RYA Shorebased Almanac!

[scotty123]

When doing chartwork, it is usual to find a course to steer in *(T), then adjust for variation to *(M), then adjust for deviation to *(C)

On the back cover of this tool, used in RYA Shorebased courses, there is a deviation table.

However, this deviation table only shows *(C) + deviation, but not *(M), as is usual.

Some of the questions, require an answer in *(C), so how is it possible to do this using an incomplete deviation table?

 

[capnsensible]

The variation shown on the compass roses on RYA charts 3 and 4 will permit you to resolve the puzzle.

 

[Philiz]

Don't really understand your question. Deviation is Compass deviation, the deviation card in the back of the almanac is for the hyperthetical RYA boats compass and works fine. Variation is obtained from the compass rose, 7 degrees west I think.

 

[RichardS]

Obviously, a compass always indicates the compass bearing. The deviation card for that compass will show what the deviation is in degrees West or East for a particular compass heading as shown by that compass.

Just remember to make the corrections in the right order: TeleVision Makes Dull Children AlWays

True - Variation - Magnetic - Deviation - Compass - Add West

(and therefore deduct East)

and reverse this if going the other way, deducting any Westerly deviation and variation and adding Easterly.

Richard

 

[Elessar]

When doing chartwork, it is usual to find a course to steer in *(T), then adjust for variation to *(M), then adjust for deviation to *(C)

On the back cover of this tool, used in RYA Shorebased courses, there is a deviation table.

However, this deviation table only shows *(C) + deviation, but not *(M), as is usual.

Some of the questions, require an answer in *(C), so how is it possible to do this using an incomplete deviation table?

The thing that isn't clear enough, is that you never, ever get a deviation table in an almanac. The deviation card is found on the boat and is unique to the boat, and it's this that gets you from M to C. So it certainly isn't usual to have any table as you suggest.


The variation, which gets you from T to M is found on the compass Rose and is 7west in rya la la land.

 

[scotty123]

The thing that isn't clear enough, is that you never, ever get a deviation table in an almanac. The deviation card is found on the boat and is unique to the boat, and it's this that gets you from M to C. So it certainly isn't usual to have any table as you suggest.


The variation, which gets you from T to M is found on the compass Rose and is 7west in rya la la land.

1) Yes, I know you get variation from a compass rose (or is given as 7*W in RYA courses)
2) Yes I know that any boat has its own deviation table & is not found in a normal almanac.

However, on RYA courses, the course Practice Almanac (please refer to my original statement) does have a deviation card, which a student is expected to use.

However, unlike a deviation card found on any boat, you cannot enter *(M) to get *(C).

 

[Philiz]

The thing that isn't clear enough, is that you never, ever get a deviation table in an almanac. The deviation card is found on the boat and is unique to the boat, and it's this that gets you from M to C. So it certainly isn't usual to have any table as you suggest.


The variation, which gets you from T to M is found on the compass Rose and is 7west in rya la la land.

You are correct, and the deviation card in the back of the almanac relates to the compass on the RYA imaginary boat for the purposes of the course. If you look on you tube you will find several videos explaining how to do the conversions. Duncan Wells videos are very good.

 

[RichardS]

1)
However, unlike a deviation card found on any boat, you cannot enter *(M) to get *(C).

As far as I can remember, the RYA deviation card shows the degree of deviation, W or E, for every heading of the boat compass. Using this card you can go from *M to *C or from *C to *M. I'm not sure what else you need?

Richard

 

[Solitaire]

1) Yes, I know you get variation from a compass rose (or is given as 7*W in RYA courses)
2) Yes I know that any boat has its own deviation table & is not found in a normal almanac.

However, on RYA courses, the course Practice Almanac (please refer to my original statement) does have a deviation card, which a student is expected to use.

However, unlike a deviation card found on any boat, you cannot enter *(M) to get *(C).

There is a bit of confusion getting in the way here. The deviation card is designed to correct from degrees C to degrees M. A good compass swinger can often adjust the compass so it is reading M but in some cases this can't be done. So the deviation is shown so as to get back to magnetic. The ship's head is already in Compass as that is what it is, so taking the RYA almanac example on a heading of 000 the deviation is 4west so the magnetic heading will be 356M moving down the card and coming to 180C the deviation is 4east so the magnetic heading is adjusted to read 184!


This might help to make it clearer:

And a compass swinger at work:

 

[timbartlett]

However, unlike a deviation card found on any boat, you cannot enter *(M) to get *(C).

I suspect this is the crux of your question.
Unfortunately you are labouring under a misapprehension. Deviation cards do not always show both. In fact I'm not at all sure that one could even say they "usually" show both.

In your parallel thread on the lounge, I have posted a photo of a real deviation card that does not have both (click on the quote box below): it shows Deviation at different Headings (C) but not at Headings (M)

If you really want both, you can easily make up your own, but there is generally very little point.

.