made-good, then I suggest you pick a UTC reference for those calculations, like noon Zulu. You can always leave your GPS set in UTC, but I recommend changing all the other clocks on board and shifting watches, meal times etc at appropriate intervals. Even on a fast boat this won't be more frequent than every two or three days. The gradual change allows your body's internal clock to adjust, so you won't be "jet-lagged" on arrival at your destination.

Kevin
I always assumed all of you sailors were sticklers for time and you liked the vanity of tracking your 24 hour progress. Your point is valid, 24 hours is 24 hours regardless of timezone. If we shift a hour forward, I should just move our 24 hour progress to that time (11am one day, 10am the next).

Shifting schedules makes sense as it is what everyone does when the fly, why not do it when on the water? I am sure I will adhere to this when we hit the water.
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Old 10-05-2008, 11:50   #8
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I always assumed all of you sailors were sticklers for time and you liked the vanity of tracking your 24 hour progress.
There may be other things for sailors to be vain about, but tracking the boat's miles made good over a 24 hour period is not one of them.

Good passage planning requires coming up with an estimate of where you expect the boat will be, day by day. Having a passage plan with expected noon positions will allow you do download GRIB weather files for each of those daily positions, so you'll have some idea of what to expect, weatherwise. This may cause you to revise your passage plan.

Tracking distance made good from noon to noon (or midnight to midnight, if you prefer), comparing it with your passage plan, and making necessary adjustments to the plan, is one of the basic navigation tasks performed each day while at sea.
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Old 10-05-2008, 17:40   #9
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I always assumed all of you sailors were sticklers for time and you liked the vanity of tracking your 24 hour progress.
Only Joyon, Macarthur et al. I'm hoping to take a laid-back approach when cruising.

Quote:
If we shift a hour forward, I should just move our 24 hour progress to that time (11am one day, 10am the next).
Now I'm going to have to be the stickler - if you shift an hour forward, then it should be 10am one day, 11am the next.

If you're just doing San Fran to Hawaii, then there's really nothing wrong with switching to Honolulu time once you're past the Golden Gate. Since it's only a 2 or 3 hour change (depending on the time of year) it shouldn't mess with your circadian rhythm. Not recommended for longer passages, unless having lunch when it's dark and enjoying sundowners at sunrise tickles your fancy.

Kevin
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Old 10-05-2008, 19:38   #10
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Thanks all who responded, one of the things I think I am hearing is that I should keep two clocks on the ship.

I should run my logs by clock a (UTC perhaps), use this as a way of tracking my progress. I am also hearing it is smart for the crew to roll the clock with the timezone changes so you do not get jetlag (sealag?).

That was my plan and the more people respond to this thread, the more it makes sense.

I am planning on sailing through the South Pacific, so keeping a clock on par with the different time zones and keeping all of my crew (aka me and my wife, I don't think the cats care too much about time zones) on that clock makes the most sense. I should then take a constant reading at noon UTC every day so I can track our progress.

I am a engineer by trade, so I may be over engineering this...
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Old 10-05-2008, 19:56   #11
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There may be other things for sailors to be vain about, but tracking the boat's miles made good over a 24 hour period is not one of them.

Good passage planning requires coming up with an estimate of where you expect the boat will be, day by day. Having a passage plan with expected noon positions will allow you do download GRIB weather files for each of those daily positions, so you'll have some idea of what to expect, weatherwise. This may cause you to revise your passage plan.

Tracking distance made good from noon to noon (or midnight to midnight, if you prefer), comparing it with your passage plan, and making necessary adjustments to the plan, is one of the basic navigation tasks performed each day while at sea.
HUH!~!


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Old 10-05-2008, 23:25   #12
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You can create whatever local time you want. Just put a notation on the chart when you change your local time and note what time that was in Zulu time. Do your watches by local time and your celestial in Zulu.
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Old 10-05-2008, 23:44   #13
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HUH!~!


I think the point is that it is not vanity to keep track of your daily run. I agree, of course.
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Old 11-05-2008, 01:52   #14
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What I have done for the last 25 years on numerous ocean passages is simply this:

You Log Local time based on your longitude and always make a notation at the top of the page of that Time Zone.

When you pass a Time Meridian heading West or East, you apply that I hour time change (add or Subtract) at the Midnight Watch by splitting it between the two watches, so that it is only a half hour longer or shorter and no one complains.

As Midnight is usually the start of a new page in the Log book, your first notation is that you are in a new Time Zone and have advanced or set back the clock One hour

This works well for bigger crews but for just a few, whatever feels comfortable
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Old 11-05-2008, 04:22   #15
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I set half the clocks in my house ahead an hour, and the other half back an hour Saturday, and spent 18 hours in some kind of space-time continuum loop, reliving Sunday (right up until the explosion).
I was able to exit the loop, only by reversing the polarity of the power source on exactly e*log(pi) clocks in the house, while simultaneously rapping my dog on the snout with a rolled up newspaper.
Accordingly, I will be in to work on Monday, either late, or early.
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