Conference unifix::sailing

By flux-gate compass I assume you mean an electronic compass using a 
flux-gate to give magnetic heading. Why do you want one and why doesn't 
a traditional mechanical compass fit your needs?

Electronic compasses are expensive (several hundred dollars US), less
reliable, and require electrical power (a total electrical system
failure means no compass). The only real advantage (to me as a cruiser) 
of electronic compasses is that they can be used with a satnav and a
knotmeter to provide automatic dead reckoning. In my view, an electronic
compass absolutely should not be the only steering compass on board. A
good traditional compass (eg, Danforth, Ritchie, Silva, Plath) isn't
expensive and should last for years with no maintenance. 

While, I gather, at least some electronic compasses have no deviation, 
they still must be mounted away from magnetic materials (such as the 
engine). Some electronic compasses, the flux-gate among them, must be
vertical to be accurate (a recent Practical Sailor test of the new
Autohelm flux-gate electronic handbearing compass showed that a small
deviation from vertical -- a few degrees -- could result in a 20 degree
error in its reading). 

    Another aspect is the feel of the compass when steering.  The flux-gate
    I have seen have a set time for the calculations and readout precluding
    a steady "view" of the real boat motion.  
    
    I have one I use for bearings and for that it is great.  I stick
    with my no batteries required magnetic compass for getting where
    I want to go.
    
    Hank
    

    I agree with Alan in that an electronic compass should not be the
    only or even the primary compass on board.  Too many things can
    go wrong with it.  The major advantage I see with them (from a cruising
    perspective) is that they can be integrated into your instrumentation
    and even that is no big deal for cruising.  
    
    We have the Sailcomp system and it worked perfectly.  We got pretty
    good at steering to the digital readouts and even got to the point
    where the card compass just didn't have the exactitude we could
    steer to.  The other advantage is that you can put the readouts
    any where providing a "line of sight" that does not reguire the
    helmsman to move his/her head to get the compass heading.  That
    spoils you real quick!
    
    Dave

I, too, agree with Alan, for all the reasons he mentions.  Other than 
interfacing with electronic nav systems, the one other advantage we 
enjoyed using the fluxgate compass on the Condor 40 was the ability to 
"dampen" the motion to any desired level.  Data is collected at an 
impressively fast rate, of course, but the averaging calculations can be
made over smaller or bigger chunks of that data, thus allowing one to go
from display updates of well under a second on up to perhaps ten seconds. 

Something around 3-5 secs suited us fine, given that we were doing nearly
20 kts at times in the 8'+ waves and 30+ kt winds.  This kept the constant 
little wave hits which yawed the boat back and forth several degrees each
time from disrupting the helmsman's attention to the course being sailed.

J.

    
    I was toying with the idea of building an auto-pilot this winter
    using a flux-gate compass (like autohelm), but found that the
    flux-gate compass costs more than the autohelm, which contains
    a flux-gate compass!!
    
    I've given up the idea, but I'm still curious about who manufactures
    flux-gate compasses and how much they cost if purchased directly
    from them.  Does anyone know?
    
       Jim (Irish Mist)
    

    A good well proven fluxgate can be had from Brookes & Gatehouse
    in the UK, but you will need a very deep pocket.
    The Autohelm Fluxgate Personal Compass proved itself to me during
    last season in all conditions and was especially useful for taking
    repititive bearings on other vessels while crossing the English
    Channel at night.
    
    Cheers......Pete