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Old 13-11-2018, 21:02   #1
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OK Navigators, what are these for?

Actually I think I have a fairly decent idea, I just hadn't seen them before. We visited the Queen Mary yesterday and the guide in the bridge said "no one knew what these numbers were for." Well? anyone know?......
Keep in mind this ship could do 30 knots and these boards were right in front of the helmsman.
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Old 13-11-2018, 21:03   #2
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Re: OK Navigators, what are these for?

Magnetic Variation or Deviation..?
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Old 13-11-2018, 21:50   #3
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Re: OK Navigators, what are these for?

The 264 is obviously the course, we used to have them on the older container ships, but the + and - numbers I am not so sure about. Maybe allowance for set and drift? Or deviation, but if it was deviation I'd expect it to be East or West. She didn't have a gyro, so its not gyro error high or low.

Another thought is it might be the difference between the steering compass and the standard compass.
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Old 13-11-2018, 22:16   #4
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Re: OK Navigators, what are these for?

Magnetic Variation - Depending on if its East or West it can be + or - Charts will also have the Magnetic Variation on them so you can go from True to Magnetic and then to Compass if you want with Deviation
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Old 13-11-2018, 22:24   #5
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Re: OK Navigators, what are these for?

I too think it is variation, but..... out west here on coastal BC waters, the variation right now is roughly 22 added to the magnetic course. So no room on the board to do that.
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Old 13-11-2018, 22:27   #6
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Re: OK Navigators, what are these for?

Quote:
Originally Posted by CSY Man View Post
Magnetic Variation or Deviation..?
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There's a spot to write variation on the blackboard.

Tide flow and direction?
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Old 13-11-2018, 22:39   #7
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Re: OK Navigators, what are these for?

Since it’s next to the course, is that perhaps the allowable variation (shows that the required course is 264, but 262 is ok, over 264 isn’t)
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Old 13-11-2018, 23:04   #8
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Re: OK Navigators, what are these for?

Maybe gyrocompass error correction? She had a Sperry MK14 and a Sperry gyropilot. (thanks Google)
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Old 14-11-2018, 01:50   #9
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Re: OK Navigators, what are these for?

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Since itís next to the course, is that perhaps the allowable variation (shows that the required course is 264, but 262 is ok, over 264 isnít)

^ That would be my guess, too.
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Old 14-11-2018, 04:05   #10
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Re: OK Navigators, what are these for?

Quote:
Originally Posted by Don C L View Post
Actually I think I have a fairly decent idea, I just hadn't seen them before. We visited the Queen Mary yesterday and the guide in the bridge said "no one knew what these numbers were for." Well? anyone know?......
Keep in mind this ship could do 30 knots and these boards were right in front of the helmsman.
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Old 14-11-2018, 05:05   #11
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Re: OK Navigators, what are these for?

Quote:
Originally Posted by Don C L View Post
Actually I think I have a fairly decent idea, I just hadn't seen them before. We visited the Queen Mary yesterday and the guide in the bridge said "no one knew what these numbers were for." Well? anyone know?......
Keep in mind this ship could do 30 knots and these boards were right in front of the helmsman.

So Don What is your fairly decent idea?
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Old 14-11-2018, 05:20   #12
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Re: OK Navigators, what are these for?

Steered offshore by autopilot.... upper numbers refer to gyro error which is refered to as + or - .... not E or W....

Rarely if ever more gyro error than 2* high or low.

She had gyro and autopilot as built.. Part 16
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Old 14-11-2018, 06:03   #13
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Re: OK Navigators, what are these for?

Added bit... gyro error is referred to and written as either Hi and Lo or as + or -

On that board I would expect that to be the gyro course to steer.... suprised there is no sign of the true course anywhere to be seen.....on the blackboard or elsewhere...
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Old 14-11-2018, 10:11   #14
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Re: OK Navigators, what are these for?

Course to steer. The dummy log is always set to the course to steer by the,steering compass, whether it is magnetic or gyro.

Compass error, i.e. variation plus deviation if no gyro compass aboard and steering by magnetic.
Or
Gyro error, if steering by gyro.
Or
Difference between course to steer and course made good.

Modern American ships will generally have a board marked, or a dummy log showing, the course to steer by gyro and the checking (magnetic compass) course. If a board, sometimes it will also be marked with gyro error or other data. The AB steering only concerns himself with the course to steer. After a course change he will check the magnetic and mark down the checking course.

In the picture, a magnetic compass is to the right. The brass thingie on the left is a gyro repeater and most probably is what the ship was steered by, though the wheel is not shown in the pic.

On modern ships the binnacle (the housing for the magnetic compass) is up on the flying bridge, up on the roof of the bridge, you might say. There is a periscope sort of arrangement whereby the AB or other interested party can look up at the compass to check magnetic, or in an emergency to steer by it.
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Old 14-11-2018, 11:39   #15
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Re: OK Navigators, what are these for?

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Magnetic Variation or Deviation..?
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