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Old 11-09-2008, 17:56   #1
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Where to Locate Fluxgate Compass - Raymarine st 4000+

Installing a Raymarine ST4000+ on a Pearson 35. Having problems figuring out where to locate the Fluxgate compass. Instructions say aft on centerline, if possible. Problem is engine is aft with all it's electrical interference problems. How close can I get it to the engine without causing problems. Instructions say to swing boat and check deviation of hand held compass from boats compass. Unfortunately, can't do that as I'm a long way from home and single handing. Hoping your experience will substitute.

Best location is next to the batteries about 3' away from the engine. Seems far enough away but fear electrical pollution. Next best position is next to the stove but will be in a location that is perfect for storing food in tin cans. Doubt the steel cans can't be good for the compass's accuracy. Could put the compass on the lazarette bulkhead but that's the best place to keep the stern anchor with it's chain. The problem with the least electrical problems is on the bulkhead in line with the mast. That's a bit far forward for acceleration errors if I'm reading the installation instructions correctly. Just wonder how senstive these fluxgate compasses are to magnetic and dynamic forces??

How much current does the Autopilot draw on standbye mode?? Wonder whether I should have a separate switched power source for the autopilot vice running it with a common power source for the other instruments?? I'll have about 150watts of solar panels but am going to be in the PNW which isn't known for sunshine. Will have to run engine to supplement the solar input and hate to do that. Only have 200 amps of house batteries so don't want to run them down unnecessarily when sailing. Won't be using the A/P when sailing as I also have windvane steering.

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Old 11-09-2008, 21:42   #2
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I mounted my fluxgate right at the base of the rudder shaft where it comes thru the hull. There is nothing within 6' that is magnetic.
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Old 11-09-2008, 21:57   #3
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For the fluxgate for an autopilot compass, it does not matter much where you mount it. Its sole purpose is to provide a reference, irrespective if what it thinks is magnetic north is correct or not. This is why you have an adjustable magnetic compass on board with a deviation table. You don't want your fluxgate to be the compass you do your navigation with in the first place. Its sole purpose is to hold a course. Of course you want your fluxgate away from magnetic fields than can come on or off with the flick of a switch. Don't though rely on your unadjusted fluxgate compasss to tell you magnetic north. If you have a choice, mount it as close to the vessels center of mass as possible so as to minimize the effects of acceleration. (pitching, rolling, yawing)
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Old 12-09-2008, 17:10   #4
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Originally Posted by roverhi View Post
Installing a Raymarine ST4000+ on a Pearson 35. Having problems figuring out where to locate the Fluxgate compass. Instructions say aft on centerline, if possible.
I would tend to have a bit of a flexible mind with regard to the need to be close to the point of least motion in the boat. Our own is located about 9 or 10 foot up the mast (as our boat is steel) and it works fine with the only times it has got "lost" for a few seconds (as seen on the electronic steering compass) is in very steep, heavily breaking tidal rip waves where it would be madness to do anything but steer manually anyway and a card compass is also having problems from the violent motion.

We do not have a ST4000+ though, but a ST6001+ Control Head, Type 300 Course Computer with fluxgate located as stated. I suspect there is no difference likely to be found due to that though.

So I would tend to try it in the boat where it is reasonably clear of magnetic influences which may change their character and give that location methodology preference over motion. Maybe just do a temporary install first and try it in some violent seas.
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Old 12-09-2008, 17:26   #5
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For the fluxgate for an autopilot compass, it does not matter much where you mount it. Its sole purpose is to provide a reference, irrespective if what it thinks is magnetic north is correct or not. This is why you have an adjustable magnetic compass on board with a deviation table. You don't want your fluxgate to be the compass you do your navigation with in the first place. Its sole purpose is to hold a course. Of course you want your fluxgate away from magnetic fields than can come on or off with the flick of a switch. Don't though rely on your unadjusted fluxgate compasss to tell you magnetic north. If you have a choice, mount it as close to the vessels center of mass as possible so as to minimize the effects of acceleration. (pitching, rolling, yawing)
I can't agree less. Improper placement of the fluxgate, especially with Raymarine, but including most units, will have your autopilot wandering all over the place and doing lots of strange things. And getting as far away from the engine is a must. Try to mount it as close to centerline as possible but that is not as critical and also try to keep it as far aft as you can but it does not have to be in the stern. Ours is mounted in the center of the boat under our dinette. Look for possibly inside a cabinet or hanging locker or under a berth or settee. Be sure it won't get wet. You really have a lot of flexibility but do be careful of magnetic influences.
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Old 12-09-2008, 17:28   #6
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Best location is next to the batteries about 3' away from the engine. Seems far enough away but fear electrical pollution
I had trouble on the last boat finding a place. What you can do is take the compass to near where you want to mount is and connect it all up and rotate it with your hands to see the display. You need to find a place where it will read all 360 degrees. When you do the calibration you will steer in circles. This lets the computer build a deviation table based on your boat. It then saves it for later use. You really just need a place where you can swing a full 360 circle. It may not be perfect but with slight deviations it will work.

On the last boat it was forward near the V berth and it failed. It worked near the starting battery and that is where the new owner has a compass that works a treat.
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Old 12-09-2008, 17:45   #7
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On the last boat it was forward near the V berth and it failed.
Paul - do you know whether that was due to pitching motion or a nearby magnetic influence (such as chain, etc)?

Just asking out of interest to add to the fund of experiences.

John
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Old 12-09-2008, 20:05   #8
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Paul - do you know whether that was due to pitching motion or a nearby magnetic influence (such as chain, etc)?
It was do to some interference. We could find nothing on the boat but it was real. The guy that helped me was a good auto pilot guy and he has found many times there does not really seem to be an obvious reason though some times the owner shifts something on the boat that drive the fluxgate nuts. We unmounted it and rotated the compass to prove there was something. We then had a long cable and went to various places to find a spot that worked. Using that method you can find a place that will work. I don't see that it matters where as much as if it works.
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Old 12-09-2008, 22:13   #9
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Thanks for the response Paul.

I certainly agree with your last 2 sentences. I've even known of them working ok inside steel yachts after a try and see (in fact a hand held compass works surprisingly well inside our steel sail boat).

People often look askance when they discover our fluxgate is up the mast but when one looks at the boat in pitching it is for us just around about the same distance from point of pitching rotation as having it low in the boat around 2/3 of a boat length from the stern. It is subject to higher roll accelerations though but they not very great in a sailboat, of course, so hasn't been a problem.

(And just to clarify so we don't have others getting into a lather , as I said before our boat is steel so I am not recommending the mast as the place for others to put their fluxgate. Am just elaborating on the "try anywhere" theme .)

John
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Old 13-09-2008, 05:20   #10
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I certainly agree with your last 2 sentences. I've even known of them working ok inside steel yachts after a try and see (in fact a hand held compass works surprisingly well inside our steel sail boat).
The guy that helped me installs them, on commercial tug boats.

If you add a long cable to the compass there is no reason you can't move it around until you find "the place". It would be nice if it was in a place where you won't be storing your anchor or something that will effect the compass.
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Old 13-09-2008, 05:37   #11
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I put one in last year and used duct tape [where would we be without it] as a temporary hold. I followed the directions and did about 15 circles on the water. [you may have heard about me] Anyways, the fluxgate turned out to be faulty and Raymarine swaped it quickly. Just wanted to add that caution. I mounted mine in a starboard compartment below the water line...about 10 feet from any magnetic metals, as directed. It works fine [the duct tape has been replaced w screws...]
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Old 13-09-2008, 10:05   #12
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I put one in last year and used duct tape [where would we be without it] as a temporary hold. I followed the directions and did about 15 circles on the water. [you may have heard about me] Anyways, the fluxgate turned out to be faulty and Raymarine swaped it quickly. Just wanted to add that caution. I mounted mine in a starboard compartment below the water line...about 10 feet from any magnetic metals, as directed. It works fine [the duct tape has been replaced w screws...]

That is a good point since I have done several installations where the fluxgate from Raymarine was defective.
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Old 27-09-2008, 15:01   #13
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I have Pearson 34 and mounted the compass in a storage compartment adjacent to the gally sink, down low. It needs to be as low as possible and as near the center of the boat as possbile. This works for me. I keep the auto pilot on Standby all the time in case I need to use it. I don't recall how much power it draws but is very little and I also have it same circutiy as by GPS and wind instrument.
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Old 27-09-2008, 15:06   #14
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Right between the engine block and the big magnet you use to collect the car keys from the bottom.




























Or on centerline, low, and in the center of the boat.
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Old 27-09-2008, 16:37   #15
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HNS 134: sounds like your compass is mounted quite close to the engine. How far away?? I'd love to mount it on the engine room bulkhead but afraid of compass error from being so near such a large hunk of iron.

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