Seamanship: Change In Draft And Tpi Example Formulas, Problems, And Solution (part 1)

PROBLEM and SOLVING Number 1:
A ship (vessel) of 10,000 tons displacement
and TPI of 46
sailed from sea water to water of 1,010 oz. density.
Find her Change in Draft in water of 1,010 oz. density, also in fresh water.

Formula:
C in D = Displacement x (1025 – GD) / (TPI x 1000)

Solving:

C in D = Displacement x (1025 – GD) / (TPI x 1000)

C in D = 10,000 x (1,025 – 1,010) / (46 x 1,000)

C in D = 10,000 x (15) / (46,000)

C in D = 10,000 x 15 / 46,000

C in D = 150,000 / 46,000

C in

Therefore, the Change in Draft in water of 1,010 oz. density is 3.26 inches.

Now, the next problem to solve is to find her Change in Draft in Fresh Water.

C in D = (Displacement x 1) / (TPI x 40)

C in D = (10,000 x 1) / (46 x 40)

C in D = (10,000) / (1,840)

C in D = 10,000 / 1,840

C in D = 5.43 inches

Therefore, the Change in Draft in fresh water is 5.43 inches.

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PROBLEM and SOLVING Number 2:
Find the ship’s TPI in water of 1,020 oz. density,
if her change in draft is 4.5 inches
and her displacement is 15,000 tons.

C in D = (Displacement x 1025 - GD) / (TPI x 1000)

C in D x (TPI x 1,000) = (Displacement x 1,025 – GD)

TPI = (Displacement x 1,025 - GD) / C in D x 1000

TPI = (15,000 x 1,025 – 1,020) / 4.5 x 1,000

TPI = (15,000 x 5) / 4,500

TPI = (75,000) / 4,500

TPI = 75,000 / 4,500

TPI = 16.67 tons per inch

Therefore, ship’s tons per inch immersion is 16.67