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Old 20 May 2011, 04:25   #11
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Reality of a rib's compass

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Originally Posted by biffer View Post
i've never been able to get a magnetic compass to perform that well on a rib, there are too many things to influence it in such a small area, if you have cable steering it will affect your compass when there is a larger amount of steering cable in the console at full lock, bags in the console that weren't there when you swung it, keys on the dash, throttle controller in gear(nearer the compass), the list goes on, you get it as near as you can and it will all change next year when it will need correcting again, i hate to say this being old school but electronic's are the way forward and a compass on a rib should be used for general reference
That, of course, is the reality. I use the compass as back-up also.
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Old 20 May 2011, 04:28   #12
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Good advices here, there is no easy cure. Even in professional shipping, magnetic compasses is an issue as various cargoes, change in draft of the vessel, type of cargo among others affects the result. That's one of the reason why gyros was invented, and magnetic compasses are used only as an emergency back up.

One option is to do only a rough deviation table, without any adjustments to the compass. That's easy to update over time. I have never sailed a smaller boat with a accurate magnetic compass and when You needs it most, the heading is going anyway +-15 degees
On paper charts its easy to note the magnetic compass reading when You are doing a specific route in controlled conditions. That is then useful data, but only for that specific course.
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Old 20 May 2011, 09:40   #13
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In the great plan of things gps is a relatively new addition to boating, we had decca before that but for a long long time it was only available to commercial craft and was notorious for errors but we still got around without electronic nav.
Steering to a compass is a skill and needs practising when the vis is reasonable to gain confidence cos you really won't believe the compass when the fog drops. Of course we rely totally on gps these days, even yachtmaster exams use gps as the main mode of navigation and why not, time moves on and we should use what is available and not cling to the past....however when the gps fails (and one make we had was very good at failing as soon as it got a little damp and foggy) or your wiring lets you down (surely not ) then the compass should still be there needing no electrickery, albeit a few brain cells, to work it.
Thats why on advance courses we have folk steer to the compass at night with the gps switched off (well the one they can see ).
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Old 20 May 2011, 11:57   #14
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Originally Posted by wavelength View Post
Of course we rely totally on gps these days, even yachtmaster exams use gps as the main mode of navigation and why not, time moves on and we should use what is available and not cling to the past....however when the gps fails (and one make we had was very good at failing as soon as it got a little damp and foggy) or your wiring lets you down (surely not ) then the compass should still be there needing no electrickery, albeit a few brain cells, to work it.
Indeed. It's the same in aviation. General Aviation has embraced GPS as primary navigation, allowing vertical separation minimums to be halved in European Airspace. Lately GPS has been approved for precision approaches. Even the big boys use GPS as a primary interface to their flight management systems. I guess it's good enough for us...
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Old 20 May 2011, 12:27   #15
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Originally Posted by wavelength View Post
Thats why on advance courses we have folk steer to the compass at night with the gps switched off (well the one they can see ).
i hope it's in front of the helm
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Old 20 May 2011, 17:11   #16
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Thanks to all for your views. Seems there is no quick fix...

regards
Jan

PS
Alternative to compensation 'd be to remove again the external speaker of the VHF, but that's no option.
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Old 21 May 2011, 10:07   #17
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Quote:
i hope it's in front of the helm
the compass is
but the 2nd fixed gps is on the back of the helm's seat
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