Advanced Piloting Course (Coastal

Navigation)

Chapter 8

Effects of Winds/Current

Educational Officer – Dave Westdwest@voyager.net - 651-429-3840

Assistant Educational Officer – David Moberg

davidmoberg@att.net – 715-386-8582 Instructor – Art Mollica

artmollica@usfamily.net - 651-777-0277

United States Power Squadrons®

22APPENDIX A - WEEKEND CRUISE

PART 4

33

24) You arrive at “1” BELL at the entrance to Menemsha Basin at 1300 and secure your boat to a dock. You call your friend and he tells you to check the tide charts to determine when you will be able to raft up to him. His dock is in 3’ of water at MLW. You need 2’ of clearance & your boat draws 3.0 feet.

24) You arrive at “1” BELL at the entrance to Menemsha Basin at 1300 and secure your boat to a dock. You call your friend and he tells you to check the tide charts to determine when you will be able to raft up to him. His dock is in 3’ of water at MLW. You need 2’ of clearance & your boat draws 3.0 feet.

1300

QHG1

MPG1

44

04 54

24a) Using the tide charts for Gay Head determine if you could raft up with your friend at 1400. Will you have enough water for clearance? NO clearance 12 inches under keel

24b) Which government agency is located at Menemsha Basin? Coast Guard

Slide 5

Currents – Horizontal Movement

Flood Current – from sea towards shore or up tidal river or estuary

Ebb Current – away from shore or down a tidal river or estuary

Slack – time at which horizontal movement stops

Slide 6

Why Worry About Currents

Slide 7

Perfect World – No Currents

SeabedCOG 276M

C 276MCourse through water

Course Over Ground

Slide 8

With Current – Crabbing

Seabed

COG 265M

C 276MSteered 276M

Course Over Ground

Slide 9

With Wind – Leeway

Seabed3º

C 276MSteered 276M

Course Over Ground 273M

Slide 10

Watch Your Wake

Steering steady course

No current/leewayC

ours

e s

teere

d

Current/leeway

Cours

e s

teere

d

Slide 11

Three VariablesWith Current Against Current

C 115M

Current

C 295MCurrent

Cross Current

Current

C 115M

S 8.0 S 8.0

SOG 9.5 COG 115M

SOG 6.5 COG 295M

1.5kn current

SOG ??? COG ???M

Slide 12

Current Vectors

Current Direction – Set

Current Speed – Drift

From sea toward land

Away from land

Slack water

Not Always Opposite Directions

Different Maximum Speeds

FLOOD 095

EBB 255

Slide 13

Rule of Twelfths (50-90)

Slack Water

Time Intervals

90%

100%

50%

50%

90%

100%1/3 1/3 1/3 1/3 1/3 1/3 1/3 1/3 1/3 1/3 1/3 1/3

Maxim

um

Flo

od S

peed

Maxim

um

Ebb S

peed

Sla

ck

Sla

ck

Sla

ck

Flood

Eb

b

Slide 14

Rule of Twelfths (50-90)Slack Water 0421

0616

0811

Max Flood 1006

1133

1300

Slack Water 1427

1520

1613

Max Ebb 1706

1805

1904

Slack Water 2003

5hr45min = 345min / 3 = 115min

4hr21min = 261min / 3 = 87min

2hr39min = 159min / 3 = 53min

2hr57min = 177min / 3 = 59min

0.0kn

0.8kn

1.4kn

1.5kn

1.4kn

0.8kn

0.0kn

1.3kn

2.3kn

2.6kn

2.3kn

1.3kn

0.0kn

50%

90%

90%

50%

50%

90%

90%

50%

Slide 15

Table 1

Slide 16

Table 2

10 9 8 7 6 5 4 3 2 1

10 MINUTE BREAK

PLEASE TAKE YOUR SEATS

Slide 18

Estimating CurrentOne Part at a Time

• Slack to Max Flood/Ebb

• Max Flood/Ebb to Slack

• Slack to Max Flood/Ebb

• Max Flood/Ebb to Slack

Determine Time Interval

Use Percentages

• Slack to Max

• Max to Slack

Slide 19

Example 1Location: Marblehead Channel (Sub-Station 996)

Reference Station: Boston Harbor (Deer Island)

Calculate speed & direction on 18 May 2004 1400 EDT

Figure 8-4 & 8-5

Marblehead Channel 998Boston Harbor (Deer Island)

18 May 2004 1300

10261429 E 1.2

+ 01 09+ 01 09 0.3

11351538 E 0.4 105

153811350403243

81

1135 1256

81

1417

81

1538

81

0.4E 50 0.2 105

Figures 8-7 & 8-9

JJ – Exercise 8-1

Chris G – Exercise 8-2

Karen – Exercise 8-3

Figures 8-11 & 12

Terry – Exercise 8-4

Dean – Exercise 8-5

Chris S – Exercise 8-6

Slide 20

Exercise 8-1Location: 0.2nm west of West Chop, Ma (Sub-Station 1941)

Calculate speed & direction on 1 Sep 2004 1000 EST

West Chop 0.2nm West 1941Pollack Rip Channel

1 Sep 2004 1000

0751 F1056

2.2 + 01 34+ 01 50

1.3 0925 F1246

2.9 059

124609250321201

67

0925 1032

67

1139

67

1246

67

2.9F 90 2.6 059

Slide 21

Exercise 8-2Location: Waquoit Bay Entrance (Sub-Station 1926)

Calculate speed & direction on 26 Aug 2004 1100 EST

Waquoit Bay Entrance 1926Pollack Rip Channel

26 Aug 2004 1100

0811 E0536

1.4 + 04 01+ 03 40

0.8 1212 E0916

1.1 203

121209160256176

59

0916 1015

59

1114

59

1213

59

1.1E 90 1.0 203

Slide 22

Exercise 8-3Location: Southeast of Nobska Point (Sub-Station 1946)

Calculate speed & direction on 24 Sep 2004 0100 EST

Nobska Point 1946Pollack Rip Channel

24 Sep 2004 0100

0210 F2225

1.8 + 02 15+ 02 33

1.3 0425 F0058

2.3 071

042500580327207

69

0058 0207

69

0316

69

0425

69

0.0F 0 0.0 ----

Slide 23

Exercise 8-4Location: 0.8 miles east of Yellow Bluff (Sub-Station 551)

Calculate speed & direction on 1 Sep 2004 1000 PST

0.8 miles east of Yellow Bluff 1946Golden Gate Bridge

1 Sep 2004 1000

1122 F0819

3.6 + 00 15+ 00 19

1.0 1137 F0838

3.6 022

113708380259179

60

0838 0938

60

1038

60

1138

60

3.6F 50 1.8 022

Slide 24

Exercise 8-5Location: Richardson Bay Entrance (Sub-Station 601)

Calculate speed & direction on 26 Aug 2004 1100 PST

Richardson Bay Entrance 1946Golden Gate Bridge

26 Aug 2004 1100

1243 E1507

1.0 - 02 34-03.06

0.3 1009 E1201

0.3 225

120110090152112

37

1009 1046

37

1123

37

1200

37

0.3F 90 0.3 225

Slide 25

Exercise 8-6Location: 0.75 miles east of Angel Island (Sub-Station 586)

Calculate speed & direction on 24 Sep 2004 0100 PST

0.75 miles east of Angel Island 1946Golden Gate Bridge

24 Sep 2004 0100

2342 E2000

2.2 + 01 50+ 01 33

0.5 0132 E2133

1.1 192

013221330359239

80

2133 2253

80

2413

80

0133

80

1.1F 100 1.1 192

Advanced Piloting Course (Coastal

Navigation)

Chapter 9

Piloting with Wind/Currents

Educational Officer – Dave Westdwest@voyager.net - 651-429-3840

Assistant Educational Officer – David Moberg

davidmoberg@att.net – 715-386-8582 Instructor – Art Mollica

artmollica@usfamily.net - 651-777-0277

United States Power Squadrons®

Course

Direction Traveled Between Two Fixes

Actual Direction of Travel Over Ground

Current

Track

Speed

Speed of Advance Intended Speed along the Track (SOA)

Direction boat is steered (C)

Course Made Good (CMG) - Track Made Good (TMG)

Course Over the Ground (COG) Direction of flow (Set) – speed of current (Drift) Intended Direction of Movement (Trk)

Rate of motion through water (S)

Terminology

Course to SteerUse same baseline for each vector

Distance between 1130DR and 1130 GPS = 4nm

Direction from 1130DR to 1130 GPS = 042º

Time = 2hrs

COG 305M

0930 GPS

1030 GPS

1030

1130

1130 GPSSet 042 Dft 2.0

C 305M S 10.0

C 295MS 10.0C 295M S 10.0

Set 042

Dft 2.0

Determine course to steer to maintain COG 305M

Apply expected Set/Drift from 1130 GPS

Draw arc equal to boat speed = 10.0kn

Draw course from Set/Drift to intersection

Distance from 1130 GPS to intersection = SOG

From 1130 GPS draw course line at 295M

SOG 9.0

60D = ST S = 60 X 4.0 / 120 Dft = 2.0nm

Course to SteerUse same baseline for each vector

Exercise 8-1 Computed Set 059º Drift 2.6

What is course to steer to reach destination from N”3” at 15kn?

COG 130M

Dest

C 139M S 15.0

SOG 14.8

N “3”

Set 059 Dft 2.6

1hr

2hr

3hr

BBR4

BBG7

Plot waypoints R”4” Fl R 6s BELL as BBR4 and G“7” Fl G 4s as BBG7

Depart BBR4 at 1000 for BBG7, speed 10kn

At 1031, BBG7 bears 239ºM at 4.5nm

Determine set and drift and plot new course to BBG7

Qualify new course

1000 Visual

C 251M

S 10.0

1031 GPS

1031

239M

D4.5

60D = ST D = 10.0 X 31 / 60 D = 5.16 = 5.2

1031

T = 002 V = 15 W M = 017

60D = ST S = 60 X 1.2 / 31 S = 2.3nm

T = 236 V = 15 W M = 251M = 239 V = 15 W T = 224

Set 017M Dft 2.3

T = 212 V = 15 W M = 227 C

227

M

S 1

0.0

CMG 262M

SMG 9.0

T = 247 V = 15 W M = 262

COG

239

M

Set 017M Dft 2.3

SOG

9.0

Exercise 9-1

COG T = 236 V = 15 W M = 251

Set T = 355 V = 15 W M = 010

Course T = 227 V = 15 W M = 242

SOG 9.9

Set 010M Dft 2.1

COG 251M

C 242

M

S 11.

0

Plot waypoints R”4” Fl R 6s BELL as BBR4 and G“7” Fl G 4s as BBG7

Speed of advance is 9.9kn,

Set is 010ºM and drift is 2.1kn.

What is the course to steer?

What is the required boat speed?

Qualify the course.

What would you do?

BBG7

BBR4

C 242

M

S 11.

0

BBG5

NLT 251

M

Exercie 9-2

C 255M

Track T = 250 V = 15 W M = 265

Set T = 355 V = 15 W M = 010Course T

= 240 V = 15 W M = 255

SOA 9.9

Set 010M Dft 2.1

S 11.0

Trk 265M

BBR6

Track T = 211 V = 15 W M = 226

Trk

226M

C 255M

S 11.0

Plot waypoints R”4” Fl R 6s BELL as BBR4 and G“7” Fl G 4s as BBG7

Speed of advance is 9.9kn,

Set is 010ºM and drift is 2.1kn.

What is the course to steer?

What is the required boat speed?

Qualify the course.

What would you do?

BBG7

BBR4

Exercise 9-2 (another solution)

Plot waypoints RN”2” (Shark River) as SRR2 and R“2” Fl R (Oyster River) as ORR2 – depart ORR2 at 0945.

Minimum speed to arrive RN”2” by 1100?

You leave with boat speed of 6.8kn.

At 1030 your GPS position is L 41º 41.7’N Lo 71º 58.4’W - determine current set and drift.

You fish and end up at GC”3” at 1100 and decide to head back to ORR2 at a reduced speed of 4.0kn. Assume set/drift remains the same.

What is your DR course to ORR2?

What is your COG and SOG to ORR2?

What is your ETA at ORR2?

SRR2

ORR2 0945 Visual

D 6

.55

1100 – 0945 = 0115 = 75min

60D = ST S = 60x6.6 / 75 S = 5.27 = 5.3kn

C 0

29M

S

6.8

T = 014 V = 15 W M = 029

1030 – 0945 = 45min

60D = ST D = 6.8 X 45 / 60 D = 5.1

1030 GPS

1030

5.3kn

T = 117 V = 15 W M = 132

60D = ST S = 60x1.1 / 45 S = 1.5

Set 132M Dft 1.5

1100 Visual

T = 159 V = 15 W M = 174

T = 175 V = 15 W M = 190

Set 132M Dft 1.5

CO

G 174M

SO

G 5.0

C 190M

S 4.0

190M

174M 5.0kn

60D = ST T = 60x6.2 / 5.0 T = 74

1100 + 74 = 1214

1214

C 190M

S 4.0

Exercise 9-3

Slide 34

Questions ? … Comments

Slide 35

Finish Weekend Cruise

Next Class – 24 May

Homework