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Trimming - Ship stability for masters and mates

Ship stability for masters and mates page 237-246 ( blak and white)

SECTION 12 - Introduction to trim (black and white)

12.1 Terms relating to ship length.

12.2 Draught marks and reading the draught.
Example 1 - What is the draught reading for each of the waterlines shown in Figure

12.3 Trim

12.4 Change of trim
Example 2 - Ship floats at draughrs Fwd 6.00 m and Aft 6.20 m. A weight then shifted forward. The final draughts are Fwd 6.080 m amd aft 6.120 m . What change of trim has occured?
Example 3 - Ship floats at draughrs Fwd 5.00 m and Aft 4.64 m. A weight then shifted aft. The final draughts are Fwd 4.68 m amd aft 4.96 m . What change of trim has occured?

12.5 Moment to change trim by one centimetre (MCTC)
Example 4 - A weight of 150 tonnes is moved aft by distance of 20m. If the MCTC for the current draught is 250t-m determine the final trim of the ship if the initial trim was 0.2 m by the stern.

12.6 Formula for calculating MCTC.
12.7 Longitutional centre of flotation. (LCF or F)


12.8 Calculaing the final draughts when a weight is shifted.
12.8.1 Ship with LCF amidships

Example 5 - A ship floats at draughts F 6.5 m and A 6.8 m. Dtermine the final draughts if 25 tonnes is moved 45 m forward given that MCTC is 112,5 t-m and the LCF is amidships.
12.8.2 Ship with LCF not amidships
Example 6 - A ship has initial draughts F 10.25 m and A 10.15 m. A WEIGHT of 95 tonnes is moved aft through a distance of 42m. Calculate the final draughts given that LBP is 100m, LCF is 48 m foap and MCTC is 285 t-m.

12.9 The effect of loading and discharging weights.
Example 7 - A ship 100 m in length floats at draughts F 7.0m and A 6.8 m. Calculate the final draughts id 150 t is loaded 20m foap given that TPC is 15 and MCTC is 150 t-m and LCF is 45 m foap.

12.10 Multiplie weight problems.
12.11 Weight to shift to reduce trim by a specified ammount
12.12 Weight to load to bring the ship to even keel
12.13 Weight to transfer to reduce the deepest draught by a specified amount


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SECTION 20 - Trim using hydrostatic data. (color version)

20.1 True mean draught - displacement when trimmed

20.1.1 True mean draught when LCF is Amidships
20.1.2 Thrue mean draught when LCF is not Amidship
20.1.3 Calculating the true mean draught

Example 1 - A ship LBP 148 m floats at draught F 4.6m A 5.8m and has LCF 69.0 m foap. Calculate the true mean draught.
Example 2 - A ship LBP 120 m floats at draught F 4.62m A 5.4m. Calculate the true mean draught if the LCF is 66m foap.
Example 3 - A ship LBP 166 m floats at draughts F 7.32m A 6.84m. Calculate the true mean draught if the LCF is 80m foap.
Example 4 - A ship LBP 120 m floats at draughts F 4.62m A 5.40m. Calculate the true mean draught if the LCF is 80m foap.
Example 5 - A ship LBP 166 m floats at draughts F 7.32m A 6.84m. Calculate the true mean draught if the LCF is 80m foap.

20.2 Trim calculations using hydrostatic data - Taking moments about the Mean LCF.
Example 6 - Ship arrives in port with draughts F 4.0 m A 4.2 m. Calculate the final draughts. Calculate the weight of ballast to transfer from 6 P+S DB ballast tank (lcg 42.19 m foap) to the fore peak tank (lcg 162.04 m foap) to ensure that the ship sails with a trim of 0.6 m by the stern.
Solution A
Solution B

20.3 Trim calculations using hydrostatic data - Trim by consideration of the relative positions of the LCB and LCG

20.3.1 Calculating the final draught - Ship initially on even Keel.
Example 7 -Ship has an even keel draught 5.1m. Calculate the final draughts after loading and discharging.

20.3.2 Calculating the final draught - Ship initially trimmed.
Example 8 (same as Example 6) - Ship arrives in port with draught f 4.00 m A 4.2 m. Calculate the final draughts after loading operations. Calculate the weight of ballast to transfer from 6 P+S DB ballast tank to the fore peak tank to ensure that the ship sails with a trim of 0.6 m by the stern.
Solution A
Solution B

20.4 Various Examination style Problems involving trim.

20.4.1 Maximum cargo to load in each space for the ship to complete at the maximun draught
Example 9 - Ship is loading a bulk cargo in port and has draughts F 7.36 m A 8.24 m in salt water. Calculate the maximum draught on departure will bw 8.4 m. Note - the requirement is that the maximum amount of cargo be loaded and the draught is not exceed 8.4 m. This means that the ship must complete on an even keel draught of 8.4 m.
Solution A - Taking moments about the mean LCF
Solution B - By (LCB~LCG) method taking moments about AP

20.4.2 Maximun cargo to load in each space for the ship to complete at the load displacement with a desired trim
Example 10 - Ship has draughts F 9.46 m A 10.14 m in salt water and is to complete loading to the summer displacement. The remaining cargo is to be loaded into hold no. 2 and hold no. 5. How much of the remaining cargo must be loaded into each hold for the ship to complete cargo with a trim of 0.2 m by the stern.
Solution A - Taking moments about the mean LCF
Solution B - By (LCB~LCG) method taking moments about AP

20.4.3 Where to load a single weight to keep the Aft Draught Constant.
Example 11 - Ship has draughts F 4.24 A 4.98 m and 436 tonnes of deck cargo remains to be loaded. Calculate the position foap to load the weight in order that the aft draught remains constant; Calulate the final draught forward.
Solution A
Solution B

20.4.4 Calculating the weight to load to reduce the deepest draught by a given amount
Example 12 - Ship has draughts F 5.62 M A 6.48 M. Calculate the ammount of ballast to pump into the fore peak tank ( lcg 162,04 m foap) to reduce the draught aft to 6.20 m. Calculate the final draught forward.
Solution A
Solution B

20.5 Change in Draught and Trim Due to Change in Water Density

20.5.1 Cause of change of Trim due to change of Water Density

20.5.2 Calculating the Final Draughts
Example 13 - Ship has draughts F 9.28 m A 10.32 m when floating in salt water. Calculate the draughts in fresh water.

20.5.3 Alternative Formula for calculating the change of trim

20.5.4 Considering Change of Trim due to change of density when conducting trim problems
Example 14 - Ship arrives in port with draughts F 8.60 m A 9.10 m. The aft peak tank is full. Calculate the amount of ballasr water to discharge from the aft peak tank in order that the ship arrives at the berth with a trim by stern of 0.20 m . The RD of the dock water ar the berth is 1.006.

 

 

Проверенный способ, который есть в Excel:

 

20.4.1 или 20.4.2

 

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