Staility – I : Chapter 2

1. Find the thrust exprienced by a flat keel plate 10m x 2m when the draft is 8m in SW.

Solution :  Area of the flat keel plate = (10 x 2)
                                                  = 20m²
               Pressure = (depth x density)
                                           =    (8 x 1.025)
                                          =  8.2t /m²
              Thrust = (pressure x area)
                                       = 8.2 x 20 =164 t .

2. A box-shaped vessel 150m x20m x 12m is floating in a dock of RD 1.010 at an even keel draft of 10m. Find the total water pressure experienced by the hull.

 Solution: The total water pressure exerted on the hull to the water =  (Thrust of keel plate which acting   horizontally + Thrust of forward and aft  which act vertically +Thrust of  port and stbd side which act vertically)
Thrust of Keel plate = (pressure x area)
Pressure = (depth x density)
              =10 x1.010 t/m²

Area = 150m x 20m = 3000m²
Thrust =(10 x1.010 x 3000) = 30, 300 t

Thrust of forward and Aft =(pressure x area)

Pressure = depth x density
            =( 5 x1.010)t/m²

Area =L X B
           =(20 x10)
           = 200m²

Thrust = (P x A)
              = (5×1.010 x200)
              = 1010t

Thrust acting both forward and aft = (1010 x2)
                                                               = 2020 t

Thrust of port and stbd  side = (pressure x area)

Pressure  =( depth x density)
                   =( 5×1.010)

Area = (L X B)
          = 150m x 10 = 1500m²

Thrust = ( P X A )
              = 5 x 1.010 x1500
              = 7575 t

Thrust acting on Both sides = 7575 x 2
                                                =15150 t

Hence , Total pressure on the hull = (30300 +2020 + 15150)
                                                  =47,470 tonnes.