Improvement of Sailing Yacht Performance Prediction by Including Force-Moment Equilibrium for the Calculation of Helm Angle in a Velocity Prediction Program

1995 ◽  
Author(s):  
Peter van Oossanen
Keyword(s):  
Mathematical Model ◽  
Performance Prediction ◽  
Model Tests ◽  
Side Force ◽  
Prediction Program ◽  
Moment Equilibrium ◽  
Force Moment ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
Rudder Angle

Contemporary Velocity Prediction Programs (VPP's) consider the equilibrium of forces acting on a sailing yacht in the thrust direction and in the direction of the developed side force on canoe body and appendages. In addition, force-moment equilibrium is considered in the transverse plane of the yacht. In this way a solution is found for the three main unknowns in performance prediction, viz: boat speed, leeway angle and heel angle. The impact of helm angle on performance is herein ignored. In the velocity prediction program developed by Van Oossanen & Associates, a fourth equilibrium condition is included, viz: force-moment equilibrium in the horizontal plane for the calculation of the helm angle required for the equilibrium sailing condition. In this paper a description is given of some of the main problems that need to be solved when introducing this fourth equilibrium requirement. One of these is associated with the development of accurate mathematical expressions for the calculation of rudder side force and resistance, as influenced by heel angle and the proximity of the free surface. Model tests can be utilized for obtaining insight into the physical phenomena involved in such cases. Model tests were carried out in the context of an optimization study for the design of a yacht according to the International Level Class 40 (ILC40) Rule, under the International Measurement System (IMS). The analysis of some of the results of these tests with respect to improving the mathematical model for rudder side force and resistance, is described in the paper. The effect of including this mathematical model in a VPP is demonstrated in the paper by providing the results of calculations which reveal that a variation in rudder angle causes significant speed differences. It is shown that the IMS VPP that is used to calculate the rating and speed potential of ILC40 and other IMS Class yachts, in not taking into account the significant variations in performance associated with different values of the equilibrium rudder angle (and the associated rudder side force and resistance), is not sufficiently accurate.

BATOPERF, A Performance Prediction Software and Its Influence on Modern Yacht Design

1997 ◽  
Author(s):  
Sylvain Fargeas ◽  
Juan Kouyoumdjian
Keyword(s):  
Performance Prediction ◽  
Transverse Plane ◽  
Side Force ◽  
Moment Equilibrium ◽  
Force Moment ◽  
Boat Speed ◽  
A Performance

BATOPERF considers the equilibrium of the forces acting on a boat when sailing in the thrust and in the canoe body and appendages side force directions. A transverse plane force moment equilibrium is also considered solving for three principal unknowns: boat speed, leeway and heel. In this paper an overall description will be given of the fundamental solving principles of BA TOPERF and its force models. Finally a comparison will be made against the IMS VPP in the context of the importance of accurately predicting boat speeds when designing an IMS boat.

Approximation of the Calm Water Resistance on a Sailing Yacht Based on the 'Delft Systematic Yacht Hull Series'

1999 ◽  
Author(s):  
J. A. Kenning ◽  
U. B. Sonnenberg
Keyword(s):  
Water Resistance ◽  
Force Production ◽  
Data Set ◽  
Side Force ◽  
Prediction Program ◽  
Resistance Increase ◽  
The Past ◽  
Calm Water ◽  
Velocity Prediction ◽  
Sailing Yacht

Over the past years a considerable extension has been given to the Delft Systematic Yacht Hull Series (DSYHS) The DSYHS data set now contains information about both the bare hull and appended hull resistance in the upright and the heeled condition, the resistance increase due to the longitudinal trimming moment of the sails, the side force production and induced resistance due to side force at various combinations of forward speeds, leeway angles and heeling angles. New formulations for the relevant hydrodynamic forces as function of the hull geometry parameters have been derived to be able to deal with a larger variety of yacht hull shapes and appendage designs. During the past two years some results of this research have already been published. In the present paper an almost complete picture of the relevant expressions which may be used in a Velocity Prediction Program (VPP) will be presented.

A Velocity Prediction Program for a Planning Dinghy

2005 ◽  
Author(s):  
Todd Carrico
Keyword(s):  
Hydrodynamic Resistance ◽  
Side Force ◽  
Prediction Program ◽  
Fundamental Goal ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
Series Of Experiments ◽  
College Of Engineering ◽  
The University ◽  
Visual Basic 6.0

This paper summarizes the author’s graduate thesis in Naval Architecture accepted by the University of New Orleans, College of Engineering. The author sought to investigate the complicated interactions between the hydrodynamics and aerodynamics of a sailboat. The type of sailboat investigated was the Olympic dinghy class called the Laser. It was the author’s understanding that at that time, no work has been completed in the area of velocity prediction for this type of sailboat. Thus, the fundamental goal of this thesis was to develop a velocity prediction program specific to the Laser. In order to accomplish the goal of creating a velocity prediction program, multiple essential pieces of the data were needed. In particular, the hydrodynamic resistance data, aerodynamic drive and side force data, and hydrodynamic side forces were needed. To determine the dynamic trim of the dinghy, a series of experiments were conducted. In addition, a data acquisition system was developed in which full scale tow testing could be done. Next, a complete tow test series was conducted for the Laser. The aerodynamic sail coefficients were derived from Marchaj’s Aero-Hydrodynamics of Sailing. To determine the hydrodynamic side force, a two dimensional approach was employed. The coding of the velocity prediction program was done using Microsoft’s Visual Basic 6.0 and Excel 2000. The algorithms published in the 15th Chesapeake Sailing Yacht Symposium and Principles of Yacht Design pertaining to velocity prediction were used as a baseline. Finally, validation and verification was performed with the shareware program PCSAIL.

scholarly journals VPP-Driven Sail and Foil Trim Optimization for the Olympic NACRA 17 Foiling Catamaran

2021 ◽  
Vol 5 (01) ◽  
pp. 61-81
Author(s):  
Kai Graf ◽  
Oliver Freiheit ◽  
Paul Schlockermann ◽  
Jan C. Mense
Keyword(s):  
Olympic Games ◽  
Strong Impact ◽  
Large Set ◽  
Prediction Program ◽  
Velocity Prediction ◽  
Rudder Angle ◽  
Boat Speed ◽  
The Olympic Games

Abstract. The Nacra-17 catamaran is currently the only type of multihull that participates in the Olympic Games. It features semi-L-shaped daggerboards, allowing the boat to foil. For maximizing boat speed, the sailors have to cope with a large set of trimming parameters. Boat speed depends on sail trim, but additional trim parameters also have a strong impact on boat speed: the rake of the daggerboard and the rudder, the platform trim and heel angle and the rudder angle. The project described here tries to assist the sailors in finding an optimized set of trim parameters. This is done with the help of a proprietary velocity prediction program, which - besides solving for equilibrium of all forces acting on the boat - searches for the set of daggerboard and rudder rake, rudder angle, heel angle and platform trim, for which performance yields a maximum. The paper describes the method as well as some of the results.

Toward Numerical VPP with the Full Coupling of Aerodynamic and Hydrodynamic Solvers for ACC Yachts

2005 ◽  
Author(s):  
Erwan Jacquin ◽  
Yann Roux ◽  
Bertrand Allessandrini
Keyword(s):  
Degrees Of Freedom ◽  
Computational Method ◽  
Motion Equations ◽  
Towing Tank ◽  
Six Degrees Of Freedom ◽  
Prediction Program ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
Full Coupling ◽  
Classical Interpolation

The classical approach of Velocity Prediction Program is to find the balance of Hydrodynamic and aerodynamic sensors acting on the yacht to determine sailing conditions and associated performance. Usually, this approach is based on the data given by towing tank, wind tunnel or numerical computations. We present in this paper the unsteady coupling between an hydrodynamic RANSE with free surface solver and a panel aerodynamic solver that allow to directly find the sailing condition of the yacht, and its performances, compute bay solving the six degrees of freedom motion equations of the ship in the hydrodynamic solver. The main advantage of this computational method is the decrease of numerical evaluation, compared to the classical interpolation approach to determine performances of a hull, and to directly rank several hills in the term of performances and not only in the term of drag in fixed conditions. Further, improvements will allow to simulate unsteady maneuvering of sailing yacht, and focus will for example on restart behavior after tacking, dynamic behavior in waves.

Schooner Brilliant Sail Coefficients and Speed Polars

2001 ◽  
Author(s):  
Howard Grant ◽  
Walter Stubner ◽  
Walter Alwang ◽  
Charles Henry ◽  
John Baird ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Wind Pressure ◽  
Scale Model ◽  
Experimental Program ◽  
Side Force ◽  
Prediction Program ◽  
Wind Speeds ◽  
Velocity Prediction ◽  
Horizontal Side ◽  
Study Performance

The sail coefficients for a schooner rig, as a function of wind angle and heel angle, are presented, based on an experimental program, for historic vessel research, at Mystic Seaport, using the 61'6" schooner Brilliant. The coefficients were determined by full-scale sailing tests and 9- scale model tow-tank tests. Sail coefficients CR and Cttare defined as the drive force and horizontal side force , due to the sails, rigging, and hull above the waterline, per unit of sail area, per unit of wind pressure. These coefficients can be used to study performance of historic schooner­rigged vessels, predict performance of new designs, and compare performance of schooners and sloops. Sail coefficients for sloops have long been available. A velocity prediction program for the schooner was also developed. The predicted and actual ship speeds agree, with standard deviation of0.028 in the ratio. Upwind sail coefficients for the schooner are found to be lower than for historic sloops, and display the expected droop with heel. The schooner velocity made good upwind is largest with the sail plan of four lowers plus fisherman staysail. The schooner and sloop both point higher as wind increases. The sloop outpoints the schooner at all wind speeds, by about 10°. On a beam reach or broad reach, schooner speed is largest with the sail plan of big jib, golliwobbler, and mainsail. This sail plan also produces the largest downwind velocity made good. The polars suggest that the schooner has the advantage over the sloop on a beam reach.

scholarly journals A Performance Depowering Investigation for Wind Powered Cargo Ships Along a Route

2020 ◽  
Vol 5 (01) ◽  
pp. 47-60
Author(s):  
Fredrik Olsson ◽  
Laura Giovannetti ◽  
Sofia Werner ◽  
Christian Finnsgård
Keyword(s):  
Degrees Of Freedom ◽  
Structural Integrity ◽  
Prediction Program ◽  
Force Magnitude ◽  
Speed Performance ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
The Impact ◽  
Ship Speed ◽  
A Performance

Abstract. For a sailing yacht, depowering is a set of strategies used to limit the sail force magnitude by intentionally moving away from the point of maximum forward driving force, potentially reducing the ship speed. The reasons for doing this includes among others; reduction of quasi-static heeling angle, structural integrity of masts and sails and crew comfort. For a wind powered cargo ship, time spent on a route is of utmost importance. This leads to the question whether there is a performance difference between different depowering strategies and if so, how large. In this research, a wind-powered cargo vessel with rigid wings is described in a Velocity Prediction Program (VPP) with four-degrees of freedom, namely surge, sway, roll and yaw, with a maximum heel angle constraint. The resulting ship speed performance for different depowering strategies are investigated and the implications in roll and pitch-moments are discussed. The wind conditions when depowering is needed are identified. A statistical analysis on the probability of occurrence of these conditions and the impact of the different depowering strategies on the required number of days for a round-trip on a Transatlantic route is performed.

Hull - Appendage Interaction of a Sailing Yacht, Investigated with Wave Cut Techniques

1997 ◽  
Author(s):  
Jonathan R. Binns ◽  
Kim Klaka ◽  
Andrew Dovell
Keyword(s):  
Approximate Method ◽  
Wave Pattern ◽  
Wave Resistance ◽  
Full Scale ◽  
Research Centre ◽  
Cooperative Research ◽  
Prediction Program ◽  
Velocity Prediction ◽  
Sailing Yacht

The research explained in this paper was carried out to investigate the effects of hull-appendage interaction on the resistance of a sailing yacht, and the effects these changes have on the velocity prediction for a sailing yacht. To accomplish this aim a series of wave-cut experiments was carried out and analysed using a modified procedure. The processed results have then been incorporated into an existing velocity prediction program. For the purposes of this research two variables were investigated for the Australian Maritime Engineering Cooperative Research Centre (AMECRC) parent model 004, a model derived from the Delft IMS series of yachts. Wave-cut procedures inevitably raise questions about scaling procedures for full scale extrapolation as the inviscid wave-pattern resistance is calculated to be less than the residuary or wave resistance. These questions have been dealt with by an approximate method, briefly explained in this paper.

RVPP: Sailing Yacht Performance Prediction fully integrated into a RANSE based flow code

2011 ◽  
Author(s):  
Christoph Böhm ◽  
Kai Graf
Keyword(s):  
Equations Of Motion ◽  
Flow Simulation ◽  
Body Motion ◽  
Fully Integrated ◽  
Prediction Program ◽  
Velocity Prediction ◽  
Sailing Yacht ◽  
Ranse Solver ◽  
Hydrodynamic Data ◽  
Physical Phenomena

One of the most important tools in today’s sailing yacht design is the Velocity Prediction Program (VPP). VPPs calculate boat speed from the equilibrium of aero and hydrodynamic flow forces. Consequently their accuracy is linked to the accuracy of the aero- and hydrodynamic data used to represent a yacht. These data are usually derived from experimental or CFD results and processed by means of linearization and interpolation to represents the actual sailing state of the yacht, this interpolation being a source of inaccuracy. Furthermore, viscosity related effects are often estimated by simplified theoretical or empirical models potentially neglecting complex physical phenomena. The paper proposes a method circumventing these inaccuracies. It is based on the idea to directly derive Sailing Yacht performance from a RANSE flow simulation. This is done by coupling the prediction of sail forces with the hydrodynamic forces calculated by the flow code and solving the resulting imbalance in the equations of motion in the RANSE solver. The paper discusses implementation steps for the inclusion of sail forces and body motion into the flow code as well as calculation and grid setup. Results of the method christened RVPP are shown for a generic yacht design and are compared with results from a classical VPP approach on the same design. The paper finishes with a discussion of the pros and cons of the method and an overview at future development steps of RVPP.

Guides to the Approximation of Sailing Yacht Performance

1989 ◽  
Author(s):  
Olin J. Stephens
Keyword(s):  
Simple Form ◽  
Input Data ◽  
Full Range ◽  
Stability Estimates ◽  
Prediction Program ◽  
Design Program ◽  
Velocity Prediction ◽  
Minimal Data ◽  
Sailing Yacht ◽  
Limited Input Data

Two computer programs are presented for use, either singly or in sequence. The first will derive, from minimal data, a consistent set of parameters which, entered into the second, a velocity prediction program (VPP), will predict a sailing yacht's speed and course over a full range of wind strength and direction. Due to the limited input data as well as to the simple form of the VPP, approximate results must be accepted. The design program combines guidance with flexibility so that reasonably accurate and consistent dimensions, largely empirically derived, including weight and stability estimates, are quickly produced and tested, by the VPP, for performance.

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