Â **Marine Navigation Cruise**

Finding the answers to the cruise is like solving a puzzle.Â You piece together the "clues" and determine your course and position, plotting on the chart.

Part of the challenge of the cruise is knowing where to start. Here is a list of the lat/lon positions of key locations in part 1 of the cruise. Latitude is in degrees N, longitude is degrees W. If you see any errors below, please let me know.

G â7â Fl G 4s 41Â° 37.4' N, 071Â° 50.0' W

G C â1â at the entrance to Blackfish Creek 41Â° 34.6' N, 071Â° 53.8' W

G C â3â within the Creek. 41Â° 33.9' N, 071Â° 54.4' W

âG â3â Q G 41Â° 39.4' N, 071Â° 39.4' W

R N â2â near the breakwater at Perkins Cove 41Â° 36.3' N, 071Â° 42.4' W

Abandoned lighthouse west of Perkins Cove.41Â° 34.4557' N, 071Â° 42.0797' W

Fl R 6s 24 ft 5M â4â 41Â° 35.9' N, 071Â° 42.0' W

CHIMNEY to the west of Haven Bluff. 41Â° 33.4' N, 071Â° 50.6' W

The cruise is found in Appendix A, p 97 of the Student Manual.

The cruise is taken on Bowditch Bay.Â For all questions, use a variation of 15 W

Plot the 1634 fix at G "7".Â Â

Plot the course from G "7" to G C â1â .Â Measure the course and convert to magnetic, and label that leg.

T = 225Â°

V = 015 W

C = 240Â° M

You arrive at G C "1" at 1642. You slow down to 5.0 kn and enter the creek. You arrive at G C â3â at 1653.âÂ Â Measure the course to G C "3", convert to magnetic, and label that leg.Â Plot the 1653 fix at G C "3"

T = 212Â°

V = 015 W

C = 227Â° M

Plot and label your course.

At 1845 you are between R NÂ â2â and G C â1â. You change course to 168Â°Â M and slow down to 5.0 kn and continue to G C â7â.Â Â You arrive close aboard G C â7â at 1903.Â

Plot that leg of the voyage.

You must convert from magnetic to True.

T = 153Â°

V = 015 W

M = 168Â°

You change the course to 140Â°Â M and arrive closeÂ aboard the dock at 1914.Â

Plot that leg of the trip.

You must convert from magnetic to True.

T = 125Â°

V = 015 W

M = 140Â°

Plot that leg of the trip.

According to the text, the last leg of the trip lasted from 1903 to 1914.Â I used 60 D ST to estimate the length of that leg.Â

Time = 1914 - 1903 = 11 min

60 D = S T

D =Â __5.0 x 11__

âÂ Â Â Â Â Â 60

D = .92 rounds to .9 nm.Â I plotted this as a fix at 1914.

You return to G C â1â. You plan to travel toÂ Perkins Cove.

The most logical course would be to go to R N â2â near the

breakwater at Perkins Cove. However, the sunset will be at 1821 and the entrance to the cove couldÂ be dangerous in darkness.Â

The abandoned lighthouse (Tower) west of Perkins CoveÂ (L 41Â° 34.5' N, Lo 071Â° 42.1' W) is illuminated.

You plan to use the tower and the Fl R 6s 24 ft 5M â4âÂ beacon (L 41Â° 35.9' N, Lo 071Â° 42.0' W)Â Â as a range, to lead to the entrance of the cove.Â

Plot and label the range.Â Hint:Â use a dashed line for a "Predefined Range" as shown in Figure 13 of the "Plotting and Labeling Standards."

Measure the range (true) and convert to magnetic bearing.Â Label the range.

T = 184Â°

V = 015 W

C = 199Â° M

To avoid the breakwater you layÂ a course of 081Â°Â M for G â3â Q G . Your speed will be 20 kn.âÂ Plot the 081Â°Â M course.

At 1816 you decide to monitor your progress.Â With your hand bearing compass you take a bearing of 227Â°Â on the CHIMNEY to the west ofÂ Haven Bluff. Â At the same time,Â you take a bearing of 312Â° onÂ G â7â Fl G 4s to your

northwest.Â

The FIX indicates you are right on course and coincides withÂ your DR plot.

First, calculate and plot your 1816 DR.

Time =Â 1816

Â Â Â Â Â Â -Â __1802Â __

Â Â Â Â Â Â Â 0014 min

60 D = S T

Â Â Â DÂ =Â __20 x 14__

Â Â Â Â Â Â Â Â 60

Â Â Â D = 4.67Â =Â 4.7

Then, plot and label the bearings on the chimney and G "7":

ChimneyÂ Â Â Â Â Â Â Â G "7"

T = 212Â°Â Â Â Â Â Â Â Â Â Â Â Â T =Â 297Â°

V = 015 WÂ Â Â Â Â V = 015 W

C = 227Â° MÂ Â Â Â Â C = 312Â° M

Plot and label the 1816 fix.

Calculate the ETA of the intersection of the 081Â° M course with the 199Â° M range.

Measure the distance from your 1816 fix to the intersection of the course with the range.Â Calculate the time required to travel that distance.

60 D = S T

Â Â __60 x 5.1__Â = T

Â Â Â 20.0

Â T = 15.3Â Â round to 15 min.

ETA:

Â 1816

1831