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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #21  
Old 08-06-2014
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Re: Bad compass?

When I screw it to bulkhead card was reacting on screwdrivers magnetic tip.
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Re: Bad compass?

I found this info interesting on Natural and Artificial Magnetic Anomalies:

http://prntscr.com/4a7jhf
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  #23  
Old 08-06-2014
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Re: Bad compass?

If there were a Natural and Artificial Magnetic Anomalies then other compasses would be affected...easy enough to rule out, any other compasses handy and are they working correctly?
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Re: Bad compass?

if your compass card reacts to the steel screwdriver, i'd say you have an adjustment/calibration problem, not a mechanical problem with the jewell. It's kind of difficult to describe without a visual but imagine: the compass card is a circle and it needs to be in "sync" (not the best term) with another circle (the magnetic field). you use a set of magnets or ferrous parts to bring the two circles such that their centers match. they are never quite exact which is why when you have a compass professionally adjusted, you will get a "deviation" chart which is unique to every compass on every boat. it is also why the degree of deviation will be different with each magnetic heading.

you can use a hand-bearing compass or an orienteering compass to roughly calibrate. you can also use a gps either set to magnetic or with variation taken in to consideration as long as you are moving while you adjust and there is no influence of wind or tide.

Your Danforth compass looks a lot like the Plastimo "Contest". I highly doubt that Danforth make this compass. Do take a pic of the back of the compass so we can all see where adjustments may be made. there should only be two adjustments. One for each axis.
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Re: Bad compass?

Quote:
Originally Posted by hangupndrive View Post
there should only be two adjustments. One for each axis.
There is two screws. One right under "0" at bottom on compass. Another one on bottom right side off compass.

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Re: Bad compass?

Here's why I couldn't find the calibration/compensation/swing procedure:

Danforth are bulkhead mount compasses originally made by the Aquameter Co.. When ITT purchased the Aquameter Co. the Saturn was manufactured by Rule Industries and sold as part of the Danforth Compass line. The Saturn compasses were discontinued in 2009. This compass was not a repairable compass, it was permanently "glued" together and cannot be disassembled. If your compass has an air bubble or the card is tilted at an angle the only choice is to replace the compass.

It does not say that it "isn't adjustable". Here's what I would do: the two screws are likely the adjustment screws. one is for north/south, one is for east/west. When you're faced north, adjust the bottom right screw (I think). When you're faced east or west, use the screw on the front. I think you can tinker with it at the dock to see if it will work then once you get the hang of the adjustment, grab another person and do it properly on the water.

Here is the procedure from the Ritchie website. I know, different make but they all work essentially the same way.

https://www.ritchienavigation.com/me...structions.pdf

Keep us posted
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Re: Bad compass?

Once you've got it swinging and can adjust it, Get out on open water,no wind or current. Using a GPS course 0 degrees adjust screws (mini Bishop's Balls) to match as close as possible. Change course E 90 do it again and so on ,'boxing the compass' Smaller increments as you get the hang of it. Finally go around again and record the errors (+ and -)on a paper. Start at N and then each cardinal point on a line from 0 to 360 The recorded points should form a regular shaped sinusoidal wave. This is your error card info. Gps set to magnetic of course.
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Re: Bad compass?

Quote:
Originally Posted by Capt Len View Post
Once you've got it swinging and can adjust it, Get out on open water,no wind or current. Using a GPS course 0 degrees adjust screws (mini Bishop's Balls) to match as close as possible. Change course E 90 do it again and so on ,'boxing the compass' Smaller increments as you get the hang of it. Finally go around again and record the errors (+ and -)on a paper. Start at N and then each cardinal point on a line from 0 to 360 The recorded points should form a regular shaped sinusoidal wave. This is your error card info. Gps set to magnetic of course.
Ah, very good!!! We used to put a float in the water & run up & down in all directions. Was never quite sure what my Dad was doing? He said he was boxing the compass. We managed to stay off the rocks, so I guess he did know what he was doing?

Paul T
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Re: Bad compass?

Showed compass to guys in marina, verdict: junk, return it if you can, if not garbage can is right there.
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Re: Bad compass?

Not surprised from what I read about that model. Even still, kind of anti-climactic!
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