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Old 04-06-2011, 09:05   #16
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Re: Mounting Fluxgate Compass in Aluminium Yacht

Where is it dry on a boat in the tropics?
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Old 05-06-2011, 07:41   #17
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Re: Mounting Fluxgate Compass in Aluminium Yacht

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Where is it dry on a boat in the tropics?
well, not under my leaking hatches now that rainy season started to become serious

ciao!
Nick
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Old 05-06-2011, 08:44   #18
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Re: Mounting Fluxgate Compass in Aluminium Yacht

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Where is it dry on a boat in the tropics?
Under sprayed on foam insulation which is very common on aluminum boats. The foam dampens the noise so your boat does not sound like an old metal garbage can and the foam stops condensation on the inside.
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Old 05-06-2011, 08:54   #19
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Re: Mounting Fluxgate Compass in Aluminium Yacht

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Does the aluminium act as a magnetic shield.
Good question.
I have a fluxgate installed inside my aluminium mast. My experience is that aluminium reduce the sensitivity of the fluxgate. Does the alu mast act as a Faraday cage? I have put the question to Raymarine they are not sure. At first it seem to work fine with a reported deviation of 3 which is good for a steel boat but when the going get tough it can feed false information to the system with annoying and dangerous consequences. By the way I use nylon fastener.
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Some fluxgates allow you to run a circle with the boat which creates an electronic deviation table which compensates for the iron onboard.
Also at the end of the swinging process of the fluxgate compass a deviation number will be provided. According to the manufacturer if a number of any value is produced the making of a deviation table is recommended. On my boat I also have two fluxgate installed on the stern. The deviation is as follow.
Pilot
ST4000 stern starboard 15d
S-1 stern starboard 9d
X-5 stern portside 5d
I always run two fluxgate on the same time, one as an independent compass, the other as system. Further to a similar thread I find the use of radar as one of the easiest way of producing a deviation table
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Old 05-06-2011, 09:01   #20
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Re: Mounting Fluxgate Compass in Aluminium Yacht

Aluminum itself has absolutely no effect on the strength or direction of a magnetic field.

Faraday cages affect the path of electrons, not the strength of magnetic fields. Any magnetic effects from a Faraday cage would be caused by the material of the cage if it has iron and from induced magnetic fields caused by DC current.
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Old 05-06-2011, 09:12   #21
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Re: Mounting Fluxgate Compass in Aluminium Yacht

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Aluminum itself has absolutely no effect on the strength or direction of a magnetic field.

Faraday cages affect the path of electrons, not the strength of magnetic fields. Any magnetic effects from a Faraday cage would be caused by the material of the cage if it has iron and from induced magnetic fields caused by DC current.
Good on you.
Just my experience.
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Old 05-06-2011, 09:33   #22
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Re: Mounting Fluxgate Compass in Aluminium Yacht

"Does the alu mast act as a Faraday cage?"
Yes, any conductive metal "box" is a Faraday cage. Just bear in mind that mast will probably conduct a lightning strike right past your compass and the resulting electromagnetic induction may render the fluxgate worthless anyhow. For all purposes aluminum is the same as copper here. Both conduct electricity and neither has anything to do with magnetism in normal circumstances, although induced electromagnetic effects can happen. (In some recycling plants, induced magnetism is used to pull aluminum objects. See Physics Demonstrations - Magnetism for something similar on that.)

After a lightning strike, you would need to distrust ALL magnetic and electronic gear on board until proven otherwise.
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Old 05-06-2011, 09:38   #23
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Re: Mounting Fluxgate Compass in Aluminium Yacht

Stainless in many aluminum alloys is no better than using bronze. If not properly insulataed with some sort of agent...they will weld themselves into the hole from corrosion...or if wet enough...the aluminum seems to eat away enough that the threads don't hold on screws...through bolting is better and the oversized hole can keep more insulating compound in it.
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Old 05-06-2011, 10:52   #24
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Re: Mounting Fluxgate Compass in Aluminium Yacht

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"Does the alu mast act as a Faraday cage?"
Yes, any conductive metal "box" is a Faraday cage. Just bear in mind that mast will probably conduct a lightning strike right past your compass and the resulting electromagnetic induction may render the fluxgate worthless anyhow. For all purposes aluminum is the same as copper here. Both conduct electricity and neither has anything to do with magnetism in normal circumstances, although induced electromagnetic effects can happen. (In some recycling plants, induced magnetism is used to pull aluminum objects. See Physics Demonstrations - Magnetism for something similar on that.)

After a lightning strike, you would need to distrust ALL magnetic and electronic gear on board until proven otherwise.
Does not really need a strike just some good static will render on board electronic questionable as for the path of a lightning strike, mast or rigging who knows? In some case the radio aerial carrying the static to ground will affect the fluxgate. By the way the good old kWh meter had a rotating aluminium disk. For the OP the best place for a fluxgate is where the manufacturer recommends it. When it is necessary to compromise a well-protected strong stern railing can offer good result so long the outboard motor is kept well away.
Nice to read you Hellosailor
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Old 05-06-2011, 12:55   #25
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Your aluminum mast might affect the fluxgate compass sensitivity. Interesting question. Depends, like Raymarine said. The fluxgate compass uses an AC field to sense the 'DC' earth's magnetic field so the aluminum could definitely affect it's operation. Especially if it is nearby and closed like a mast.
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Old 07-06-2011, 12:00   #26
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Re: Mounting Fluxgate Compass in Aluminium Yacht

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Your aluminum mast might affect the fluxgate compass sensitivity. Interesting question. Depends, like Raymarine said. The fluxgate compass uses an AC field to sense the 'DC' earth's magnetic field so the aluminum could definitely affect it's operation. Especially if it is nearby and closed like a mast.
And mostly if it is a mast of a complex shape of various thicknesses.
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Old 07-06-2011, 12:52   #27
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Re: Mounting Fluxgate Compass in Aluminium Yacht

The metal is no issue still note that most manufacturers recommend mounting theirs close to the center of the boat, not up the mast.

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Old 07-06-2011, 14:04   #28
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Re: Mounting Fluxgate Compass in Aluminium Yacht

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The metal is no issue b.
Steel not an issue?
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Old 07-06-2011, 15:01   #29
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Re: Mounting Fluxgate Compass in Aluminium Yacht

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Steel not an issue?
The thread says aluminum. Aluminum is a metal, isn't it. Aluminum is no issue, is it.

Clearer now?

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Old 07-06-2011, 15:13   #30
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Re: Mounting Fluxgate Compass in Aluminium Yacht

Moving from theoretical physics, which still cannot explain it'd s own basic premises much less prove them, right back to more immediate matters, has anyone ever seen proof of any ali mast ever experiencing eddy currents caused by anything that created any magnetic field for any time in that mast?

Lightning strikes don't count. Local EMP devices don't count. Hitting lowhanging power transmission lines only counts if they didn't total the boat.

Reality check, please.
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