TO CHECK IF YOU WOULD FLOAT IN A

DAMAGED CONDITION YOU WOULD NEED TO

KNOW YOUR RESERVE BUOYANCY AND THE

ANGLE OF IMMERSION.

AS A THUMB RULE, THE RESERVE BUOYANCY

= FREEBOARD X TPC

IF THE DISPLACEMENT OF THE COMPARTMENT

DAMAGED IS MORE THAN THE INITIAL

RESERVE BUOYANCY, THE SHIP WILL

DEFINITELY GO DOWN.

THE ANGLE OF DECK EDGE IMMERSION CAN BE OBTAINED FROM THE GENERAL ARRANGEMENT OF MIDSHIP PLAN BY USING THE NEW DRAFT AND A PROTRACTOR.

WE NOW FURTHER NEED TO CALCULATE THE FOLLOWING TO CHECK THE SURVIVABILITY OF THE VESSEL

1. DRAFT,

2. TRIM

3. GM, AND

4. ANGLE OF HEEL.

TO START WITH , YOU MUST HAVE THE

STABILITY DATA OF YOUR ORIGINAL INTACT

CONDITION AVAILABLE. ALL THE

CALCULATIONS HERE ARE BASED ON THE “

CONSTANT DISPLACEMENT” METHOD OF

CALCULATION.

CALCULATING MEAN DRAFT

MEAN SINKAGE = (V)/ (A-a)

= PERMEABILITY

V= VOLUME OF COMPARTMENT

A=WATER PLANE AREA = 100 TPC/1.025

a= WATER PLANE AREA OF DAMAGED

COMPARTMENT

NEW MEAN DRAFT = INITIAL MEAN DRAFT

+ SINKAGE.

CALCULATING GM

G IS THE SAME POSITION AS BEFORE.

HOWEVER, M MOVES . THE INITIAL KG IS

KNOWN

FINAL GM’ = KM’-KG

KM’ = KB’ + B’M’

THEREFORE

GM’ = KB’ + B’M’ – KG

NEW KB’ = (KB + V (D +S/2) / = VOLUME OF DISPLACEMENT

(UNCHANGED)

KB = INITIAL KB

V= VOLUME OF COMPARTMENT

D= INITIAL DRAFT

S= SINKAGE (PREVIOUSLY CALCULATED

TO FIND B’ M’ (WHEN NOT HEELED) B’M’ = BM – l b3/12 BM =INITIAL BM Where l = length of W.P.Area of Compt. b = breadth of ----------do ------------. = initial displacement . THE ABOVE IS TRUE FOR ONLY FOR

SYMMETRICAL FLOODING ( NO LIST ). TO FIND B’ M’ (WHEN HEELED) B’M’ = BM – l b3/12 - l b X2/ WHERE X – DISTANCE OF WATER PLANE

AREA OF COMPARTMENT FROM

CENTERLINE ( THIS CAN BE MEASURED OF

FROM THE GENERAL ARRANGEMENT

PLAN)

THEREFORE NEW OR FINAL

GM’ = KB’+ B’M’ – KG

TO FIND THE TRIM, WE NEED TO FIND THE

MCTC AND THE NEW LCF. MCTC = GML/ 100L BML/100L

WHERE L = LBP.

B’ ML’ IS FOUND IN A SIMILAR WAY AS

THE TRANSVERSE BM.

NEW B’ML’ = BML- bl3/12 - lbY2/

WHERE Y = DISTANCE OF WATER PLANE

AREA OF COMPARTMENT FROM

CENTERLINE ( THIS CAN ALSO BE

MEASURED OF FROM THE GENERAL

ARRANGEMENT PLAN)

BML OR KML IS FOUND IN THE STABILITY

BOOKLET KML = KM + BML

TO FIND THE POSITION OF THE NEW LCF

POSITION OF NEW LCF = (A LCF – a Y ) /

(A-a)

REMEMBER THAT LCF WILL SHIFT

TOWARDS THE DAMAGED

COMPARTMENT.

Y=CENTER OF GRAVITY OF

COMPARTMENT FROM AMIDSHIPS

A=WATER PLANE AREA

a= WATER PLANE AREA OF DAMAGED

COMPARTMENT

LCF = ORIGINAL LCF FROM AMIDSHIPS

TO FIND TRIM :

CHANGE IN TRIM = VY’ / MCTC

V= VOLUME OF COMPARTMENT

Y’ = DISTANCE OF CENTER OF GRAVITY OF

COMPARTMENT FROM NEW LCF

MCTC = PREVIOUSLY CALCULATED.

 

NEW TRIM = OLD TRIM CHANGE IN TRIM

CHANGE IN TRIM WILL BE IN THE

DIRECTION OF THE DAMAGED

COMPARTMENT. THIS CAN BE APPLIED TO

THE NEW HYDROSTATIC DRAFT

CALCULATED EARLIER.

TO CALCULATE ANGLE OF HEEL :

TAN = VX/ GM’

= ANGLE OF HEEL

V= VOLUME OF DAMAGED COMPARTMENT

X = DISTANCE OF CENTER OF GRAVITY OF

COMPARTMENT FROM CENTER LINE.

(VX= LISTING MOMENT)

= DISPLACEMENT

GM’ = NEW GM ( CALCULATED EARLIER).