Set and Drift

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

Return to Chapter 8
http://../Chapt-08.pdf


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


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

Return to Chapter 8


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

Return to Chapter 8


5/7

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.

Return to Chapter 8


6/7

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but first erase the old course line, as it is no longer valid.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.

Return to Chapter 8


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

Set and Drift

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