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Old 10-03-2015, 01:25 PM   #1
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Flat card vs. magnified globe compass

Does anyone use a large, flat-card ships steering compass versus the standard globe compass with magnified card? I have an opportunity to grab a new Saura model for an excellent price - to be used as the primary steering compass. Even with a 6" card the numbers are quite small to read, although it is down to the degree.

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Old 10-03-2015, 01:30 PM   #2
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You are required to have one, but who uses a compass anymore? Mine is only there to run my old autopilot. Buy something you will like looking at?
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Old 10-03-2015, 02:28 PM   #3
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I have a flat 4 3/4 inch card, it is part of the auto-pilot system.
Has a magnifier mounted over the face where read. Also a Saura.
I still have the one from my previous boat with a 9 3/4 inch card, will likely
investigate the possibility of changing the pick-up sensor on the bottom.
Bigger, steadier equals better control.

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Old 10-03-2015, 03:37 PM   #4
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Greetings,
Mr. X. We use our compasses (upper and lower) on a regular basis as/with reference to our paper charts. Granted, it's NOT our primary "direction finder" but quite useful all the same IMO. Our AP (Wood Freeman) has it's own compass in a locker and to refer to it I would have to get down on my hands and knees, grab a flashlight, crawl into the locker and take the cover off the WF.
Which reminds me, I'll have to get our compass adjusted one of these days.
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Old 10-03-2015, 03:50 PM   #5
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Quote:
Originally Posted by makobuilders View Post
Does anyone use a large, flat-card ships steering compass versus the standard globe compass with magnified card? I have an opportunity to grab a new Saura model for an excellent price - to be used as the primary steering compass. Even with a 6" card the numbers are quite small to read, although it is down to the degree.

Looks a bit like a "Sestrel Captains Compass" copy, i like it.
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Old 10-03-2015, 08:49 PM   #6
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We use our magnetic compass to hold a heading, using the two plotters to confirm the heading or change it when the current or/and wind changes. This makes it far easier and more accurate to maintain the desired course than chasing the plotters around and always being a little bit late with the corrections. We removed the autopilos from our boat when we bought it so we hand steer it. For us, the magnetic compass is as useful a tool as the plotters.
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Old 10-03-2015, 11:02 PM   #7
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Compensation on steel boat

On my steel hulled boat the pilothouse was wood, so both compasses (the Wood Freeman and the Ritchie) were easily adjusted to a couple of degrees accuracy on all points.

However on this new build, the compass will be pushed right up against the forward bulkhead of the pilothouse, which is all steel. Does anyone with compensation skills out there know if having the plate steel literally one or two inches away will be too much to compensate for?
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Old 10-03-2015, 11:07 PM   #8
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Greetings,
Mr. m. I think this configuration of compass is the traditional mounting method in steel vessels. I don't know how the close proximity of a steel bulkhead would affect accuracy...

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Old 10-04-2015, 07:36 AM   #9
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The flat card , with the proper gear is easier to take a bearing with.

The dished cards are easier to see and steer with.

Wit a working Auto Pilot , a hand held bearing compass is easier to get in the clear outside ,
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Old 10-04-2015, 08:18 AM   #10
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RT Firefly: Steel Bulkheads do effect the accuracy. That is what those big balls are for on either side. Fine tuning.
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Old 10-04-2015, 08:40 AM   #11
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Greetings,
Mr. U. Oh, I think I understand the concept of the "tuning" balls on a steel vessel. My comment regarding accuracy was in reference to the steel bulkhead in that the "tuning" balls may not compensate enough for the closeness of the aforementioned steel (I'm guessing ferrous) bulkhead.
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Old 10-04-2015, 08:46 AM   #12
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I've had them on steel boats sitting in steel, next to steel bulkheads, and steel overhead. Pretty much can tune it to one or two degrees.
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Old 10-04-2015, 09:07 AM   #13
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Greetings,
Mr. U. Well, maybe that's Mr. m's solution then.
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Old 10-04-2015, 09:45 AM   #14
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I have that type of compass mounted in a box on my bridge deck. Still working fine after 79 years.
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Old 10-04-2015, 09:51 AM   #15
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I use a Flat card permanently mounted. Allows checking heading and quick bearing checks.
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Old 10-04-2015, 01:54 PM   #16
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None of my 3 compass sources match....GPS, AP and Magnetic.
I'm assuming I need to shim my Fluxgate AP sender mount to match the GPS heading numbers, then adjust the 2 magnetic compasses to match those. Do fluxgates have adjusters? Any better ideas?

Source for plastic compass adjusting tools?
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Old 10-05-2015, 06:30 AM   #17
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Any better ideas?

Sure , the AP is going to be working 99% of most trips , so just make up a card with the various errors posted and leave it where it can be seen for comparison.

You can still steer with any one of the compasses , just use the dev card.

No tools , just a quick pencil exercise.
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Old 11-12-2015, 09:40 PM   #18
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I made a comment at the beginning of this thread and I would like to retract it.

While running in the dark a night or two ago, we arrived at Pender Harbour around midnight, only to confront a thick fog that plugged the entrance. My buddy, a tow-boat captain, was driving. He used the radar and the compass exclusively, did not look at either plotter and when I asked him how he was navigating he said "you cannot rely solely on a plotter to navigate up the Fraser River with three barges or a log raft in tow, you need instantaneous feedback to course changes and only a compass will do." He was a bit rude that my compass light had baked and I had not thought it important enough to fix.

Although we are mostly pleasure boaters and are normally tied up or anchored on a night such as tonight, things happen and a good functioning radar and a compass are essential. Mine is a flat card and despite having used the other kind my entire flying career, flat is best for a boat, I think.
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Old 11-12-2015, 10:31 PM   #19
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Quote:
Originally Posted by Heron View Post
None of my 3 compass sources match....GPS, AP and Magnetic.
I'm assuming I need to shim my Fluxgate AP sender mount to match the GPS heading numbers, then adjust the 2 magnetic compasses to match those. Do fluxgates have adjusters? Any better ideas?

Source for plastic compass adjusting tools?

Sometimes you can put a offset in your AP or re spin the AP(compass) under a recalibration menu.
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Old 11-12-2015, 10:33 PM   #20
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Mako, can't help you on the magnetic compass' but for your autopilot I highly recommend getting a Satellite compass for the AP, you can also get them with a display that will show different styles of compass data. My sat compass is accurate down to 0.3 degrees, it made a big difference over the fluxgate that couldn't escape deviation.
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