Abstracts: 16^" Chesapeake Sailing Yacht Symposium

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1 Abstracts: 16^" Chesapeake Sailing Yacht Symposium The Yaw Balance of Sailing Yachts Upright and Heeled /. A. Keunitig, Shiphydromechanics Department Delft University of Tecltnology K. J. Vermeulen, Sliip/iydromeclianics Department Delft University of Tecltnology The present paper describes the resuhs of a study carried out to improve the frequently used prediction methods for assessing the longitudinal position of the Center of Lateral Resistance (CLR) of a sailing yacht hull. To formulate these improvements use is being made from the extensive database of the Delft Systematic Yacht Hull Series (DSYHS) containing yaw moment measurements under various conditions with respect to speed, heeling angle and leeway. The data has been used to formulate alternative procedures and formulations for the existing methods for prediction of yaw moment as previously presented by J.Gerritsma (1971) and K.Nomoto (1979). The outcome of this modified procedure is compared with the experimental results obtained both within the DSYHS and the Delft Systematic Keel Series (DSKS). In the DSYHS one keel and rudder have been tested under a variety of hulls and in the DSKS a variety of keels have been tested under one particular hull. Finally the results are checked against the measured data obtained from two series of tests in the Delft Shiphydromechanics Laboratory with very large sailing yachts with low aspect keels. By matching these hydrodynamic data with the wind tunnel results on the position of the Center of Effort (CoE) of the sails and it change due to heeling angle a better analysis of the balance of the yacht can be made. Computational Fluid Dynamics for Downwind Sails Horst J. Richter, Kevin C. Horrigan, Thayer School of Engineering, Dartmouth College, Hanover, NH, U.S.A. J.B. Braiin, North Sails, Marblehead, MA, U.S.A. In recent years computational fluid dynamics (CFD) has demonstrated the ability to predict sail and appendage forces under upwind conditions or at angles of attack conducive to attached flow. Few sail or yacht designers would be without this tool, at least to check or confirm performance estimates made with other methods. More advanced codes (RANS) solve the full Navier-Stokes equations, thus including viscous effects and placing relatively less importance to fiilly attached flow. Due to the large proportion of downwind sailing, where the sails might operate in separated airflow, it is useful to evaluate the performance of sails as used off wind despite the added uncertainty resulting from the elasticity of the light material that must be used to allow the sails to fill properly at the low relative wind speeds. While downwind sail forces have been often tested in wind tunnels, CFD codes are now sufficiently advanced to predict such forces with confidence similar to that achieved in prediction of upwind forces.

2 This paper presents a new method of linking a CFD code with a Finite Element Analysis (FEA) computer program, for evaluating the sail shapes and proper trim for known sail materials and fiber orientation. A VPP (Velocity Prediction Program) is used to predict leeway, heel, and boat speed for a given true wind angle and wind speed. Then the CFD code computes the airflow around the sails for the given onset flow conditions and provides the pressure distribution on the sails as needed for the FEA program. This is done in full scale considering the boundary layer above the water. This process of updating the pressure for the FEA program from the CFD code is repeated several times until optimal trim and sail shapes can be obtained for best sailing performance, e.g., the maximum driving force. Thus, this method can be considered a "Virtual Wind Tunnel" (VWT). Downwind Load Model for Rigs of modern Sailing Yachts for Use in FEA Guentei- Gnibe, Yacht Research Unit, University of Applied Sciences, Kiel, Germany Standard approaches to define loads for a rig start with the righting moment of a yacht at 30 degrees of heel. This is a quite good approach for defining maximum lateral forces of the sails on upwind courses. For downwind courses this procedure may be questioned because the forces from the sails are no longer limited by the righting moment. In this paper the loading for rigs of modern sail yachts in the downwind sailing condition is discussed. A load model based on sail areas and apparent wind speeds for application in FEA is developed. The load model will be evaluated by comparing real size rig measurements performed on the Technical University of Berlin's research sailing yacht, DYNA, with a finite element analysis of her rig. Analysis of Hull Shape Effects on Hydrodynamic Drag in Offshore Handicap Racing Rules ///;; Teeters, Director of Research for US Sailing; Member, International Technical Committee Rob Pallard, Technical Officer, Institnte for Marine Dynamics; Member, International Technical Committee Caroline Miiselet, Research Officer, Institute for Marine Dynamics US Sailing and the Institute for Marine Dynamics (IMD) in St. John's, Newfoundland, are collaborating in a joint research program to investigate the effects of hull shape variations on hydrodynamic drag. The results of this program are being used to support the development of rules that handicap racing yachts. A fleet of 9 models has been designed with systematic variations in the most fundamental parameters: displacement and beam for fixed length. Six of those models have been tested both appended and bare-hull, in calm water and head seas. Analysis of residuary resistance, both upright and heeled, has been used to improve the Velocity Prediction

3 Programs (VPPs) employed by both the International Measurement System (IMS) and AMERICAP rules. Changes to Sail Aerodynamics in the IMS Rule Jim Teeters, Director of Researcli for US Sailing; Member, International Technical Committee Robert Ranzenbach, GLM Wind Tunnel, University of Maryland; Quantum Sail Design Group, Annapolis, Maryland, USA Martyn Prince, Wolfson Unit MTIA, University of Southampton, UK US Sailing, the Offshore Racing Council (ORC), the Glenn L. Martin Wind Tunnel (GLMWT), Quantum Sail Design Group (QSDG), the Wolfson Unit and North Sails have collaborated on a series of wind tunnel test programs to investigate the performance of both upwind and offwind sails. These programs were initiated in response to perceived inequities in the ratings of boats of various rig designs sailing under the International Measurement System (IMS). Observations of on-the-water performance have lead to the conclusion that there are biases within the rule with respect to rig planform design. Specifically, it has been concluded that large spinnakers are penalized so that a fractional rig, with its small spinnaker, is favored when sailing offwind, that there are un-rated benefits to a masthead rig upwind, and that there are errors in the relative handicapping of overlapping and nonoverlapping jibs. The IMS Rule uses a Velocity Prediction Program (VPP) in which sail forces are represented by algorithms that are based on a combination of science and reverse engineering from the measured sailing performance of real boats. The results of investigations at both GLMWT and Wolfson have been used to modify this IMS aerodynamic model, thereby reducing the pre-existing biases. On the Use of CFD to Assist with Sail Design Andrea Schneider, University of Florence, Italy Andrea Arnone, University of Florence, Italy Marco Savelli, Mascalzone Latino Sailing Team Andrea Ballico, Mascalzone Latino Sailing Team Paolo Scutellaro, Mascalzone Latino Sailing Team In the last twenty years the theoretical approach to aerodynamic design by means of Computational Fluid Dynamic (CFD) has evolved substantially. The recent improvements in computer performance have made the use of Reynolds Averaged Navier-Stokes equations (RANS) feasible for practical design applications, thereby opening new frontiers in aerodynamic design. RANS codes have broadened the availability of design tools and expanded the design criteria.

4 The latest generation of racing yachts has greatly benefited from the use of these new tools in the design of hulls, appendages and sails. The proposed contribution is focused on the use of RANS in assisting the sail designer. A fully viscous incompressible research code originally developed for aerospace applications has been extended for use in sail plan analysis, thereby allowing the designer to test and compare a large number of sail modifications in a relatively short amount of time. A parametric approach to sail design in upwind conditions will be presented for an America's Cup Yacht. The benefits, weaknesses, and potential of 3D RANS solutions will be discussed in detail. Numerical Simulation using RANS-based Tools for America's Cup Design Geoff Cowles, histitiit de Matliématiques, Ecole Polytechitique Fédérale de Lausanne, Switzerland Nicola Parolini, Institui de Matliématiques, Ecole Potytecltnique Fédérale de Lausanne, Switzerland Marii L. Sawley, Granulair Teciinologies, Lausanne, Switzerland The application of Computational Fluid Dynamics simulations based on the Reynolds Averaged Navier- Stokes (RANS) equations to the design of sailing yachts is becoming more commonplace, particularly for the America's Cup. Drawing on the experience of the Ecole Polytechnique Fédérale de Lausanne as Official Scientific Advisor to the Alinghi Challenge for the America's Cup 2003, the role of RANS-based codes in the yacht design process is discussed. The strategy for simulating the hydrodynamic flow around the boat appendages is presented. Two different numerical methods for the simulation of wave generation on the water surface are compared. In addition, the aerodynamic flow around different sail configurations is investigated. The benefits to the design process as well as its limitations are discussed. Practical matters, such as manpower and computational requirements, are also considered. Sailing Yacht Design for Maximum Speed Bob Dill, Burlington VT This paper reviews the performance of ice and land yachts and the factors that determine their top speeds. The data clarify a century of misunderstanding about top iceboat speeds and serve as background for discussing the design and performance of the author's land yacht, the Iron Duck. This yacht was built as an amateur project and holds the world record for speed in a land yacht at mph. It appears that it is, currently, the fastest sailing yacht on any surface. Finally, the paper provides perspective on a variety of aspects of speed sailing on dirt and ice. Composite Sail Batten Design

5 Audrey Sery, Université de la Méditerranée, Marseille, France Jean Paul Cliarles, Université de la Méditerranée, Marseille, France This paper relates the results of our investigations to improve the design of.full-length, composite battens. The paper starts by describing the technologies used to manufacture battens and the role they play in sail equilibrium. A method is then proposed to help in the design of battens. It is a blend of theory and experiment that focuses on the strength of the battens. Wlien a batten is close to rupture, it is subject to large rotations and must therefore be modeled by non-linear computations of the slender beam type. In addition, we have calculated the stress distribution in a laminated composite. As for the tricky problem of the maximum allowable stresses for composite materials, we have shown that a specific characterization test is necessary. With a series of examples, we show that stronger battens can be developed through selection of the cross-sectional areas and the materials. Analysis of 2D Coupled Sails: Use of an Optimization Technique Based on Turbulent Viscous Flows Giovanni Lombardi, Department of Aerospace Engineering, University of Pisa, Italy Francois Beux, Scuola Normale Superiore di Pisa, Italy Mattia de. Michieli Vitturi, Department of Mathematics, University of Pisa, Italy In this study the optimization of a complete 2D flying sails configuration is considered. An optimum shape design problem is then defined considering the maximization of the drive force on the sails, constrained by the heeling force, and complete flow modchng including turbulent effects. The corresponding numerical algorithm is based on a gradient descent method coupled with a discrete shape grid-point parameterization. The descent direction is obtained by an exact computation of an incomplete discrete gradient associated with a muhilevel strategy. The numerical behavior of the present formulafion has been illustrated by the optimization of real 2D configurafions of an America's Cup yacht. Experimental Study of a Directionally Stable Sailing Vehicle With a Free-Raking Rig and a Self-Trimming Sail Akira Sakurai, Dept. Aeronautics and Astronautics, Kyushu University, Japan Takeshi Nakamura, Dept. Aero, and Astro., Graduate School, Kyushu U. Yuya Nakamoto, Dept. Aero, and Astro., Graduate School, Kyushu U. There exists an exact dynamic analogy between a sailboat and a sailplane, if it can be assumed that the sail does not generate moment around the mast and that the yawing moment due to heel can also be eliminated. It is shown, both theoretically and experimentally, that a direcfionally stable sailboat can be realized. It is also shown that the above assumption of no-sail-moment can be realized by introducing a new type of

6 mast which can elastically rake in the pitch direction and a wing sail which can freely rotate around the mast. The effectiveness of these sail and rig is verified by experiments. Student Research Projects for the New Navy 44 Sail Training Craft Paul H. Miller, Naval Architecture and Ocean Engineering Department, United States Naval Academy, Annapolis, Maryland NAOE Naval Architecture and Ocean Engineering Department Offshore-capable sail training craft (STC) specifically designed and buih for the United States Naval Academy (USNA) have been a cornerstone of its seamanship training program since Currently the fourth generation of these craft is under development and this paper summarizes research projects performed by eight midshipmen in the areas of parametric design criteria, structures, appendage development and analytical tool evaluation. While the resuhs are oriented toward the new sail training craft, they are general enough to apply to any medium-sized offshore sailing vessel. Experimental Force Coefficients for a Parametric Series of Spinnakers William C. Lasher, James R. Sonnenmeier, David R. Forsman, Cheng Zhang and Kenton White, Penn State Erie, The Behrend College, Erie, Pennsylvania, USA A parametric series of eight spinnaker models was built and tested in a wind tunnel according to the theory of statisfical Design of Experiments. In these models, three sail shape parameters were varied - cross-section camber ratio, sail aspect ratio, and sweep. Lift and drag forces were measured for a range of angles of attack, and the thrust force coefficient was determined as a funcfion of apparent wind angle for each of the eight sails. It was found that fiat spinnakers are faster than full spinnakers and that spinnakers with low sweep (more vertical) are faster than spinnakers with high sweep. This is consistent with general sailing pracfice, which maximizes projected sail area by pulling the pole back and down. The infiuence of aspect ratio on drag coefficient was small and within experimental error. A description of the sail shapes and corresponding force coefficients is presented for future validation of Reynolds Averaged Navier-Stokes simulations. The Rise of the Hydrofoil and the Displacement of the Hull: The Design, Construction and Performance Measurement of a 6m Flying Catamaran Edward Chapman, South Brent, Devon, UK. George Chapman, South Brent, Devon, UK. The evolution of an all-round 6-metre hybrid displacement/fiying day-sailing catamaran is described. A 4.9m prototype was a relafively conventional, but wide, beach-cat type platform with a single fractional rig. Fitted with mechanically incidence-controlled horizontal lifting surfaces beneath the twin daggerboards and a single inverted T rudder.

7 the boat could be sailed in one of three modes: fully displacement with the lifting foils locked in neutral; one hull displacement and the other flying under automatic height control; two hull flying. The small size and structural fragility of the 4.9m boat led to the construction of a 2-man 6m version which, despite being overweight, performs satisfactorily over a wider range of operating conditions than her predecessor. A simple VPP suggested that a second pair of lifting foils with greater area would enlarge the fully foilborne performance envelope upwind, although reducing top speeds on other courses. In practice these foils performed poorly other than on flat water. Other errors contributed to the uhimate failure of one foil-strut assembly, the mode of which is described in detail. Prior to this it was found that operating the foils as stabilisers, i.e. in their active mode but with the hulls in the water, provided a remarkably comfortable, safe and fast ride, particularly upwind in gusty weather. Subsequently, "flying displacement" became the preferred upwind mode, with the original, smaller lifters. Because the author's working hours have limited the opportunity to sail against other similar sized beach cats, instruments to record the boafs performance have been developed. Based around readily available low cost microcontroller technology, the data gathered is processed to identity short, steady periods of sailing. The resulting polar diagrams have compared favourably with predicted performance. Supporting the weight of a boat, as well as resisting roll and pitch moments, through a more subtle combination of dynamic foil lift and hull displacement than presented here provides a continuing opportunity for further developments. Numerical Simulation of Maneuvering of "Naniwa-maru," A Full-scale Reconstruction of Sailing Trader of Japanese Heritage Yutaha Masuyama, Kanazawa Institute of Tecltnology, Katiazawa, Japan Kensaku Noinoto, Prof. Enierittis, Osaka University, Osaka, Japan Akira Sakurai, Kytisliu University, Fukuoka, Japan Numerical simulation of maneuvering of "Naniwa-maru" was performed to clarify the maneuver characteristics in particular with wearing operation. "Naniwa-maru" belongs to a type called Higaki-kaisen, and the Higaki-kaisen is a type of the more generic class of vessels named "Bezai-ship". Bezai-ship are typical Japanese sailing traders in the 18th to the mid- 19th century which have different appearance and construction from, those of Western tall ships. The present paper shows the numerical simulation of her wearing operation, and the results compared with the measured data. The equations of motion dealt with coupled ship motions of surge, sway, roll and yaw with co-ordinate system using horizontal body axes. The numerical simulation indicates ship response according to the measured time history of rudder angle, and shows the ship trajectory and the sailing state parameters such as heading angle, leeway angle, heel angle and velocity. The calculated resuhs indicated the ship performance very well.

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