Ship Stability

Question 1

how freeing ports assist in maintaining the stability of the ship

Answer 1

by allowing us to unship the large amounts of water that can be retained by the ships side shell, they are connected at the bullwark and sheerstrake. the prevent a raised center of gravity, reduced effective metacentric height, reducing in GZ, a large free surface effect and also prevents capsizing. the freeing port will also relive bending stresses

Question 2

what is free surface effect

Answer 2

it’s an effect that occurs when liquids and aggregates of small solids such as sand or seeds that can act as liquids move in the same direction of a vessel reducing the effective GM

Question 3

why is free surface effect important in ro-ros

Answer 3

it is important because the large cargo or vehicle deck can allow large amounts of water to slosh around. also ro ros have a low freeboard.

Question 4

possible stability effect when transferring fuel from low tanks to high tanks

Answer 4

a raised center of gravity
a reduction in the metacentric height
a reduction in GZ
possible listing
possible freesurface effect

Question 5

important checks made before transferring fule

Answer 5

check the line/valves
inform and check with bridge for stability
check tank levels
trace heating
quantity to be moved

Question 6

checks to be made during fuel transfer

Answer 6

check if its going to corret tank
check for leaks
pump pressure
check it is not effecting stability

Question 7

why you would bunker to wing tanks before double bottoms

Answer 7

so that the centre of gravity lowers in vessel
you see an increase in the metacentric height
and an increase in GZ
makes the ship more stable
reduces chance of free surface effect
reduces list

Question 8

a measurement that gives indication of ships stability

Answer 8

the metacentric height

Question 9

explain the measurement of the metacentric height

Answer 9

it is the distance between G and M

Question 10

what is stable stability

Answer 10

G below M

Question 11

what is unstable stability

Answer 11

G above M

Question 12

what is neutral stability

Answer 12

G and M together

Question 13

when transferring from low tanks to hight tanks what are the effects on the vessels stability

Answer 13

G moves up
reduction in the effective metacentric height
reduction in GZ
possible listing
possible fse