World Leader in Rating Technology OFFSHORE RACING CONGRESS ORC VPP Documentation 2019 5 2 Copyright c 2019 Offshore Racing Congress All rights reserved. Reproduction in whole or in part is only with the permission of the Offshore Racing Congress. CONTENTS 1 Background 13 2 Introduction 15 2.1 Scope . 15 2.2 Overview . 15 2.3 Layout . 15 3 VPP Methodology 17 3.1 Solution Method . 17 3.2 Boat Model . 18 3.2.1 Functional relationships . 19 3.3 Equations of Equilibrium . 21 3.3.1 Driving Force - Drag . 21 3.3.2 Heeling Moment - Rolling Moment . 22 3.4 Water Ballast and Canting Keel Yachts . 23 3.4.1 Canting Keel . 23 3.4.2 Daggerboard (Centreline lifting appendage) . 23 3.4.3 Daggerboard and Bilge boards . 23 3.4.4 Water ballast . 24 3.4.5 Measurement . 24 3.5 Dynamic Allowance (DA) . 24 3.5.1 Credits (2012) . 25 3.5.2 Calculation Procedure . 25 3.6 Non Manual Power . 25 4 Lines Processing Program 27 4.1 Hydrostatics . 27 4.2 LPP Output parameter definitions . 28 4.2.1 Measurement Trim . 28 4.2.2 Sailing Trim . 28 4.2.3 Second Moment Length (LSM) . 28 4.2.4 Appendage stripping . 28 4.2.5 Beam Depth Ratio (BTR) . 29 4.2.6 Maximum Effective Draft (MHSD) . 30 4.2.7 Bulb/Wing Effects . 31 4.3 Appendage wetted areas and lengths . 34 4.3.1 Conventional Fin keel and rudder . 34 4.3.2 Other appendages . 34 4.4 Righting Moment . 34 4.4.1 Righting Arm Curve . 35 4.4.2 Hydrodynamic Centre of Pressure . 36 4.4.3 Crew righting moment . 36 4.4.4 Dynamic Righting Moment. RMV . 37 4.4.5 Rated Righting Moment . 37 3 4 5 Aerodynamic Forces 39 5.1 Methodology . 39 5.1.1 Individual Sail Areas and 2-Dimensional Aerodynamic Force Coefficients . 39 5.1.2 Simplified Rigging Coefficients . 40 5.1.3 Optimization and De-powering . 41 5.2 Sail Areas & Coefficients . 43 5.2.1 Mainsail . 43 5.2.2 Jib or Genoa . 46 5.2.3 Spinnakers . 48 5.2.4 Spinnaker tack position Power Function . 51 5.2.5 Headsails set flying . 52 5.3 Windage Forces . 55 5.3.1 Rigging . 56 5.4 Total Aerodynamic Lift and Drag . 56 5.4.1 Lift and Drag of complete sail set . 57 5.4.2 Center of Effort Height . 57 5.4.3 Induced Drag . 58 5.4.4 Twist Function . 60 5.5 Resolution of Forces . 60 5.5.1 PHI UP ............................................. 60 5.5.2 Thrust and Heeling Force . 61 5.5.3 Aerodynamic heeling Moment . 61 5.6 Blanketing functions . 61 5.6.1 Mainsail . 61 5.6.2 Jib . 62 5.6.3 Mizzen, Jib Downwind, Spinnaker . 62 5.6.4 Mizzen Staysail . 62 6 Hydrodynamic Forces 63 6.1 Viscous Resistance . 63 6.1.1 Canoe body . 63 6.1.2 Appendages . 63 6.2 Propeller . 65 6.2.1 Shaft Installation . 65 6.2.2 Strut drive . 67 6.2.3 In aperture . 68 6.2.4 Tractor propellers . 68 6.2.5 Twin screws . 68 6.3 Residuary Resistance . 68 6.3.1 Canoe body . 68 6.3.2 Appendages . 70 6.4 Drag due to heel . 71 6.5 Induced Drag . 71 6.5.1 Correction Factors . 74 6.6 Immersed transom . 75 6.7 Rail-under drag . ..