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| M/V JERLYN KEANNU at anchor |
Today I'm going to tackle a question submitted to yours truly from someone who is having his review. He said he has encountered this question on his reviewer for marine deck office. so here it is.
The anchorage is loacated 20nm north of a vessel with a speed of 15knots,A current hava a set of 3knots E,calculate the course to steer in order to drop her anchor to the charted anchorage on the spot,ans:349degrees
Given:
current = 3 knots
Own ship speed = 15 knots
Distance to anchorage = 20 nm
Find:
Course to steer
Analysis:
The anchorage is located north from our ship at a distance of 20 nautical miles. If the ship proceeds to that anchorage (000°) she will be swayed away from the mark since there's a current from here port side. So what would be her course to steer?
1. Get the steaming time.
Time = Distance
Speed
= 20 nm
15 nm/hr
= 20 nm
15 nm/hr
= 1.33333 hrs or 1hr and 20 mins
2. So while steaming to the anchorage area for 1hr and 20 mins, you are also swayed or be drifted off the mark because of the current which is 3 knots. And to solve your distance from the anchorage is we are going to multiply the current speed and the ship's steaming time.
1.33333 hrs x 3 nm/hr = 4 nm
We can picture-out that there's plane triangle made; the 20 nm being the adjacent and the 4 nm as the opposite from the angle of your initial position. So get the angle by using tangent function.
Tan Angle = 4 /20
= 0.2
= arc tan 0.2
Angle = 11.31 degrees.
3. So to calculate course to drop anchor right on the spot, we have to subtract 000 degrees by 11.31 degrees. And the result would be 348.69 or simply 349 degrees.
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The anchorage is loacated 20nm north of a vessel with a speed of 15knots,A current hava a set of 3knots E,calculate the course to steer in order to drop her anchor to the charted anchorage on the spot,ans:349degrees
Given:
current = 3 knots
Own ship speed = 15 knots
Distance to anchorage = 20 nm
Find:
Course to steer
Analysis:
The anchorage is located north from our ship at a distance of 20 nautical miles. If the ship proceeds to that anchorage (000°) she will be swayed away from the mark since there's a current from here port side. So what would be her course to steer?
1. Get the steaming time.
Time = Distance
Speed
= 20 nm
15 nm/hr
= 20 nm
15 nm/hr
= 1.33333 hrs or 1hr and 20 mins
2. So while steaming to the anchorage area for 1hr and 20 mins, you are also swayed or be drifted off the mark because of the current which is 3 knots. And to solve your distance from the anchorage is we are going to multiply the current speed and the ship's steaming time.
1.33333 hrs x 3 nm/hr = 4 nm
We can picture-out that there's plane triangle made; the 20 nm being the adjacent and the 4 nm as the opposite from the angle of your initial position. So get the angle by using tangent function.
Tan Angle = 4 /20
= 0.2
= arc tan 0.2
Angle = 11.31 degrees.
3. So to calculate course to drop anchor right on the spot, we have to subtract 000 degrees by 11.31 degrees. And the result would be 348.69 or simply 349 degrees.
P.S. Like what you read? Please click the share button below to share this post to your friends. Sharing is caring...
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