Compass issues

[bushymac]

Hello all, I have a compass on the port and starboard side of my hatch in the cockpit. There doesn't seem to be anything that could affect them but they both are showing wrong headings on fairly much all points of the compass. Is there some way of shielding them...maybe with a lead liner around the base or similar? In my berth, they are both showing 135 when it is meant to be 167....normally they are both showing a different reading.
It is frustrating not to be able to rely on them....any suggestions?

[Wotname]

More information will be helpfull

Where is the nearest ferrous material to the compass? Like engine or hatch or hull etc.

Lead won't work, it has no magnetic properties. In fact sheilding won't work but compensation might.

It really depends on the location of compass to the various bits of steel or other magnets nearby.
You can always get a compass adjuster to have a look but they usually don't come cheap.

[onestepcsy37]

Have you swung both compasses? Not hard to do nowadays what with GPS and all.

[barnakiel]

Is your boat steel, fc, wood&iron nails?

And which of the two is wrong?

b.

[JPA Cate]

Bushymac,

Read up on swinging your compasses. Armed with that knowledge, you should be able to work out deviation cards for them.

You probably have some ferrous material (as Wotname suggested) that is affecting one or both of them. Anything iron or steel will do that. Also, hifi speaker magnets, or other magnets. Paint spray cans. Keep plastic stuff around compasses, nothing ferrous. You may have to re-arrange your stowage to relieve your magnets.

Do you have access to a hand-held compass you could borrow, to compare their bearings. Seems to me that at this point you don't really know if either of your bulkhead compasses is correct.....

Cheers,

Ann

[Bill Seal]

http://msi.nga.mil/MSISiteContent/StaticFiles/HoMCA.pdf


Everything you ever wanted to know about magnetic compasses.

Like was suggested, GPS may be the way to go..