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True North?

Discussion in 'General Yachting Discussion' started by JWY, Feb 7, 2019.

  1. JWY

    JWY Senior Member

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  2. wdrzal

    wdrzal Senior Member

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    It's always changing. about ~10 years ago the runway numbers were changed at Ft. Lauderdale Executive airport even though the runway didn't move just the magnetic heading moved enough so it had to be re-numbered.
  3. Oscarvan

    Oscarvan Senior Member

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    The strength is also decreasing. At some point it will be zero and then flip to where your compass will point South. While that happens all the stuff is going to fall from the fridge and the birds will get lost.
  4. Seasmaster

    Seasmaster Member

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    Youse guys are doing it wrong. Don't need no compai. Have GPS, and besides.
    "I'm as constant as the Northern Star.", I say.
    "Constantly in the darkness?", JWY would ask (knowing full well the answer).
    "If you want me, I'll be in the bar"...I retort. . .

    PS. Santa has geo-stationary navigating reindeer!
  5. bayoubud

    bayoubud Senior Member

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    Just read an article about North pole changing position and wondering the same thing. Thinking GPS doesn't care except heading sensor might steer you wrong?
  6. Capt J

    Capt J Senior Member

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    It is always good to swing the compass every year or two. Also, it's necessary if the boat changes geographic areas, such as NY in the summer and FL in the winter as the deviation is much different.
  7. bayoubud

    bayoubud Senior Member

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    Says heading towards Siberia. Uh-ho, does this mean when longitude is to the east/west it become latitude? My scientist neighbor received some recognition years back for calculating the North pole wasn't where it was reported to be. I will ask him about this next time we talk.
  8. Seasmaster

    Seasmaster Member

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    When I was sailing in the US Merchant Marine, we swung ship every year AND after the shipyard. For the yachties, I figure it's probably a good idea to do the same - especially the super-yachties with metal boats. When the ship fitters start replacing and bending metal. That changed the ship's magnetism and deviation. In the plastic boats, I figure the metal beer coolers may have more effect!! (unless you did a "re-power") LOL

    And for Cap'n J: I think you meant to say "variation" not deviation. (just a gentle "nudge":)
  9. JWY

    JWY Senior Member

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    Don't call Capt J a deviant - it will start a whole long thread! Ok, I had to do something to try to make peace - hoping humor will help.

    I know about the recommended schedule for swinging a compass in general, but I was asking specifically if perhaps all compasses need to be swung now because of the "correction." Relying on GPS isn't foolproof.

    :D
  10. Seasmaster

    Seasmaster Member

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    Wow! Deviant & swinging. . . all in the same message? OK. it's up to me to realign this thread. LOL (And I thought professional Merchant Mariners were deviants!! Sigh)

    In all my 23 years of shipping, there is only one time that I recall using a magnetic compass continuously. And even then, GPS was our real "compass". The USNS vessel I was on suffered a casualty to the gyrocompass. And consequently, we steered in hand steering by magnetic headings. However, we tracked our true course via GPS.

    As a matter of "normal" operation, I cannot forsee someone using magnetic headings continuously in deep sea. I can't speak about working on the Great Lakes. Ok, if you're in a life raft, and you don't have your solar operated phone charger you will have to "get by" with the magnetic compass. Don't most WAFI's and stink-potters have more than one GPS aboard? So we (for the most part) have redundancy, right? And some of us even are using the Russian constellation of satellites. I don't think the GPS/GLONASS are going to cease operation. Well, OK. IF THEY BOTH DO, THEN WE HAVE A WHOLE OTHER PARADIGM TAKING PLACE!!

    We all need to keep in mind, that a one degree in error of the compass, yields a 1-mile error after transiting 60 miles (and that's at the equator; it's less as you move N or S of that line. So, aside from an academic exercise, I'm thinking there isn't much to do here.
  11. Capt J

    Capt J Senior Member

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    Well magnetic North has been slowly changing for quite some time now, it's not like it just happened yesterday. It's just that it has finally changed enough over time for the change to be acknowledged and relevant enough. Yes it would be a good idea to swing the compass, which usually takes only a few minutes anyways.
  12. gr8trn

    gr8trn Member

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    What is involved in this swinging a compass, what is the procedure to have one's ship swung?
    If it is a simple maneuver why not just do it when ever latitudes change or equipment is worked on?
    Do tell. I would just search the internet but I can't know what source to trust, how could this forum steer me wrong:)
  13. Capt Ralph

    Capt Ralph Senior Member

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    Swinging an AP compass just takes a few minuets. In Florida, we have been blessed with minimum error all along. Later chart updates will help with data to correct your error card for your ships mag compass. If your concerned with PSC, then invest in a proper compass master to help adjust your mag compass and make a new error card. But your compass should always be set to mag north. I would not adjust anything unless mods have been made to your ship.

    Lat / Log is Lat / Log, regardless of magnetic north. Your GPS and AP will still get you there.
  14. Capt Ralph

    Capt Ralph Senior Member

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  15. Oscarvan

    Oscarvan Senior Member

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    OK....I hope you all are just pulling the poor guys leg because I'm reading a metric crap ton of BS from a few people up here.

    DEVIATION is compass error introduced by the SHIP or aircraft. Blobs of metal, electronic equipment and all that. It needs to be checked (swung) after the removal or installation of same, or on specified intervals. Swinging is putting the vessel or aircraft on known cardinal headings around the rose and recording the compass errors on the compass card. It has NOTHING to do with geographic location. VARIATION is the difference between the magnetic and north pole. It has EVERYTHING to do with location. It is NOT recorded on the compass card. Variation is derived from charts, based on location, and applied to navigation then and there.

    I've been staring at (not using mind you, we never do anymore) compass cards every working day, and many of the vacation days of my life starting half a freaking century ago. Every time the electronics configuration changes the poor maintenance bastards have to swing the thing, and if the card is missing we're grounded. But we never use it. (As an aside, and as one coherent voice above stated, the errors are less than the accuracy of my steering so it's pointless anyways.)
    Last edited: Feb 11, 2019
  16. gr8trn

    gr8trn Member

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    I think recreational boaters with boats using compass bearing are not swinging the boat and updating the compass cards. Heck I didn't even know what a compass card was. Then I looked at the procedure for updating Deviation from time to time and thought, not gun do'it.
  17. Oscarvan

    Oscarvan Senior Member

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    Correct, not many recreational boaters do, and as mentioned above they don't need to because they can't steer that accurate to begin with, not to mention the fact that very few steer a course anymore. They drive in a general direction and figure it out with the GPS when they get close

    Now, for those that actually still pay attention to a compass swinging should be done at least once in your boat ownership to see if there's anything whacky going on. (My parents got to the brink of divorce thanks to a hand held radio in a green velvet lined teak holder less than two feet from the compass). And, if you have a steel boat you really better swing the thing if you ever want to believe your compass.
  18. Beau

    Beau Senior Member

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    Oscarvan, you are a very colorful guy...or gal. Glad you joined us. Instances of deviational influence do not only have to be aboard. It can be that volcanic mountain you're passing....or that artificial reef made of steel...or Manhattan.
    Last edited: Feb 12, 2019
  19. JWY

    JWY Senior Member

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    Hey, Beau -- pretty colorful yourself. "Deviational influence"? We're not supposed to talk politics on YF. :D What a great term. Succinct, relevent, and self-explanatory. I think you might have made that up, but it's a keeper. Gotta find a way to use that in a YF yacht review. Anybody else hear of DI or have I lost my bearing?
  20. Oscarvan

    Oscarvan Senior Member

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    I'm a guy.... 61, 6', grey, blue eyes...... I like long walks on the beach and sipping hot chocolate in front of the fire.... :D

    And yes, you are correct on local influences affecting deviation. And if you're staying in THAT spot you would swing the compass. Of course that's pointless as you need the compass to go somewhere else. (Unless you're standing anchor watch and doing bearings every hour).

    Not sure about the terminology either...... DI.... but I do like it.

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