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-   -   Get a fix without using the chart (much)? (http://www.sailnet.com/forums/general-discussion-sailing-related/44851-get-fix-without-using-chart-much.html)

davidpm 07-09-2008 10:59 PM

Get a fix without using the chart (much)?
 
Most of my "new" ideas are either common practice that I just never heard of before or a dumb idea. So what do you think about this idea?
The problem:
You are sailing in home waters and you can see a known mark but for whatever reason no other marks are visible and you want a fix without GPS. The solution of course is a running fix but you donít want to draw on your chart because these are home waters and keeping your chart readable is important.
You happen to have a few plotting worksheets in the nav kit that are just blank pieces of paper with a compass rose and a scale photocopied on an 8.5 by 11 inch copy paper.
So this is what you do to get a pretty good fix without having to draw on your chart.
<DIR><DIR>1. Write down your course (150 degrees), time 0900, speed 6 knots, bearing to known mark 180 degrees.
2. On your worksheet you draw a line for the course (150 degrees). (Where doesnít matter, just make it the correct course.)
3. Draw another line representing the bearing to known mark (Where doesnít matter as long as it intersects the course). This represents your start point.
4. Put a mark on the bearing line to represent the known mark. (Where on the line doesnít matter just make it look about right and it has to be on the bearing line.
5. Decide how long you are going to maintain your current course lets say one-half hour. Multiply your time times your speed ( .5 x 6 = 3 miles)
6. Use any scale, 1" = 1 mile, 1.5" = 1 mile, it doesnít matter, and mark off the distance you are going to travel, in this case 3 miles from the start point along the course to new point, the DR point. Luckily our plotting worksheet has a couple of scales printed on the side for easy reference or you can use any handy scale.
7. Draw a line through the DR point parallel to the bearing to the known mark. This is the "Advance bearing".
8. All this takes about minute or less. Now all you have to do is relax for the predetermined length of time, in this case one-half hour and stay on course.
9. At the end of the time take a new bearing to the known mark.
10. Draw a line on the worksheet at the new bearing so that it intersects the known mark and the advance bearing line.
11. Using the same scale you used to advance the first bearing, find the distance from the known mark to the point where the advanced bearing and second bearing cross.
12. Now it is dead simple. On the real chart hold any straight edge, even an envelope, at the new bearing so it goes through the mark. Just do an eyeball distance, on my chart one thumb is one mile, from the mark along the bearing and you can put your finger on your position without marking up your chart.
</DIR></DIR>This process is 95% from the book a standard running fix. The wrinkle is that I believe you can use this process on a blank worksheet and not mess up your chart.
What do you think?

sailingdog 07-10-2008 12:57 AM

Or you could use a clear cover overlay on the chart, a grease pencil, and a Post-It note sticky arrow for the boat location.

Omatako 07-10-2008 06:15 AM

Or use a soft enough pencil that erases easily (4B) and don't make it too sharp. Then a simple running fix is a walk in the park.

I haven't got the patience for the sort of exercise outlined, truth be said, I never even had the patience to read it all :)

Andre

davidpm 07-10-2008 09:46 AM

What I'm really looking for is some kind of sixth sense to just zen a location. I've tried the overlay and 4B pencil trick and it works some times but here in the sound it is often damp if not wet on board and often it made a mess. Maybe I just haven't found the right pencil yet.
Not sure the worksheet idea is a keeper either but it has two advantages.
No mess on the chart and a record of what you did if you want to check yourself.

As far as complication goes it is just a standard running fix, just at the end the distance from the mark is taken off a scale. Any running fix is a lot more complicated to describe than to do.

sailingdog 07-10-2008 10:10 AM

One major problem with doing it the way you're suggesting is the plain piece of paper doesn't show you the rocks, shoals and other navigation hazards. So, while you may have some idea of how far you've run and such, it doesn't really help in terms of good navigation and avoiding the hazards without having to copy it over to the chart.

soulesailor 07-10-2008 07:32 PM

you could add a little ease into your process by using sheets of maneuvering boards. these are for radar work, mostly, but have angles and scaled distances on them already. buy a pack and photocopy them forever.

sailaway21 07-10-2008 08:03 PM

When I sailed as Second Mate we always carried a version of Scotch tape that you can write on with a pencil. For charts that were used often and the DR track was the same, which is commonly the case on a merchant ship, I'd lay out the course on the chart, confirm it with the Master, and then lay a couple of strips of that tape over it side by side. They were just enough for you to plot your fix and easily erasable afterwards.

davidpm 07-11-2008 09:15 AM

Quote:

Originally Posted by sailingdog (Post 339580)
One major problem with doing it the way you're suggesting is the plain piece of paper doesn't show you the rocks, shoals and other navigation hazards. So, while you may have some idea of how far you've run and such, it doesn't really help in terms of good navigation and avoiding the hazards without having to copy it over to the chart.


So true. I have an advantage in local waters however of putting a gel coat barcode on every underwater obstruction.

sailingdog 07-11-2008 09:57 AM

At least you'll know which one you hit that way. :)
Quote:

Originally Posted by davidpm (Post 340142)
So true. I have an advantage in local waters however of putting a gel coat barcode on every underwater obstruction.



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