Conference unifix::sailing

I used mineral oil, (the kind you buy in drug stores) in my Aquameter.  I 
mixed it with the existing fluid with excellent results.  It was a little 
difficult to get all the air bubbles out but I eventually succeeded.  The 
reason that bubbles formed in the first place was that the filling plug 
screw hole was stripped.  The screw is stainless and the housing is 
plastic.  I had to dril out the hole, tap it, and replace the plug with a 
larger screw.  It's been working great.

I ended up calling Ritchie and they told me that they use mineral spirits. I 
filled it last night and was able to remove all but a small (1/16" dia) bubble.

Dave

>
>I ended up calling Ritchie and they told me that they use mineral spirits. I 
>filled it last night and was able to remove all but a small (1/16" dia) bubble.
>


Do you mean like paint thinner?  Isn't that aromatic, somewhat volatile, 
and flammable? I'm sure that was not what was in my compass.  The mineral 
oil has worked fine.

John 

    I second the concern regarding mineral spirits. Mineral oil has the
    properties needed. I don't know why mineral spirits would be suggested.

    Yeah. I use mineral spirits to clean my paint brushes......
    
    
    Gregg

I just called the manufacturer again and confirmed that they do in fact use
mineral spirits. They said that mineral oil would be too viscous to give the
kind of response they want. 

On a related subject, I tried the compass out in my car just for the hell of it.
While driving in a straight line in my driveway (very slowly) I noticed that
even within a 10' - 15' distance there was a swing of as much as 20� to 30�. I
assume that that was due to the other car in the driveway. In any case, How do
they make compasses that can be used in a car, which is surrounded by steel and
electrical currents? 

Dave

    They make compasses for a car the same way as for a boat - with
    compensating magnets that you can adjust to tweak out as much deviation
    as possible. If you are guessing that car compasses aren't very
    accurate, given the steel environment, you are getting the right idea.
    
    After all, one does not have the option of changing their course a few
    degrees in a car, usually. The heading info needed in a car is much
    more gross than when navigating in free space.
    
    Bill
    

    
    	Which is why the excitement of GPS coupled with a map on ROM or
    whatever. All major companies have `em, but I think only Toyota and
    Chrysler are experimentally marketing them.
    	Between the phone taking up one's ears and this screen on the dash
    catching the eye, larger bumpers and air bags may become prevalent as
    well...

    Isn't this where field effect compasses come in?  I would like to know
    more about them - from what I understand they measure the field in 2
    directions at 90degrees to each other and then electronically determine
    the difference.  This supposedly does away with interference.  Anyone
    know more about them?
    
    

    I think that field effect compasses suffer from interference the same
    as other magnetic compasses, however they have no moving parts, so do
    not suffer from swinging and other such problems.
    
    The other advantage is that they give an electronic readout, suitable
    for Integrated instruments etc.
    
    Chris
    

What is the fluid in a compass?  My RDF compass has developed a big 
bubble which is starting to affect the compass card's rotation.
Steve
 

    Steve it could be either alcohol or very light oil........Mine was
    topped up by the manufacturer for free.......
    
    Pete

    More than likely a light oil. The mfgr. or any compass repair
    should easily handle this...  Eldridge lists them.
    
    JIm

    I did a nav. course once where the instructor said that it was alcohol,
    he even suggested the use of Gin if you were in a fix.
    
    Fortunately I have Loran so can use the Gin in other ways.

    I wonder if some compasses aren't filled with silicone fluid.  It is
    available in various viscosities, won't freeze, and won't cause
    corrosion.  It is a logical choice I would think.
    
    

    I called the maker of my compass, 'richie' and they said mineral
    spirits, as they sent my a quart.  

    Does anybody have experience with disappearing bubbles in
    the compass fluid? This summer my compass developed a small
    bubble, about 3 mm, which disappeared by itself. LAter in the
    fall, a bubble appeared again and this time kept increasing is
    size. I decresed its size by venting and squeezing the diaphragm,
    but the damn thing kept growing. At theend of the season, it had about
    2 cm diameter. I removed the compass and brought it home, and there
    before my eyes, over three weeks period the bubble shrank and 
    eventually disappeared. It this period the compass was completely
    stationary and somewhat warm, being in my basement (70 to 75 F).
    
    The only explanation I can think of is that the gas (air) disolved
    in the fluid (I presume mineral oil). I would appreciate any sharing
    of similar experience, and/or possible remedies. If it happened
    once, I am sure it will happen again. Is it time to replace the
    fluid? Is there a good source for compass compatible stabilized
    mineral oil? 

>                           -< Compass fluid bubbles >-
 My previous boat had a compass containing a bubble which filled the top of the 
compass (a grid compass!). (The surveyor did comment that it was the biggest one
 - bubble, that is -  he had seen in 25 years.)


	I filled it up with about 3 tablespoons of Turpentine. WARNING*- this is
covered by MSDS's  as a hazardous material. (But it smells  w o n d e r f u l)


	Do not use TURPS SUBSTITUTE with does not mix with the compass oils.



	I had no further trouble. 


	Fair winds


		Gregg

My guess is there is a small leak that will vent air but not fluid.
I have seen this on other things.

    We just bought a used boat that has a pedestal mounted compass. It is
    somewhat discolored. Either the card or the fluid in the compass has
    yellowed. Is this due to being exposed to the sun over a long period of
    time or is it a defect with the compass?
    
    Can this be corrected or do I need to replace the compass?
    
    
    Bob

My friend's boat had a large bubble in the compass for ages. On night 
passage we realised the compass gave wild readings. Turn out the card was 
touching the bottom of the bowl.

It was our only nav aid aboard so I drilled a hole in the top and poured 
in Castor Oil (from the First Aid cabinet). The compass worked OK and the 
fluids mixed. 

The compass type is a Sylva 4" sphere, bulkhead mounting. The bowl is made 
of plastic, acrylic or something. I sealed it with adhesive the next day.
The bubble came back after a few weeks, but not so big.

Steve

    Re .17
    
    I had a  compass that did the same thing. The bubble would disappear
    as the summer heated up and then reappear in the fall. So I agree that
    it's related to temperature, but I have no explanation.
    
    Paul 

re .17:

Most compasses can be overhauled/repaired. I would suggest sending your 
compass to a competent repair facility. (Robert White in Boston repaired 
our backup steering compass for a reasonable price some years ago.)  The
bubble indicates a problem that will likely need expert attention. 

It is worth remembering that the pivot bearing on which the card rotates 
wears and eventually will cause the card to stick or respond slowly. 
Also, the plastic domes used in the majority of compasses are degraded 
by sunlight and eventually craze (develop minute cracks). Depending on 
the age and quality of your compass, replacement might be an alternative. 

The dome on our compass has some crazing, and when it is time to replace 
the compass in the next few years, I will spend the extra money for a 
Plath with a glass dome.

    re .20
    Sunlight UV eventually breaks down the UV inhibitor particularly
    in some earlier compasses. The fluid  turns yellowish and may even
    stain the card. If possible the fluid should be replaced.
    
    re. 17
    In that note I asked for information on bubbles that seem to be
    appearing and dissappearinf as a funtion of temperature. I have
    since talked with people at Robert White of Boston and Andrews
    Compass Service at Mattapoisett. It appears that this is a rather
    common problem typically due to microcracks in either the dome,
    the rubber O-ring "equatorial" gasket, or the rubber expansion
    bellows. When cold, and in paticular after it has lost
    some fluid, the compass sucks in air through microcracks due to
    the fluid contraction. When it warms-up, the air slowly disolves
    in the fluid. The permanent fix is to feplace the offending part.
    In my case since the compass is mada by an obscure french firm parts
    are near impossible to find, according to the two repair shops. 
    They have suggested however, that if I refill the compass to replace
    lost fluid, I should be able to prolong the inevitable replacement.
    I am planning to buy a pint of compass "oil" (actually a highly
    refined, uv stabilized mineral spirit) from Robert White and keep 
    in fine-tipped squezzable bottle on the boat. I do like the performance
    of by compass and I want to keep it as long as possible. When the
    rate of bubble size increase reaches intolerable magnitude I will
    replace the whole thing.
    
    /Dimitri