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Thread: magnetic field

  1. #11
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    Default Re: magnetic field

    Scientists believe that the Earths magnetic fields have flipped in the past.

    Some believe that Global warming is a precursor to the flip.
    No one knows for sure what will happen.
    Vic

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  3. #12
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    Default Re: magnetic field

    It's a good job that we all have GPS is everybody heading to Scotland would end up on the Isle of Wight
    Rob Page R855150 - British & Commonwealth Shipping ( 1965 - 1973 ) Gulf Oil -( 1973 - 1975 ) Sealink ( 1975 - 1986 )

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    Default Re: magnetic field

    For anyone wanting to study navigation the old and trusted way , it is not something you can pick and choose with and jump in with whatever knowledge of different aspects you may think you have.i would advise anyone who wants to really have an understanding of to start. The old way and first and read about the principles of navigation first. This entails the world we all live in and it’s relation to the planets and stars. Little things like what is latitude and what is longitude. And a host of other things the likes of the three horizons that exist before you ever start with celestial navigation. For terrestrial navigation which consisted of plane or parallel sailing , followed by Mercator sailing which was good for up to 600 n.m. , you have to know the principles behind it. Shipboard navigation only became more adaptable the more you used it and it came second nature to you. Today you have GPS and no matter how much people say they also can navigate the old way as were told at school , I have my doubts they would be very competent at it, judging what I observed. It’s only a matter of time before it disappears , as like the old sailing ships there will be no one to teach it. You have to want to know navigation to learn it, and most of us are lazy and take the easy way out. I don’t decry anyone for that as tend. To do the same myself. A large amount of learning as regards shipping is self learned or commonly known as experience , soon it will be computers are the only ones with any knowledge. And even then it will all depend who put that personal knowledge there, just the same as Google who so many rely on. Cheers JS
    Last edited by j.sabourn; 11th January 2019 at 11:39 PM.

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    Default Re: magnetic field

    #10... The old magnetic rule of like poles repel and unlike poles attract, always reminds me of today’s sexual laws, how could they ever pass a permissive law like homosexuality.? JS

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    Default Re: magnetic field

    When you read about the sea passages made by lifeboat of the past. All one needed was a sextant to get your latitude once a day when the sun was at its highest altitude , local apparent noon. Subtract the angle from 90 degrees and apply your suns declination. You would have a good idea of this to within a couple of minutes as would have been using it daily on the ship before being castaway., your longitude of course you could not get as required a chronometer and almanac. So would be an estimated one. Steering due east or west would be the obvious choice if you knew what land stood in the way. JS.....
    Last edited by j.sabourn; 12th January 2019 at 03:51 AM.

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    Default Re: magnetic field

    Anyhow when Cappy opened this post with the earth shattering news that variation as applied to magnetic compasses was not doing what it was told. This has brought out climate change , and various aspects of what could be to some, the sandwich board man walking the streets with the placard the end of the world is nigh. All it takes now is some lecky to throw in the pot maxwells corkscrew rule, and we”ll all be scrambling for the lifeboat , with I hope a sextant and if remember grab the almanac and wel”ll get a more accurate latitude. A few cases of beer might come in handy as well. Cheers JS

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    Default Re: magnetic field

    Pole variation has been going on since Cocky was in the egg. Scientists will tell you that at one time what we now know as north was actually south.

    Good friend in Texas involved with all manner of flying told me some time ago about the problem of aircraft arriving at airports off line with the runways.
    They had been non auto but it was not picking up the variation in polar variation.




    But of course we all know Cappy has a problem, he relies on Mary to stick her leg out of the car window to see which way the wind is blowing, this would cause anyone to go off course.
    Happy daze John in Oz.

    Life is too short to blend in.

    John Strange R737787
    World Traveller

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    Default Re: magnetic field

    We're about 11.5 degrees east here.. Not being a good teacher I've struggled to explain to some crew why the compass is different to the GPS and gyro readings.

    Haven't looked at a chart for a while but I think it decreases by a little under another 1/10 a year, so in about a 120 years I wouldn't have to have the conversation!

    SDG

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    Default Re: magnetic field

    It’s a good post really by Cappy, makes people think, and is good for a nautical site, as takes us right back to the beginnings of mans journeys on the oceans of the world. Most of us on here were brought up with it in all manners of ships , standing on the wheel with the steering board in front of you with the true course written with chalk, togerher with the magnetic cpurse , variation and deviation in some ships written on it , course to steer. On the advent of gyro , also the gyro course to steer, and also the gyro error. The gyro was never smack on, nearly always had a couple of degrees error , usually called high or low. Could be east or west . Where Keith’s east least, and west best. Could be used as well to remind one. A compass error by celestial observation was mandatory on most ships at least once a watch, weather permitting. Today don’t think too much stress is put on this , with the advent of GPS and all the other aids. Is history today to what it used to be. Like most lighthouses around the British Coast they stick a racon on and don’t worry too much about the lights anymore. Very short sighted I think. But we were seamen and had to work with what our Lords and masters decided was sufficient. Until of course something goes wrong.Then the culprit is usually the lack of safety observed by the operators of vessels, well there has to be someone or something to blame doesn’t there ? Cheers JS
    Last edited by j.sabourn; 12th January 2019 at 06:55 AM.

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    Default Re: magnetic field

    Quote Originally Posted by j.sabourn View Post
    It’s a good post really by Cappy, makes people think, and is good for a nautical site, as takes us right back to the beginnings of mans journeys on the oceans of the world. Most of us on here were brought up with it in all manners of ships , standing on the wheel with the steering board in front of you with the true course written with chalk, togerher with the magnetic cpurse , variation and deviation in some ships written on it , course to steer. On the advent of gyro , also the gyro course to steer, and also the gyro error. The gyro was never smack on, nearly always had a couple of degrees error , usually called high or low. Could be east or west . Where Keith’s east least, and west best. Could be used as well to remind one. A compass error by celestial observation was mandatory on most ships at least once a watch, weather permitting. Today don’t think too much stress is put on this , with the advent of GPS and all the other aids. Is history today to what it used to be. Like most lighthouses around the British Coast they stick a racon on and don’t worry too much about the lights anymore. Very short sighted I think. But we were seamen and had to work with what our Lords and masters decided was sufficient. Until of course something goes wrong.Then the culprit is usually the lack of safety observed by the operators of vessels, well there has to be someone or something to blame doesn’t there ? Cheers JS
    I know of at least 2 unlimited ABs trained and certified here in the US that didn't know what Cardinal marks were nor that the IALA bouy system is different (reversed) in other parts of the world.

    Also recall a 'lecture' from a local captain about bad weather - the other crew member present was an unlimited mate who has sailed the world, he and myself having seen some pretty crap weather looked at each other with the expression saying this guy has no idea of what bad weather is. I'm sure I've seen nothing compared with some here, but my 25-35 ft North Sea weather was being compared to his 8-10 ft of horrendous weather... Another AB friend recently experienced the Bay of Biscay in bad weather, he is a competent, reliable and down to earth guy but admitted to being never more scared in his life.

    With respect I'm young and inexperienced compared with most posters here but close on 50 I feel very old and experienced around so many crew and officers these days. In fact on one of my last UK trips as Master when the mate was doing the safety brief I was reading the crew list and at ? 43 I really was the 'Old Man' by about - minimum of 20 years!

    The experience of the past is being lost way too fast.

    SDG
    Last edited by Shaun Gander; 12th January 2019 at 08:15 AM.

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