Seamanship: Change In Draft, And Effect Density On Draft Example Formulas, Problems, And Solution (part 3)

PROBLEM and SOLVING Number 6:
A ship with a fore draft of 18 feet 06 inches
and aft draft of 20 feet 06 inches
has a displacement of 18,000 tons
and a TPI of 62 in sea water.
Find her new draft in
water of 1,015 oz. density,
also the new draft in fresh water.

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

C in D = (18,000 x 1,025 – 1,015) / (62 x 1,000)

C in D = (18,000 x 10) / (62,000)

C in D = (180,000) / (62,000)

C in D = 180,000 / 62,000

C

Therefore, Change in Draft in water of 1,015 oz density is 2.9 inches

Fore Draft in Seawater = 18 feet 06 inches
+ Increase in Fore Draft = 2.9 inches
Fore Draft in 1,015 oz density = 18 feet 08.9 inches

Aft Draft in Seawater = 20 feet 06 inches
+ Increase in Aft Draft = 2.9 inches
Aft Draft in 1,015 oz density = 20 feet 08.9 inches

Let us now solve her new draft in Fresh Water:

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

C in D = (18,000 x 1) / (62 x 40)

C in D = (18,000) / (2,480)

C in D = 18,000

C in D = 7.26 inches

Fore Draft in Sea Water = 18 feet 06 inches
+ increase in Fore Draft = 7.26 inches
Fore Draft in Fresh Water = 18 feet (13.26 inches – 12 inches and add to feet)
Fore Draft in Fresh Water = 19 feet 01.26 inches

Aft Draft in Sea Water = 20 feet 06 inches
+ increase in Aft Draft = 7.26 inches
Aft Draft in Fresh Water = 20 feet (13.26 inches – 12 inches and add to feet)
Aft Draft in Fresh Water = 21 feet 01.26 inches

Click the link to go back to main page (1st page) http://expertscolumn.com/content/seamanship-how-use-hydrometer

Note:

Effect Density on Draft:

From Sea Water to Fresh Water the draft increases (sink +)
From Fresh Water to Sea Water the draft decreases (rise -)

From higher density to lower density draft increases (sink +)
From lower density to higher density draft decreases (rise -)