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7/28/2019 Set and Drift
1/7
Set & DriftStep 1: DR, Fix, CMG, SMG
1
200Fix
1230D
R
1230Fix
Set
CMGSMG
DRCours
e&Sp
eed Drift
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http://../Chapt-08.pdf7/28/2019 Set and Drift
2/7
Set & DriftStep 2: Find New Course To Steer
1230D
R
1
200Fix
1230Fix
1. Erase Course from DR to Destination2. Draw Course from most recent fix to destination
This is the course you need to make good.
4. Draw the set & drift you expect to encounter over this time period.
3. Pick a time interval for your new set& drift triangle (say 30 min.)
5. Setting your dividers on the
distance you will travel in the
time chosen for your triangle,swing an arc from the end of
the set & drift vector to intersect
your course to make good.
Return to Chapter 8
http://../Chapt-08.pdf7/28/2019 Set and Drift
3/7
1230D
R
1
200Fix
1230Fix
6. The direction of this line is your course to steer.
Cours
eto
stee
r
7. Your vessel will actually track along the line from the fixto the destination, and the length of this side of the triangle will
represent your speed made good, remembering to convert it to a
run of a whole hour.
Speedma
degood
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4/7
Once more, with numbers
First, print this chart out.You can plot on it to follow along.
1
200Fix
123
0DR
0 5 mi. 10 mi.
1230Fix
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Once more, with numbers
1
200Fix
123
0DR
064T,2
0kts.
1. From a fix, draw your course to the destination
2. Plot a DR for some future time (well use 1230, or 1/2 hour)
3. Get a fix at 1230, and plot the course you have made good. This is 079
0 5 mi. 10 mi.
1230Fix
CMG079
SMG24.4
kts.
4. Calculate your speed made good. This is 12.2 miles, in 1/2 hour, thus 24.4 knots
5. Calculate the set you experienced. This is 126
6. Calculate the drift you experienced. This is 3.5 miles in 1/2 hour, or 7 knots
1267kts.
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Once more, with numbers, cont.
123
0DR
064T,2
0kts.
7. From the 1230 fix, draw your new course to the destination,
but first erase the old course line, as it is no longer valid. The new course line is the
course you need to make good.
8. Draw the set & drift vector that will affect you for the duration of the triangle
you will draw (in this case, 1/2 hour)
0 5 mi. 10 mi.
1230Fix
CMG079
SMG24.4
kts.
10
mil
es
9. With your dividers set on the distance you will run in 1/2 hour (the durationof this triangle), swing an arc to intersect the new course to make good,
and draw a line from the end of the set & drift vector to that point.
The length of this line is determined by using your speed by revolutions,
and the time of the triangle,
or 20 kts. x 1/2 hour = 10 miles.
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7/7
Once more, with numbers, cont. (2)
123
0DR
064T,2
0kts.
10. The direction of this line is the course to steer
0 5 mi. 10 mi.
1230Fix
CMG079
SMG24.4
kts.C
ours
eto
ste
er0
28
11. To find the speed you will make good on this leg, measure the distance from
your 1230 fix to the intersection of the course to steer line. This is the distance you
will run in the time interval of the triangle (1/2 hour).
10miles
SMG
=10.4m
i.x1/2h
r=20
.8kts12. Convert this to speed using the speed/time/distance formula.
Return to Chapter 8
http://../Chapt-08.pdf