CONTENTS 



CHAPTER 68— LAYOUT OF THE ABOVEWATER FORM— Continued 



68.14 Shaping and Positioning of Superstructure 



and Upper Works 561 



68.15 Design of Facilities for Abovewater Smoke 



and Gas Discharge 563 



68.16 Reducing the Wind Drag of the Masts, 



Spars, and Rigging 566 



68.17 Consideration of Increased Draft Through 



the Years 566 



68.18 Preparation of Hull Lines for Model Tests . 566 



CHAPTER 69— THE GENERAL DESIGN OP THE PROPULSION DEVICES 



69 . 1 Introductory Comment 567 



69.2 Type and Number of Propulsion Devices . . 667 



69 . 3 Positions and Limiting Dimensions .... 568 



69.4 Effect of Type and Design of Propelling 



Machinery 570 



69 . 5 Number and Position of the Engines . . . 570 



69 . 6 Use of Systematic Wake Variations .... 572 



69.7 Rate and Direction of Rotation of Propul- 



sion Devices 572 



69.8 Design to Equalize or to Apportion the 



Powers of Multiple Propellers 573 



69 . 9 Powering Allowances 574 



69.10 Graphic Representation of Powering Allow- 



ances and Reserves 576 



69.11 Selection of Feathering, Adjustable, Rever- 



sible, or Controllable Features 578 



69 . 12 Propulsion Devices to be Used with Contra- 

 Vanes, Contra-Guide Sterns, and Contra- 



Rudders 579 



69 . 13 Disadvantages of Unbalanced Propulsion- 

 Device Torque 579 



69.14 Propulsion-Device Design to Meet Maneu- 



vering Requirements 580 



69.15 Relation of Propulsion-Device and Hull- 



Vibration Frequencies 580 



CHAPTER 70— SCREW-PROPELLER DESIGN 



70 . 1 General Considerations 582 



70 . 2 Design Requirements for a Screw Propeller . 583 



70.3 Comments on Available Design Methods 



and Procedures 583 



70.4 Requirements for. Availability of, and 



Listing of Propeller-Series Charts .... 584 



70.5 Comments on and Comparison of Propeller- 



Series Charts 589 



70.6 Preliminary-Design Procedure, Employing 



Series Charts 592 



70.7 Modification of Series-Chart Procedure for 



Other Design Problems 596 



70.8 Preliminary Comments on Propeller-Design 



Features 596 



70.9 Selection of Propeller Diameter 597 



70.10 Determining the Rate of Rotation .... 597 



70.11 The Proper Pitch-Diameter Ratio; Pitch 



Variation with Radius 598 



70.12 Choice of Number of Blades 599 



70.13 Use of Raked Blades 600 



70.14 Propeller-Hub Diameter; Hub Fairing . . . 601 



70.15 Determination of Expanded-Area Ratio; 



Choice of Blade Profile 602 



70.16 Selecting and Applying Skew-Back .... 603 



70.17 Design Considerations Governing Blade 



Width 605 



70.18 Selection of Type of Blade Section .... 605 



70. 19 Shaping of Blade Edges and Root Fillets . 606 



70.20 Partial Bibliography on Screw-Propeller 



Design 606 



70.21 Design of a Wake-Adapted Propeller by 



the Circulation Theory 609 



70.22 ABC Ship Propeller Designed by Lerbs' 



1954 Method 611 



70.23 Choice of the Number of Blades for the 



ABC Design 612 



70.24 Determination of Rake for the ABC Pro- 



peller 612 



70.25 Propeller-Disc and Hub Diameters .... 612 



70.26 Calculating the Thrust-Load Factors and 



the Advance Coefficients 613 



70.27 First Appro.ximation of the Hydrodynamic 



Pitch Angle and the Radial Thrust Dis- 

 tribution 615 



Second Approximation of /3, and the Radial 



Thrust Distribution 616 



Determination of the Lift-Coefficient Product 

 and the Hydrodynamic Pitch-Diameter 



Ratio 617 



Finding the Blade-Thickness Distribution . 620 

 Blade-Section Shaping by Cavitation Cri- 

 teria 621 



Procedure When Cavitation in Not Involved 625 

 Corrections for Flow Curvature and Viscous 



Flow 625 



Final Blade-Section Shapes for the ABC 



Design by Lerbs' Method 627 



Introducing Skew-Back in the ABC Blade 



Profile 627 



Drawing the Propeller 629 



Calculating the Expected Propeller Efficiency 629 

 Summary of Design Steps for Lerbs' Short 



Method; Schoenherr's Combination . . . 630 

 Avoiding Air Leakage with Inadequate Sub- 

 mersion 631 



Design Comments on Propellers for the 



Supercavitating Range 631 



Design of Bow Propellers, Coupled and 



Free-Running 632 



Open- Water and Self-Propelled Model Testa 632 

 Mechanical Construction; Tjrpe of Hub; 



Shaping and Finish of Blades 633 



Blade Strength and Deformation 634 



Propeller Materials and Coatings to Resist 



Erosion 635 



70 . 46 Prevention of Singing and Vibration .... 636 



