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#1
01-08-2017, 10:07 AM
 stlamont Join Date: Jan 2017 Rep: 10 Posts: 1 Location: Kingston Jamaica

1. Need urgent help in how to calculate total cargo weight a ship carry.

2. A ship is expected to sail a distance of 3,200 n.m. at an average speed of 12

knots. Calculate her expected time of arrival if she departed on December 28,

2014 at 2200 hours.
#2
01-08-2017, 12:03 PM
 Olav arch. nav. Join Date: Dec 2003 Rep: 460 Posts: 277 Location: Filia pulchra Lubecę
1:

Payload = Total displacement - light ship weight - provisions (fuel, lube oil, food,...) - ballast water

2:

Distance travelled: 3200 nm
Avg. speed: 12 kts = 12 nm/h

--> Time en route: 3200 nm/(12 kts * 24 h) = 11.11111 d.

Since 2014 was no leap year, the time of arrival is on

March 11th, 2014 (Feb 28th + 11 d), at 0.11111 d - 2 h (remaining two hours from Feb. 28th), thus at 0:40 in the morning (assuming the vessel stays within one time zone).

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All the best, Olav GER-1045 ____/)_/)/)___
#3
01-08-2017, 03:55 PM
 Heimfried Senior Member Join Date: Apr 2015 Rep: 37 Posts: 154 Location: Berlin, Germany
Quote:
 Originally Posted by stlamont [...] she departed on December 28, 2014 at 2200 hours.
Quote:
 Originally Posted by Olav [...] the time of arrival is on March 11th, 2014 [...] Was this your homework, stlamont?
No, no, the homework is: doublecheck the results of your friendly helper.
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Gruss, Guenter
#4
01-08-2017, 04:59 PM
 Olav arch. nav. Join Date: Dec 2003 Rep: 460 Posts: 277 Location: Filia pulchra Lubecę
Oops!

Correction: January 8th, 2015 at 0040.

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All the best, Olav GER-1045 ____/)_/)/)___
#5
01-08-2017, 07:31 PM
 Mr Efficiency Senior Member Join Date: Oct 2010 Rep: 677 Posts: 5,246 Location: Australia
Question 1 looks tricky to me !
#6
01-08-2017, 08:24 PM
 kilocharlie2 Junior Member Join Date: Nov 2016 Rep: 20 Posts: 22 Location: Left Coast, North America
Compliments to Olav, who makes the answers seem simple!

Question 1 involves a technique known to mathematicians as subtraction. Question 2 involves a method known as division.

Of course it leaves out choice of route, time of year, winds, current, coriolis effect, and error.

On the ocean, we do not plow through distance, we plow through moving water and wind. It's a blasted good ship design that makes 12 knot in all weather and current, and a phenomenal skipper who stays on course around 1/8th of the planet, although our GPS / computer combo is making solid inroads into this last part.
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Measure twice, cut once. It prevents "Damnit! I've cut it 3 times and it's still too short."