Magnetic Compass Zones

[JDGreenlee]

Informed that my Ritchie SP-5 will require a new $350 compass capsule to modify for southern hemisphere. Should I just buy a used compass when I get there? What are the chances of finding a reliable one in the Caribbean? Where does one find good used compasses for the southern zones? I'd prefer to stow one until needed versus roll the dice when needed if the risk is more than negligible. Advice?

[Rex Delay]

Who ever told you this is full of it. A compass is a compass anywhere. The earth's magnetic field is relatively constant and the changes are predictable. Variation is known for any place you might want to wander. All you need is the local variation. No, people south of the equator do not stand inverted, nor do their compasses.

[Adax]

Well I thought the same thing and then I googled...

Apparently there are Northern and Southern compasses. The difference is where the weight is placed on the needle . In "Northern" compasses it is placed on the south end of the needle, whereas in "Southern" ones the weight needs to be on the north end of the needle. So if your weight is on the wrong end your needle won't rotate freely.

Geomagnetism Frequently Asked Questions

Your practical question of what to buy where I can't answer though.

[cal40john]

Originally Posted by Rex Delay

Who ever told you this is full of it. A compass is a compass anywhere. The earth's magnetic field is relatively constant and the changes are predictable. Variation is known for any place you might want to wander. All you need is the local variation. No, people south of the equator do not stand inverted, nor do their compasses.

Away from the equator the field lines dip into the earth. Compass needles are unevenly weighted to keep one end of the needle from trying to point down and therefore not want to spin freely. Some compasses have bearings and cards that can handle the dip.


Compass Balance And World Zone Chart

I see I was beat to the answer.

[Rex Delay]

That is why a ship's compass floats in fluid. No weights. Did Captain Cook have a compass for each hemisphere? Somehow he figured out where he was.

[ka4wja]

JD,
1) E.S. Ritche will gladly re-balance your Globemaster SP-5 fopr whatever magnetic zone you need....
But, I cannot fathom that they'd charge you more than $100....

Have you contacted them???
(781) 826-5131
service@ritchienavigation.com
http://www.ritchienavigation.com/ser...albalance.html
Ritchie Navigation - Home

For the ultimate in accuracy, the dials in magnetic compasses should be balanced to compensate for dip caused by the earth's magnetic field. All Ritchie Compasses come standard balanced for Zone 1 (essentially all of the Northern Hemisphere).
When requesting balancing for Zone 2-7, please indicate the zone most central to your boating area. Once balanced for a specific Zone, the compass will maintain accuracy for one Zone north or south.
For additional information, please call our service department at (781) 826-5131.
Email: service@ritchienavigation.com

Their recommendations will depending on where you're sailing, and how long you'll be in any specific zone.....
Give 'em a call.....


2) As for buying a "spare" compass????
In over 40 years of boating / offshore sailing, I've never seen a hi-quality magnetic steering compass (such as Ritchie Navigator or Globemaster) fail.....ever....
So, I'd say a spare Globemaster, etc. is not neceessary at all....

In my case, I have two wheels/helms, and hence two Ritchie 4.5" Navigator 201 Steering compasses, so I have a built-in "spare".....
But on previos boats (and the first one I sailed across the Atlantic on), our "spare" compasses were hand-bearing compasses and compasses in bincos, etc.....


3) Also, I'm not clear where you're sailing???
(since neither Texas nor the Caribbean are in the Southern Hemisphere)
Where you're sailing is what will determine what you should do.....

But, specific to your question about "finding a compass dipped for the Southern Hemisphere, in the Caribbean".....that would be highly unlikely!!!

And, buying a used compass just seems like a bad idea to me.....
Just my opinion, but faded numbers and ludder lines on the card, crazed domes, etc. are what you're likely to find on used comapsses.....even if you could even find one already balanced for the souther hemisphere....

Buying a new compass, AFTER you arrive in the southern hemisphere????
This might be the best option overall.....
BUT, I'd still defer to the guys at Ritchie.....
As. I said.....give 'em a call....


4) As for the others who question why this is needed????
It is the "dip" that needs to be "balanced".....


I hope this helps....

{BTW, the guys at Ritchie are REALLY nice guys.....a few years ago, they refered me to a compass adjuster to professionally do mine....give 'em a call, and they'll be able to help you out.....}

John
s/v Annie Laurie

[JDGreenlee]

Was typing at same time other posts posted... Ritchie wants to sell me the capsule. Please refer to the original post...I don't think the original question has yet been addressed. I beg your pardon if wrong. Also, see Compass in southern hemisphere (Auckland) - Page 2 - Yachting and Boating World Forums that implies the problem is not so great as the physics imply. However, I'd like to hear from someone who has gone north to south or vice versa and compared their ship's compass against GPS - or some other experimentally based observations. Does the compass need (or have to) be modified between N30 and S30 to be an acceptable backup to GPS - especially if we record the difference between GP and the ship's compass so that in need, we will have correction factors? If it needs correcting, are there options other than a new $350 capsule?

[ka4wja]

JD,
It appears that we were typing at the same time.....

1) Although, I did answer your original question.......
I'm not clear if Ritchie recommended replacing the compass capsule, rather than rebalancing your existing compass????
Or is this their recommendation based on you desiring to have a compass balanced for the Northern Hemispere now, and then changing as you get into other magnetic zones???

In either case you've got the definative answer directly from them....
And, nobody here can possibly do better....


2) Now as for your further questions, in your latest post......
(I've personally not sailed from the N. hemi to the S. hemi....)
I have a few pretty decent places for you to get the best advice....

a) Perhaps Evans (or another hi-latitude circumnavigator) will respond....
b) Perhaps posting on the SSCA Disc Boards will get you some real world info... SSCA Discussion Board • Index page
c) Those that make the Pacific Puddle Jump, from US West Coast / Mexico / Panama and then onto Aus / NZ, etc.....pass from Zones 1 and 2 on thru to Zones 3, 4, and 5.....
Perhaps querying those on the PPJ list would get you some info...
d) Asking the guys at Ritchie....


Assuming you're haeding across the Pacific, I'd ask Ritchie to balance it for Zone 3 or 4....and confirm with them the accuracy when you're +/- only one zone...and ask them about being down two or three zones, such as would be the case going to Aus and NZ???



3) I am confused by your question regarding the compass being accurate enough as a back-up for GPS????
Not sure what you're asking.....as the compass and GPS do very different things.....

EVERY OCEAN GOING VESSEL SHOULD HAVE AN ACCURATE STEERING COMPASS......no matter what method the use for position fixing....
Uisng a COG reading from a GPS does not tell you where you're pointed....


I hope this helps....

John
s/v Annie Laurie

[roverhi]

We sailed our boat south of the equator and our Ritchie compass continued to work just fine. That was from Zone 1 to Zone 3-4. None of the boats that went south to NZ or OZ reported any problems with compass accuracy. Got a feeling it's a matter of difference between an okay accuracy and extreme accuracy. The problem is that a cruising yacht is never stable enough to make extreme accuracy an issue. Maybe if your yacht is a 500 footer like that Russian's it might make a difference. If you are going to be sailing in zone 4-7 constantly, it might be worth the expense.

To tell you the truth, I've been sailing for most of my life and many 10s of thousands of miles and this is the first time I've heard of a compass zone

[JDGreenlee]

This may be of interest...it's redacted a little and in reverse chronological order.

Hi James,

Yes, Land, Sea, and Sky Unlimited in Houston is one of our Authorized Ritchie Service Stations.

Zone Balancing:
Zoned Capsules are custom made. They are not a stock item. You would want to purchase it directly from us. An SP-5 capsule is part # CS-0009-P1 ($338.52 plus shipping). When ordering you would want to specify balanced for Zone 5
There is usually a week lead time from when order is placed. Parts can be ordered with a MC or Visa by calling our service department at 781-709-3202.

I have attached a page of our service manual [note omitted from CF post] showing how an SP-5 is assembled. You will see that the compass capsule (#2,3) is easy to remove. It is a matter of removing 2 screws (#1) (to remove stainless binnacle) and loosening one "clamping screw" (#16) on the base to be able to lift the capsule out of the base.

The actual compass card is balanced for the appropriate zone. And yes, I would recommend having a Zone 2 dial put in your existing SP-5 compass capsule. This can be done at our factory if you would like to send it to us or Land, Sea, Sky should be able to do it also.

Let me know if you need additional information.

Regards,

Service Department


-----Original Message-----
From: JDG
Sent: Thursday, January 13, 2011 1:05 PM
To: Ritchie
Subject: Re: southern hemisphere

Excellent response! Thank you.

Should I re-calibrate the SP-5 for zone 2 for use in Zones 1, 2 and 3?

Should I buy a compass capsule that modifies the SP-5 for Zone 5 for use in
Zones 4, 5 and 6?

Does the selection of the model of the compass capsule depend on whether I
re-calibrate my SP-5 for Zone 2 first (see above)?

Are compass capsules available directly from Ritchie? How much do they cost? I
used Land, Sea and Sky in Houston to refurb the SP-5 four months ago. Are they
on your radar? http://www.landseaskyco.com/store/

Should I purchase the compass capsule prior to departure or are they readily
available from your dealers in South America? If so, please forward contact
info.

Can I install the compass capsule without special tools? Are instructions
included?


----- Original Message ----
From: Ritchie
To: JDG
Cc: SS
Sent: Thu, January 13, 2011 8:18:34 AM
Subject: RE: southern hemisphere

Hello James,

When someone is purchasing compasses and they are going to be used from Zone 1
thru Zone 6, we recommend they have 2 compasses. One for Zones 1,2,3 and one for
zones 4,5,6.


With an SP-5 a compass capsule can be purchased and swapped out at the
appropriate time (compass would not have to be recompensated because the
existing comp base would be used) and used for the southern zones. A zone 5
compass would work well in zones 4, 5, & 6.


An HB-70, you would need a second HB-70 balanced for Zone 5. The compass would
have to be compensated.

Regards,

Service Department

-----Original Message-----
From: JDG
Sent: Monday, January 10, 2011 7:35 PM
To: Ritchie
Subject: Re: southern hemisphere

S: Advice requested. Am planning westward circumnavigation from Galveston
via Panama Canal over Australia and under Cape of Good Hope from Zone 1 through
6 and back to 1 again. What should be my compass strategy? Regards, James


----- Original Message ----
From: Ritchie
To: JDG
Sent: Mon, January 10, 2011 9:24:51 AM
Subject: RE: southern hemisphere

Hello,

The SP-5C compass if balanced for northern hemisphere will only work
properly without major dip until Zone 3.

See our website www.ritchienavigation.com and under my compass see zone
balancing for the location of zone 3.

Sincerely,

SS

-----Original Message-----
From: JDG [mailto]
Sent: Monday, January 10, 2011 9:36 AM
To: Service
Subject: southern hemisphere

Please advise procedure to verify in Houston that Ritchie SR-5 #088 and
Ritchie
HB-70 #970000000443 will work south of the equator.

[JDGreenlee]

Annie Laurie:

By using the compass to backup the GPS I meant that if I lost (or lost faith in) the GPS heading indication then the compass, despite being "upside down," would work adequately to navigate as in the old days. "Upside down" being a figure of speech for "below the equator." I wouldn't really hold it upside down (would I?). LOL. But seriously, if the sun spot activity picks up in 2012/2013, then the GPS may not be as reliable. That leaves the compass(es).