Compass Problem

jere1972

Petty Officer 2nd Class
Joined
Nov 1, 2011
Messages
183
there were 2 Compass units mount on my boat when I bought it, one was factory installed but the glass was very distorted and unreadable, so I'm guessing thats why the other was added, both units seem to always point N-NE no-matter which way I'm going, they are about 8inches away from each other, could the magnets be conflicting????? one is surface mounted the other is on a bracket
 

drrpm

Senior Chief Petty Officer
Joined
Oct 24, 2008
Messages
707
Re: Compass Problem

You could take one out and see what happens. Its more likely that some other electrical component is interfering with the compasses. The magnetic field of a regular compass is pretty small so its easy to inerfere with it but unlikely to interfere with anything else.
 

Ned L

Commander
Joined
Sep 17, 2008
Messages
2,266
Re: Compass Problem

Any speakers, microphones, electronics mounted nearby? Among other things, the magnets in them will reek havok with a compass. as has been said, the easiest thing to do would be to remove the compass & see how it behaves when well away from any magnets & ferrous metals.
 

jere1972

Petty Officer 2nd Class
Joined
Nov 1, 2011
Messages
183
Re: Compass Problem

now that you say that there is a pair of Pioneer 6x9 mounted in the cabin on the cover assembly that covers the access panel to the helm electronics right under where the compass is the speakers have 3' magnets speakers are about 10-12 inches away from compass
 

TerryMSU

Senior Chief Petty Officer
Joined
Jul 31, 2007
Messages
743
Re: Compass Problem

That is almost certainly the issue. I had a smaller speaker that distance from my compass and it almost totally screwed up my compass. In theory, it is possible to compensate for a fixed magnetic field (such as a speaker magnet) near the compass using the screws on the compass, but I have never figured out how to do that. Alternatively, an electronic compass can automatically compensate for a fixed magnetic field, but a pure magnetic compass is almost 100% reliable (as long as you don't move one of those speakers).

TerryMSU
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: Compass Problem

Pioneer is a goood brand speakes and they have large magnets in them. However, if they are not marine speakers, they will not be sheilded. even if you move them to a different location they may still interfere with the compasses. Add to that the fact that if they are not marine speakers, they will not last too long.
Best case would be to buy sheilded marine speakers and move them as far as possible from the compass
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: Compass Problem

The compass in my speedboat always pointed due North....right at my steel fuel tank.

Be aware that magnets are not the only things that will alter a compass' operation. Also, Wires with current in them are magnets as well.
 

Ned L

Commander
Joined
Sep 17, 2008
Messages
2,266
Re: Compass Problem

I think you have your answer. I doubt there is anything you can do to compensate for those big magnets so close. If you move the speakers it would probably have to be a good 3 feet minimum. You can try moving the speaker different distances and boxing the compass to see how the deviation decreases at the different distances, then decide what you want to live with.
 

jere1972

Petty Officer 2nd Class
Joined
Nov 1, 2011
Messages
183
Re: Compass Problem

Thanks guys, gonna just remove the speakers from the cabin, I have surface speakers mounted on my T-Top so they will suffice, hope it's just those pioneers causing my prob, again thanks guys for helping find the obvious, I feel like an idiot for not thinking about those damn speakers, before posting! but you probably saved me from disecting my dash to remove the compasses
 

Ned L

Commander
Joined
Sep 17, 2008
Messages
2,266
Re: Compass Problem

That should help you a lot. Having the two compasses 8" apart may still cause some issues. If one of the compasses comes out easilly I'd suggest securing the boat in a direction, take an exact compass bearing, 'remove' one compass (move it a good 5 feet away), and see if the bearing on the remaining compass changes at all. Repeat this a number of times (i.e.4) about 90? apart. This will give you a pretty good idea if they are screwing each other up.
 

soggy_feet

Senior Chief Petty Officer
Joined
Oct 10, 2009
Messages
713
Re: Compass Problem

That is almost certainly the issue. I had a smaller speaker that distance from my compass and it almost totally screwed up my compass. In theory, it is possible to compensate for a fixed magnetic field (such as a speaker magnet) near the compass using the screws on the compass, but I have never figured out how to do that. Alternatively, an electronic compass can automatically compensate for a fixed magnetic field, but a pure magnetic compass is almost 100% reliable (as long as you don't move one of those speakers).

TerryMSU

'Swinging' a compass (it's a PDF link)

I tried to do it on my boat, but I gave up. No way for me to hold the boat still and steady on a heading to make an adjustment, and considering it's a steel boat, it needs A LOT of adjustment.
 

Ned L

Commander
Joined
Sep 17, 2008
Messages
2,266
Re: Compass Problem

Yep, boxing, or swinging a compass is a bit tedious. My suggestion would really only give an idea if the two compasses in close proximity were screwing each other up, and would not result in any 'correction' (which is what boxing or swinging does).
 
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