Compass rebalancing for southern hemisphere

[Streetcar]

I need to re-balance my Danforth Constellation compass for southern hemisphere.

I have been advised that it is possible to do it myself by opening it up and removing the weight (usually solder) from the S pole of the card and adding the right amount to the N pole. Apparently I can refill the bowl with Isopar L (parafin)...

Has anyone got any experience of doing this? Is it straightforward? If so any tips?

[Jim Cate]

Have not done it myself, but did have our Danforth rebalanced when we sailed from SF to Auckland some years ago. Compass seized up around 30 south... rather a nuisance. There was a nautical instrument repair fellow in Auckland then and he did it easily, but not in my presence.

Part of the trick is in getting the new balance to work in your prospective cruising areas, wherever that may be. We settled on an "equatorial" balance that worked from ~10 S down to ~43 S (as far as we went in that boat).

And FWIW, seems that Danforth compasses are more prone to these difficulties than are Ritchie models. The Ritchie on our current boat has worked from Oz to Japan and thence to Alaska and the Caribe and back to Oz without alteration.

Good luck with the project.

Jim

[Montanan]

Indeed a compass needs to have its dip adjusted.

https://en.wikipedia.org/wiki/Magnetic_dip

And while your at it as soon as your dip is swung proper along the specific inclination line be sure to be using the corrected map for reference otherwise your compass adjustment will be for naught, [erhh, for knot].

Do not that as the magnetic pole moves, so does the inclination angle change.

[Jim Cate]

Actually, Montanan, if I were doing this job I'd simply place the weight in such a place that the card was level. Why would you worry about lines on a chart when you have the definitive instrument for measuring the dip on the bench in front of you?

Takes steadier hands than mine, but I don't think it requires much research into geomagnetism!

Jim

[Montanan]

Originally Posted by Jim Cate

Actually, Montanan, if I were doing this job I'd simply place the weight in such a place that the card was level. Why would you worry about lines on a chart when you have the definitive instrument for measuring the dip on the bench in front of you?

Takes steadier hands than mine, but I don't think it requires much research into geomagnetism!

Jim

Jim:

The real challenge is trying to balance the compass when the sea is rocking the boat and all the while one is holding a beer.

Oh, yeah, I would avoid using a magnet as the counterweight for the card.

[captmikem]

Originally Posted by Streetcar

I need to re-balance my Danforth Constellation compass for southern hemisphere.

I have been advised that it is possible to do it myself by opening it up and removing the weight (usually solder) from the S pole of the card and adding the right amount to the N pole. Apparently I can refill the bowl with Isopar L (parafin)...

Has anyone got any experience of doing this? Is it straightforward? If so any tips?

I have a Danforth constellation southern Hemisphere Compass I would sell if you are interested.

M

[surazo]

sorry , but I agreed with Jim .Usually and always I use a tiny copper wire and balance again the compass .The magnetic lines or magnetic variation it's another matter

[olivert]

When I used to work for Sestrel compass manufacturers in a previous lifetime, I would have said a 4deg dip was liveable and probably less painful than doing a refill job! As others have said, re-balancing the card is not a great problem, the real problem is refilling without getting bubbles later. When the instrument was built, the diaphragm was pulled just a little so the contents are under a very slight pressure when the plug is screwed in and the diaphragm released. I you don't do this, every time the temperature drops, the liquid contracts more than the compass and a bubble forms. You may then find the damping is not so good because the liquid can swish around to easily.

If you do decide to have a go, put your liquid in the freezer for a few hours before refilling and if you can pull out the diaphragm a wee bit as well, overfill and screw in the plug quick.

Most important, never use alcohol in the compass, only in the technician

[Streetcar]

Originally Posted by olivert

When I used to work for Sestrel compass manufacturers in a previous lifetime, I would have said a 4deg dip was liveable and probably less painful than doing a refill job! As others have said, re-balancing the card is not a great problem, the real problem is refilling without getting bubbles later. When the instrument was built, the diaphragm was pulled just a little so the contents are under a very slight pressure when the plug is screwed in and the diaphragm released. I you don't do this, every time the temperature drops, the liquid contracts more than the compass and a bubble forms. You may then find the damping is not so good because the liquid can swish around to easily.

If you do decide to have a go, put your liquid in the freezer for a few hours before refilling and if you can pull out the diaphragm a wee bit as well, overfill and screw in the plug quick.

Most important, never use alcohol in the compass, only in the technician

Good advice. Thanks. It sounds do-able. The card is tipped enough to the South (in Australia) so that it doesn't swing freely when turning. I'll get the parafin and the alcohol ready.