compass

With GPS the compass has sort of become an ornament on the helm.

How accurate is yours?

During the remodel I had to remove two small magnets mounted near my compass. Now I don't know where the heck they were mounted. So this weekend I plan on compensating my compass.

I broke out the Chapmans and started to read. This looks like it may take the whole weekend.

SD

Mine are both "ok" but I do not have a compensation chart.

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Your compass reads the same as your GPS?

accounting for variation and deviation.

SD

Last summer I was on a friends boat.* We were crossing Rosario Straight in a dense fog and 2-3' seas.* Not rough, but enough to require constant helm input. * He doesn't have an autopilot, and I was at the helm trying to maintaing a course towards Deception pass.** The GPS could tell me if I was generally on the right course, but the update rate was too slow to steer by.* Enter the compass. It was the only thing I could use as a point of reference to keep from wandering all over the water.* It didn't have to be accurate, I just had to find a heading that put me on the right GPS heading.*

Around here, given the currents,* there's no need for a compass to be accurate, but it still needs to be stable.

bobc wrote:
Around here, given the currents,* there's no need for a compass to be accurate, but it still needs to be stable.

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* * * ** My feelings, exactly.

SeaHorse II wrote:bobc wrote:
Around here, given the currents,* there's no need for a compass to be accurate, but it still needs to be stable.

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* * * ** My feelings, exactly.

*Good point. *I make a habit of recording headings and minutes to and from places I go often, just in case I should find myself without any electronics or line of sight. *I don't know whether my compass is accurate or not, but the headings and minutes of travel on those headings are consistent (I check them from time to time), and my compass is of great comfort to me that way. *Of course....I do live in the Bermuda Triangle, so.....


-- Edited by healhustler on Friday 2nd of September 2011 11:42:55 AM

My autopilot compass and GPS are consistent and accurate on my steel boat.* Nevertheless, both my boat's regular magnetic compass as well as the binocular compasses read only between S and SW regardless of the boat's direction.* (The engine is behind and to the left of the compass.)* The boat's builder said not to bother compensating the compass before a year has passed.

skipperdude wrote:
With GPS the compass has sort of become an ornament on the helm.

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Well, no it hasn't, depending on how you run your boat.* For a number of reasons we removed the autopilot from our boat shortly after acquiring it.* So we hand-steer it.**I do as Bob stated earlier--- the two GPS plotters we have are great but they tell you what's happened, not what's happening.* Granted, the update rate is very fast but nevertheless it takes a moment or so for a course deviation to be apparent on the "noodle."** So I hold our course with the compass which reacts instantly to any deviation from heading.* I use the GPS to confirm that the compass heading is correct and I hold that heading until I see on the GPS that a current change has rendered that compass heading invalid at which point I make the necessary correction and then hold*the new compass heading.

But the reality is I use all three indicators, the noodle on one chart plotter, the bearing-course-steering info on the other plotter, and the compass to hold the basic course.

Another*nice thing about steering with the compass is that because of where it's*mounted, looking at it automatically puts the water out ahead of me in my field of view.* And since all I'm doing is keeping two very obvious white lines aligned, I'm not*focusing my eyes on a screen all the time with all its detail that can easily suck you in to the point where you forget to watch what's in front of the bow.

My wife uses the compasss in the same way, too, when she's driving but not as much as I do.* She seems to prefer using the noodle to hold her course.

markpierce wrote:
.......Nevertheless, both my boat's regular magnetic compass as well as the binocular compasses read only between S and SW regardless of the boat's direction.* (The engine is behind and to the left of the compass.)* The boat's builder said not to bother compensating the compass before a year has passed.

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*Why wait a year to adjust your compass?*

Larry M wrote:*Why wait a year to adjust your compass?*

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* * * * * Ditto!* :confuse: *

Larry M wrote:
Why wait a year to adjust your compass?*

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*I's expecting you fellas to tell me.

Our compass is largely ceremonial. In the Neuse and in the ICW, I don't see the use. We tried it when we first bought her, but as much as she wanders, it's about pointless to me.

Your compass is only ceremonial untill you have an electrical "issue" then it saves your ass in the fog/dark. It is more important inland than offshore! Go west young man is the get home activity on the east coast.

I wondered about the waiting one year to swing compass myself. What is different in one year that would affect the compass?

"Waiting a year to swing the compass."
Maybe the manufacturer thinks new owners will be adding "stuff" ( stereo, speakers, ornaments etc.) which might affect the compass?

Steve W

Mark:* Get a hold of your builder and put the question to him.

Steve wrote:Maybe the manufacturer thinks new owners will be adding "stuff" ( stereo, speakers, ornaments etc.) which might affect the compass?

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* * * * That's about the only reason I can think of and a good one too! I must say, however, that "swinging" your compass is no big deal. There are a lot of shops around that will do it for you.

SeaHorse II wrote:Steve wrote:Maybe the manufacturer thinks new owners will be adding "stuff" ( stereo, speakers, ornaments etc.) which might affect the compass?

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* * * * That's about the only reason I can think of and a good one too! I must say, however, that "swinging" your compass is no big deal. There are a lot of shops around that will do it for you.

*

Since Mark's compass always reads between S and SW, my bet is the*compass has some magnetic interference that must be found and dealt with before he or someone can "swing"*his compass.*

Larry M wrote
Since Mark's compass always reads between S and SW, my bet is the*compass has some magnetic interference that must be found and dealt with before he or someone can "swing"*his compass.*

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******** Good point, Larry!

******* In fact, the interference may not only be magnetic.

Although I think a good, properly calibrated compass is cheap insurance, my experience with the Azimuth 1000 * has been stellar. So easy to calibrate, agrees with the GPS info & is extremely stable when holding a course in almost any sea condition. If you have a catastrophic electrical failue, (no GPS, etc.) then a calibrated ship's compass & card is mandatory. (IMHO)












-- Edited by SeaHorse II on Sunday 4th of September 2011 12:00:34 PM

Larry M wrote:
Mark:* Get a hold of your builder and put the question to him.

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*I'm planning on that.* Thought we'd all "stew" about it and come up with an answer first.

Larry M wrote:markpierce wrote:*The boat's builder said not to bother compensating the compass before a year has passed.

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*Why wait a year to adjust your compass?*

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According to Bowditch:
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*"After a ship (boat) is launched, over time, it will lose some of *its original magnetism.** The magnetism of the ship's (boat's) various structures will change as a result of cruising, vibration, and aging".
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"If compass error is not allowed for (corrected), the compass will be reduced from a precise navigation instrument, to a rough and frequently unreliable approximation".
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"With a 10 degree error, a vessel may be set off on it's intended course by 1 mile for every 5.7 miles run. This could have serious consequences, especially when making landfall in conditions of poor visibility".

GPS is great, but if craps out on you, it's nice to know you can rely on your own accurate compass navigation.***** KJ



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-- Edited by KJ on Sunday 4th of September 2011 12:30:00 PM

KJ wrote:*

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According to Bowditch:
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*"After a ship (boat) is launched, over time, it will lose some of *its original magnetism.**...

*I had suspicion that some "degaussing" could occur over time.

I've not used my compass very much but when I have I'm grateful It's stable. All the compasses Iv'e used before have been almost impossible to read/follow/use. Not so w the compass on my Willard and I do think it's the original. I don't know if it could be improved upon. Sometimes I wonder if the damping and reaction rates should be idealized to each boat as they all have different motion. I went half way across Dixon Entrance in a thick fog (six miles offshore) steering by the compass and found it was easy to do. It was frustrating w the GPS. The compass required constant attention but as long as my attention didn't wander (and my attention tends to do so) steering w the compass Willard provided is safe and easy to do. But most of the time I don't even even look at the GPS compass ....just the chart and "noodle" (I think cursor) as Marin calls it. And on rare occasions when the cursor or noodle goes over land on the chart I'm not worried as I can see that I'm not.

That first year of navigation could be a tough one.
What ever happened to re swing the compass? An argument not to correct in the first year is hardly good seamanship. A post accident marine inquiry would be hard to defend with "My builder told me I didn't have to swing it for the first year" An unseaworthy vessel can be cause for insurance denial.

I keep my compass calibrated, if for no other reason than to estimate the wind direction.

Sailor of Fortune wrote:
That first year of navigation could be a tough one.
What ever happened to re swing the compass? An argument not to correct in the first year is hardly good seamanship. A post accident marine inquiry would be hard to defend with "My builder told me I didn't have to swing it for the first year" An unseaworthy vessel can be cause for insurance denial.

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*I do have several other "compasses" aboard (flux-gate, GPS, binocular, and handheld) and radar and don't intend to leave the sight of land in the near future.


-- Edited by markpierce on Sunday 4th of September 2011 10:32:31 PM

markpierce wrote:
*I do have several other "compasses" aboard (flux-gate, GPS, binocular, and handheld)...

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*Mark:* If you put the handheld compass in the area that your regular compass is installed, does it just read S-SW?* I think you said you binoculars also only read S-SW.* If they all read the same, you have some magnetic interference some where.

Larry, I intend to test the portable magnetic compasses in different areas of the boat.* By the time the Coot gets out of the boatyard and I go on my two-week transatlantic cruise (Norwegian Sun), it will be well into October before the tests.

Just make sure that Norwegian Sun has a good, working, magnetic compass on it before you ship out!
Bon voyage
Steve W.

Thanks, Steve.* The Norwegian Sun has been refitted since my 2009 Alaskan voyage (the one where heavy fog cancelled entry into Tracy Arm) on her.* Trusting the revisions didn't mess up its compass.

Entry into Tracy and Endicott Arms on a clearer day in 2011.* Ended up in Endicott Arm since Tracy was overfilled with other cruise ships.* This was second time advertised destination was cancelled!

Sailor of Fortune wrote:
That first year of navigation could be a tough one.
What ever happened to re swing the compass? An argument not to correct in the first year is hardly good seamanship.

Click to expand...

*
While a boat is being built it will acquire "induced" magnetism from the construction itself, as well as the local magnetism of the area of the yard. This induced magnetism is not part of the boats "permanent" magnetism. A deviation table could be in error if established while the foreign induced magnetism is still influencing the boat. *It can take some time for the boat and the compass to become adjusted to the area in which the boat will be finally used.
The skipper or navigator should be checking the deviation every time the boat is used and record the deviation at different headings. *The locally induced magnetism, i.e., sitting in her own slip for a period of time, will become part of the boats permanent magnetism. Eventually the table should stabilize.
If you rely mainly on your compass for navigation, you should have a professional "swing ship", which should give your compass a pretty high degree of accuracy which then should be quite reliable. Back-up compasses should be used for rough estimates of position, never for precise navigation. ***

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-- Edited by KJ on Monday 5th of September 2011 08:00:06 PM