fluxgate compass
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Mary & Roger
- admiral
- Posts: 105
- Joined: Wed Mar 26, 2008 2:52 pm
fluxgate compass
Has anybody had to move the fluxgate compass on a powercat? I can't get less than 15 degrees deviation, and it needs to be boxed/swung fairly often. I don't have any motors or tools within 3.5' of the compass. I have an inverter, and a 100amp battery charger under the lower helm, but all is over 3' away. It has worked well in the past, and the compass checks out good. Gremlins????? Roger on Teamwork
Re: fluxgate compass
Where is your fluxgate head presently mounted? Mine (hull 34012 - old style interior) is under the forward seat back of the dinette.
Candy Chapman and Gary Bell in Stray Cat, MV34 hull 12
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Mary & Roger
- admiral
- Posts: 105
- Joined: Wed Mar 26, 2008 2:52 pm
Re: fluxgate compass
Hey Stray Cat, my compass is in the aft seat stbd side of the dinette. I can't change to where yours is, as I have a central vacuum under center seat. Still more than 3' from compass. I wish the GPS compasses would come down in price soon. Roger on Teamwork.
Re: fluxgate compass
I am on my 2nd replacement fluxgate and each cures the deviation problem. Mine is also located in the stbd side seat (each of them) so I suspect the issue is the compass not its location. Sorry.
John Sawyer
Katlin
34/076
John Sawyer
Katlin
34/076
Re: fluxgate compass
What brand and model of fluxgate compass do you folks have, and what sort of navigation do you do?
Mine is a 2002 Raymarine outfit (warts and all), and I don't 'swing the compass' rather I go through Raymarine's 'linearization' procedure, where after aligning the compass on a single heading to the GPS COG (done when/where currents and winds are not an issue) and and then under prompting from the system brain, I follow two or more slow circle courses with a constant rate of turn. Usually after the second or third orbit, the system says it is done, and at that point the brain computes and corrects all the deviations it observed, so that the readout on the autohelm and other displays is corrected for deviation. I am fortunate in operating in an area of the world where the variation is pretty much constant wherever I go, and have told the brain to factor that out as well, so that my autohelm display is in True rather than Magnetic or Compass. This is the easiest for me to track and correlate on my entirely independent Coastal Explorer laptop system and an equally independent iPad iNavX system, and particularly for offshore work where we are minus the customary river landmarks, on the backup paper charts.
So, for offshore work I run all those systems in parallel. Belt and suspenders (describes what I wear just now too!). OK. Call me what you like, I navigated 4000 ton destroyers all around the North and South Pacific, and old habits die hard. Stray Cat is now berthed in Multnomah Channel, a branch of the Willamette River where it joins the Columbia near Portland, Oregon, and mostly my day to day 'navigation' amounts to keeping the bows between the green and the red buoys. I teach Coast Guard Auxiliary boat crews and commanders (coxswain) navigation for much of the small boat recreational boating safety and search and rescue patrols hereabouts. All that said, we swan about here with landmarks everywhere to be seen, and so real navigation using real compass courses and carefully considered speeds carefully plotted on currently corrected paper charts are no more significant than you would use such things to drive your car into town.
My point? If you boat outside of sight of handy landmarks like riverbanks, headlands, buoys and daybeacons (don't forget getting caught in the fog or disoriented in unfamiliar settings!), AND if you don't have or understand your radar, AND if the batteries for your several GPS systems are all exhausted (including today nearly all the smartphones)--THEN you really need fully corrected compass courses that you can relate to a paper chart so that you can produce a Kosher DR plot.
When I leave my river and venture outside of sight of land I have everything going, particularly including a paper chart plot. In the normal course of events I don't expect to ever need all that, but it works out that way particularly because I have all that redundant navigation.
What, and how much corrected navigational information that can be plotted on a paper chart do you need? In my river environment I frequently set the autohelm to keep a course that I don't record, or pay any attention to the numeric value of, simply because it is not information I will use. 'Iron Mike' usually is steering here because 'he' can hold an arrow straight course and it is easily corrected with plus or minus one or ten degree buttons; but the number on the display is of no interest.
Mine is a 2002 Raymarine outfit (warts and all), and I don't 'swing the compass' rather I go through Raymarine's 'linearization' procedure, where after aligning the compass on a single heading to the GPS COG (done when/where currents and winds are not an issue) and and then under prompting from the system brain, I follow two or more slow circle courses with a constant rate of turn. Usually after the second or third orbit, the system says it is done, and at that point the brain computes and corrects all the deviations it observed, so that the readout on the autohelm and other displays is corrected for deviation. I am fortunate in operating in an area of the world where the variation is pretty much constant wherever I go, and have told the brain to factor that out as well, so that my autohelm display is in True rather than Magnetic or Compass. This is the easiest for me to track and correlate on my entirely independent Coastal Explorer laptop system and an equally independent iPad iNavX system, and particularly for offshore work where we are minus the customary river landmarks, on the backup paper charts.
So, for offshore work I run all those systems in parallel. Belt and suspenders (describes what I wear just now too!). OK. Call me what you like, I navigated 4000 ton destroyers all around the North and South Pacific, and old habits die hard. Stray Cat is now berthed in Multnomah Channel, a branch of the Willamette River where it joins the Columbia near Portland, Oregon, and mostly my day to day 'navigation' amounts to keeping the bows between the green and the red buoys. I teach Coast Guard Auxiliary boat crews and commanders (coxswain) navigation for much of the small boat recreational boating safety and search and rescue patrols hereabouts. All that said, we swan about here with landmarks everywhere to be seen, and so real navigation using real compass courses and carefully considered speeds carefully plotted on currently corrected paper charts are no more significant than you would use such things to drive your car into town.
My point? If you boat outside of sight of handy landmarks like riverbanks, headlands, buoys and daybeacons (don't forget getting caught in the fog or disoriented in unfamiliar settings!), AND if you don't have or understand your radar, AND if the batteries for your several GPS systems are all exhausted (including today nearly all the smartphones)--THEN you really need fully corrected compass courses that you can relate to a paper chart so that you can produce a Kosher DR plot.
When I leave my river and venture outside of sight of land I have everything going, particularly including a paper chart plot. In the normal course of events I don't expect to ever need all that, but it works out that way particularly because I have all that redundant navigation.
What, and how much corrected navigational information that can be plotted on a paper chart do you need? In my river environment I frequently set the autohelm to keep a course that I don't record, or pay any attention to the numeric value of, simply because it is not information I will use. 'Iron Mike' usually is steering here because 'he' can hold an arrow straight course and it is easily corrected with plus or minus one or ten degree buttons; but the number on the display is of no interest.
Candy Chapman and Gary Bell in Stray Cat, MV34 hull 12
Re: fluxgate compass
The heading on my autopilot has always been way off from my actual course - currently about 90 degrees off. I've got an 04 MV34 with the flux gate compass in the starboard salon seat. I'm not aware of anything close that would interfere with its operation. I tried the Raymarine technique of driving around in circles for a while which, as I recall, improved the situation temporarily but I don't think its ever been less than 15 degrees off. I've just taken to ignoring the number on the autopilot, which so far hasn't had any adverse consequences. My magnetic compasses are spot on so I'm feeling pretty safe with this approach but it is annoying. Should I be more concerned and consider replacing the fluxgate compass? Any input would be appreciated.
Jerry Shinn
MV 34-45
SHINNDIG
Jerry Shinn
MV 34-45
SHINNDIG
Re: fluxgate compass
we have pretty much operated for 7 years like jerry with no problems. i think it all boils down to how you want to use the autopilot. we just set it and fine tune the cross track error manually. if you want more than this, as i know teamwork does, then the alignment becomes important.
john & diane cummings
duetto mv34 #23
duetto mv34 #23