DEGREE PROJECT IN VEHICLE ENGINEERING, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2017 Design of a free-rotating wing sail for an autonomous sailboat CLAES TRETOW KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING SCIENCES ! ! ! ! Design of a free-rotating wing sail for an autonomous sailboat Claes Tretow ! ! ! ! ! ! ! ! ! ! Degree Project in Naval Architecture (30 credits) Degree Programme in Naval Architecture (120 credits) Degree Programme in Vehicle Engineering (300 credits) The Royal Institute of Technology 2017 Supervisors: Jakob Kuttenkeuler, Mikael Razola Examiner: Jakob Kuttenkeuler ! ! 2 Abstract There is an accelerating need for ocean sensing where autonomous vehicles can play a key role in assisting engineers, researcher and scientists with environmental monitoring and colleting oceanographic data. This thesis is performed in collaboration with a research group at The Royal Institute of Technology that currently develops an autonomous sailboat to be used as a sensor carrying platform for autonomous data acquisition in the Baltic Sea. This type of vehicle has potentials to be a helpful and cheaper alternative to a commercial research vessel. The thesis presents the design, construction and experimental testing of a rigid free-rotating wing sail for this autonomous sailboat. The goal is to design a rig that can sustain under all occurring weather conditions in the Baltic sea while ensuring sailing performance, robustness, reliability and low power consumption, which are key aspects driving the design. The rig is designed through the utilization of analysis and design methods involving a Vortex Lattice Method combined with a Velocity Prediction Program in order to achieve best possible aerodynamic performance with respect to the application requirements. The rig is manufactured as a sandwich structure with a light core material, reinforced with fiberglass and laminated using advanced resin technology. The main challenges in the development process are structural arrangement, rigidity and weight as well as integration of subsystems and achieving overall robustness. Initial experimental testing, sailing under radio control, has been performed showing promising results. The vehicle was operated under moderate weather conditions, 8 – 10 m/s NE winds, at Baggensfjärden, Sweden, where expected behaviour, wing structure rigidity, boat speed and manoeuvrability was successfully demonstrated. Future challenges are now to further develop navigational control and guidance strategy, pushing the technology front forward in autonomous sailing. ! ! 3 ! ! 4 Acknowledgement Big thanks to all people involved in this project: Jakob Kuttenkeuler, Mikael Razola, Ulysse Dhomé, Filip Wängelin, Thomas Abzikhir and Julian Fraize. I also want to thank the KTH Maritime Robotics Laboratory, KTH Lightweight Structure Laboratory and KTH Centre for Naval Architecture for using your facilities and supporting me in the design process.!! ! 5 Table of Contents ABSTRACT .............................................................................................................................. 3 ACKNOWLEDGEMENT ....................................................................................................... 5 1. INTRODUCTION ............................................................................................................. 10 1.1 MARIBOT VANE: SAILBOAT FOR AUTONOMOUS OFFSHORE ENVIRONMENTAL MONITORING .............................................................................................................................................. 10 2. ANALYSIS AND DESIGN ........................................................................................... 12 2.1 INTRODUCTION TO SAILBOAT MECHANICS ....................................................................... 12 2.2 RIG REQUIREMENTS ........................................................................................................ 14 2.3 ANALYSIS METHOD ......................................................................................................... 16 2.4 VORTEX LATTICE METHOD ............................................................................................. 16 2.5 PARAMETRIZATION ......................................................................................................... 17 2.6 CONCLUSIONS ................................................................................................................. 25 2.7 RIG PLAN FORM ............................................................................................................... 26 2.8 HULL MODEL ................................................................................................................... 27 2.9 VELOCITY PREDICTION PROGRAM .................................................................................. 27 2.10 RIG SIZE AND PERFORMANCE DIAGRAM ........................................................................ 29 2.11 FLAP DESIGN ................................................................................................................. 30 2.12 WING PROFILE ............................................................................................................... 31 3. STRUCTURAL DESIGN CONSIDERATIONS ........................................................ 32 3.1 STRUCTURAL DESIGN REQUIREMENT SPECIFICATION ...................................................... 32 3.2 INTERNAL STRUCTURE .................................................................................................... 34 3.3 RIG SUPPORT STRUCTURE ................................................................................................ 35 3.4 ADJUSTMENT CAPABILITIES ............................................................................................ 36 4. MANUFACTURING ..................................................................................................... 37 4.1 CORE ASSEMBLY ............................................................................................................. 37 4.2 LAMINATION ................................................................................................................... 38 4.3 FLAP ACTUATION AND EXPERIMENTAL SET UP ................................................................ 40 4.4 RIG DATA ........................................................................................................................ 41 5. EXPERIMENTAL TESTING ...................................................................................... 42 5.1 RADIO CONTROLLED TEST SYSTEM .................................................................................. 42 6. DISCUSSION AND CONCLUSIONS ......................................................................... 44 REFERENCES ....................................................................................................................... 46 APPENDIX A: ANALYSIS METHOD ............................................................................... 47 APPENDIX B: RIG PARAMETER DEFINITIONS ......................................................... 48 APPENDIX C: HULL ........................................................................................................... 50 APPENDIX C.1 HULL WEIGHT AND CENTRE OF GRAVITY DETERMINATION ............................ 50 APPENDIX C.2 HULL PARTICULARS ....................................................................................... 51 APPENDIX C.3 HULL DIGITALIZATION .................................................................................. 52 APPENDIX C.4 BASED ON THE LINES DRAWING BELOW, A CAD-MODEL IS ESTABLISHED. .... 53 APPENDIX C.5 HULL LINES DRAWING ................................................................................... 54 APPENDIX D: MANUFACTURING .................................................................................. 55 APPENDIX D.1 WING PRINTOUT ............................................................................................ 55 APPENDIX D.2 DIVINYCELL ASSEMBLY PLAN ....................................................................... 56 ! 6 APPENDIX D.3 ADDITIONAL PICTURES FROM THE MANUFACTURING PROCESS ...................... 57 APPENDIX E: DATASHEETS ........................................................................................... 59 APPENDIX E.1 CORE MATERIAL DATASHEET ......................................................................... 59 APPENDIX E.2 RESIN TECHNOLOGY DATASHEET ................................................................... 60 APPENDIX E.3 SAERTEX FIBERGLASS TECHNICAL DATASHEET .............................................. 61 APPENDIX E.4 ACTUONIX MINI LINEAR ACTUATOR DATASHEET ........................................... 62 List of Figures Figure 1 : Maribot Vane general specifications ....................................................................... 11 Figure 2: Sailboat mechanics for an unhealed boat ................................................................. 12 Figure 3: A principal sketch of the forces acting on a slice in the XY-plane of the free-rotating wing, in Figure 2, mounted on an unhealed boat. The figure is a simplification of the reality, showing a 2D-perspective. ................................................................................... 13 Figure 4: Sketch of the lift forces acting on the rig. The picture is from the first experimental testing of Maribot Vane. .................................................................................................. 14 Figure 5: Rig model