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Old 18-09-2009, 15:12   #1
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Compass and Charts

So I'm doing the electronics on my boat,a 63 ft steel shrimp boat conversion, and I'm looking at compasses. Some books stress how important they are and say to get the best you can afford, but with the redundancy of electronic compasses and GPS systems, how often do you really rely on a free-standing compass? I've got a Raymarine E120 with a Coursemaster autopilot.
What do you guys use and recommend?
Also, how detailed are your paper charts And how often do you pull them out?
Sorry about these dumb questions, but I'm a few days from pushing off and know nothing.
Don't worry, she's real slow and loud, a DD with straight exhaust, so I won't be sneaking up on you. You'll hear me for a good hour before I come over the horizon.
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Old 18-09-2009, 16:22   #2
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Lorenzo, I have a good compass on my boat, I must say I almost never use it but I would not want to be without one I've been caught in a thick fog it is amazing how quick one can get completely disoriented. It is unlikely that you'll be caught in fog and have the electronics go out at the same time but maybe in a thunderstorm they could go out and have low visibility in heavy rain.
I almost always have paper charts at the helm for the area I am cruising I keep a marker on the chart and move it along the course to have a position if anything goes wrong with the electronics.
I'm glad you are progressing well, my wife and I will be up your way Monday morning and try to drop by. I'll phone you this weekend.
Steve
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Old 18-09-2009, 18:15   #3
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how often do you really rely on a free-standing compass? .

Never.

Except when in the really dense early part of a squall where the boat has been knocked off its course and the Auto Pilot turns itself off... it happened 2 or 3 times across the Pacific... when I drag my bum on deck (half asleep usually) its only the compass that can orientate me.

So I would always have one... but I wouldn't be spending $1,000 on it!

At anchor to see where the sun is going to rise / set or where north is....

At night mine is always covered as the red light is too bright... could eve cut it off and use a torch on the few occasions I look at it.

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Old 18-09-2009, 20:26   #4
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Just like MarkJ…I use a magnetic compass as an emergency backup orientation, rather than a precise navigational tool. So no need to buy and install an expensive one. Just get one that is made well and will stand up to the environment.

Modern boats are filled with electronics so compass deviations are often both large and variable, depending on what is turned on (especially on a steel trawler)

The trick to making the most of your magnetic compass is to have a “Mag Heading” column in your Log right beside “True Hdg” so that you record both readings at the same time, whenever you make an entry.

That way, if lightning or water ever wiped out navigational electronics, you have developed within your log a reliable “as used” Magnetic reference for the various headings, based on your actual compass installation.

Personally, I never set sail without charts that I have already prepared with safe parallel index lines and Bold course lines for coasting, showing safe distances to clear hidden dangers that I have highlighted and circled to make them jump right out at me.

If you don’t know how to use Charts and prepare them to verify what your electronics are telling you…., then buying them is a waste of time.

Then again, where we cruise, I don’t have the luxury of calling for help if I run aground!
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Old 19-09-2009, 03:56   #5
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... The trick to making the most of your magnetic compass is to have a “Mag Heading” column in your Log right beside “True Hdg” so that you record both readings at the same time, whenever you make an entry.

That way, if lightning or water ever wiped out navigational electronics, you have developed within your log a reliable “as used” Magnetic reference for the various headings, based on your actual compass installation...
It’s called a deviation card. The boat’s compass should be swung to prepare card’s for both “electronics on” and for “electronics off” (ie: as in lightning damaged) conditions.
The deviations may be substatially different (or not).
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Old 19-09-2009, 08:39   #6
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It’s called a deviation card. The boat’s compass should be swung to prepare card’s for both “electronics on” and for “electronics off” (ie: as in lightning damaged) conditions.
The deviations may be substatially different (or not).
Well, its another thing that doesn’t need to be done. Heading is relative.

As we all have backups for our GPS and the US won't turn the system off, then the compass need never be used solo therefore its heading is only relative.

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Old 19-09-2009, 14:25   #7
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I use the magnetic compasses(1port-1stbd) almost exclusively and paper charts. The charts are in a chart bag in the cockpit if I'm in unfamiliar waters. I use the GPS as a backup. At night I establish my heading, pick a star to head for, and turn off the compass lights. Most think I'm crazy, girlfriend agrees, but I ain't been lost yet. My boats have minimal electrical systems so deviation from that source is minimal as well. Dave
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Old 19-09-2009, 14:49   #8
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It’s called a deviation card. The boat’s compass should be swung to prepare card’s for both “electronics on” and for “electronics off” (ie: as in lightning damaged) conditions.
The deviations may be substatially different (or not).
I understand swinging a compass to make deviation cards, but on small steel boats there is not enough space for compensating magnets to stabilize the field, so I mistrust them.

By using the ship’s log to continually update the magnetic compass error from true heading and doing a few tests without any electronics turned on I can get a pretty good historical feel (and record) for the amount of error on each heading.

Where it becomes interesting is if you have been in a marina for a while and there has been welding going on, but then by always logging, that change becomes apparent and you can adjust accordingly.

Whenever I can, on a trip, I will confirm her true heading on cardinal points, just to see how the mag is behaving.
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Old 19-09-2009, 18:44   #9
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Q - how often do you really rely on a free-standing compass?
A - often enough to justify a high grade compass at the helm, a hand-bearing one in the pocket, and a spare one in the locker,

Q - how detailed are your paper charts?
A - as detailed as called for by the kind of sailing we do,

Q - how often do you pull them out?
A - we do not, they are already on the table when we set off,

Hugs & good luck,
barnie
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Old 19-09-2009, 21:11   #10
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We went to West Marine and got a good compass and binoculars with a gift certificate we've been sitting on, but still haven't figured out the charts. I've been looking at the NOAA site and downloading 8 by 11s and it's obvious that a big chart is the way to go. We're going to be leaving La. and heading east and south down the coast of Fl. and then up the east coast and I really don't want to buy 60 charts at $20 each for areas I'm just passing through and not coming back to.
What's the solution?
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Old 19-09-2009, 22:17   #11
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I see two solutions: develop computer skills or visit cruiser flea markets and buy 2nd hand charts.

ciao!
Nick.
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Old 21-09-2009, 07:48   #12
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Q - how often do you really rely on a free-standing compass?
A - often enough to justify a high grade compass at the helm, a hand-bearing one in the pocket, and a spare one in the locker,

Q - how detailed are your paper charts?
A - as detailed as called for by the kind of sailing we do,

Q - how often do you pull them out?
A - we do not, they are already on the table when we set off,

Hugs & good luck,
barnie
Yep. I plot DR on the chart and check it against the GPS. If something fries, it probably won't be the compass and log
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Old 21-09-2009, 08:05   #13
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I really don't see the advantage of plotting DR when the satellites are up & running, other than something to pass the time.

We plot GPS positions on the chart and regularly check if the compass is indeed indicating the same course as the computer indicates it should, that's all. If something fries, you have all you need and start DR from there on. You have a much better start than just DR this way because the past GPS positions reveal factors like current and drift which normally are just estimated guesses for places without accurate current info.

The compass used often aboard is the one in the binoculars. The steering compass is used for course corrections like "go 15 degrees to port" or when hand steering without visible point to steer to. But we don't hand steer much...

cheers,
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Old 21-09-2009, 08:19   #14
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I would never go to sea without a steering compass - it's the only instrument on the boat that works in real time. Add to that a light on it for night use.

I have had experience of electronics failures - I sail professionally as a delivery skipper and I would not take a boat without a steering compass.
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Old 21-09-2009, 10:00   #15
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Well, we do not plot the DR either, unless there is a reason to do so (somehow can't remember the last time we did). We plot the fix - the GPS fix. We also check the GPS fix against other data (like e.g. the depth or a bearing) - once because it is an old habit of mine not to rely on one method of positioning, twice - because I still sometimes make mistakes when transferring from electronics to the paper.

But I think it is OK to go just by electronics (GPS and plotter) if this is what the type of sailing dictates on the day and if we have a way of effectively and timely working backwards and retro fitting the DR / sun fix should anything go terribly wrong.

b.
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