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02-06-2011, 21:13
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#1
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Registered User
Join Date: Jul 2009
Location: Cruising the West coast of Sumatra and the offshore islands, surfing!!
Boat: Feltz Skorpion mark 11A, Aluminium 39' sloop, constructed Hamburg. https://photobucket.com/eloise_01
Posts: 703
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Mounting Fluxgate Compass in Aluminium Yacht
Hi, I am about to mount a fluxgate compass into my aluminium yacht, do I have to treat it like a steel yacht and mount it outside or can I treat it likea grp yacht and mount it inside?
Does the aluminium act as a magnetic shield, doesn't appear to effect the hand held compass inside the yacht?
Thanks for your advice?
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02-06-2011, 21:22
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#2
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Registered User
Join Date: Dec 2009
Posts: 2,959
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Re: mounting fluxgate compass in aluminium yacht
Aluminum is the same as FRP as far as earth's magnetic field is concerned: no effect on compass sensing.
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02-06-2011, 21:44
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#3
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Registered User
Join Date: Jul 2009
Location: Cruising the West coast of Sumatra and the offshore islands, surfing!!
Boat: Feltz Skorpion mark 11A, Aluminium 39' sloop, constructed Hamburg. https://photobucket.com/eloise_01
Posts: 703
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Re: mounting fluxgate compass in aluminium yacht
Thanks Daddle, very helpful, as always!
Cheers from Keith.
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02-06-2011, 22:24
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#4
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Registered User
Join Date: Mar 2003
Location: Philippines in the winters
Boat: It’s in French Polynesia now
Posts: 11,368
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Re: mounting fluxgate compass in aluminium yacht
Just be sure to use bronze or nonferrous screws to mount it.
__________________
Faithful are the Wounds of a Friend, but the Kisses of the Enemy are Deceitful! ........
The measure of a man is how he navigates to a proper shore in the midst of a storm!
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02-06-2011, 22:30
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#5
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Registered User
Join Date: Dec 2009
Posts: 2,959
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Re: mounting fluxgate compass in aluminium yacht
Quote:
Originally Posted by delmarrey
Just be sure to use bronze or nonferrous screws to mount it.
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Aaaack! Never put a bronze, brass or copper part onboard an aluminum boat. That's what I heard...it might fall somewhere and corrode a hole. Better to use a stainless screw that has been checked with a magnet, or checked near a compass, that it hasn't somehow ended up with some ferromagnetism.
The aluminum boat I was on didn't even allow pennies to come aboard in purses or pockets.
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02-06-2011, 22:43
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#6
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Registered User
Join Date: Mar 2003
Location: Philippines in the winters
Boat: It’s in French Polynesia now
Posts: 11,368
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Re: mounting fluxgate compass in aluminium yacht
Quote:
Originally Posted by daddle
Aaaack! Never put a bronze, brass or copper part onboard an aluminum boat. That's what I heard...it might fall somewhere and corrode a hole. Better to use a stainless screw that has been checked with a magnet, or checked near a compass, that it hasn't somehow ended up with some ferromagnetism.
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Just use some Tef-gel on the treads. TEF-GEL - Ultra safety systems - Home page
__________________
Faithful are the Wounds of a Friend, but the Kisses of the Enemy are Deceitful! ........
The measure of a man is how he navigates to a proper shore in the midst of a storm!
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03-06-2011, 10:46
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#7
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֍֎֍֎֍֎֍֎֍֎
Join Date: Apr 2006
Posts: 15,136
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Re: Mounting Fluxgate Compass in Aluminium Yacht
Some aluminum alloys react very badly to the presence of any copper. Supposedly if you put a penny (then copper) in the bilge of an aluminum boat fifty years ago, it would "burn" a hole through the hull in just a few months. While different alloys have supposedly reduced that problem to near-nil...I think I'd rather see a (wood, etc.) block glued to the hull, and any screws inserted into that block, so there's no metal-to metal contact possible, no problem possible. TefGel or not.
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03-06-2011, 13:24
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#8
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Registered User
Join Date: Dec 2008
Location: St. Georges, Bda
Boat: Rhodes Reliant 41ft
Posts: 4,131
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Re: mounting fluxgate compass in aluminium yacht
Quote:
Originally Posted by daddle
Aaaack! Never put a bronze, brass or copper part onboard an aluminum boat. That's what I heard...it might fall somewhere and corrode a hole. Better to use a stainless screw that has been checked with a magnet, or checked near a compass, that it hasn't somehow ended up with some ferromagnetism.
The aluminum boat I was on didn't even allow pennies to come aboard in purses or pockets.
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I am straying a bit here, but never use bilge pump switches containing Mercury in an Aluminum boat.
The liquid eats right thru Aluminum very quickly.
__________________
so many projects--so little time !!
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03-06-2011, 18:51
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#9
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Registered User
Join Date: Jul 2009
Location: Cruising the West coast of Sumatra and the offshore islands, surfing!!
Boat: Feltz Skorpion mark 11A, Aluminium 39' sloop, constructed Hamburg. https://photobucket.com/eloise_01
Posts: 703
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Re: Mounting Fluxgate Compass in Aluminium Yacht
Wow................ Thanks heaps guys!
Compass is mounted below aft bunk and ok!
Did find a copper/brass penny in the motor bilge when cleaning it out, sitting in salt water, but had not corroded at all and was not shiny, no holes in the bilge yet???
Plus about 10 screws/pop rivets/washers etc washing around???
Have got 1 milliamp voltage from the positive battery terminal to the hull, but no direct connection whatsoever, enough to light up a very small led, but it lights up if I hold one end and touch the hull as well?
Did have 150 milliamps on the hull until I removed the leaking salt water pressure pump, now have hand salt water pumps and a double pole switch on the fresh water pressure pump.
I thought alloy boats were maintenance free???? Ha! ha!
Off to Chenang beach today from Rebak, then Penang Tuesday for visa and the Sumatra over the weekend!
You Beauty!!!! Cheers from Keith.............
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03-06-2011, 20:23
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#10
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Registered User
Join Date: Mar 2006
Location: Winnipeg
Boat: None at this time
Posts: 8,462
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Re: Mounting Fluxgate Compass in Aluminium Yacht
Kanter even nickle plate bronze through hulls. I repeat what others have said, never use bronze on an aluminum boat.
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03-06-2011, 23:18
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#11
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Moderator Emeritus
Join Date: Sep 2007
Location: Eastern Tennessee
Boat: Research vessel for a university, retired now.
Posts: 10,406
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Re: Mounting Fluxgate Compass in Aluminium Yacht
It's an old wives tale that copper will burn a hole through aluminum. I have had an aluminum hull boat for over twenty years and have pulled bronze screws out of the bilge...no damage. Modern pennies are mostly zinc by the way.
I mounted my fluxgate using stainless steel screws. Mount it as far way from the engine and 12 volt DC wires as you can. Some fluxgates allow you to run a circle with the boat which creates an electronic deviation table which compensates for the iron onboard.
I used to have bronze thruhulls when the boat was inspected because the USCG did not allow plastic thruhulls. I used isolators to stop any corrosion which worked fine.
With an aluminum hull you want what is called a floating DC system. Absolutely none of your 12 VDC system should electronically attach to the hull. None of your AC system as well except for things like the frame of your inverter.
You can have bronze touching the aluminum on an aluminum hull....just not where it gets wet. I have this all over the inside of my cabin where bronze screws and bolts attach the interior trim to the hull and bulkheads. No corrosion for a boat built in 1975.
__________________
David
Life begins where land ends.
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03-06-2011, 23:42
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#12
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Registered User
Join Date: Jan 2008
Location: Hong Kong
Boat: Custom Freya 20m
Posts: 1,020
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Re: Mounting Fluxgate Compass in Aluminium Yacht
I had an alloy yacht which had jacklines attached to U-bolts on the deck. The wires had copper swages which lay on the alloy and ate through 3mm deep over period of three months or so. Have had copper wiring pieces fall into the bilge and do the same thing where the paint had lifted away. All for keeping copper out of alloy boats and being very careful/clean when working on the electrics. Have not tried coins with copper content.
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03-06-2011, 23:59
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#13
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Moderator Emeritus
Join Date: Sep 2007
Location: Eastern Tennessee
Boat: Research vessel for a university, retired now.
Posts: 10,406
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Re: Mounting Fluxgate Compass in Aluminium Yacht
That's exactly it. Where it is wet or might get wet, you do not want copper touching aluminum. Where it is dry there is no problem.
__________________
David
Life begins where land ends.
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04-06-2011, 03:13
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#14
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Registered User
Join Date: Dec 2009
Location: Cherbourg - France
Boat: Le Guen Hémidy, Lévrier de mer, 16 m / 53 ft, "AZAWAKH"
Posts: 157
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Re: Mounting Fluxgate Compass in Aluminium Yacht
We have several fluxgate compass inside Azawakh (aluminium) and they all work fine since years.
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Fair winds
Eric - S/Y Azawakh
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04-06-2011, 07:05
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#15
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always in motion is the future
Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 19,052
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Re: Mounting Fluxgate Compass in Aluminium Yacht
Quote:
Originally Posted by David M
That's exactly it. Where it is wet or might get wet, you do not want copper touching aluminum. Where it is dry there is no problem.
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Correct. For electrolysis to occur you need all three:
1. Anode
2. Cathode
3. Electrolyte (= water in this case)
which means that copper & aluminium in a dry environment is not a problem.
ciao!
Nick.
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