OIC-NW Reviewer Blog: 2014

Finding ZT Of Place B

The ZT at Place A is 0800. If the longitude of A is 49° 30' W, what is the ZT of Place B in longitude 83° 15' W?

Given:

Longitude of Place A = 49° 30' W
Longitude of Place B = 83° 15' W
          ZT at Place A = 0800

Find:

ZT of Place B

Solution:

1. Divide the longitude of Place A and Place B by 15. By doing this, we are converting it to ZD.

Longitude of Place A = 49° 30' W ÷ 15 = 3° 18'. The minutes is less than 30, therefore the ZD would be +3.

Longitude of Place B = 83° 15' W ÷ 15 = 5° 33'. The minutes is more than 30, therefore the ZD would be +6.

2. Next is to subtract the ZD of places A and B to get the time difference.

ZD of Place B =    +6
ZD of Place B = - +3
Time difference = 3

4. We can solve now for the ZT of Place B.

   ZT of Place A = 0800
Time Difference = - 3       (subtract since Place B is located west of A)
                           0500 is the ZT of Place B

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How To Determine Storm's Position

Hello dear readers,

It's been good that many are following this blog of mine, and many of them interacted with yours truly. Having made this site (to help those who review to become marine deck officer) doesn't mean I'm all knowing.

So since there are questions submitted to me which I am incapable to answer to, therefore I posted these questions from time to time hoping others may see ,and, if they know, would give us the answer. Or who knows it is you who can help us here.

And this is one those questions. This is regarding how to determine the storm's position. If you know, use the comment box below and we would be glad to read it.

a rough guide, in the absence of an accurate meteorological data, if the corrected barometer reading is 5 hPa (0.15 in.) lower than the local normal and the wind force is about 8, the tropical cyclone's center will be about how far away? answer:100nm

thanks in advance

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Finding LMT And Date of Place B

At Place A, Long. 175° 10.5’ W, the LMT is 16h 02m 03s. Find the LMT and date at place B, Long. 32°08’ W.

Given:

Longitude of Place B = 32° 08' W
Longitude of Place A = 175° 10.5' W
       LMT of Place A = 16h 02m 03s

Find:

LMT and the date of Place B

Solution:

1. Subtract the longitude of Place A and Place B.

Longitude of Place A = 175° 10.5' W
Longitude of Place B = - 32° 08' W                                                                          143° 2.5' E

2. Convert the difference of longitude into time.

    143° 2.5'
÷ 15
9h 32m 10s

3. Add the answer in #2 to the date and time of Place A.

Dec 3 16h 02m 03s
+      9h 32m 10s
              25h 34m 13s
       + 1 -24h                Since it is more than 24 hours.
    Dec 4 01h 34m 13s       is the date and LMT of Place B.

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What Size Of Manila Rope Is Required

Here again we have to solve another question submitted to us. This is regarding how to solve for the size of manila rope. Here it is...

What size of manila line is required to hold a weight of 932 lbs., if you use a safety factor of six? Your Answer :: 3.0? Correct Answer :: 2.5? what is the solution of this

Given:

             Load = 932 pounds
Safety Factor = 6

Find:

Size of the Manila rope

Solution:

Since the unit of weight is pounds, the formula for Manila rope's breaking strength would be C² × 900, where C is the circumference. So, BS = C² × 900.

We can solve for the Manila rope's size by using this formula:

SWL = BS
          SF

So by transposition we can have BS = SWL x SF
    C² × 900 = SWL x SF
                                        C² × 900 =932 x 6
                                                   C = √932 x 6
                                                              900
                                                    C = √5592
                                                              900
                                                    C = √6.21333
                                                    C = 2.49265 or simply put 2.5" is the final answer.

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How Many Barrels Would You Expect To Unload

Hello dear friends,

Here's a question submitted to this blog from one of our readers.

A cargo of oil has a coefficient of expansion of .0005 per degree F. If this cargo is loaded at 70?F, and a cargo temperature of 90?F is expected at the discharge port, how many barrels would you expect to unload if you loaded 10,000 barrels? answer: 10100 can you please show me the solution? thanks in advance.

Given:

70 °F - Cargo temperature when loaded
90 °F - Cargo temperature expected at discharge port
0.0005 °F - Coefficient of expansion
10, 000 bbls - Total barrels of oil loaded

Find:

Number of barrels expected to unload

Analysis:

Our cargo is loaded at 70°F but to be discharged at the temperature of 90°F. This means there's an increase of temperature of our oil cargo. Therefore there must be an increase of volume due the increase in temperature. So it is to be expected that the number of barrels that will be discharged is more than 10,000 bbl.

Solution:

(90°F - 70°F) x 0.0005 x 10,000 = 100 bbls
+ 10,000 bbls
10, 100 is the total barrels of oil to be unloaded.

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Finding Latitude Of The Observer At Meridian Transit

What is the latitude of a place where the sun is at the zenith of observer at local apparent noon of June 21 or 23?

Given:
Date: June 21 & 23

Find:
Latitude of the observer

Solution:

June 21 or 23 is summer solstice, and the declination of the sun on this date is 23° 27' N.

If the Sun is at the Zenith it means that Altitude( Ho) = 90°
- 90°
ZD = 0°
Declination of the Sun on June 21/23 = 23° 27’ N
Lat = 23° 27’ N

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Finding Ship's Distance Off The Second Bearing And When Abeam

A ship on course of 253° T at 14 knots. At 2329 a lighthouse was observed bearing 282° T. At 2345 the same lighthouse bears 300° T. Find the ship’s distance off the second bearing and when abeam?

Given:

              Course = 253°
               Speed = 14 knots
     First Bearing = 282°
Second Bearing = 300°

Find:
             A.) Ship’s distance off the second bearing
             B.) Ship’s distance when abeam

Solution:

1. Find first Angles A, B, C:

       a.)Co = 253° T
        Brg1 = 282° T
Angle A = 29° R

      b.) Co = 253° T
         Brg2 = 300° T
   Angle B = 47° R

     c.) Angle B = 47° R
          Angle A = 29° R
          Angle C = 18° R

2. Then solve for AB (Distance Run Between 1st & 2nd Observation)

               AB = ( Time 2 – Time 1 ) x Speed
   = ( 2345 – 2329 ) x 14 knots
   = 16 minutes x 14 knots
                AB = 3.73 nautical miles

3. Solve for Distance off at second bearing (BC): (By SINE Law)

                BC = Sin A x AB
                              Sin C
                 BC = Sin 29° x 3.73
                              Sin 18°
                 BC = 5.9 nautical miles (Distance off at 2nd bearing)

4. Solve for Distance at Abeam (CD) : (By SOH – CAH – TOA)

CD = BC x Sin B
                CD = 5.9 x Sin 47°
                CD = 4.3 nautical miles ( Distance at Abeam)

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Question From Readers #20 Calculate The New KG

A vessel's displacement is 2,400 tons and her KG is 10.8 meters. What is the new KG if a weight of 50 tons already on board is raised 12 meters vertically?

Given:

Displacement = 2, 400 tons
       Distance = 12 meters
         Weight = 50 tons
               KG = 10.8 meters

Find:
          New KG

Solution:

1. Shifting of Weights

GG1 = Weight x Distance
                                            Displacement
                                      = 50 tons x 12 m
                                            2, 400 tons
                                      = 600 ~~tons~~ meter
                                            2, 400 ~~tons~~
                             GG1 = 0.25 m

2. The problem states that a weight is shifted vertically to 12 meters, so we can see that the weight is shifted upwards because our KG is only at 10.8 m. From this given situation we can conclude that KG will increase. So, what we are going to do this is to add our answer in step 1 to the old KG.

   Old KG = 10.8 m
   GG1 =   0.25 m
                          New KG = 11.05 m will be the height of the center of gravity

Thank you for submitting this question. If you have more or you want clarification, feel free to raise it. Once again, Thanks.

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Solving For ETA And LZT Of Arrival

You are on a voyage from New York, USA to San Francisco, USA. The distance from pilot to pilot is 5,132 miles. The speed of advance is 13.5 knots. You estimate 32 hours of bunkering at Colon and 14 hours for the Panama Canal transit. If you take the departure of 0600 hours (ZD +4) on May 16, what is your ETA (ZD +7) at San Francisco.

Given:

           Distance = 5, 132 miles
               Speed = 13.5 knots
       Bunkering = 32 hours
Panama Transit = 14 hours
LZT Departure = 0600 16th May

Solution:

LZT departure = 0600 16th May
      ZD departure = (+)4 (W) +    (E – / W +)
GMT departure = 1000 16th May
+ Steaming Time = 2009 15days    (Steaming Time: always + )
                GMT arrival = 3009 31st May
             ZD arrival = (+)7 (W) – (E + / W –)
                 LZT arrival = 2309 31st May
                   Bunkering = 32 +                 (Any Delays: always +)
Panama Canal Transit = 14 + (Any Delays: always +)
                 LZT arrival = 2109 02nd June is the final answer

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Question From Readers #19: Metacentric Height

Metacentric Height

A vessel with a beam of 72 feet, has an average rolling period of 18 seconds. What would be her metacentric height?

Given:

Beam = 72 feet
Rolling period = 18 seconds

Solution:

Metacentric Height = ((Beam x 0.44) ÷ Rolling Period)²

I used 0.44 to multiply the ship's beam because the unit is feet.

GM = ((B x 0.44) ÷ RP)²
= ((72 ft x 0.44) ÷ 18)²
= (31.68 ft ÷ 18)²
= (1.76)²
= 3.09 ft will be the metacentric height(GM)

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Question From Readers #18: Fresh Water Allowance And Dock Water Allowance Formula

Fresh Water Allowance And Dock Water allowance Formula

A vessel has a mean draft of 25'-00", her displacement is 10000 tons and the TPI is 42. Find the increase of draft in a water density 1010 kgs/m³.

Given:

Displacement = 10, 000 tons
Water density = 1010 kgs/m³
TPI = 42

Solution:

We are going to use two formulas to solve this problem.

1. Fresh Water Allowance = Displacement
40 x TPI
= 10000 tons
40 x 42 tons per inches immersion
= 5.95 inches

2. DWA = FWA x (1025 - New Density)
25
= 5.95" x (1025-1010)
25
= 3.57" is our final answer

If you want to contribute or say something, you may do so by using the comment box below...

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Question From Readers #17: Calculate Righting Arm Of A Vessel

Calculate The Righting Arm

Calculate the righting arm of a vessel whose GM is 0.65 m when inclined at an angle of 12°.

Given:

GM = 0.65 m
Angle of Inclination = 12°

Solution:

Righting Arm = GM x Sin Angle of Inclination
= 0.65 m x Sin 12°
= 0.135 meter is the answer

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Question From Readers #16: Calculate Allowable Draft Increase

Allowable Draft Increase

The FWA being 6" for vessel M/V Seafarers. What is the increase of draft allowed in water of RD 1.010?

Given:

Fresh water allowance = 6 inches
Relative density = 1.010

Solution:

Allowable Draft Increase = FWA ( Change in density)
25

= 6 inches ( 1025 - 1010)
25
= 3.6 inches is the answer

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Question From Readers #15: Calculate Time To Empty The Tank

How Long Will It Take To Empty The Tank

A tank measures 3 feet x 32 feet x 40 feet. How long will it take to empty the tank if the pumps discharge rate is 120 gallons per min.

Solution:

1. Calculate the volume of the tank.

               Volume = 3 ft x 32 ft x 40 ft
                           = 3, 840 cubic feet

2. Convert cubic feet into gallons. But how many gallons in 1 cubic foot? It's 7.48 gallons.

              3, 840 ft³
         x       7.48
28, 732.2 gallons
÷          120      gal/min to get time to empty the the tank
   239.36 minutes
   ÷    60            to convert it into hours
              3.98933 hrs or 3 hrs 59 min 21 sec to empty the tank

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Question From Readers #14: Calculate Cargo To Be Loaded

Find The Cargo To Be Loaded

Find the cargo to be loaded if initial draft aft is 10.873m, Trim Corr. = 14.408, TPC = 38.37 and final draft aft = 10.9m.
Ans. 89.19tons

Solution:

1. Subtract final draft and initial draft.

10.9 m

- 10.873 m

0.027 m

2. Convert the 0.027 meter difference into centimeter so that we can apply the TPC.

0.027 m x 100 cm = 2.7 cm

1 m

3. Multiply the TPC by 2.7 to get tons of cargo.

38.37

x 2.7

103.599 tons

- 14.408 trim correction

89.191 tons of cargo to be loaded

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Question From Readers #13: Sag Correction

Sag Correction

A reader has brought up this question. If you know how to solve this problem, let us know.

Good day,

Calculate sag correction basis TPC=41.06, MTC=481,LBP=163.6 and estimated sag = 4cm. Ans. 117.2 MT

Ship's hull is sagging

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Calculate Time For A Star To Rise

Your vessel is at the equator at midnight on 1 January, and a star is observed rising. At what time will this same star rise on 1 February, assuming your vessel's location is still at the equator?

Solution:

One should know how many hours is one sidereal day, and of course a solar day.

1 solar day = 24hr
1 sidereal day = 23h 56h 4s
0h 3m 56s is the time difference
x 31 since there a 31 days from Jan. 1 to Feb. 1
2h 01m 56s total difference
Midnight 1 Jan = - 24h 00m 00s
21h 58m 04s on 1 February that the star will rise

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Question From Readers #12: Dead Reckoning

Dead Reckoning

gud eve... i need you help with this. SHIP AT 0800 OCT 10 2011 LAT 9 2 N LONG 116 49.5E TRUE COURSE 38 SPEED 16 KTS FIND DEADRECKONING POS. AT 1600 OCT 10 2011

Solution:

Step 1. Get the steaming time.

Time of arrival = 1600 10 Oct

Time of departure = 0800 10 Oct

8 hrs is the steaming time

Step 2. Solve for the distance traveled for 8 hours.

Distance = Speed x time

= 16 kts x 8 hrs

= 128 nautical miles

Step 3. Solving for Dlat.

Dlat = Cos 38° x 128 nm

= 100.86 nm

÷ 60 to convert it to degrees and minutes

Dlat = 1° 40.86' N North because the ship is northward

Step 4. Add Dlat and your latitude at position 1 to get the latitude of your new position.

Dlat = 1° 40.86' N
Latitude 1 = 9° 2' N (Add because same name)

Latitude 2 = 10° 42.86' N

Step 5. Solving for the departure and Dlo.

Departure = Sin 38° x Distance

= Sin 38° x 128 nm

= 78.80 nautical miles

÷ Cos 10° 42.86' to get Dlo. But if in equator, Dep = Dlo

80.2 nm

÷ 60 to convert it to degrees and minutes

1° 20.2' E is the Dlo

Step 6. Solving for the new longitude.

Long 1 = 116° 49.5' E

Dlo = 1° 20.2' E same sign; add

Long 2 = 118° 9.7' E

So the new position of the ship is 10° 42.86' N, 118° 9.7' E.

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Finding Observed Altitude

At meridian passage, upper passage, the observer's latitude was found to be 43° 34.7' N, Dec. is 1° 46.3' N. Find observed altitude.

Given:
Lat = 43° 34.7' N
Dec = 1° 46.3' N

What is asked?

Observed altitude (Ho)

Solution:

Lat = 43° 34.7' N

Dec = 1° 46.3' N (Always reverse sign)

Lat = 43° 34.7' N

Dec = 1° 46.3' S (Subtract because it has different name)

ZD = 41° 48.4' N

- 90° (Always minus 90° to get observed altitude)

Ho = 48° 11.6' N

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Question From Readers #11: Solving for TPI

Formula for TPI

Can you please show me the solution of solving this problem:

A vessel 580 ft x 60 ft, with a waterplane coefficient of 0.84 is floating in freshwater at a draft of 21 feet. How many long tons shall it take to increase the mean draft by 1 inch?
Answer (According to our reviewer): 67.6 tons

Solution:

Step 1. Multiply the ship's length by it's breadth and then by its water plane coefficient.

580 ft x 60 ft x 0.84 = 29, 232 square feet. This is your area of water plane.

Step 2. Divide your area of water plane by 432 since the ship is floating on freshwater.

29232 ÷ 432 = 67.6 is your TPI

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Question From Readers #10: ETA Costa Rica to Los Angeles

ETA: Costa Rica to Los Angeles

Here's a question being asked to me. No matter how I tried my answer is different from his review material. My answer is 0136H 08 FEB. I have to deferred my solution for a time being for I want to know your answer to this question. If you may, why not show your solution? Hope you do.

You are on a voyage from Limoy, Costa Rica , to Los Angeles USA. The distance pilot to pilo is 3150 miles. The speed of advance is 14 knots. YOu estimate 24 hours for the Panama CANAl Transit. If you take departure at 1836 hours (ZD+6) on 28 January, find your ETA (ZD +8) at LOs Angeles?

ANS: 1336, 08 Febuary

Question From Readers #9: Solving For ETA (estimated time of arrival)

What Is Your ETA?

AT 0800 zone time, on 15 april, your vessel is heading west in position LAT. 15?10? N, LONG. 165?15? W at a speed of 22 knots. The distance to your destination at LAT. 15?10?N, LONG. 135?15? E is 3600 nautical miles. What is your ETA???ANS: 2339, 22 APRIL

This is a question submitted from someone who is new to this blog. The answer according to his review material is 2339, 22 April. But when I tried to solve it, my answer is 0338H, 22 April. I'm going to show my solution.

Solution:

Step 1. Get the steaming time.

Time = Distance
Speed
= 3600 nm
22 nm/hr
= 3600 nm
22 nm /hr
= 163.63636 hrs is the steaming time

163.63636 hr ÷ 24 = 6.81818 days

0.81818 days x 24 = 19.63632 hrs

0.63632 hrs x 60 = 38 mins

6 days 19 hours 38 mins steaming time

Step 2. Add steaming time to the time of departure. Add because your ship is east-bound.

15 0800 April
+ 6 day 19 hr 38 min
21 day 27hr 38 min April
+ 1 - 24
22 day 03 hr 38 min April

Simply put 0338H, 22 April as your ETA

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Question From Readers #8: Find The KG

Find the KG

A ship is inclined by moving a weight of 30 tons a distance of 30 ft. from the centerline. A 28-foot pendulum shows a deflection of 12 inches. Displacement including weight moved is 4,000 tons. KM is 27.64 feet. What is the KG?

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OIC-NW Reviewer Blog

Pages

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Finding ZT Of Place B

How To Determine Storm's Position

Finding LMT And Date of Place B

What Size Of Manila Rope Is Required

How Many Barrels Would You Expect To Unload

Finding Latitude Of The Observer At Meridian Transit

Finding Ship's Distance Off The Second Bearing And When Abeam

Question From Readers #20 Calculate The New KG

Solving For ETA And LZT Of Arrival

Question From Readers #19: Metacentric Height

Question From Readers #18: Fresh Water Allowance And Dock Water Allowance Formula

Question From Readers #17: Calculate Righting Arm Of A Vessel

Question From Readers #16: Calculate Allowable Draft Increase

Question From Readers #15: Calculate Time To Empty The Tank

Question From Readers #14: Calculate Cargo To Be Loaded

Question From Readers #13: Sag Correction

Calculate Time For A Star To Rise

Question From Readers #12: Dead Reckoning

Finding Observed Altitude

Question From Readers #11: Solving for TPI

Question From Readers #10: ETA Costa Rica to Los Angeles

Question From Readers #9: Solving For ETA (estimated time of arrival)

Question From Readers #8: Find The KG