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post #9 of Old 07-30-2011
MarkSF
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Quote:
Originally Posted by kwindancer View Post
Hello All,

Hope you can answer and explain the answer to this question:

Let's say my point of departure is at point A and destination is to point B.

The track (Course to Make Good) from A to B is 145 degrees magnetic.

The winds are west at 22 knots when I depart point A at 1530. Let's say the leeway is 4 degrees and the boat speed is 6 knots. What course, corrected for leeway, should I steer from point A to point B?

Thanks so much.
I'd avoid describing the wind like that. It's ambiguous. Is it from the west, or to the west? Better to use the term westerly, or "from the west".

I just did ASA Coastal Navigation and the leeway is normally added at the end. So you want to go 145 degrees and the leeway is 4. If the wind is westERLY, from the west, you should steer 149. From the east, 141.

There is no leeway per mile or any such calculation. Leeway is assumed to be a constant difference between the direction the boat is pointed in, and where it's actually going. So it is added or subtracted from the course to steer depending on the wind direction.

If this is an ASA question it will assume use of the deviation table for your compass.

You want to go 145 mag and want to know the compass reading.

Remember it like this :

TVMDC AW - True Variation Magnetic Deviation Compass, Add West. I remember it like this : Timid Virgins Make Dull Company, Add Whiskey

Desired course = 145 Mag. Find the compass deviation from the table. For example, 10W. Add west, 145 +10 = 155C. Add leeway, 159C.

Interestingly the question throws in some irrelevant data - the boat speed, departure time are both non-sequiturs.

The only way you can get to the 115 in the answers is with the wind from the east, and / or a hugely inaccurate compass!
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