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Old 19 August 2006, 16:14   #11
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So what you are saying Dave is that it will work when my boat is upside down?
Don't really know now I've read it again Maybe that bottle of red has something to do with it now! But let me know if you try it
Dont know why there is all this problem with compasses - we run down the leading lights in and out every trip and they are bob on, and our stock courses we use for nav excercises all work fine with the compass. Being an old(ish) git, before even Decca was available for little boats we ran to our fishing marks on a compass and watch in all sorts of visibility. Mind you it was worth it then cos there was something left in the sea to catch !
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Old 19 August 2006, 16:20   #12
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Cheers Dave-those compensation instructions are most useful.

Do the speakers not have magnets in anymore on vhf then? New one on me!
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Old 19 August 2006, 19:07   #13
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Originally Posted by Nos4r2
Do the speakers not have magnets in anymore on vhf then? New one on me!
Yes course they do. They are sheilded by another magnet that sits in the base of a can that in-tern is glued over the speaker coil magnet.

All clever stuff!
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Old 19 August 2006, 19:47   #14
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I did wonder-I was trying to work out if it was possible for them to be using a pair of electromagnets working against each other instead of one fixed and one coil but I guess it'd be too costly.
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Old 20 August 2006, 06:02   #15
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Nos everybodys getting very technical, BUT are you likely to do a channel crossing or navigate 20miles or more out to sea.

JUST TO CONFUSE THE ISSUE THERE ARE 3 HEADINGS FOR NORTH BEING TRUE / MAGNETIC AND GRID, SO WHEN YOU ARE FOLLOWING THE COMPASS WHICH IS MAGNETIC AND PLOTTING ON TO A CHART (WHICH IS GRID) YOU ARE ALWAYS GOING TO HAVE A DEVIATION, FOR CENTRAL SOUTH COAST THIS IS 3 DEG WEST, WHICH IS 300M'S AT 1 MILE.

So i guess if your not travelling at 50 knots plus over 20 miles or more out to sea with no visual references DONT WORRY. buy a GPS
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Old 20 August 2006, 06:13   #16
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No, it's there for emergencies. I've got a GPS onboard but were it to decide not to work at the wrong time then I could be right in it.

I was a yottie for years so I guess thats why I was so worried about deviation. Never used one before on a RIB-with 20 deg variance while moving anyway it's good enough for finding NSEW.
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Old 20 August 2006, 17:31   #17
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Dont know where the grid came from?? Are you talking O.S. there
but variation here at the moment is around 4 degrees west.
Our leading lights here are 156 degrees (two big lighthouses in transit)- anything on the chart is in degrees true, it has to be cos magnetic varies-hence variation. Working on "variation west compass best and variation east compass least" that gives us 156 plus 4 = magnetic course of 160. And it is- bang on with all three compasses.
The only other set of numbers you could have would be "degrees compass" as opposed to just magnetic which you would get after taking into account the compass error (deviation) from a deviation card and I've never had need of one on a rib or any small boat for that matter. Just on yachtmaster practical and theory on bigger boats!
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Old 21 August 2006, 04:19   #18
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thanks for correcting me wavelength. im afraid im still talking to flying terms i did not know sea charts did not read from grid.

this forum is designed to educate, i have been educated.

Blackpool has 4 degrees, southampton has approx 3 degrees variation.
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