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  1. #1
    Join Date
    Feb 2004
    Location
    Boat (500m E of) the Clyde
    Posts
    3,814

    Default Compass in southern hemisphere (Auckland)

    My son is going to be sailing a racing dinghy in New Zealand. He has been told his racing compass won't work properly down under and needs a different one.

    Is somebody trying to "sell us a left handed teapot" ?
    Is there any real issue ?

  2. #2
    Join Date
    Jun 2006
    Location
    South East Coast - United Kingdom
    Posts
    7,078

    Default Re: Compass in southern hemisphere (Auckland)

    Well, I have to admit, "NORTH" will point towards the sun so he will have to be careful!
    regards David - DSW Marine Engineering
    www.dswmarineengineering.com

  3. #3
    Join Date
    Jun 2002
    Location
    Oxonia
    Posts
    60,610

    Default Re: Compass in southern hemisphere (Auckland)

    Completely true, and has been asked many times before. The needle needs to be counterbalanced so it will rotate correctly, as the needle is pulled downwards at different angles (non technical explanation)

  4. #4
    Join Date
    Sep 2004
    Posts
    4,180

    Default Re: Compass in southern hemisphere (Auckland)

    I suggest that you get some advice (specific to your compasses) from the national body that supports dinghy sailing at international championship level in your country so that the advice is authorative and no unexpected worries - but I suspect that the advice you have already been given is incorrect.

    Dinghy race compasses (assuming that is what your son has), as far as I am aware - but stand to be corrected-, are not of a type that need correction for dip for the hemispheric zone the boat is in (seems sensible too given the rate some of these boats compete across many zones) - many have no compensation at all, given that relative tactical use may be more important than the actual magnetic heading.

    (PS I assume the boat is 420 class)

    John
    <span style="color:blue">www.sailroom.co.uk</span>

  5. #5
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    19,651

    Default Re: Compass in southern hemisphere (Auckland)

    I agree with BrendanS, this topic has been discussed many times on the forums and articles on it have appeared in the magazines. I am guessing that the bulkhead compasses fitted to many cruising yachts might suffer only minor problems ( although I do know that Plastimo make a different model of the Contest for the southern hemisphere ) but a large diameter racing compass might be a very different matter. However, the advice to ask the RYA is good: I guess they have some experience in Sydney, not that far away!
    Answers to some technical queries at http://coxengineering.sharepoint.com

  6. #6
    Join Date
    Jun 2005
    Posts
    17,271

    Default Re: Compass in southern hemisphere (Auckland)

    It needs to be turned upside down
    If I'd wanted to live in a Banana Republic I'd have gone to South America.

  7. #7
    Join Date
    Feb 2004
    Location
    Boat (500m E of) the Clyde
    Posts
    3,814

    Default Re: Compass in southern hemisphere (Auckland)

    Thanks for your help. We will try to get some advice from the RYA coaches - as you say, they must have some experience from Sydney (though cost would not have been an object for that event) !

    And congratulations on deducing that this is the 420 class (World Championships in Auckland in January) - finger well on the pulse here !

  8. #8
    Join Date
    Sep 2004
    Posts
    4,180

    Default Re: Compass in southern hemisphere (Auckland)

    Good luck in Auckland over New Year, I will keep an eye out for the UK Open performances.

    I would be interested in the outcome of the Dip question.

    I have commissioned new boats in the Southern Hemisphere, for delivery to the Northern with Northern corrected compasses, in a region of very high magnetic Southern dip (around 75 degrees, that not in NZ) and even though with the large dip and also the wrong opposite correction was only sometimes a problem on a dead magnetic south heading when the angle of dip and the large exaggeration of the incorrect correction tipped the card enough to occasionally foul.

    So I cannot imagine an uncorrected type compass having any problems whatsoever (especially as they are made to work most everywhere) but would be interested in the outcome.

    John
    <span style="color:blue">www.sailroom.co.uk</span>

  9. #9
    Join Date
    May 2003
    Location
    Here or there
    Posts
    74,433

    Default Re: Compass in southern hemisphere (Auckland)

    wot happens on the Equator then, or say 200 mls either side of it [img]/forums/images/graemlins/confused.gif[/img]
    Brexit: ‘taking back’ what we had never lost, in order to lose everything we had...

  10. #10
    Join Date
    Dec 2001
    Posts
    140

    Default Re: Compass in southern hemisphere (Auckland)

    I would have thought that you need to be pretty close to a magnetic pole for dip to have a serious effect. Auckland is only 37deg S.

    I seem to remember that a compass should be swung if there is a large change of latitude, but as I presume super accurate compass navigation is not required this is probably not an issue.

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