Friday, January 12, 2007

New compass

A compass is a basic requirement on Lady Jane, however I'm discovering that this compass business is a little more tricky than you would think.

New compassHere you see the current state of the wheelhouse, with my new compass now mounted there on the left, the inset, in the bottom right, shows the making of the bracket.

The thing with putting a compass into a steel boat is that it doesn't necessarily point north. There are small adjustment magnets which need to be fiddled with to compensate for all the steel about, and so get the compass pointing north as it should.

Because Lady Jane is not ready to go to sea, I can only set the compass up for a north/south orientation (she happens to be pointing north). I'm told a similar alignment needs to be done on an east/west bearing, then compensate on the north/south and so on until the compass is as accurate as possible.

Before gps, this was presumably done by professionals using a gyro compass, which once oriented correctly would stay accurate, as the gyros would keep the compass pointing north correctly regardless of any magnetic influence.

I'm hoping that when I move Lady Jane round to the Itchen I'll have the chance to set my compass up using the gps for the right orientation. If that fails I'll have to get someone in to 'swing' my compass for me.

Oh yes, I know there is a big bunch of wires sticking out all over the place in that picture. I've still got more instrumentation to mount, and the compass internal light to wire up, then this should all get tidied away.

4 comments:

  1. Anonymous5:24 PM

    Tim,
    Since you'll never eliminate all the deviation on your vessel, you should look into an electronic compass that automatically compensates for the influences of the diviation. See one example at:http://www.kvh.com/products/product.asp?id=25

    Sent by: ArtW

    ReplyDelete
  2. Hi, thanks for the comment.

    I had wanted a permanent, non electronic compass, in case of a lightening strike, or similar type of disaster.

    I am planning to use my current gps for routine navigation requirements.

    I also have moving map software and a handheld gps which I've been planning on experimenting with.

    This keeps the cost down right now, but without compromise.

    Longer term, and once I start using Lady Jane more I'll need radar etc.

    Regards

    Tim

    ReplyDelete
  3. Anonymous2:06 AM

    If your getting your ship insured your compass has to meet certain requirments/standards...as you know the insurance crowd are a picky lot...the information on compasses are endless...http://en.wikipedia.org/wiki/Magnetic_declination#Adjustable_compasses
    Good Luck.Tony Roberts,St.Anthony,Newfoundland.

    ReplyDelete
  4. Thanks Tony. I'll look into that.

    ReplyDelete