Date:         Sat, 27 Jan 2007 17:22:00 -0600
Reply-To:     Chuck Mathis <cmathis@HOUSTON.RR.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Chuck Mathis <cmathis@HOUSTON.RR.COM>
Subject:      Re: Target Compass
Content-Type: text/plain; charset=US-ASCII; format=flowed

Loren,

How steady is that small marine compass?  Is it sensitive to the
electronics in the dash?  I have always assumes a magnetic compass
would be pretty close to useless in an automobile.

In the mid '90's I was the Operations Officer/Navigator on a Coast
Guard 110' patrol boat.  When the boat came from the manufacturer the
magnetic compass was mounted directly on the bridge console.  Being off
level and close to all the electronics there the damn thing was
impossible to adjust reliably.  Every time somebody tweaked the
instrument lights the compass moved.  Fitting a teak base helped that
problem some but it still swung every time the HF radio transmitted.  I
managed to adjust it to a reasonable and consistent error except at 135
degrees where it had a 12 degree spike that I could not figure out.  We
installed a flux gate compass in the electronics space behind the
bridge with a display next to the magnetic compass.  After the initial
set up it worked great for the couple of years I was there and my
replacements told me it was still working fine four years later.  Of
course that unit was a fairly sizable marine unit not one of the Target
variety.

Chuck
'85 Wolfsburg Westy - 'Roland the Road Buffalo'

> Date:    Sat, 27 Jan 2007 13:08:41 -0800
> From:    Loren Busch <starwagen@GMAIL.COM>
> Subject: Re: Target Compass
>
> RE: compasses
> Actually a Vanagon related subject I know something about.
> Although not familiar with the specific compass you are referring to
> I'm
> familiar with the general type, the small flux gate (or electronic)
> compass.  I used to work for a firm here in Seattle that did virtually
> all
> the compass adjustment/calibration for virtually every vessel on Puget
> Sound, and that includes the carrier Abraham Lincoln.  Two members of
> the
> staff were considered world experts on the compass.  I managed to
> absorb a
> little information along the line.
> First, the small flux gate compasses are VERY sensitive to position.
> There
> was one model of hand held that we refused to stock it was so prone to
> error
> if not held absolutely level.  This translates into big errors if not
> mounted exactly as the manufacturer instructs.  Newer models tend to
> be less
> sensitive to this problem.  They are also much harder to compensate
> for or
> adjust in a vehicle.
> As for the good old fashioned magnetic compass, I have one of these
> mounted
> dead center of the cover over my instrument cluster:
> http://www.thecompassstore.com/51pilot.html
> and it works perfect.  To my pleasant surprise it needed virtually no
> adjustment when mounted in that location and has been working fine for
> five
> years now.  Well damped, I've never had the various problems with it
> that
> I've encountered over the years with other dash mounted compasses.
> The compass at Target may well be a great unit but be warned that the
> small
> flux gate compasses can be very temperamental.
> YMMV
>