Introduction t oduct o A Number of Requirement q • The size of the ship should be such that it can : • a) carry a specified deadweight at a reasonable stowage rate AND/OR • b) provide sufficient volume for the accommodation of a specified number of passengers AND/OR • c) provide sufficient volume for the stowage of specialised cargo. cargo 2. The proportion and form should be suitable for a specified speed. 3. Special conditions may affect the choice of the principal dimensions, e.g. • a) length, breadth or draught restrictions OR • b) extra stability for 'heavy lift' requirements. 1. • • Items (1) (1), (2) and (3) are instrumental in making a design an “individual” individual . In addition there are general requirements implicit in any design in next slide : A Number of Requirement • • • • 4. Adequate propulsion machinery with properly designed propeller(s). 5 A suitable 5. i bl standard d d of f stability bili . 6. Acceptable trim in all normal conditions of loading 7 Seaworthiness e.g. 7. eg a) provision of reserve buoyancy (normally accounted for by the Load Line Regulations and Subdivision Regulations) b) Satisfactory behaviour in a sea state representative of the route concerned. 8. Sufficient strength to take the loads imposed on the structure when in service normally accounted for by Classification Society Regulations ). 9. Sufficient tank space for a) water ballast b) oil fuel c) fresh water (drinking, (drinking domestic and boiler). boiler) • • A Number of Requirement • • • • • • 11. Suitable crew accommodation (minimum standards are laid down in Crew Accommodation d Regulations). l ) 12. Freedom from vibration. 13 Adequate and efficient cargo handling facilities. 13. facilities 14. Manoeuverability, particularly for vessels trading into restricted waters. 15. Good appearance particularly for passenger ships. 16. Economy in first cost and running costs etc. Design es g Problem ob e The Design Problem (a) For Deadweight carriers Displacement = Ship Mass Available displacement = LxBxdxCb x 1.025 + shell etc Ship mass = Deadweight + steel mass + wood and outfit mass + machinery mass • The h f first problem bl is to f find d the h principal l d dimensions and d f form to fl float the h ship h at its design draught. • If the mass of the ship p were known then it would be possible p to find dimensions and form to provide an equivalent displacement. If it were only necessary to provide displacement, then it would be possible to use any combination of L, B, d and Cg which gives the required displacement. displacement • At this stage of the design, however, the total mass of the ship is not known. Deadweight is specified but steel mass, outfit mass and machinery mass depend upon the h size, i proportions i and d f form of f the h hull h ll (machinery ( hi mass also l depends d d upon speed, but this would be specified in a particular case). In other words in order to find the required displacement, and hence estimate dimensions etc., it appears that it is necessary to know the dimensions to start with. The Design Problem (b) For Capacity carriers Passenger ships are specified in terms of number of Passengers. From this it is possible to determine the volume of accommodation required including : ‐ public rooms, ‐ passageways, p g y , etc). ) To this must be added the volume of crew accommodation. In addition: ‐ the volume of machinery spaces, ‐ t k spaces, tank ‐ storage spaces etc. The principal dimensions of the main hull can then be chosen to provide this volume. These dimensions must be such that the proportions and form are satisfactory from the point of view of stability, resistance etc. Refrigerated cargo ships are specified in terms of net volume of refrigerated cargo space. To this must be added the volume of insulation, refrigeration machinery space etc. to obtain the gross volume required. After this the process is basically one of providing a hull which contains this volume, together with engine room, tanks etc.