Stability Information Booklet Priority Pontoon Lightship
Index General Particulars...3 General Details...4 Plan - GA...5 Plan - Frames...6 General Precautions against capsizing...7 Special Notes Regarding the stability and Loading...7 Metric Conversions...8 Hydrostatic particulars...9 Capacities and Centres of Gravity... 9 Notes on Free Surface Moments...9 Cross Curves of Stabilities (KN Curves)... 10 Deadweight Sale...10 Trim and Stability Calculation...11
General Particulars Ships Name Priority Official Number Owner No: 3139 PLA No: 19459 Port of Registry London Owners Name and Address Marine Support Thames MST Ltd 10 Swanbridge Road Bexleyheath Kent DA7 5BP Builders Name, Address and Ship Number Currently Unknown Date Keel Laid Currently Unknown Moulded Dimensions (in metres) LOA 36.6 LBP 36.6 Beam 9.2 Depth 2.5 Summer Load Draught (in metres) 0.6 (Lightship) Block Coefficient 0.9422 (Lightship) Displacement (in tonnes) 184.45 (Lightship) Deadweight (in tonnes) 184.45 (Lightship) Gross Tonnage Currently Unknown Net Tonnage Currently Unknown
General Details Stability information booklet for the pontoon Priority, in Lightship condition with the base of the spud legs flush with the keel of the pontoon The vessel is considered as a pontoon by MSIS003, Part 8, Paragraph 8.17.1 because: It is non-self propelled It will be unmanned during movement There will only be deck cargo The block coefficient is greater than 0.9 (0.9422 Lightship) The breadth/depth ratio is greater than 3 (3.68) There are no hatchways in the deck, except small manholes closed with gasketed deck covers. Hydrostatics and cross curves of stability were produced for the pontoon by a hydrostatics package. The lightship weight and centre of gravity was calculated from a weights and centres calculation of the structural elements of the pontoon. Appendix 5. From these calculations a light weight of 125.35 Te and KG of 1.207m was obtained. A conservative weight of 140 Te with KG of 1.4m was used in the stability calculations.
Plan - GA
Plan - Frames
General Precautions against capsizing Compliance with the stability criteria indicated overleaf does not ensure immunity against capsizing regardless of the circumstances or absolve the master from his responsibilities. Masters should therefore exercise prudence and good seamanship having regard to the season of the year, weather forecasts and the navigational zone and should take the appropriate action as to speed and course warranted by the prevailing circumstances. Care should be taken to ensure that the cargo allocated to the ship is capable of being stowed so that compliance with the criteria can be achieved. If necessary the amount should be limited to the extent that ballast weight may be required. Before a voyage commences care should be taken to ensure that the cargo and sizeable pieces of equipment have been properly stowed or lashed so as to minimize the possibility of both longitudinal and lateral shifting while at sea, under the effect of acceleration caused by rolling and pitching. Special Notes Regarding the stability and Loading This vessel ship is required to comply with Schedule 2, Part 1, Paragraph 2 of MSN 1752(M) by the Merchant Shipping (Load Line) Regulations 1998, it is most important to ensure that in any sailing condition the stability complies at least with the following minimum criteria:static Stability Curve
Under MSIS 003, Part 8, Paragraph 8.17.4, for pontoons, if the vessel characteristics make compliance with paragraph 2(2)(c) of Schedule 2 for MSN 1752(M) impossible the following criteria can be used: Metric Conversions Multiply By 0.03937 0.3937 3.2808 2.2046 0.0009842 0.9842 2.4998 8.2014 187.9767 0.01745 To Convert From Millimetres Centimetres Metres Kilogrammes Kilogrammes Tonnes (1000Kg) Tonnes per centimetre (of immersion) Moment to change trim one centimetre (tonnes meter units) Meters radians Meters degrees To Obtain To Obtain Inches Inches Feet Pounds Tons (2240 lbs) Tons (2240 lbs) Tons per inch (of immersion) Moment to change trim one inch (foot ton units) Feet degrees Meter radians To Convert From 25.400 2.5400 0.3048 0.45359 1016.047 1.016 0.4000 0.122 0.0053 57.30 Multiply by Relationship between weight and volume 10 mm cubed = 1 cubic centimetre 1 cubic centimetre of freshwater (S.G. 1.0) = 1 gramme 1000 cubic centimetre of freshwater (S.G. 1.0) = 1 Kilogram (1000 grammes) 1 cubic metre of freshwater (S.G. 1.0) = 1 Tonne (1000 Kilos) 1 cubic metre of saltwater (S.G. 1.025) = 1.025 Tonnes 1 tonne of saltwater (S.G. 1.025) = 0.975 Cubic Metres 1 cubic metre = 35.316 cubic feet 1 cubic foot = 0.0283 cubic metres
Hydrostatic particulars Hydrostatics were calculated by Freeship software, using a model of the pontoon. The data is contained within Hydrostatics and Windage sheets in Appendix 3 Capacities and Centres of Gravity The weights and centres for the loading condition were calculated based on the following: o Lightship A conservative weight of 140 Te with KG of 1.4m was used, based on the results of a weights and centres calculation of the structural elements of the pontoon. o Deck Cargo Spud legs with bottom of spud leg flush with the keel of the pontoon. No other deck cargo loaded o Tanks No tanks. Pontoon compartments are to be kept empty during operation o Spud Leg Tubes The lost buoyancy and free surface of the spud tubes is included The data is contained within Weights and Centres in Appendix 2 Notes on Free Surface Moments Provided a tank is completely filled with liquid no movement of the liquid is possible then 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 effects". This adverse effect on the stability is referred to as a "loss in G.M." or as a "virtual rise in V.C.G." and is calculated as follows: N.B. The "free surface effects" of a proportion of all oil-fuel, fresh water, feed- water and service tanks should be taken into account in both the Arrival and Departure Conditions.
Cross Curves of Stabilities (KN Curves) KN values were calculated by Freeship software, using a model of the pontoon. The data is contained within KN Curves in Appendix 4 Deadweight Sale
Trim and Stability Calculation Trim and stability was calculated for the Lightship condition of Priority in excel using standard Naval architecture formulas. Full calculations are contained within: Trim and Stability Calculation in Appendix 1 The resultant GZ curve and adherence to the required criteria was: