stability and trim sheets

CONTENTS General Particulars Diagram to show Draught mark locations Datum Reference Information Unit Conversion Table Arrangement of Tanks Sample Tank Capacity Table Notes to the Master

STABILITY INFORMATION

BOOKLET

my " "

DATE:

K N

M

WATER LINE

CONTENTS

General Particulars

Diagram to show Draught mark locations

Datum Reference Information

Unit Conversion Table

Arrangement of Tanks

Sample Tank Capacity Table

Notes to the Master

Angles of down flooding

Notes on Free Surface Moments

Notes on use of KN Curves

General Stability Requirements

Sample form for calculating Loading Condition

Explanation and notes on completing Sample Stability Form

Max KG limiting criteria (not compulsory)

Freeboard Loadline Marks

Loading Conditions

Hydrostatic Properties

Cross Curve Stability Plot

General Particulars

Ship’s Name

Official Number

Port of Registry

Owner’s name and address -

-

-

Classification Society

Builder

Yard Number

Date of keel laying

Dimensions

Length overall (LOA) m

Length between perpendiculars (LBP) m

Max Beam m

Depth m

Assigned Freeboard m

Max Summer loaded draught m

Max Displacement at Summer Load Draught T

Gross Tonnage

Diagram to show Draught mark locations

Datum Reference Information

Longitudinal datum = amidships

Transverse datum = centreline

Vertical datum = base line

Aft Perpendicular = ? metres aft amidships

Fwd Perpendicular = ? metres fwd amidships

Aft Draught Marks = X metres aft amidships

Fwd Draught Marks = Y metres fwd amidships

LBP (m)

Unit Conversion Table

0.00098421 KG Tons (2240 lbs) 1016.0

0.98421 Tonnes (1000 KG) Tons (2240 lbs) 1.016

2.4999 Tonnes per cm Tons per inch 0.40002

8.2017 Tonnes metres units

(MCTC) Ton feet units (MCTI) 0.12193 187.98 Metre Radians Foot Deg 0.0053198

Relationships between Weight and Volume

10mm cubed = 1 cubic cm

1 cubic cm of fresh water (S.G = 1.0) = 1 gram

1000 cubic cm of fresh water (S.G 1 = 1.0) = 1 kg (1000grams)

1 cubic meter of fresh water (S.G 1 = 1.0) = 1 tonnes (1000kg)

1 cubic meter of salt water (S.G 1 = 1.025) = 1.025 tonnes (1025kg)

1 Tonne of salt water (S.G 1 = 1.025) = 0.975 cubic metres

1 cubic metre = 35.316 cubic feet

1 cubic foot = 0.0283 cubic metres

Arrangement of Tanks

1 Fuel Oil Tank Stb

2 Fuel Oil Tank Port

3 Fresh Water Tank Stb

4 Fresh Water Tank Port

5 Grey Water Tank

6 Aft Ballast Tank Stb

7 Aft Ballast Tank Port

8 Lub Oil Tank

7

6

5 4

3

2

Sample Tank Capacity Table

Tank Name XX

Contents FW/FO etc

Capacity Max YY

Sounding Depth

(m) % Full Mass (MT) VCG (m) LCG (m) FSC (m)

Notes to the Master

1 General Instructions

A stamped, approved copy of this booklet must be kept on board the vessel at all times It must also be complete, legible and readily available for use If this booklet is lost or becomes unusable a replacement copy of the approved booklet must be obtained

immediately

MCA operating Restrictions (if any)

Min liquids to be carried in arrival condition (if any)

The loading conditions shown in this booklet represent typical service conditions It is emphasised that a separate calculation is necessary for all differing conditions of loading Master’s Shipboard procedures are to be followed at all times

2 Tank Usage and Free Surface Moments

Provided a tank is completely filled with liquid no movement of the liquid is possible and the effect on the ship’s stability is precisely the same as if the tank contained solid

material

Immediately a quantity of liquid is withdrawn from the tank the situation changes

completely and the stability of the ship is adversely affected by what is known as the

‘free surface effect’ This adverse effect on the stability is referred to as a ‘loss in GM’ or

as a ‘virtual rise in VCG’ and is calculated as follows:

(Tonnes)

nt Displaceme Vessel

m Tonnes Mmt

Surface Free

GM of

When preparing loading conditions, it is to be noted that free surface effects must be allowed for the maximum number of tanks which are slack or shortly to become slack in that given loading condition This will mean that, for departure conditions all main fuel tanks as well as fresh water tanks are considered to be slack

The number of slack tanks should be kept to a minimum Where port and starboard tanks are cross coupled, such connection should be closed at sea to minimise the reduction in stability

Where ballast tanks are used they should be ‘pressed full’ or ‘empty’ as far as possible Dirty water in the bilge’s must be kept to a minimum

3 Precautions against capsize

Before a voyage commences care should be taken to ensure large items of equipment and stores are properly stowed All external hull doors and flush hatches (list them) are to be closed and secured If poor weather is likely to encountered during the passage

additionally storm boards and shutters should be fitted

The number of slack tanks should be kept to a minimum Where port and starboard tanks are cross coupled, such connection should be closed at sea to minimise the reduction in stability

Compliance with the stability criteria does not ensure immunity against capsize or

absolve the Master from his responsibilities Masters should therefore exercise prudence and good seamanship having regard to the season of year, weather forecast and the

navigational zone

4 Masters ship board procedures

Internal sliding WT doors, may be left open, but should be closed when risk of hull

damage and flooding increases eg, in fog, in shallow rocky waters, in congested shipping lanes, when entering and leaving port and at any other time the master considers

appropriate

Sliding WT doors should be checked daily to ensure that nothing has been placed in way

of the door or where it might fall into the opening and prevent the door from closing

Notes on use of KN Curves

KN curves for displacements of X to Y tonnes are presented for angles of heel at intervals between 0 and Z degrees

To obtain righting arm (GZ) curves at a given displacement, the following equation should be used:

EQ.2 GZ =KN−KGsinθ

This enables the value of GZ to be calculated at each of the heel angles presented, and subsequently plotted as in the loading conditions presented herein

K N

M

WATER LINE

θ

Angles of down flooding

This is the angle of heel at which progressive down flooding of the vessel will occur due

to the immersion of an opening

Description Area of

Opening (m2) ANGLES OF IMMERSION (degs)

100% Consumable 10% Consumable

General Stability Requirements

It is import ant to ensure that in any sailing condition the stability of the vessel complies with the following minimum criteria of section 11.2 of the Code of Practice for Large Commercial Sailing and Motor Vessels

A Area under the curve up to 30o is to be not less than 0.055 metre-radians

B Area under the curve up to 40o, or the angle of down flooding (which ever is less)

is to be not less than 0.090 metre-radians

C Area under the curve between 30o and 40o or the angle of down flooding (which

ever is less), is to be not less than 0.030 metre-radians

D Maximum GZ is to occur at angles of heel preferably exceeding 30o but not less

than 25o and the GZ value must be at least 0.20 metres at an angle of heel equal to

or greater than 30o

E Initial GM is to be not less than 0.15 metres

The curves of righting levers (also known as GZ curve), for each condition of loading should be obtained at the trim shown in the condition by interpolation between the

appropriate sets of trimmed cross curves (KN curves)

Areas under the curve may be calculated by a suitable numerical method Alternatively the values of GZ righting arm levers may be plotted against heel angles on graph paper and the number of squares under the curve may be manually counted

0 o

C

D

E

10 o 20 o 30 o 40 o 50 o 60 o 70 o

Angle of heel (degs)

GZ (m)

Sample form for calculating Loading Condition

TABLE 1

% WTMT LCG m

aft amidships

L Mmt

m –MT

VCG

m -BL V

Mmt

m-MT

FSM m-MT

MT Load % WT

MT LCG m

aft amidships

L Mmt

m –MT

VCG

m -BL V

Mmt

m-MT

FSM m-MT

1 Fuel Oil Tank Stb A

2 Fuel Oil Tank Port B

3 Fresh Water Tank Stb C

4 Fresh Water Tank Port D

5 Grey Water Tank E

6 Aft Ballast Tank Stb F

7 Aft Ballast Tank Port G

8 Lub Oil Tank H

Displacement (MT)

Note: Lightship weight includes x, y and z items

TABLE 2

Stability Calculation

Fwd Draught METRE S

Aft Draught METRE S

Displacement MT

VCG METRES

KMT METRES

GMT (solid) METRES

FSC METRES

GMT (fluid) METRES

TABLE 3

Trim Calculations

LCF Draught (above base line) METRE S

LCG (fwd/aft of amidships) METRE S

LCF (fwd/aft of amidships) METRE S

LCB (fwd/aft of amidships) METRE S

Explanation and notes on completing Sample Stability Form

Table 1 Calculating the Displacement and Centres of gravity

• Fill in the weights in column 3 (WT)

• Fill in the longitudinal and vertical centres of gravity in columns 4 (LCG) and

6(VCG) respectively

• Multiply the weight of each item by its centre to get the longitudinal and vertical moments and enter moments in column 5 (L Mmt) and Column 7 (V Mmt)

• Record all the tank loads and enter the % into column 2 (load %)

• From the tank capacity plan enter the tank weights into column 3 (WT), LCG’s into column 4, VCG’s into column 6 and FSC into column 8

• Multiply the weight of each tank by its centre to get the longitudinal and vertical moments and enter moments in column 5 (L Mmt) and Column 7 (V Mmt)

• Sum up columns 3,5 and 7 and enter total in Dead Weight row

• Add Dead Weight mass to Light Ship mass and enter new total in Total Displacement row column 3

• Add Dead Weight LCG Mmt to Light Ship LCG Mmt and enter new total in Total Displacement row column 5

• Divide Total Displacement row column 5 by Total Displacement row column 3 to calculate overall estimate of LCG location for loading condition Enter calculation into Total Displacement row column 4

• Add Dead Weight VCG Mmt to Light Ship VCG Mmt and enter new total in Total Displacement row column 7

• Divide Total Displacement row column 7 by Total Displacement row column 3 to calculate overall estimate of VCG location for loading condition Enter calculation into Total Displacement row column 6

• Sum up column 8 (FSC) and enter total into Total Displacement row column 8

Table 2 Calculating the Stability

• Transfer the value of the overall VCG from table 1 and enter it in table 2

• Record fwd and aft draught estimates in table 2

• Subtract fwd draught from aft draught (noting if trim is stern down or bow down), and enter trim value in table

• Using the trim estimate and the displacement value calculated in Table 1 determine hydrostatics values of KMT, LCB, MCTC, LCF and LCF draught, and enter in table

3

• Subtract the overall VCG value in table 1 from KMT to obtain GMT solid, enter in table

• Subtract the overall FSC value from table 1 from GMT solid to obtain GMT fluid, enter in table

Table 3 Calculating actual trim

• To obtain the trim lever take the difference between LCB and LCG, enter in table

• To obtain an estimate of the actual trim multiply the displacement by the trim lever and divide that sum by the MCTC This provides the trim in cm units

• If the LCG is fwd of the LCB the vessel is trimmed bow down, and conversely if the LCG is aft of the LCB the vessel is trimmed stern down

• The aft draught may be found by dividing the LCF value by the X (m) value shown

on the ‘Diagram to show Draught mark locations’ and multiplying that value by the trim, and adding or subtracting that value to or from the LCF draught value

depending on the direction of trim If the vessel is trimmed stern down, then add, otherwise subtract

• The fwd draught may be found by dividing the LCF value by the Y (m) value shown

on the ‘Diagram to show Draught mark locations’ and multiplying that value by the trim, and adding or subtracting that value to or from the LCF draught value

depending on the direction of trim If the vessel is trimmed stern down, then add, otherwise subtract

• Using the newly calculated values for fwd and aft draughts calculate the revised estimate of the trim Compare this revised trim value to the original estimate of trim

in table 2 Iterate to convergence

Max KG limiting criteria (not compulsory)

Table or Graph as appropiate

Freeboard Load line Mark

In accordance with the load line regulation the following Plimsoll mark is to be attached

to the vessel

Top of Deck at side

Assigned

summer

freeboard

25mm

Summer

Draft

USK

underside of keel

300mm 450mm

25mm

Note: Loadline approving classification societies initial to be inserted on Plimsoll mark

Loading Conditions

Stability Form and stability criteria code assessment to be presented in the following conditions;

• Lightship

• Departure (100% consumables)

• Half Load (50% consumables) (OPTIONAL CONDITION)

• Arrival (10% consumables)

Hydrostatics

Tabular output showing Displacement, Draught, LCG, VCB, KMT, KML, TPC and

MCTC across the range of operational draughts and trims

Suggested at Trims of –0.5m, -0.25m, 0m, 0.25m & 0.5m

NOTE:

Water Density =1.025 T/m3

K is to underside of keel at amidships

Draught is to underside of keel at amidships

Cross Curve Stability Plot

Tabular Output showing KN curve values across the range of operational displacements and trims

Suggested at Trims of –0.5m, -0.25m, 0m, 0.25m & 0.5m

NOTE:

Water Density =1.025 T/m3

VCG = zero m