Page 19 - Practical Ship Design

XVI

7.4.5 Self-pitching propellers ........................ 211
7.4.6 Other propeller types ......................... 211
7.4.7 Nozzles ................................ 211
7.4.8 Propeller position ........................... 215
7.4.9 Paddle wheels ............................. 215
7.4.10 Waterjet propulsion .......................... 215
7.4.1 1 The future ............................... 216
7.4.12 General ................................ 216
7.4.13 Open water efficiency ......................... 216
7.5 Propulsive efficiency .............................. 216
7.5.1 Slow revving propellers ........................ 218
7.5.2 Slow revving propellers on twin screw ships .............. 220
7.5.3 Optimising open water efficiency ................... 220
7.5.4 Specifying propeller design conditions ................ 221
7.5.5 Propeller design ............................ 222
7.5.6 Efficiency of a controllable pitch propeller .............. 222
7.6 Hull efficiency ................................. 222
7.7 Trial and service allowances .......................... 223
7.7.1 Trial power .............................. 223
7.7.2 Weather and fouling - historical treatment .............. 224
7.7.3 Fouling with modern anti-fouling paints ................ 224
7.7.4 Weather allowance .......................... 225
7.8 Devices to improve propulsive efficiency ................... 226
7.8.1 Pre-rotating ............................... 226
7.8.2 Post propeller recovery ........................ 227
7.8.3 Efficiency claims ........................... 228
7.9 Design optimisation for powering ....................... 228
7.9.1 Block coefficient ........................... 228
7.9.2 Length ................................. 229
7.9.3 The effect of LIV”’ .......................... 229
7.9.4 B/Tratio ................................ 230
7.9.5 B/T ratio of the ballast condition .................... 230

Chapter 8 . Design of Lines
8.1 Objectives ................................... 231
8.2 The bow and stern ............................... 232
8.2.1 Normal or bulbous bow ........................ 232
8.2.2 Bulbous bow shapes .......................... 233
8.2.3 Bows above the waterline ....................... 234
8.2.4 Sterns ................................. 235
8.2.5 Flow to the propeller .......................... 235
8.2.6 Large propellers ............................ 236
8.2.7 Stern lines above the propeller ..................... 237