Full Scale Test Case For Sailing Yacht Performance Master of Science Thesis in Naval Architecture and Ocean Engineering MAËL GORMAND Department of Shipping and Marine Technology Division of Marine Design CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden, 2012 Report No. X-12/274 ii This thesis is an attempt at evaluating performance of sailing yacht using full scale data as measured by regular onboard sailing instrumentation. Us- ing standard sailing instruments connected to a computer, key performance data can be retrieved. Once processed, a database of performance can be obtained. Results of theoretical calculations from VPPs and DVPPs can be compared with reality for validation. It is proved that full scale performance data has become precise enough to be used scientifically. This research has involved two sailing yachts, more than a year of sailing, a dozen of crew members, many advisors, family and friends. To all of you, thank you for your support, comments, help, friendship and understanding. Maël GORMAND The front page picture was taken on board “Le RM 1050” while going up the estuary of the Tagus, reaching Lisbon, Portugal. All rights are owned by LBDA and the crew of “Le RM 1050”. c©MAËL GORMAND, 2012. Technical report no X-12/274 Departement of Shipping and Marine Technology Chalmers University of Technology SE-412 96 Göteborg Sweden Telephone +46 (0)31-772 1000 Abstract The present master thesis investigates the possibilities of producing a full scale test case of the performance of sailing yachts. With such a test case, it is believed that instantaneous and absolute performance of sailing yacht evolving in real conditions can be investigated. An out-put of this study is the ability to validate a velocity prediction program with full scale data. Through the use of a sailing yacht, a procedure for performance measure- ment at sea was developed. This procedure involves the use of on-board electronic instrumentation, displacement measurement and inclining test. A code is developed in Excel c©, using VBA c© to sort all the data gathered during the measurement campaign. The sorting of data involves the compi- lation of a database used for plotting the performance of the yacht in two different ways: the first to analyse the instantaneous behaviour of the yacht; the second to analyse the maximum potential performance the yacht can reach. The measurements can then be compared with simulations produced in the “same” sailing condition using a VPP. In this paper, two VPPs are investigated: SailSim c© from SSPA AB and WinDesign c© from the Wolfson unit at the University of Southampton. The first software has dynamical ca- pabilities but was not used in the end for this research. The second one has only static capabilities and was used for the simulations in the present work. From the comparison between the measurements and the simulations, the quality of full scale data is established and the possibility to validate a VPP using standard sailing electronics is demonstrated. Further development is also suggested and further analysis involving full scale data is proposed. In the present master thesis a universal method to record sailing yacht’s per- formance data at sea was developed. Then a code to process these data and sort them into a general database useful for further studies was built. It was proven that the quality of nowadays electronics make scientific studies possi- ble. Finally it was demonstrated that standard velocity prediction programs can be validated by full scale data. Keywords: VPP, DVPP, Yacht, Performance, Full Scale, Measurement iii iv ABSTRACT Contents Abstract iii Contents v List of Tables ix List of Figures xi List of Symbols and Abbreviations xiii Acknowledgements xv 1 Introduction 1 1.1 Tools used in Naval Architecture . . . . . . . . . . . . . . . . 1 1.1.1 CAED design . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.2 Empirical studies and sailing theories . . . . . . . . . . 2 1.1.3 CFD and CSE . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.4 Velocity Prediction Programs . . . . . . . . . . . . . . 3 1.2 Genesis of the project . . . . . . . . . . . . . . . . . . . . . . . 4 1.2.1 Voile Magazine, Fora Marine and M. Lombard . . . . . 4 1.2.2 Journey with “Le RM 1050” . . . . . . . . . . . . . . . 5 1.2.3 SSPA and Chalmers . . . . . . . . . . . . . . . . . . . 7 1.2.4 Gabriel Heyman and Mr and Mrs Eklund . . . . . . . . 9 1.2.5 The Wolfson unit and WinDesign c© . . . . . . . . . . . 9 1.3 Goal of this master thesis . . . . . . . . . . . . . . . . . . . . 11 1.3.1 A procedure to measure performance of yachts . . . . . 11 1.3.2 The use of VPPs in the design process . . . . . . . . . 11 1.3.3 A test case for various weather conditions . . . . . . . 12 1.3.4 Validation of a Velocity Prediction Program . . . . . . 12 1.4 Organisation of the work . . . . . . . . . . . . . . . . . . . . . 13 1.4.1 Literature and “tools” survey . . . . . . . . . . . . . . . 13 1.4.2 Workflow diagram . . . . . . . . . . . . . . . . . . . . 14 v vi CONTENTS 1.4.3 Measurements . . . . . . . . . . . . . . . . . . . . . . . 15 1.4.4 Data treatment . . . . . . . . . . . . . . . . . . . . . . 15 1.4.5 Computer simulation . . . . . . . . . . . . . . . . . . . 15 1.4.6 Validation, discussion and conclusion . . . . . . . . . . 16 2 Measurements: theory, goal and set-up 19 2.1 Goal of the measurements . . . . . . . . . . . . . . . . . . . . 19 2.1.1 Create a polar curve database in still water and waves 19 2.1.2 Full scale data measurement . . . . . . . . . . . . . . . 20 2.1.3 Measurement procedure . . . . . . . . . . . . . . . . . 21 2.2 General procedure for measurements . . . . . . . . . . . . . . 21 2.2.1 Preparation of the work and data to be recorded . . . . 22 2.2.2 Electronic instrumentation . . . . . . . . . . . . . . . . 24 2.2.3 Preparation of the boat . . . . . . . . . . . . . . . . . . 25 2.2.4 Hull displacement . . . . . . . . . . . . . . . . . . . . . 27 2.2.5 Inclining test . . . . . . . . . . . . . . . . . . . . . . . 28 2.2.6 Sailing procedure and measurements . . . . . . . . . . 32 2.2.7 “External” recordings . . . . . . . . . . . . . . . . . . . 34 3 Measurements: first and second campaigns 37 3.1 Measurements with “Le RM 1050” . . . . . . . . . . . . . . . . 37 3.1.1 General characteristics of the boat . . . . . . . . . . . 37 3.1.2 Instrumentation available on board . . . . . . . . . . . 38 3.1.3 Instrumentation set-up . . . . . . . . . . . . . . . . . . 40 3.1.4 Inclining test . . . . . . . . . . . . . . . . . . . . . . . 46 3.1.5 Displacement . . . . . . . . . . . . . . . . . . . . . . . 47 3.1.6 Measurements recorded . . . . . . . . . . . . . . . . . . 48 3.1.7 Problems encountered . . . . . . . . . . . . . . . . . . 50 3.1.8 Problem induced by simulations . . . . . . . . . . . . . 55 3.2 Measurements with “Vågvis” . . . . . . . . . . . . . . . . . . . 56 3.2.1 General characteristics of the boat . . . . . . . . . . . 56 3.2.2 Instrumentation available on board . . . . . . . . . . . 57 3.2.3 Instruments set-up . . . . . . . . . . . . . . . . . . . . 58 3.2.4 Displacement . . . . . . . . . . . . . . . . . . . . . . . 60 3.2.5 Inclining test . . . . . . . . . . . . . . . . . . . . . . . 62 3.2.6 Measurements recorded . . . . . . . . . . . . . . . . . . 66 3.2.7 Problems encountered . . . . . . . . . . . . . . . . . . 67 3.3 Future recommendation . . . . . . . . . . . . . . . . . . . . . 68 3.3.1 Availability and distance . . . . . . . . . . . . . . . . . 68 3.3.2 Reliability and Electronics . . . . . . . . . . . . . . . . 70 3.3.3 Set-up and testing . . . . . . . . . . . . . . . . . . . . 70 CONTENTS vii 3.3.4 Large Data Recording . . . . . . . . . . . . . . . . . . 70 4 Data Treatment 73 4.1 Data Treatment: Finding the right tools . . . . . . . . . . . . 73 4.1.1 The Specificities of the NMEA 0183 language . . . . . 73 4.1.2 Mathematical Software: First Trial . . . . . . . . . . . 74 4.1.3 Programming With Better Languages . . . . . . . . . . 74 4.1.4 Mathematical Software: Second Trial . . . . . . . . . . 76 4.2 Data Treatment: Proceeding With Excel c© and VBA c© . . . . 76 4.2.1 Data Treatment Procedure . . . . . . . . . . . . . . . . 76 4.2.2 Reading of result produced . . . . . . . . . . . . . . . . 77 4.2.3 The Importance of Details: Preparing Future Work . . 80 4.2.4 VBA code . . . . . . . . . . . . . . . . . . . . . . . . . 80 4.3 Resulting code: failures and achievements . . . . . . . . . . . 81 4.3.1 Identified problems . . . . . . . . . . . . . . . . . . . . 81 4.3.2 Ship Time Response . . . . . . . . . . . . . . . . . . . 81 4.3.3 Quality of the Resulting Code . . . . . . . . . . . . . . 85 4.3.4 Quality Analysis of the Treated Data . . . . . . . . . . 87 4.3.5 Plots for Analysis . . . . . . . . . . . . . . . . . . . . . 87 4.4 Future Possible Development of the Code . . . . . . . . . . . . 89 4.4.1 Using a Better Language for a Faster Process or a Data-Base software . . . . . . . . . . . . . . . . . . . . 89 4.4.2 Incorporating External Data in The Process . . . . . . 91 4.4.3 Ship Behaviour Module . . . . . . . . . . . . . . . . . . 92 4.4.4 Plot Production and Plot Analysis Modules . . . . . . 92 5 Computer Simulations 93 5.1 SailSim c© by SSPA AB . . . . . . . . . . . . . . . . . . . . . . 93 5.1.1 Characteristics and Capabilities . . . . . . . . . . . . . 93 5.1.2 Preparation Work for “Le RM 1050” . . . . . . . . . . 94 5.1.3 Preparation Work for “Vågvis” . . . . . . . . . . . . . . 94 5.1.4 Reasons Why No Further WorkWas DoneWith SailSim c© 95 5.2 WinDesign c© by The Wolfson Unit . . . . . . . . . . . . . . . 95 5.2.1 Characteristics and Capabilities . . . . . . . . . . . . . 95 5.2.2 Preparation Work for “Vågvis”: LPP c© . . . . . . . . . 96 5.2.3 Running WinDesign c© . . . . . . . . . . . . . . . . . . 97 5.3 Limitations of the Simulations . . . . . . . . . . . . . . . . . . 97 5.3.1 SailSim c© . . . . . . . . . . . . . . . . . . . . . . . . . 99 5.3.2 WinDesign c© . . . . . . . . . . . . . . . . . . . . . . . 99 5.3.3 Dynamical Behaviour of Ships . . . . . . . . . . . . . . 100 viii CONTENTS 6 Analysis and Discussion 103 6.1 Analysis of the Results . . . . . . . . . . . . . . . . . . . . . . 103 6.1.1 Description of the results . . . . . . . . . . . . . . . . . 103 6.1.2 Comments on the results . . . . . . . . . . . . . . . . . 104 6.1.3 Quality assessment of the results . . . . . . . . . . . . 107 6.2 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 6.2.1 Interest of recording large amount of data . . . . . . . 108 6.2.2 Ship Response and dynamics . . . . . . . . . . . . . . . 110 6.2.3 Validation of a VPP: WinDesign c© . . . . . . . . . . . 111 7 Conclusions 121 7.1 Full Scale Measurements . . . . . . . . . . . . . . . . . . . . . 121 7.2 Data treatment . . . . . . . . . . . . . . . . . . . . . . . . . . 122 7.3 Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 7.4 Limitations of the Project . . . . . . . . . . . . . . . . . . . . 124 7.5 Suggested Future Work . . . . . . . . . . . . . . . . . . . . . . 124 A VBA code: description 127 A.1 Explaining the code . . . . . . . . . . . . . . . . . . . . . . . . 127 A.1.1 Overall structure of the code and philosophy . . . . . . 127 A.1.2 Importing the data to Excel c© . . . . . . . . . . . . . . 129 A.1.3 Main . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 A.1.4 CheckSheetExistence . . . . . . . . . . . . . . . . . . . 132 A.1.5 CopieData . . . . . . . . . . . . . . . . . . . . . . . . . 133 A.1.6 ConvertTime . . . . . . . . . . . . . . . . . . . . . . . 135 A.1.7 AnalysisPart1 . . . . . . . . . . . . . . . . . . . . . . . 140 B VBA code: Full code 149 B.1 VBA code: Main . . . . . . . . . . . . . . . . . . . . . . . . . 149 B.2 VBA code: CheckSheetExistence . . . . . . . . . . . . . . . . 153 B.3 VBA code: CopieData . . . . . . . . . . . . . . . . . . . . . . 154 B.4 VBA code: ConvertTime . . . . . . . . . . . . . . . . . . . . . 155 B.5 VBA code: AnalysisPart1 . . . . . . . . . . . . . . . . . . . . 159 Bibliography 181 List of Tables 3.1 Height of the Centre of Gravity for different cases for “Le RM 1050” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2 Freeboard Height Measurement for “Le RM 1050” . . . . . . . 48 3.3 Freeboard Height Measurement for “Vågvis” . . . . . . . . . . 63 3.4 Inclining test sensibility study for “Vågvis” . . . . . . . . . . . 65 ix x LIST OF TABLES List of Figures 1.1 The crew of “Le RM 1050” the day of departure in La Rochelle, Sunday 3rd of July 2005. From left to right: Florian Le Bouli- caut, Stanislas Paillereau, Mael Gormand and Gregory Ramain 5 1.2 “Le RM 1050” sailing off the coast of Madeira the 5th of September 2005, two months after departure. . . . . . . . . . . 6 1.3 The journey of “Le RM 1050” from July 2005 to June 2006 . . 8 1.4 The journey with Vågvis in May-June 2007 . . . . . . . . . . . 10 1.5 Detail of the journey with Vågvis on the island of Bornholm . 10 1.6 Vågvis in Christiansø, Denmark during the displacement mea- surement. Notice the calm weather condition encountered. . . 17 1.7 General Workflow diagram . . . . . . . . . . . . . . . . . . . . 18 2.1 The measurement procedure contains seven steps, dispatched over five main locations. The numbers refer to the different sections describing each stage in the report) . . . . . . . . . . 22 2.2 Inclining test procedure . . . . . . . . . . . . . . . . . . . . . 29 2.3 Sailing procedure . . . . . . . . . . . . . . . . . . . . . . . . . 35 3.1 Picture of the chart table of “Le RM 1050” with the chart plotter, the laptop used for measurements and the location of the multiplexer . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.2 Picture of the cockpit of “Le RM 1050” with the speedometer/sound- meter, the autopilot, the electronic weathercock and the com- pass. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 3.3 Location of instruments on board and data connections on board "Le RM 1050" . . . . . . . . . . . . . . . . . . . . . . . 42 3.4 Location of instruments on board and data connections on board “Vågvis” . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.5 Chart table with computer and multiplexer inside the elec- tronics compartment under the chart table on board “Vågvis” 60 3.6 Electronics compartment under the chart table . . . . . . . . . 61 xi xii LIST OF FIGURES 3.7 Details of the electronic connections on the course computer . 62 3.8 Inclining test procedure . . . . . . . . . . . . . . . . . . . . . 63 4.1 Test case generation work process . . . . . . . . . . . . . . . . 78 4.2 Wind shift between the true wind angle calculated from the GPS or calculated from the Loch-meter . . . . . . . . . . . . . 83 4.3 Time response of Vågvis going upwind . . . . . . . . . . . . . 84 4.4 Time response of Vågvis going downwind . . . . . . . . . . . . 86 4.5 Vågvis speeds for a wind strength of 4m.s−1 for different wind angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 4.6 Vågvis typical polar plot of the measurements for one wind speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 5.1 Simulation polar curve for “Vågvis” . . . . . . . . . . . . . . . 98 6.1 Performance plot of“Vågvis”: comparison betweenWinDesign c© and the measures at 1m.s−1 . . . . . . . . . . . . . . . . . . . 112 6.2 Performance plot of“Vågvis”: comparison betweenWinDesign c© and the measures at 2m.s−1 . . . . . . . . . . . . . . . . . . . 113 6.3 Performance plot of“Vågvis”: comparison betweenWinDesign c© and the measures at 3m.s−1 . . . . . . . . . . . . . . . . . . . 114 6.4 Performance plot of“Vågvis”: comparison betweenWinDesign c© and the measures at 4m.s−1 . . . . . . . . . . . . . . . . . . . 115 6.5 Performance plot of“Vågvis”: comparison betweenWinDesign c© and the measures at 5m.s−1 . . . . . . . . . . . . . . . . . . . 116 6.6 Performance plot of“Vågvis”: comparison betweenWinDesign c© and the measures at 6m.s−1 . . . . . . . . . . . . . . . . . . . 117 6.7 Performance plot of“Vågvis”: comparison betweenWinDesign c© and the measures at 7m.s−1 . . . . . . . . . . . . . . . . . . . 118 6.8 Performance plot of“Vågvis”: comparison betweenWinDesign c© and the measures at 8m.s−1 . . . . . . . . . . . . . . . . . . . 119 A.1 Overall code structure . . . . . . . . . . . . . . . . . . . . . . 128 A.2 “Main” flow chart . . . . . . . . . . . . . . . . . . . . . . . . . 131 A.3 “CheckSheetExistence” flow chart . . . . . . . . . . . . . . . . 133 A.4 “CopieData” flow chart . . . . . . . . . . . . . . . . . . . . . . 134 A.5 ConvertTime flow chart . . . . . . . . . . . . . . . . . . . . . 136 A.6 CheckDateAndTime flow chart . . . . . . . . . . . . . . . . . 139 A.7 AnalysisPart1 flow chart . . . . . . . . . . . . . . . . . . . . . 142 A.8 ComputeTrueWindSpeed flow chart . . . . . . . . . . . . . . . 143 A.9 Leeway angle and its relation with the Magnetic and GPS headings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 List of Symbols and Abbreviations a Horizontal displacement of the pendulum during inclining test BM Distance from the centre of buoyancy and the metacentre Bmax Maximum Beam of a boat CAD Computer Aided Design CAED Computer Aided Engineering Design CFD Computational Fluid Dynamic CSE Computational Structural Engineering d Weight translation distance in inclining test experiment DC Direct Current DSYHS Delft Systematic Yacht Hull Series DVPP Dynamic Velocity Prediction Program FEM Finite Element Method GG1 Shift of centre gravity location distance in inclining test experiment GM Distance from the boat’s centre of gravity and the metacentre GMT Greenwich Meridian Time GPS Global Positioning System GUI Graphical User Interface IMS International Measurement System IP Internet Protocol IT Information Technology Iw Second moment of area of the water plane area of the boat l Length of the pendulum for the inclining test KB Distance from the keel to the centre of buoyancy of the boat KG Distance from the keel to the centre of gravity of the boat LoA Length over All, the maximum length of a boat LwL Length on Waterline, the length of a boat at waterline level Continued on next page xiii xiv LIST OF SYMBOLS AND ABBREVIATIONS m Mass of the weight used during the inclining test experiment Mac Macintosh computer (from Apple inc.) MHeeling Moment on the sailing boat that force it to heel MRighting Moment on the sailing boat opposing heeling NACA National Advisory Committee for Aeronautics NMEA National Marine Electronics Association NOAA National Oceanic and Atmospheric Administration ODE Ordinary Differential Equation PC Personal Computer Rhino Rhinoceros 3D v5.0 Wenatchee from Robert McNeel & Associates SoG Speed over Ground SoW Speed over Water Tc Draft of canoe body (draft of the boat excluding the appendages) Tmax Maximum draft of a boat (including appendages) USB Universal Serial Bus V CB Vertical centre of Buoyancy, with respect to the waterline, positive downward V CG Vertical Centre of Gravity VB Visual Basic VBA Visual Basic Application VMG Velocity Made Good VPP Velocity Prediction Program 5sailing Volume displacement of a boat in sailing condition 4lightship Weight displacement of a boat in lightship condition ρ Density of sea water in [kg ·m−3] ϕ Angle of heel achieved during the inclining test experiment Acknowledgements • Prof Lars Larsson • Nicolas Bathfield • Florian Le Boulicaut, Grégory Ramain and Stanislas Paillereau (crew of “Le RM 1050”) • Voiles Magazine, Fora Marine and all the suppliers of “Le RM 1050” • The suppliers MaxSea, CustomWare bv, GPSNavX, Plastimo SA, in particular • Marc Lombard, naval architect of “Le RM 1050” • Mr and Mrs Eklund (owner and crew of “Vågvis”) • Gabriel Heyman, naval architect of “Vågvis” • SSPA AB and Peter Ottosson, developer of SailSim c© • The Wolfson Unit at the University of Southampton, developer of WinDesign c© • I would like to thank in particular Nicolas Bathfield and Lotta Olson for their dedication in helping me finishing this work. • I would also like to thank my parents, my brothers and sister and my family in general, my girlfriend and her family for their understanding, their support and their help at moments of doubts. • I would also like to thank the many people that accepted discussing my work and helping me refine it. In particular I would like to thank Mr Bathfield, Mr Brénéol, Mr Spear, Mr Tijssen, Mr Barreveld, Mr de Leeuw, Mr Kerhian, Mr Rouzic, Mr Cao-Hui, Mr Luelmo, Ms van Kuilenburg, Ms Whitaker, Ms Warminska, Ms O’Laoire, Sailors of the Atlantic and the Baltic sea, and my fellow climbers and tango people. xv xvi ACKNOWLEDGEMENTS Chapter 1 Introduction 1.1 Tools used in Naval Architecture To better understand the importance of the work carried out during this master thesis, an insight at the art of naval architecture and its tools is necessary. Several techniques in use today in the design of sailing yacht will be discussed. 1.1.1 CAED design Since the era of computers, many things have changed in the process of de- sign. Before, drawing fair lines could take a month or more to an experienced draughtsman, now it takes only a couple of days with CAED. CAED stands for Computer Aided Engineering Design. This term covers various tools used by engineers and naval architects in today’s world: Three dimension Computer Aided Design (3D CAD); Computational Structural Engineering (CSE); Computational Fluid Dynamics (CFD); Production planning; Veloc- ity Prediction Program (VPP)... Such tools have eased significantly the design process, leaving time for engi- neers to go deeper in their search for better designs. For example, 3D CAD, allows one to design a virtual hull in three dimensions and to know quickly its stability properties and its habitability. If going further into the design, it is possible to draw various details that ensure a better comfort on board. CSE (Computational Structural Engineering) software allows engineers to ensure that the hull or any other important structural element have suffi- cient strength throughout the boat’s lifetime. CFD (Computational Fluid Dynamic) is used to optimise the shape of the hull and lower its resistance to motion. It is also used to “measure” the lift and drag resistance of the hull and different appendages in order to ensure the boat is well balanced, and 1 2 CHAPTER 1. INTRODUCTION that it has sufficient steering capabilities or engine power. Production plan- ning is a new era of CAED. With such a tool, it becomes easier to plan the production of the boat by better controlling orders and manufacturing pro- cesses; thus reducing the costs while optimising the production time. Though these tools are not used everywhere, their importance into the design process is continuously rising. The last of these software is the Velocity Prediction program (VPP). VPPs are based on empirical studies and on sailing theories. This type of software is part of the subject of the present study. 1.1.2 Empirical studies and sailing theories The art of naval architecture became slowly a science as people like Archimedes, Leonardo Da Vinci, Newton, Bernoulli, among others, started investigating flow patterns. Specially, in naval architecture, breakthrough was possible through the more specific work of Chapman, Froude and followers. In partic- ular, systematic tank testing has allowed the derivation of empirical formulae describing the resistance to motion of a boat. Since the nineteen sixties, a systematic study on sailing boats parameters influencing the behaviour and performance of a boat at sea has been carried out at the Technical University Delft, in the Netherlands. The empirical formulae derived from their research together with sailing theories as derived by Marchaj and al, at the Wolfson Unit (University of Southampton, UK) or throughout different universities worldwide, have led to the derivation of general formulae that can be used to predict performance of sailing boats. The sailing theories based on general mechanics and on fluid mechanics are, generally, too complicated to be used for engineering. The empirical formulae describing the same phenomenon but from a “practical” point of view makes engineering possible. However, the limitations are great on empirical formu- lae as only phenomenon inside the boundary of the study can be predicted to some accuracy. Even though, validation is necessary as, depending on the way the original experiment was conducted, significant deviation to the rule might be observed. The typical tool to validate theories and empirical formulae is the towing tank, where a scaled model is towed in order to measure different forces like lift and drag. Eventually, as theories are refined with more experiments and better explanation of deviations to the rules, relatively accurate prediction of performance can be obtained mathematically (typically with VPP soft- ware). Other tools like CFD or CSE counteract the problems by making use of direct exact mechanical formulae and the computing power of computers. 1.1. TOOLS USED IN NAVAL ARCHITECTURE 3 1.1.3 CFD and CSE CFD (Computational Fluid Dynamic), solves the Navier-Stokes equations of motion for a viscous fluid. CSE (Computational Structural Engineering), computes the stresses and strains in a solid. Each method requires large amount of computer power as they solve such equations for very small ele- ments (either fluids or solids) dividing a larger volume. Applying external forces and boundary conditions, it is possible to determine to some accuracy the motions and stresses (as applicable) in any element of the volume. Thus, it is possible to determine the flow pattern around a rigid body, or the de- formation of a rigid body, subject to external forces. In naval architecture, both methods are of interest. While CSE can be used for predicting both the deformation of a rigid body and the flow patterns around a rigid body, CFD applies only to prediction of flow motion where it is known to be significantly more accurate. CSE can be used to model the deformation of a ship under wave loads. CFD can be used to reduce the resistance of a boat and optimise the flow entry in the propeller disk. It can also be used to optimise the shape of sails, keels and rudders in the particular case of a sailing boat. While CSE is a good engineering tool for optimisation of sailing boat struc- tures, CFD is still too expensive and slow to perform optimisation in small design offices. The use of tables or empirical formulae is still relevant for most of the boats of today as the design process is usually significantly quicker and the resulting designs performance sufficiently accurately predicted. The last kind of software available to a naval architect uses either empirical formulae or input from CFD software to predict the velocity a boat can reach. 1.1.4 Velocity Prediction Programs Velocity Prediction Programs are the particular subject of the present work. This software uses the different tools available to a naval architect to predict the performance of sailing boats at sea. A paper by Peter van Oossanen[3] published in 1993 gathers all the necessary equations and sources of informa- tion to make a proper VPP. This paper has been the starting point of most VPPs developed to date. VPPs, as described in Van Oossanen paper, use parametric definitions of the hull, sails and appendages of a boat to solve either empirical or theoretical equations of motions, resistance and equilibrium. As a result, it is possible, if the parameters are within the boundaries of the studies defining the math- ematical models, to calculate the speed a sailing boat can reach being given a particular wind strength and direction. Typically, VPPs give as an output, 4 CHAPTER 1. INTRODUCTION polar curves that describe, for every true wind angle and strength, the speed the boat achieves. With such output, it is possible to adapt the design to suite particular needs like increasing the overall velocity made good (VMG), or getting a better reaching speed, etc. VPPs have been developed in newer versions called DVPP (Dynamic Veloc- ity Prediction Program). This second set of VPPs is different in that it can simulate the motion of the boat in waves instead of a static boat on a static sea, thus being dynamic. The interesting feature of this particular type of VPPs is that performance can be output for different sea states. Ocean rac- ers but also ocean sailors would certainly appreciate sailing on boats that are faster or more comfortable at sea. It could also be important for designers to know what is the typical behaviour of their designs in a storm, etc. There is a large amount of possibilities with such dynamical software. The main inconvenience of VPPs and DVPPs is there dependency on experi- ments. Such experiments are typically carried out on models in towing tanks or in wind tunnels. The accuracy of a resulting design is therefore depending on the accuracy of the experiment on a scaled model and on capacity of the scientist to isolate a physical phenomenon from other phenomenon that are usually coupled together in real life. As history has shown, engineers and scientist predictions are not necessarily validated when going to full scale. Giving a tool to engineers and scientist to validate VPPs is the main goal of the present master thesis. 1.2 Genesis of the project The present project has originated from the conjunction of several unlikely events: 1.2.1 Voile Magazine, Fora Marine and M. Lombard During the first year of my master of science degree, I met Stanislas Paillereau, who was involved in a contest organised by “Voile Magazine”, a French sail- ing magazine. Stanislas, together with Florian and Gregory had presented a project to answer the call from Voile Magazine: “What would you do with a Sailing boat for one year”. The three young students presented a project involving sailing around the Atlantic ocean for a year and keeping contact with children from a Hospital in Compiègne to give them dreams to continue their fight against long illness. The three friends wanted a fourth comer to make the life on board easier. That’s how they accepted me just before they received the confirmation from Bernard Rubinstein, the chief editor, that 1.2. GENESIS OF THE PROJECT 5 Figure 1.1: The crew of “Le RM 1050” the day of departure in La Rochelle, Sunday 3rd of July 2005. From left to right: Florian Le Boulicaut, Stanislas Paillereau, Mael Gormand and Gregory Ramain they won the contest, in December 2004. From there on, with Prof Lars Larsson, main supervisor of this project, it was decided to use this opportunity to perform measurements at sea on sailing boat performance. The naval architect of the sailing boat that was to be used, Mr Marc Lombard, was contacted, as well as the Shipyard, Fora Marine c©. All the stake-holders (Fora Marine, Voile Magazine, Marc Lombard, Lars Larsson) agreed on the project’s goal. Marc Lombard only placed one condi- tion to the full use of his data: that none of the critical data like hull lines or key performance parameters could be published. This is understandable as “Le RM 1050”, the type of boat he designed and that was to be used by the winners, is a relatively new and successful design. “Le RM 1050” is presented in figure 1.2, in page 6. 1.2.2 Journey with “Le RM 1050” The journey was to take the team from France to France visiting the following countries (see also figure 1.3, page 8): • United Kingdom (The Scilly Islands, The Bermuda) 6 CHAPTER 1. INTRODUCTION Figure 1.2: “Le RM 1050” sailing off the coast of Madeira the 5th of Septem- ber 2005, two months after departure. 1.2. GENESIS OF THE PROJECT 7 • Ireland (west coast) • Spain (west coast, The Canarie Islands) • Portugal (West coast, Madeira and The Azores) • Morocco (Casablanca) • Capo Verde • Brazil (Amazon river) • Fance (Britanny, French Guyana) • Trinidad and Tobago • Venezuela (Margarita, Los Roquès, Los Avès) • The Netherlands (Curaçao) • Panama (The San-Blas) • Costa Rica (East coast) • Belize • Mexico (Yucatan coast) • Cuba (La Havana) • The Bahamas 1.2.3 SSPA and Chalmers While the measurement part of the thesis was becoming clearer, it was still necessary to find a VPP. SSPA AB had developed one such software during its different involvement with the America’s Cup in the late 90’s early 2000’s. Thanks to Professor Larsson and his contact inside the company, a copy of SailSim c©, a dynamic velocity prediction program based on SimNon c©, another in-house software from SSPA AB, could be obtained. SailSim c© was intended to be used for validation as it is a promising software (dynamic effects are taken into account in this software). Peter Ottosson from SSPA AB, helped on explaining how the software was developed and on how to use it. When it was discovered that SailSim c© could not handle twin keel design like “Le RM 1050”, he thought of some modifications that 8 CHAPTER 1. INTRODUCTION Figure 1.3: The journey of “Le RM 1050” from July 2005 to June 2006 1.2. GENESIS OF THE PROJECT 9 could be given to the software’s code to account for this specificity. However the modifications to the software were not done, due to a lack of time on SSPA AB’s side. The measurements recorded on board “Le RM 1050” had to be dropped during winter 2006-2007 and another more conventional boat was necessary to validate SailSim c©. 1.2.4 Gabriel Heyman and Mr and Mrs Eklund Gabriel Heyman, a Swedish naval architect, heard of the problems on this project. Contacted with the precious help of Nicolas Bathfield in spring 2007, he agreed on giving us his data on one of his designs and to contact the boat’s owner to see if it could be possible to come on board and do measurements. Gabriel Heyman contacted Mr Eklund, owner of “Vågvis”, a 60 feet sloop. Mr Eklund agreed to have us on board during one of his sailing journeys between Sweden and Denmark. Together with his wife, they hosted us on two occasions on board to measure the performance of Mr Heyman’s Design. Gabriel Heyman agreed on lending us the material for “Vågvis” under the condition that critical data would not be published. The journey with “Vågvis” involved a trip between Helsinborg and Copen- hagen, and a second journey between Skillinge and Kalmar. The journey can be seen in figure 1.4, page 10. Details of the second journey can be better seen in figure 1.5, page 10. “Vågvis” can be seen in figure 1.6, page 17. 1.2.5 The Wolfson unit and WinDesign c© While the work with “Vågvis” was carried on during spring 2007, it became clear that SSPA AB could not, temporarily, give support on SailSim c©. It was therefore necessary to obtain another VPP to prove that validation with full scale data was possible. The Wolfson Unit at the University of Southampton was therefore contacted. They are well known for their research on yachts and yacht design. They de- veloped a VPP (static version only) that is commercialised (unlike SailSim c© which is only for internal use at SSPA AB). WinDesign c©, the software from the Wolfson Unit, was therefore purchased by the department of naval archi- tecture at Chalmers University of Technology. In the end, WinDesign c©, was the software used for validation in the present project. 10 CHAPTER 1. INTRODUCTION Figure 1.4: The journey with Vågvis in May-June 2007 Figure 1.5: Detail of the journey with Vågvis on the island of Bornholm 1.3. GOAL OF THIS MASTER THESIS 11 1.3 Goal of this master thesis This thesis will cover four different aspects related to some extent to velocity prediction programs and their validation. All these aspects were covered, but not all reached the expectation defined at the start of the project. The different goals are described as follows: 1.3.1 A procedure to measure performance of yachts The first task was to determine the possibility of measuring the performance of a sailing boat at sea in an inexpensive manner. The goal is to give anyone a way to measure the performance of his own boat, and also to help naval architects to assess the quality of their prediction by giving them a tool to measure the performance of their new boat design. If the measurements are precise enough and if the data treatment procedure is careful enough, then, the polar curve that can be output to describe the performance of the boat at sea, should be accurate enough to understand either problems that occurred during the manufacturing process, or problems in the original conceptual design of the boat. The idea of this work is to allow designers to create their own data base of true polar curves. They can use it as verification tools, or as a backgrounds for their future designs. The goal is also to help them assess the accuracy of VPPs and to help them integrate this new kind of tool in their design process. 1.3.2 The use of VPPs in the design process In this project, VPPs are not exactly used for design but for reverse engi- neering instead. Starting from an original design and using it as an input to the VPP, we try here to get a result as close as possible to reality. This is latter explained and detailed in section 1.3.4, page 12. But, even though the VPPs are not used for design, they are used neverthe- less to obtain an accurate result that could very well be originated inside a design process. The data necessary to run two different VPPs (SailSim c© by SSPA c© and WinDesign c© by the Wolfson Unit) were collected and used to produce polar curves. The limitations of each software were also investigated as well as their strengths and weaknesses, specially with regard to the first goal of this project. 12 CHAPTER 1. INTRODUCTION 1.3.3 A test case for various weather conditions In this thesis, two VPPs were originally meant to be studied. A statical VPP (WinDesign c©) and a Dynamical VPP (SailSim c©). The interest of DVPP is that they allow evaluation of performance through “real” sea states that the boat is likely to encounter throughout its life. Validation of such a program becomes more difficult as testing a model in a wave towing tank is expensive. If one could produce accurate full scale data in different weather conditions, then validation of the prediction through real sea states could become possi- ble. Although this part of the project was well prepared, it turned out that real- isation had to face serious problems. This has greatly altered the quality of the results. Anyhow, even though the results are not of sufficient quality to be studied as such, the experience obtained should provide a good start for a more extensive investigation. 1.3.4 Validation of a Velocity Prediction Program The last goal of the project was to validate either a VPP or a DVPP with full scale data and investigate their accuracy in relation to what sailors do experience in reality. The ultimate goal of any scientific research is to under- stand reality in its complexity. However, to do so, it is necessary to isolate every aspect of the problem. In this way only, the mind manages to unravel the mysteries of nature. But if breaking down a phenomenon to different small pieces is necessary, one should not forget that in the end, all the different laws that were found have to be assembled again into one masterpiece. This is the goal of a VPP: it uses all the different mathematical definitions of the motion and behaviour of a boat at sea, in order to predict the overall picture of its performance as a polar curve. However, the masterpiece may not resemble the original picture. It happens that through our quest for understanding, sometimes, we mis-interpret facts and therefore derive the wrong equations. Validation is a key to make sure that the masterpiece is indeed accurate and a true picture of reality. The last goal of the present work is therefore to validate the accuracy of a VPP, by the use of the polar curve created from full scale measurements. Though this work does not provide answers on discrepancy in the equations of the VPP (this is far beyond the scope of the present work), it helps pointing out where the problems occur. 1.4. ORGANISATION OF THE WORK 13 1.4 Organisation of the work During this thesis, several tasks were carried out at the same time. We distinguish the following subjects: 1.4.1 Literature and “tools” survey Since the literature survey was not as successful as expected, no specific part will be dedicated to it. Special comments about literature will be inserted as needed throughout the present report. However, several points are worth noting: Literature survey The first quick insight into the literature survey shows clearly the lack of data on subjects related to sailing yacht performance. The original goal was to find either data or studies on the subject, and improve them. After extensive research hardly any papers were found on the subject. The most interesting paper used for this master thesis is the paper by Peter van Oossanen on “Predicting the speed of sailing yachts”[3]. This paper is seen by many as the corner stone of every velocity prediction program. It derives or combines all the different equations of motion for a sailing boat known at that time. This paper was used to understand the mechanism of VPPs. The second interesting book is “Aero-Hydrodynamics of Sailing” by C. A. Marchaj[1]. This book, also called “The Bible” by many naval architects, is the product of decades of research at the Wolfson Unit, at the University of Southampton. While the part about performance prediction is really short (a page), the rest of the book gives a very good insight on the workings of a sailing boat. This book was a good source of inspiration for this thesis because it describes a lot of different experiments. Lack of information on performance Even though the books and papers found, gave good insight into the subject, it would have been helpful to find more papers on the matter of sailing boat performance predictions or measurements. It is evident that many people in the yachting world do carry out a lot of research: competition is the main driver for most of the tremendous development that the yachting industry went through in the past decades. However, it seems like nobody really wants to reveal its findings, specially not naval architects or racing teams. 14 CHAPTER 1. INTRODUCTION From time to time, some research can happen with teams that have a lot of experience, but often, the researchers are bounded on their publication by secrecy agreements. This is one point of the interest of this work as it is independent from racing teams. The only restriction concerns the data about the sailing boats used for the measurements. But people interested in further study can contact each architect for more information on their designs. The tools survey The literature survey included, in our case, a tool survey. The goal was to identify the most suitable tools for the present work, being given the par- ticularities of the project. This was a much more fruitful study. If most of the solution were not kept for various reasons, it is worth noting that spe- cial recorder machine, sound Doppler velocity probes, laser Doppler velocity probes, among other solutions, were investigated. Accelerometers were also thought of, but not used as too weak on the long run for the particular scope of this project. 1.4.2 Workflow diagram Figure 1.7, page 18, shows the procedure used to achieve the different goals of this thesis. There are mainly seven groups in this procedure, as can be seen in the flow chart: 1. A literature/tool survey was carried out 2. A strategy was designed in order to achieve the goals of this thesis 3. Measurement procedures were developed and assessed with feedback from previous measurement campaigns. 4. A code was developed with Visual Basic Application (VBA c©) in order to process the measurements. The process was adapted to the speci- ficity of each boat’s electronic system. 5. Computer simulations were carried out based on the set up of the mea- surements. 6. A validation procedure was discussed and used to verify the possible validation of VPPs with reality. 7. Finally conclusions were derived from the present work. 1.4. ORGANISATION OF THE WORK 15 1.4.3 Measurements The second chapter of this work concerns measurement. This was a major part of the work in this project. The opportunity of using a sailing boat for long distance sailing over an entire year is seldom given to academics. Gathering of data was therefore of prime interest. Due to the prices of equipment and the remoteness of the journey, the decision was taken to study the performance of sailing boats, as no extra tools were necessary apart the standard navigation instruments. Two boats were used for the measurements, each with its own specificities. Each particularity influenced the measurements. The boats will be presented. This chapter will describe and explain the different methods used to measure the performance of these sailing boats at sea. The different steps will be explained and criticise. The measurement part leads to the next chapter on data treatment: 1.4.4 Data treatment The measurements being done, it was necessary to process the data in order to get an output useful for the target of the present work. Since the language of the instrumentation was not easy to use, it was necessary to build a code with Visual Basic c© to process the data and retrieve the necessary informa- tion regarding the boat performance. In this chapter, the way data was organised and the way to produce a polar curve from measurement are explained. Several plots representing the boats performance are presented. This part of the work is by far the biggest in this thesis. This is due to the complexity of the NMEA language used by most marine instrumenta- tion, and to the need to develop a code that could be further enhance in the future. This chapter will explain the code developed and some part of the development process. Further information regarding details on the code can be found in the appendices. 1.4.5 Computer simulation Computer simulations were carried out in order to compare measurement data with results from a VPP or a DVPP. Two software were investigated: 1 SailSim c© from SSPA AB 2 WinDesign c© from the Wolfson Unit 16 CHAPTER 1. INTRODUCTION The goal of the computer simulation is to prove that the results given can ac- tually be compared with full scale data. The simulation had to be carried out using the “exact” measurements environmental input in order to get a proper comparison. Simulations were therefore carried out at a later stage of the present work. However, from the start, it was ensured that the simulations could be done correctly compared to the measurements, and specially to the type of boat used for the measurements. As such, SailSim proved incapable of handling the twin keel design of “Le RM 1050”, which led to the use of “Vågvis” for the measurements. Then lack of support in the simulation stage led to the purchase of WinDesign, another VPP, as will be described later. The simulations consisted in producing a numerical model of the hull and its appendages. Both boat’s architects gave a 3D CAD file on Rhinoceros 3D c© in order to produce such numerical models. Then this numerical models were set to the actual conditions measured during the full scale experiments. The CoG and the displacement were systematically measured and used as input for the simulations. The numerical models were run in the same wind and sea conditions as during the measurements. The output, a polar curve, was produced and used in the validation. 1.4.6 Validation, discussion and conclusion At last, the results from the full scale measurements and the simulations are compared. Based on a first assessment of the quality of both results, it is possible to determine the possibility of comparing full scale performance data to simulations. Once this step is take, we can assess the accuracy of simulations compared to full scale measurements. With the comparison in hand, it is possible to validate the different VPPs used in the study based on their output polar curves data. In the end, a discussion on the method and its output will be held. Weak- nesses and strength of the presented work will be assessed and future devel- opments or connected areas of research will be proposed, ending the present study. 1.4. ORGANISATION OF THE WORK 17 Figure 1.6: Vågvis in Christiansø, Denmark during the displacement mea- surement. Notice the calm weather condition encountered. 18 CHAPTER 1. INTRODUCTION Figure 1.7: General Workflow diagram Chapter 2 Measurements: theory, goal and set-up 2.1 Goal of the measurements 2.1.1 Create a polar curve database in still water and waves The first goal of the measurements is to create a useful database of perfor- mance of a sailing yacht, both in waves and in still water conditions. With such a database, precious information can be gathered on the performance of a sailing yacht in static but also in dynamic condition. If the static part of a yacht’s behaviour is fairly well understood and mod- elled, the dynamic part is more critical (see [1] and [3]): scale effects and wind/wave/current interactions make its modelling difficult to validate. For example, it is impossible to scale a yacht’s model to both the Reynold’s num- ber and the Froude’s number. The first one governs aero-hydrodynamical effects while the second one describes the interface between air and water and their interactions. When using full scale data, although interactions cannot be clearly identified and separated, the data are still precious to validate coupling of different numerical models. Indeed, the goal of every model is to describe reality. If most of the important physical effects are modelled and coupled together, then one should get a result close to the one obtained from a full scale mea- surement. The goal of the present work is therefore to set up a protocol to gather accurate full scale data in a useful manner for naval architects and other people interested in performance and behaviours of yachts at sea in order to perform their final validations. 19 20 CHAPTER 2. MEASUREMENTS: THEORY, GOAL AND SET-UP The data collected need to be presented in a useful way. For that polar curves are the easiest mean of understanding the performance of a sailing yacht. In sailing yacht literature, polar curves have become a standard in presenting these performance. They usually show a line of achieved speed per wind strength. A radial plot is used (hence polar) with every angle representing the true angle to the wind of the sailing boat. The speed is presented as the distance for that particular angle between the origin and the speed line. In the present work, we will use polar curves to present the results. For ease of understanding, linear curves for each wind strength will be used as will be explained in chapter 6, from page 103 and onwards. 2.1.2 Full scale data measurement To create the database in waves introduced in 2.1.1, page 19, we need to gather data on a full scale sailing yacht in its environment. This is the main part of the work carried out in the present thesis. Even though the measure- ment procedure and its implications were originally thought of as secondary, it quickly turned out to be the most important part of this research. The rest of the work is only possible when this part becomes successful. To make it successful, the use of two different sailing yachts was necessary. Measuring performance of a full scale craft is a known difficult task. The fact that environmental elements cannot be controlled or difficultly measured without impact on accuracy, make such studies relatively rare in science. In the present case, we can dissociate between two different needs: • The need for average data • The need for instantaneous data A typical polar curve interesting to a sailor does not show maximum poten- tial instantaneous velocities. These are usually obtained by a sailing boat under unlikely circumstances. Instead it shows time averaged velocities that can be obtained in a steady state. Therefore, the performance measured are to be averaged over a period of time long enough to consider the run as in a steady state. This way, impact of environmental instantaneous events be- comes small, making the study possible in uncontrolled environment. However, there is a paradox in the above demonstration: to determine if a run is long enough to be considered steady, it is necessary to measure instan- taneous environmental data over the entire run in order to determine the state of “steadiness” of the run and its magnitude. This paradox is important to keep in mind because on one side, the fluctu- ation of the instantaneous data do not matter, but on the other hand, their 2.2. GENERAL PROCEDURE FOR MEASUREMENTS 21 accurate measurement is a key to a successful measurement campaign. The present work also aims at investigating the possibility of studying more instantaneous events like boat’s dynamical reaction to wind gusts, etc. Such measurement requires more precise measurements than the ones typical sail- ing instruments could give in the past. However, with the advances of stan- dard technology, it might be possible to get sufficiently accurate recordings to study such events. This will be a first attempt, though it will not be used for the main purpose of this thesis. The second major goal for measurement is to make full scale measurements viable for the validation undertaken in the present work. 2.1.3 Measurement procedure To achieve the two goals mentioned in sections 2.1.1 and 2.1.2, page 19 and 20, a comprehensive measurement procedure has to be developed. Such a procedure needs to cover the set up of means of records (i.e. instru- mentation), as well as measuring of basic boat’s properties (such as height of vertical centre of gravity (VCG) or displacement). Finally the performance data can be recorded. The procedure is important in that it sets the boundaries of the study as well as the range of accuracy that might be expected. The procedure also ensures that all the necessary data for the study are indeed recorded correctly. The procedure possesses a standard frame valid for all kind of boats studied. The frame has to be adapted to singular ships in order to take into account specificities of each boats such as electronic equipments on board, etc. The “frame” will be presented in section 2.2, page 21 and onwards. It will then be presented from a practical point of view for the two different boats that have been used for the study: 1. “Le RM 1050”, section 3.1, from page 37 and onwards 2. “Vågvis”, section 3.2, from page 56 and onwards. 2.2 General procedure for measurements For all types of boat, 7 steps needs to be fulfilled in order to perform a good measurement campaign. These steps are explained in sections 2.2.1 to 2.2.7 from page 22 and following. The procedure is presented schematically in figure 2.1 page 22, where one can see the different locations involved by the different steps. Clearly one will quickly realise that many different locations are involved in the process 22 CHAPTER 2. MEASUREMENTS: THEORY, GOAL AND SET-UP Figure 2.1: The measurement procedure contains seven steps, dispatched over five main locations. The numbers refer to the different sections describing each stage in the report) of a measurement campaign. Being located close to the harbour where the boat is, and close to the measurement area, will be a major key of success. 2.2.1 Preparation of the work and data to be recorded The first step of the framework is to identify all the data that have to be collected in order to successfully reach whatever goal is pursued. In the present case, we are interested in assessing the performance of sailing yachts in their natural environment. We therefore need to ask ourselves what are the data that are absolutely necessary for reaching our goal. We can also wonder what else can be done to improve accuracy or if we can achieve other goals at the same time. Often the same data can be applied to several types of studies. Recording one extra piece of information could make other studies possible at a small extra cost. Thus by widening the range of the recording, 2.2. GENERAL PROCEDURE FOR MEASUREMENTS 23 better use of data can be done. Since we all know how hard it is to gather full scale data, this subject should not be neglected. All these considerations need a strong theoretical analysis of the studied object (in our case, a sailing boat). The theory allows determining what is going to be useful in the study and what is not. However, practice also proves that we often underestimate some parts of the study while other parts are overlooked. Experience (and therefore the back-and-forth analysis of the work from theory to practice), is an important element to ensure that the final goal can be met. This implies that the researcher has to regularly re- evaluate his procedures and the quality of his work. Does it has enough data to reach his goal? Is the quality of the data good enough? How can you do better? These key questions allowed good progress in the present work. The final result presented here, is the fruit of several re-assessment of the working procedure. As a result, several types of data necessary for this study have been identified. They are here presented in two families: the automatically and the manually recorded data. Data electronically recorded These data are recorded via the on-board instrumentation system intended originally for navigation. These systems can be as simple as being just a GPS giving only the speed over ground (SoG), or as extended as giving accelerations of the boat as well. Typically, for the present research, four instruments are of prime interest: The Loch-meter that provide the Speed over Water (SoW) The Anemometer that provides the apparent wind speed and angle to the ship centre line The GPS that provide the Speed over Ground (SoG), the true heading (i.e. of the true course on the ground seen by a satellite), and the precise time The Autopilot that provides the rudder angle and the magnetic heading (on modern autopilots) Once the electronic data sources have been identified, they can be further assessed in how to collect them. This is introduced in section 2.2.2, page 24. Data recorded manually Some of the data cannot be recorded automatically without using expensive equipment. Instead, careful measurements by hand can usually give accurate 24 CHAPTER 2. MEASUREMENTS: THEORY, GOAL AND SET-UP enough results. Hull displacement, height of the centre of gravity (through an inclining test), type of sails used, etc have to be assessed. However, if these measurements require a careful procedure, the equipment necessary is relatively simple and consists mainly of a long enough piece of string and a weight (to make a pendulum) and a precise ruler. This will be further presented later in this section 2.2.4 and 2.2.5, page 27 and onwards. 2.2.2 Electronic instrumentation To perform the automatic data collection, onboard instrumentation can be used. Depending on the size of the unit, the electronics available can vary drastically. Nevertheless for boats ranging from 6-7m to 25m, instruments such as loch-meter, anemometer, sound-meter, or nowadays GPS can usually be found. These sets of electronics usually use the standard language devel- oped by the National Marine Electronics Association: standard NMEA0183. This standard sets a communication language used by marine electronics. It defines how data have to be organised, named and sequenced. This allows instruments to “communicate” between one another or to the outside world. Thanks to this harmonisation of the marine electronics, it is possible to re- trieve and “understand” electronics data. The first question that needs to be answered for all cases, is: how to retrieve the data? Using a multiplexer1, the data transmitted by all the instruments can be sent to a computer and recorded for further processing. This way, using both the NMEA 0183 language and a multiplexer connected to a com- puter, all the instruments necessary for automatic data collection can be recorded and later processed. The NMEA 0183 language is more specifically assessed in section 4.1.1, page 73 and onwards. Also, it is important to keep in mind that each brand of instruments has its specificity when it comes to the language used. For example, RayMarine c© or Garmin c© instruments output information in a slightly different manner than the standard that needs to be translated. The multiplexer software translates some of the data but not all of them and not for all brands, as will be discussed later. The researcher has, therefore, to be careful with the data he/she collects and make sure he/she understands all the data transmitted by the instruments used. When it comes to the electronics, after investigating what we can retrieve and how to retrieve it, the quality of the data collected, or the rate of data 1A multiplexer is a device that collects output from several electronic devices, put them into a sequence (typically on the basis of first-in-first-out), and send them through a single channel to another multiplexer (being a computer in our case) where it can be split back for different uses. 2.2. GENERAL PROCEDURE FOR MEASUREMENTS 25 retrieved have to be investigated. Some solutions have poor data transfer rates and only few data can be recorded, thus shortening drastically the boundary of the research. Other solutions may become very expensive, etc. To reach the goal of the research, both the data rate of the instruments and the multiplexer have to be investigated carefully. If instantaneous data are to be recorded, then data rate of at least one hertz, have to be achieved in order to capture inertial impact on the performance. However, if such data is not necessary, then cheaper, older electronics might as well be sufficient. Electricity and electronics are serious matters. Collecting properly electronic data also implies electronic skills to plug the instrumentation correctly. As has happened on one occasion, mis-preparation can lead to dangerous elec- tronic short-cuts endangering not only the recording, but also the unit (see section 3.1.7, page 50 or section 3.2.6 , page 66 for example). It is important to study the systems on board before setting-up the data collection system. Electric shocks, electrical shortcuts, etc. can endanger both the people on board and equipments. To ensure that problems can be solved quickly, differ- ent options of connectivity and their implications have to be assessed. This is part of preparation work and can help reduce miscellaneous problems and hazards during the campaign. The specificity of each boat used in this research will be described in sections 3.1.2 for “Le RM1050” and 3.2.2 for “Vågvis”, pages 38 and 57 respectively. The multiplexer used for measurements on board both boats is a ShipModul 42-USB from Customware BV. This multiplexer allows connection of up to 4 instruments via electronic cabling (DC12V-5mA, typical of electronic de- vices). It possesses 4 outputs for plugging to other electronic devices, and one output-input interface using USB connection. The multiplexer has an internal data filtering system in order to avoid overflow of the outputs. The multiplexer comes with a software providing the possibility to record data on a computer and control the automatic filtering. The software works both on Windows c© based computers and on Macintosh c©. 2.2.3 Preparation of the boat Before any recording of measurements, the boat has to be prepared. Prepa- ration includes the following tasks: 1. check the output language of the electronics on board and the output electronic connections 2. check how to connect the instruments to the multiplexer 26 CHAPTER 2. MEASUREMENTS: THEORY, GOAL AND SET-UP 3. check if the multiplexer software can translate or record all the neces- sary data 4. check if the batteries have a sufficient power capacity for the system 5. plug the multiplexer and the electronics together 6. check the state of the sails, sheets, etc, on board 7. check the state of the hull (if dirty, needs to be cleaned, etc) 8. check where are located the major movable weights on board and if they are well fixed 9. check the level of fluids in the different tanks 10. set the instruments 11. plug the computer and check that the software runs properly 12. prepare a measurement procedure to check the accuracy of the mea- surements by hand Most of these stages are self explanatory. A boat needs to be ready to take the sea whether measurements have to be performed or not. Some other steps are necessary for the accuracy of the measurements, though they are of less importance for normal sailing. For example, it is recommended for obvious reasons to do the measurements with a clean hull and new sails. This is not always possible and some VPPs allow corrections for such cases (less efficient sails, higher roughness for the hull, etc). Compatibility of the electronic instruments, the multiplexer and the com- puter is very important and must be checked carefully. It is also very im- portant to ensure that the instruments or other devices give the ability to record all the necessary data for the analysis planned. The particular sen- tences transmitted by the instruments will be later detailed in section 2.2.7, page 34. Preparing the boat also means looking into where and when to collect data. The “where” depends on the type of data (deep/shallow water; main direc- tion of the wind/waves, etc.), and the “when” depends on the data itself (what is the actual sea and weather states, ect.). Knowing in advance what kind of weather we are looking for can help retrieving the right data at the right quality. However, this implies that the boat for the measurement and the crew are available at all times, which is not always the case. For other circumstances, knowing the weather forecast the day of the measure is a 2.2. GENERAL PROCEDURE FOR MEASUREMENTS 27 minimum, for both safe sailing, but also to help getting a clear idea of the conditions encountered. At last, preparing the boat is mainly preparing its crew. A trained crew will execute clear manoeuvres and make the campaign successful. Unprepared crew will signify approximate procedures and low quality data. A trained regatta crew should always be favoured as these crews tend to be efficient sailors, able to sail fast and smooth. However, this is not always possible. In any case, clear explanation of the goal to the crew is key to a successful campaign. A good skipper can help improve procedures and ensure that the crew performs to the best. 2.2.4 Hull displacement Measuring the displacement of the hull is very important. The performance of the boat during the measurements is directly linked to the displacement. It is not possible to compare the performance of a boat at two different drafts: the wetted surface, the centre of gravity, the centre of buoyancy, the moment of inertia and the moments of gyrations (among other properties) become all different. Therefore, if full scale measurements are to be compared with the results of a VPP, for example, then one must ensure that the displacement on both the record and the simulation, are the same. In the present work, the 3D CAD drawings were provided. Using naval architecture design software such as FreeShip c©, Rhino 3D c©, and others, it is possible to calculate precisely the volume below the surface, and therefore retrieve the displacement of the boat at the time of the measure. Prior to any measurement, the displacement of the boat should be recorded. To do so, one can measure the height from the top of the freeboard and the flat sea surface at 4 different locations: • the foremost point on the hull • the aft-most point on the hull • the out-most portside of the hull • the out-most starboard of the hull Only three of the points are necessary, but the fourth one makes checking errors possible. As for all sailing boats, the hull constantly keeps itself in the upright position. This means that moving a weight on board will result in a change in hull heel and trim angles. Therefore, the simple weight of the person measuring the displacement on board will introduce an error in the assertion of the boat’s displacement. This is less true for bigger boats (due 28 CHAPTER 2. MEASUREMENTS: THEORY, GOAL AND SET-UP to the fact that the weight impact becomes negligible), but very important for smaller ones. Also one thing to consider is the accuracy of the CAD model with regards to the built hull. It is common sense to accept that the hull will always bear significant differences with its original numerical definition. Assessing the difference could be a good advantage to assess the resulting error between the numerical model and the full scale hull. However, this might be a complicated task for a full scale yacht and requires large or complicated means of measurements. Another approach would be to evaluate the impact of a potential error on the measurements. This way, one can get an idea of the severeness of not measuring precisely the difference between the drawings and the real boat. If the error is, anyway, negligible, then we can assume that the displacement as calculated from the drawings is a good enough approximation. During the measurements of the displacement, the errors have to be assessed. The sources of errors are waves, oscillation of the boat, displacements of weight on board and precision of the height measurement. For both yachts used, an error calculation will also be provided. 2.2.5 Inclining test Measuring the displacement is of no use if the centre of gravity of the unit is not located at the same time. The VCG is one of the most important prop- erties used to define equilibrium, and therefore the performance of a sailing boat. There is a standard measurement procedure to evaluate the height of the VCG for ships. It consist in measuring the angle of inclination of the hull with regard to a pendulum, when the hull is subject to the shift of a signifi- cant weight on board. The height of the centre of gravity will depend on all the loads present on board, the strength and direction of the wind and as well as on the presence of mooring lines or waves at the place and time of measurement. It is hard to find a location and the weather condition to perform accurately an inclin- ing test as even a small breeze can put the boat in a small but significant oscillatory motion. The inclining test procedure performed in this thesis is based on lecture notes from C. O. Larsson et Al. [4] at Chalmers university of technology. Using a pendulum of known length, a ruler to measure either the heel angle or the transverse displacement of the heeled boat and a defined weight to shift on board, it is possible to calculate the height of the centre of gravity of the unit. This experiment is shown in figure 2.2, in page 29. The calculation procedure is derived from the first principles of ship stability: 2.2. GENERAL PROCEDURE FOR MEASUREMENTS 29 Figure 2.2: Inclining test procedure • The inclining test start from a state of static equilibrium and an even keel situation. A mass on centreline is then moved to either port side or starboard. As a result, the boats heel to that side and reaches a new static equilibrium (as shown in figure 2.2, page 29). • In the new state of equilibrium, from Newton’s first law, we get the principle of moments: to reach a static equilibrium, the moment of heeling must be equal to a restoring moment: MHeeling = MRighting (2.1) • In the inclining experiment, the heeling moment is generated by the mass m moved a distance d from the centreline. The righting mo- ment is caused by the shift of the centre of gravity GG1 related to the unchanged mass of the boat ∇ · ρ: MHeeling = m · d (2.2) ∇ · ρ ·GG1 = MRighting (2.3) ⇒ m · d = ∇ · ρ ·GG1 (2.4) ⇔ GG1 = m · d ∇ · ρ (2.5) 30 CHAPTER 2. MEASUREMENTS: THEORY, GOAL AND SET-UP • Using a simple geometric relation, as can be seen in figure 2.2, GG1 can be expressed in term of the heel angle ϕ and the height GM (i.e. the distance from the centre of gravity to the boat metacentre): tan(ϕ) = a l (2.6) GG1 = GM · tan(ϕ) (2.7) GM = GG1 tan(ϕ) (2.8) ⇒ GM = GG1 · l a (2.9) • Combining equations 2.5 and 2.9 , we get: GM = m · d ∇ · ρ · l a (2.10) Where: – GM is the distance from the metacentre to the centre of gravity of the boat – m is the weight moved on deck – ∇ · ρ is the total weight of the boat including the moved mass m – d is the distance between the original and final location of the weight – l is the height of the pendulum used to measure the heel angle of the boat – a is the transverse distance traveled by the pendulum during the test • From figure 2.2, page 29, we can define the distance KG (the height of the centre of gravity from the keel, also known as V CG) that we are looking for, in terms of KB (the height of the centre of buoyancy from the keel), BM (the distance from the centre of buoyancy to the metacentre) and GM (defined in equation 2.10): KG = KB +BM −GM (2.11) • The distance BM is the metacentric radius. It is defined in term of the second moment of area of the water plane area Iw and the dis- placement of the boat ∇ (see C.O. Larsson [4] for the mathematical demonstration): BM = Iw ∇ (2.12) 2.2. GENERAL PROCEDURE FOR MEASUREMENTS 31 • The distance KB (the height of the centre of buoyancy) can also be expressed in term of the draft of the canoe body Tc and the VCB: KB = Tc − V CB (2.13) • Finally, combining equations 2.10, 2.12 and 2.13 into equation 2.11, we can derive the height of the centre of gravity from the boat based on the data measured during the inclining test: KG = V CG = Tc − V CB + Iw ∇ − m · d ∇ · ρ · l a (2.14) The height of the pendulum is of significance. If the height of the pendu- lum is too small, the displacement of the bottom of the pendulum will be too small to measure accurately. A small breeze or other environmental effects can give rise to small oscillation of the boat during the measurement. If the induced inclination is of the same order of magnitude as the inclination due to the shift of weight, then the error will be too important for the test to be conclusive. In general terms, the higher the pendulum, the greater the accuracy. Also, we can see that the heavier the weight relative to the displacement of the boat, the greater the accuracy. On most sailing boat, unless using specially built tools, it is hard on a rigged boat to have more than 2m height clearance for a pendulum. Let us try to figure out the error in GM height for a 1cm measurement error on a 10cm displacement measurement for a 10t displacement boat where a weight of 100 kg was shifted 1 m to either port side or starboard. We have: m = 100kg (2.15) ρ · ∇ = 10t (2.16) d = 1m (2.17) l = 2m (2.18) (2.19) Using equation 2.10 for three different values of a, we get: GM− = 100 · 1 10000 · 2 0.09 = 0.222 [m] (2.20) GM = 100 · 1 10000 · 2 0.1 = 0.200 [m] (2.21) GM+ = 100 · 1 10000 · 2 0.11 = 0.182 [m] (2.22) (2.23) 32 CHAPTER 2. MEASUREMENTS: THEORY, GOAL AND SET-UP And we can calculate the relative error resulting from this: Error = 0.222− 0.2 0.2 = 11% (2.24) An error of 11% for a measurement error of only 1 cm, is not insignifi- cant. If the height of the pendulum is increased, the accuracy can be greatly improved. This calculation has to be kept in mind during the rest of the procedure. 2.2.6 Sailing procedure and measurements To perform the measurements at sea correctly, the researcher and the yacht’s crew need to know precisely what to do at sea. They need to know where to go, when, and how to sail in order to reach the goals of the study. The sailing procedure is necessary to ensure minimisation of errors during the recordings. First some parameters have to be evaluated when considering the location of measurements. Events like tide or current can greatly influence the quality of the results and therefore, have to be assessed prior to any measurements. When considering the measurements themselves, the way the data are col- lected will make it easier and more efficient to produce a full polar curve with the lowest error. To do so, the crew needs to make sure they have proper sailing conditions to do the recording. They also have to ensure that the way they perform the measurements is the simplest and the most reliable. For example, to record performance of a yacht from upwind to downwind is difficult: it is hard to keep a sailing yacht upwind or very close to the wind without initial speed; currents have also a strong influence on recordings as the current is impossible to separate from leeway with classical instrumenta- tions. A typical procedure of measurement would be: 1. Identify the currents and tides typical on the future site of measure- ment, using regular current charts 2. If tidal current is an issue, then determine the time frame for measure- ments with the lowest tidal current (tidal current varies over time and would induce large errors) 3. On site, measure the strength and direction of the current. Proceed to several measurements to make sure the current is stable (unstable current would make it impossible to do the measurements accurately) 4. proceed to the first set of recordings: 2.2. GENERAL PROCEDURE FOR MEASUREMENTS 33 (a) from a steady downwind position, slowly sail upwind either to portside or to starboard (b) stay at each interesting sailing angle over a period of time long enough to get a good average measurement (between 5 to 20 min- utes, depending on the accuracy sought, every 5◦ to 15◦ angles as necessary) (c) go as close to the wind as possible when going upwind. If feasible, try to reach a completely upwind state (d) repeat the exact same procedure on the other side (e) repeat all the previous steps once or twice for each sailing condition investigated, in order to reduce errors to the maximum 5. between each polar measurement, an assessment of the current strength and direction is strongly advised. Over a period of time of two-three hours, the current properties might have changed significantly. The recording has to be done over the entire polar range (i.e. first from downwind to upwind on portside, then from downwind to upwind on star- board). Then the recording can be post-processed to get an accurate polar curve. Once all the measurements are done (and we can see now that a single proper measurement takes at least six hours), comparing the current properties mea- sured before the measurements and after it, will give a first insight on the quality of the measurements. To measure the strength and direction of the current, only two practical ways have been found. It is impossible to mea- sure the current accurately when under sail. This is due to the fact that the “drifting” vector is composed of both the current (external to the sailing boat) and the leeway. The leeway side force is generated by the hydrody- namic appendages as soon as the boat starts to sail. As soon as the sails are up, this component will take importance and will make it impossible to determine the current. Here are two methods to estimate the strength and direction of the current: 1. The boat can be left to drift for a long enough period of time without sails. The drift direction and strength can be recorded by the GPS and should represent the main current, thought the wind blowing the boat away will introduce an error that might be of serious significance if the wind strength is important. It might also be impractical or dangerous to leave the boat drifting over a period of time long enough to get a good measure. 34 CHAPTER 2. MEASUREMENTS: THEORY, GOAL AND SET-UP 2. The boat without sails can be sailing with the engine. The drift can be recorded using the difference between the SoG and the SoW. Here too, the wind might introduce an error as it will “push” the boat away in a particular direction. However this error can be minimised by run- ning upwind and then downwind (that way, the wind component can be neglected), or in any two perfectly opposite directions. Magnetic deviation of the compass has to be taken into account, but is usually well established and shouldn’t induce significant errors. The procedure is presented in figure 2.3, page 35. 2.2.7 “External” recordings Some of the data that are important for assessing the performance of sailing boats are hard, expensive or impossible to measure at sea: wave heights and period for example. During the present research, the main external data re- quired were the waves properties, i.e., significant wave height, frequency and direction. These data are necessary to ensure that the same “waves” are used by both the simulations and the measurements. During the past hundred and fifty years, wave heights and frequencies were logged by sailors with notable errors. Accuracy arrived only with the era of weather satellites. Measurements with satellites have proven to give good accuracy for wave frequency, direction and height. However, because it is not always possible to actually observe an area due to clouds over the earth, meteorologist have developed advanced programs to estimate the weather along the oceans. These predictions are now given for 12, 24, 36, 48 up to 72 hours upfront. These estimations are reset every 12 hours with wave measurements taken by buoys dispatched along the major oceans and major sailing routes. These buoys record the major weather properties: pressure, temperature, wind speed, current speed, wave heights and frequencies, etc. These data are used as input in the new model run for the next 12 hours predictions. Although weather predictions used to be erratic at the beginning, with the increase in super-calculator power and better satellite and buoy measure- ments, the accuracy have risen up and is now very good up to 48hrs. Certain weather forecast authorities like the National Oceanic and Atmo- spheric Administration (NOAA) of the United States of America, provide on their website the wind, waves, current, atmospheric pressure and tempera- ture prediction for most of the oceans of the planet. Their data are free to download on a daily basis, but access to older data can be more complicated. For up to 72hrs predictions, if you send an email, with the area of sailing as 2.2. GENERAL PROCEDURE FOR MEASUREMENTS 35 Figure 2.3: Sailing procedure 36 CHAPTER 2. MEASUREMENTS: THEORY, GOAL AND SET-UP the subject, you get the data back (under the GRIB format). Other compa- nies in Europe also provide data for more localised sea like the Mediterranean or the Baltic sea. Retrieving these external data is essential for two reasons: 1. Sailors need to ensure the severeness of the weather before sailing and to prepare their sailing. Going out in a clear sunshine unaware that a severe storm is on its way is just dangerous if not suicidal. For the research, knowing what type of weather lies ahead can help deciding if it is worth going out to do the measurements or not. For example, if a long series of measurements in different conditions is to be done, then one might realise that the exact same weather has already been encountered and that it is worth waiting a bit more to get a different one. 2. Second, once the measurements have been done, it is important to be able to check observations and to know exactly what weather was really encountered. This way, one can ensure that all the needed information for the research use is available and correct. For example, in the case of the present study, it is important to run the simulations with the same boundary conditions as for the measurements. It might be that other external recordings are necessary for a different type of research. Once again, with the use of all the theoretical knowledge available, the researcher ensures that all the data he needs can be retrieved on time: missing data means often to start all over from scratch. After introducing our working procedure, we are now going to see how it was applied to both units used in this research. Chapter 3 Measurements: first and second campaigns After defining the measurement procedure and framework, they are applied to the yacht used for the measurements. Getting a sailing yacht for measure- ments is not an easy task or not as easy as one might think. Nevertheless, in the course of this research two yachts were used. The types of boats, their characteristics, the preparation work and the measurements done on board are described in the sections of this chapter. “Le RM 1050” is presented in section 3.1, page 37; “Vågvis” is presented in section 3.2, page 56; Finally, future recommendation on measurements are discussed in section 3.3, page 68. 3.1 Measurements with “Le RM 1050” 3.1.1 General characteristics of the boat “Le RM 1050”, the sailing boat that was used in the first part of this thesis work, is a sloop of 10.5m in length with hard shines, twin keels and a single rudder. It is made of plywood with epoxy reinforcement. The general struc- ture is light with few bulkheads and wide volumes. The beam is large and the rudder deep. It can lay on its twin keels and rudder at low tide. The keels are tapered “L-shaped” with bulbs to lower the centre of gravity while keeping a shallow draft. The rig is fractional to allow the Genoa or jib n◦1 to pass the shrouds without blockage and be trimmed closer to the mast. The rigging for a baby jib is in place and can be used in case of heavy weather conditions. “Le RM 1050” is an easy to sail, safe sailing boat. The hard shines make it 37 38CHAPTER 3. MEASUREMENTS: FIRST AND SECOND CAMPAIGNS very comfortable to sail as it oppose an extra drag force to small oscillatory aero-hydrodynamical forces. Globally, it caries relatively large amount of sail area for a leisure boat, but it doesn’t have racing capacities at such. The wide aft it exhibit makes her hard to go close to the wind. Below 45◦ to true wind, she becomes slow. However, for the same reason, she goes well when going downwind. The main characteristics of “Le RM 1050” are: LoA = 10, 47 [m] LwL = 9, 50 [m] Bmax = 3, 95 [m] Tc = 0, 41 [m] 5sailing = 5, 65 [m3] 4lightship = 4700 [kg] Tmax = 1, 6 [m] [KeelBallast] = 1800 [kg] [RudderDepth] = 1, 4 [m] [MainSailArea] = 36 [m2] [GenoaArea] = 34 [m2] [BabyJibArea] = 16 [m2] [SpinnakerArea] = 75 [m2] Other data were available for the present work but are not presented here on explicit request from the naval architect of the boat, Mr Marc Lombard. For more details on the boat itself, its performance or its fabrication, the yard, Fora Marine, can also be contacted. 3.1.2 Instrumentation available on board “Le RM 1050” was a sponsored boat. As a result, the equipment was not specifically chosen for the present work, but provided by one of the sponsor of the project, Plastimo SA. Plastimo wanted to introduce a new product to the French market for which they had exclusive dealing rights: NavMan. NavMan is a company from New Zealand specialised in navigation electronic equipment. The set of electronics on board is schematically presented in figure 3.3, page 42 and included the following: Multi 3100 a screen that groups data from the Depth-meter and the speedome- ter. mailto:info@marclombard.com http://www.rm-yachts.com/ http://www.plastimo.fr/ http://www.navman.com 3.1. MEASUREMENTS WITH “LE RM 1050” 39 Wind 3100 a screen that groups data from the anemometer and the weath- ercock. G-Pilot 3100 a screen that groups all data from the auto-pilot system Autopilot 3100 a screen that controls the autopilot system Tracker 5500 a screen that regroups all data from other instrument and the GPS and is used as a chart plotter Masthead instruments that include the anemometer and the digital weath- ercock Depth sounder a sonar based sounding device that detect the depth of sea up to 50m G-Pilot Course Computer a computer device that calculates the autopi- lot instruction necessary to steer the boat, based on wind, GPS and magnetic compass data. Gyrocompass a digital compass used by the course computer of the au- topilot system for steering the boat with regard to the magnetic north. Rudder sensor a incremental-decremental sensor attached to the rudder stock that detect the exact rudder angle. It is used by the course computer of the autopilot system for steering the boat. Speedometer a digital sensor based on a free spin wheel measuring the instantaneous speed of the boat. It measures the flow speed near the bottom of the hull (instrument placed sufficiently forward and suffi- ciently away from the hull to measure the flow outside of the boundary layer). NavBus an electronic in-house multiplexing system that allows all instru- ments from NavMan c© to be connected together. This system uses a closed proprietary language. Shipmodule 42-USB a NMEA0183 compliant multiplexer device from Cus- tomware b.v. that allow gathering 4 instruments as input and 4 instru- ments as output. The device is equipped with a USB port both in input and output mode to connect to an external computer. In the above list only the multiplexer is not from NavMan c©. All the other equipment were designed to be used as any sailing instrumentation. These instruments used an in-house system to communicate with each other called 40CHAPTER 3. MEASUREMENTS: FIRST AND SECOND CAMPAIGNS Figure 3.1: Picture of the chart table of “Le RM 1050” with the chart plotter, the laptop used for measurements and the location of the multiplexer the SeaTalk system. These instruments also complied to the NMEA0183 norm from the National Marine Electronics Association (NMEA). Because this standard was used by this electronics, it was possible to plug a multi- plexer also complying with this norm to output data from all instruments to a computer. We used both a Macintosh and a PC to collect data over the course of the project. The chart plotter, the GPS, the computer and the multiplexer are located at the chart table and can be seen in figure 3.1, page 40. The screens relaying sailing information are located in the cockpit and can be seen in figure 3.2, page 41. Finally, the course computer and the gyro-compass are located in the storage cabin behind the bathroom. 3.1.3 Instrumentation set-up The following sections describes in more details the exact set up of each instruments: 3.1. MEASUREMENTS WITH “LE RM 1050” 41 Figure 3.2: Picture of the cockpit of “Le RM 1050” with the speedometer/sound-meter, the autopilot, the electronic weathercock and the compass. Speedometer To set up the speedometer, it is first necessary to ensure that the free ro- tating wheel under the hull, is clean from seaweed and free to rotate ; that the instrument (on the screen of the Multi 3100) indicates a null speed in absolute still water while the boat is not moving. Then, when sailing in a sheltered area with no current, the boat has to reach maximum constant possible speed with the engine and without sails: the higher the speed, the more accurate the set-up; the more constant, the less error due to averaging. The GPS gives the accurate speed over ground which can be set-up as the instantaneous sailing speed of the boat. It is important that there is no current in the area of the set up. Tidal or river current can induce large errors. Also, GPS speeds are typically average as it is a speed calculated from two different exact locations. If the instantaneous speed of the boat is constant enough, then we can use that speed as an instantaneous speed. The set-up have to be checked at least three times during the opera- tion to minimised errors coming from the GPS. The best no current situation over one year of sailing was encountered off- shore, 3 days of sailing south west of Capo Verde; the GPS was giving a 42CHAPTER 3. MEASUREMENTS: FIRST AND SECOND CAMPAIGNS Figure 3.3: Location of instruments on board and data connections on board "Le RM 1050" 3.1. MEASUREMENTS WITH “LE RM 1050” 43 constant speed of 0 knots and there was absolutely no wind. To ensure absolute perfect accuracy this set-up has to be done regularly and the speed checked before any measurement campaign. Over the one year of sailing with “Le RM 1050”, this set-up was performed twice: 1. in “La Rochelle”, just before leaving for the first leg of the journey, in June 2005 2. approximatively 300 nautical miles south west of Capo Verde, during a no wind no current condition and after changing the entire set of electronics (see section 3.1.7, page 50). On top of these set-up, the hull was entirely cleaned four times over the entire course of the one year journey. Each time, the wheel of the speedometer was cleaned and the accuracy of the instrument checked carefully. The accuracy of the system was also verified on each leg by the crew. With experience sailing the boat suspicious speed indications could be spotted and the set-up corrected. Anemometer and Weathercock Subject to external elements, the anemometer and the weathercock have to be set-up regularly. Like for the speedometer, one has to ensure no object are obstructing the wheel nor the weathercock. When in absolutely perfect head wind, the control screen (Wind 3100) can be used to set the wind direction to 0◦. The easiest way to do so is to anchor the boat or to moor it by the bow only and let it come head wind on its own. Then, the weathercock can be accurately set. For “Le RM 1050”, the present set-up turned out to be relatively difficult as she was always oscillating when moored only with one line or anchored. It is suspected that the wide stern might be interacting with the wind to create sufficiently big vortex aft to actually trigger and feed these oscillations. For the anemometer, the set-up is somewhat easier. Most of the harbour actually measure and give the exact instantaneous wind speed at mast height. This measurement is relatively accurate and this type of instrument is usually quite stable over time. The height of the measurement can be an issue for boats with very tall masts. The wind profile in the boundary layer might change significantly. However, the height of the mast of “Le RM 1050” is usually within the range of the masts used for measurements in harbours. When a clear reading can be made from the reference instantaneous wind speed in the harbour, this value can be set into the system. 44CHAPTER 3. MEASUREMENTS: FIRST AND SECOND CAMPAIGNS GPS and Chart-plotter The GPS is a self setting system. If a problem in measurement is found, the entire set has to be changed. It means that the computing unit calculating the exact location via data collected from satellites, is out of order. On a more practical ground, the set up of the GPS and the chart-plotter that gives its information, consists mainly in making sure the electrical con- nections are correct. It happened several times that short-cuts provoked the temporary loss of the GPS instrumentation (causing some serious threat to the boat once, as the GPS got out of order while landing on the Scilly Is- lands in the UK, at night. The Scilly Islands are famous for their traitorous coast line). Once again, the quality of installation of the instrumentation is critical... Gyro-compass The Autopilot system is equipped with a Gyro-compass in order to auto- matically steer to a particular heading if wanted. This compass was located inside the equipment room, sufficiently far away from other metallic equip- ments. To set it up, one has to make sure it gives the same direction as the main compass once this one has been checked. The gyro-compass is set via the screens control of the auto-pilot (Pilot 3100). Rudder sensor The rudder sensor placed on the rudder stock has to be free to move. One has to ensure no objects can interact with it. The set-up is done at sea via the on-screen instruction from the Pilot 3100 screen. It asks first to sail on the engine without sails in a perfect straight line (in direction of a fixed point very far away on horizon) to set up the absolute 0deg rudder angle, then sail to maximum port side, then to maximum starboard (beware of excessive speed during the turn). Then the rest of the autopilot set-up can take place. What is important to remember here is that 0deg angle for the rudder is the angle necessary to keep the boat going in a straight line. This means that if the boat has, when sailing on the engine, a small tendency to go to either port side of starboard, the rudder has to have some angle of attack to compensate the imbalance. This means that technically, at 0deg, the rudder can actually have an angle of attack. This irregularity depends mainly on the way the yacht was manufactured, and even the best built boats can exhibit a small imbalance. 3.1. MEASUREMENTS WITH “LE RM 1050” 45 Depth sounder The depth sounder is normally not used for the present study. However, the data are output from the system like all the other data and can be exploited if desired. It can be noted that at shallow draft the performance of a boat are different from performance at larger drafts. If shallow draft investigation are sought, then the use of the depth sounder is necessary. To set up this instrument, at even keel, we use the manual sound present on every sailing boat. The sound, is made of long string marked every metre, with a lead at one end. The lead is dropped into the water and let free to dive, until it reach the bottom. The height of the water can then be measured from the lead up to the last point of wet string, or to the freeboard, if the freeboard height is known. This procedure has to take place when the sea state is perfectly flat. Small waves can introduce a significant error. Once the depth is know it can be set on the “Multi 3100” screen that also control the depth sounder settings. NavBus The NavBus c© system is a in-house multiplexing system from NavMan c©. The output from each instrument connected to the NavBus c©, is sent to all the other instruments that can make use of it, or not. It allows the autopilot’s course computer, to sail according to GPS way points, or to sail with regard to the wind, as required, etc. The problem of this system is that the data sent are encoded in a proprietary language that NavMan c© refused to share. It was also impossible to connect a computer directly to the NavBus c© system: the system is only designed for NavMan c© instrumentation. Shipmodule 42-USB The Shipmodule c© is a multiplexer, like the NavBus c©, but this time, from the third party company Customware bv, from the Netherlands. This mul- tiplexer complies with the norm NMEA0183. It was set up to retrieve data from the Muti 3100, the course computer, the GPS and the Wind 3100. The data are then output to an external computer. The multiplexer, like the rest of the electronics works in Direct Current (DC). The plugging proce- dure of the multiplexer involved connecting the positive electronic cables of each of the instruments to each input of the multiplexer and to connect the other cables to a ground. The multiplexer can then be plugged to the gen- eral electrical DC power source of the boat. Las