Fluxgate Compass location for ST4000 Autohelm

[malgase]

I have a 1986 MKI C34, and was wondering where other MKI owners have placed the fluxgate compass to minimize calibration error.  I currently have mine on the rib structure across the bilge about 14" aft of the mast step.  The best calibration error I can get there appears to be 22-23 degrees, and Autohelm recommends 15 or less.

Are there any other ideas out there that could save me doing several hours worth of circles on the water?  I already dread the the hassle of un-threading and re-threading the wiring to move the unit from its current position.

Whats driving this is trying to get a GPS and the ST4000 to communicate.  The autopilot steers to the BEARING it receives from the GPS, which could be 10-40 degrees off the intended course due to error in the ST4000 reading relative to the magnetic compass.

Thanks!
Michae

[mvazmina]

I have an 86, #27 and the compass is located under the sink, It is actually secured to the drawer just inside the access door on the side of the sink.  When mine is working it only has a 2-3 degree error.

[Captain Bob]

Mine is high in the bilge just aft of the mast compression post. Works fine and the unit is sealed against any water though my bilge is pretty dry.

[Ken Juul]

I have mine mounted in the same location as yours.  Other than the initial move when I picked up the boat I haven't used the autopilot at all.  When I did I was averaging 80-120 degrees off.  Haven't looked into it yet.  I was assuming the errors were caused by the batteries being so close, but it sounds like that may be a standard location.  Since compases are affected by magnetic fields have you tried rerouting any electrical lines that may be close or possibly shielding the fluxgate.  I have this ahead of me so any tips you learn please share.  Good luck

[Mike Smith]

Mine is under the sink, and is always within 2-3 degrees of my steering compass reading.  You might try checking a hand held compass at that location and comparing the reading to your steering compass.  If they are much different then you have a big chunk of metal or a magnet affecting the fluxgate compass at that location.  What do you keep in the sink drawer?

[rdavison]

I just moved mine from the stringer near the battery box forward to the one yours is mounted on.  Reason was that after battery upgrade with heavy wiring moved toward the center of the boat in the battery box, I could tell how much the batteries were charging by how far to the right the boat deviated!

Current location seems stable with regard to charging current and voltage.  Haven't tried calibration yet.

BTW, I just cut the wires and soldered in a new section, than sealed well with heat shrink.  Good practices required but no big deal.

Randy Davison  #1268 1993 k7voe

[sailor2mon]

it is easy and works well to mount it in the rear cabin directly under the pedestal on the bulkhead..it is "centered" that way and is not interfered with by magnetic  sources...it has worked well for me for 7yrs.