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Old 20-09-2013, 08:05   #1
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Staying on Course (without GPS)

Here is a question, although a beginner one.

Lets assume you are on a sailboat that for whatever reason does not have GPS on it, we only have paper charts.

So we've worked out our course to steer, with the waypoint not being visible from our fix, ie its beyond our visible horizon.

Now, given we need to go upwind, how do we stay on course while tacking/zig-zaging? Since we would never be going in a straight line, always at an angle to the actual course, how do we make sure we actually get to the endpoint? Do we keep track of our courses and distance as we tack and keep plotting them?
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Old 20-09-2013, 08:13   #2
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Re: Staying on course (without GPS)

Constant plot with heading, distance through the water, tidal set and drift or currents and leeway all plotted on each leg. All corrected for variation and deviation.

Getting to the waypoint is aided by going past known points and taking bearings... in open water you have to aim well to the safe side of any objective.

If you want to get there before the bar closes it is well to aim up wind up current of the harbor mouth.

Many of us managed this way for 20 years or more before the GPS. I could still do Southampton to St Malo and back by dead reckoning...I actually did it as recently as 6 yrs ago...completely flummoxed my American crew.
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Old 20-09-2013, 08:14   #3
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Re: Staying on course (without GPS)

You might need a good course on piloting and navigation. The simple answer is, you keep a dead reckoning plot on your paper charts and do regular running fixes taken from known charted objects or features. Chuck
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Old 20-09-2013, 08:20   #4
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pirate Re: Staying on course (without GPS)

You time your tacks... 2hrs whatever.. looking aft should give you a rough idea on %age of leeway, decent charts will give you approximate drift speed and direction... tie this in with average speed through water and you should be able to maintain a reasonable DR every tack..
You may well find on one tack or the other a need for it to be extended by half hour or so to compensate for leeway and drift to maintain the desired general course.
Hope your good at math..
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Old 20-09-2013, 08:24   #5
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Re: Staying on course (without GPS)

Quote:
Originally Posted by de0xyrib0se View Post
Here is a question, although a beginner one.

Lets assume you are on a sailboat that for whatever reason does not have GPS on it, we only have paper charts.

So we've worked out our course to steer, with the waypoint not being visible from our fix, ie its beyond our visible horizon.

Now, given we need to go upwind, how do we stay on course while tacking/zig-zaging? Since we would never be going in a straight line, always at an angle to the actual course, how do we make sure we actually get to the endpoint? Do we keep track of our courses and distance as we tack and keep plotting them?
Pop quiz!!!!
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Old 20-09-2013, 08:24   #6
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Re: Staying on course (without GPS)

Thank you for the answers guys. I figured there would be a lot of plotting to be done.
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Old 20-09-2013, 08:25   #7
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Re: Staying on course (without GPS)

Depends on the distance. If it's a multi-day affair, you can just maintain a DR plot and then re-adjust per tack.

A plotter is constantly taking your position and then showing a bearing towards your destination. You just do the same thing. Figure out where you are (dr plot, noon site, visual, whatever) every few hours and plot your course on a chart with a ruler and protractor.
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Old 20-09-2013, 08:26   #8
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Re: Staying on course (without GPS)

Call the Coast Guard and ask them where you are.
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Old 20-09-2013, 08:27   #9
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Re: Staying on course (without GPS)

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Thank you for the answers guys. I figured there would be a lot of plotting to be done.
If it's a long passage, in between reading, napping, and clipping your nails some chart work is a nice distraction.
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Old 20-09-2013, 08:28   #10
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Re: Staying on course (without GPS)

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Call the Coast Guard and ask them where you are.
We know where we are, question is how to get to where we want to
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Old 20-09-2013, 08:42   #11
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Re: Staying on course (without GPS)

Maybe this will help

Plotting positions and courses; Learn how to place yourself on a nautical chart to know where you are.
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Old 20-09-2013, 08:51   #12
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Re: Staying on course (without GPS)

You need to take a boating course where they will teach you how to plot. What do you think we did long be for GPS. 15 years ago there was no GPS and eletroinc charts. I also used the radar as a mean to plot if we were close enough to land compared to the charts. Save having to plot so often. In the fog I still compare the radar to the GPS/electroinc charge.
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Old 20-09-2013, 09:03   #13
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Re: Staying on course (without GPS)

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You need to take a boating course where they will teach you how to plot. What do you think we did long be for GPS. 15 years ago there was no GPS and eletroinc charts. I also used the radar as a mean to plot if we were close enough to land compared to the charts. Save having to plot so often. In the fog I still compare the radar to the GPS/electroinc charge.
The problem is courses these days do not focus much on plotting. Sure, most will teach you basics.
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Old 20-09-2013, 09:10   #14
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pirate Re: Staying on course (without GPS)

Interesting post...
Gave a good idea of those who know navigation and could answer the question... and those who rely solely on their CP's..
Also explains why many abandon ship when the engine/elec's gone... no juice for the CP... where's that frickin EPIRB..
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Old 20-09-2013, 12:47   #15
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This depends on where you are.

If headed to a coastal waypoint, I line up to fixed points. In an ideal world they are one behind the other i.e. a gunsight. Or they can have an angle on the bow. I then keep the same relative angle. Think of walking through a door

If no landmarks are available one can use visible star angles, but you have to change stars. I have seen this done, but would not even try to explain it
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