Stability – I : Chapter 4

  1. A box-shaped vessel 120m long and 15m wide has alight draft of 4m and load draft of 9.8m in SW. find her light displacement, load displacement and DWT.
Solution :

Area of box shape vessel = (L x B)
= 120m x 15m
Light draft = 4m

Light displacement = (u/w volume) x ( density)
= (L x b x d )x (1.025)
= (120 x 15 x 4) x (1.025)
= 7380 t

Load draft   = 9.8m

So load displacement = (u/w volume) x (1.025)
= ( L x b x d) x (1.025)
= (120 x 15 x 9.8) x (1.025)
= 18081t

Hence, DWT =   (Load displacement  –  Light displacement)
= ( 18081  –  7380 )
= 10, 701t

  1. A box-shaped vessel 100m long and 14m wide is floating in SW at a draft of 7.6m. Her light draft is 3.6 m and load draft 8.5m. Find her present displacement, DWT aboard and DWT available.
Solution:

Area of box shape vessel = (L x B)
= (100m x 14m)

Present draft = 7.6m
Present displacement = (Lx b x d) x (density)
= (100 x 14 x 7.6) x (1.025)
=10906 t
Light draft                = 3.6m

Light displacement = (L x B x D) x(1.025)
= (100 x 14 x 3.6 ) x (1.025)
= 5166t

When Load draft is     = 8.5m

Load displacement = ( L x b x d )x (1.025)
= (100 x 14 x 8.5) x (1.025)
= 12,197.5t

We know that

DWT aboard  =  (present displacement – Light displacement)
=    (10906 t – 5166 t )
= 5740 t

DWT available  = (Load displacement – present displacement)
=   ( 12,197.5 t  – 10,906 t )
= 1291.5t.

  1. A ship is 200m long 20m wide at the waterline. If the coefficient of fineness of the water-plane is 0.8, find her TPC in SW, FW and DW of RD 1.015.
Solution :

Given :  (L x B)  = (200m x20) , Cw = 0.8

As we know that :
Cw   =   Area of water plane / ( L x B )
0.8     = Area of water plane / (200 x 20)
(0.8 x 200 x 20) = Water plane area

A   =  3200m2

We can calculate :

TPC in SW = (A/ 100 x 1.025)
= (3200 / 100 x 1.025)
= 32.8 t/cm

TPC in FW   = (A / 100x 1 )
= (3200/100)
= 32 t/cm

TPC in RD of 1.015 =( A /100 x 1.015)
= (3200 /100 x 1.015)
= 32.48 t/cm.

Note : here “A” refers to water plane area.

About the author

Amit Sharma

Graduated from M.E.R.I. Mumbai (Mumbai University), After a brief sailing founded this website with the idea to bring the maritime education online which must be free and available for all at all times and to find basic solutions that are of extreme importance to a seafarer by our innovative ideas.

5 Comments

  • many questions have wrong answers in various exercises,,at least book ke end me answers ko chk kar lete…anyways thanks for this website

  • many questions have wrong answers in various exercises,,at least book ke end me answers ko chk kar lete…

  • what is the draft of a box shape steel (L=4 meters , B= 4 meters , Depth = 0.60 meters)
    floating in a salt water density 1.028 and the total weight of the steel box with steel on top of it is 1500 kg

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