2009 ORC VPP (Velocity Performance Prediction) Documentation manual

by ORC media on 2 Oct 2009 The Offshore Racing Congress (ORC) is pleased to announce the immediate availability of the 2009 ORC VPP (Velocity Performance Prediction) Documentation manual, authored by Andy Claughton of the International Technical Committee (ITC) and amended and edited by other ITC and ORC members.

This 68-page guide provides the offshore sailing community a complete summary of the physics and computational processes that lie behind the calculation of sailing speeds and time allowances for boats measured for the ORC International and ORC Club rating systems.'It has been years in the making,' said Bruno Finzi, Chairman of ORC, 'and designers have always had access to the VPP, but we are happy to at last present this manual to the broader public in this accessible form to help demonstrate the principles and transparency behind our rating systems.

'The ORC VPP is part of three key elements to the current ORC handicap system:- the International Measurement System (IMS) used to measure the boat, and it sails, spars, and appendages;- the performance prediction procedure which determines the parametric inputs used by the VPP to predict sailingspeed at different wind speeds and wind angles, and with different sails set;- the race management system where the results of the VPP are applied to offer race handicapping, whether generalized or specific to the conditions of the race.

'The VPP Documentation describes the methodology of the equations used to calculate the forces produced by the hull, appendages, and sails, and how these are combined in the VPP.The following excerpt from the Overview section in the manual explains the approach made in devising an effective VPP:'Predicting the speed of a sailing yacht from its physical dimensions alone is a complex task, particularly when constrained by the need to do it in the 'general case' using software that is robust enough to be run routinely by rating offices throughout the world. Nevertheless this is what the ORC Rating system aims to do.

'The purpose of this document is to describe the physical basis of the methods used to predict the forces on a sailing yacht rig and hull, and to define the formulations (equations) used by the VPP to encapsulate the physical model. In order to do this the document has been set out to first layout the broadest view of the process, gradually breaking the problem down into its constituent parts, so that ultimately the underlying equations of the VPP can be presented.

'The ORC’s rating systems are the only international, scientific, and published VPP-based rating systems used in the world today. Over 30000 boats have been certified during years of racing on five continents and across dozens of offshore racing cultures, from the Far East to South America, and from the Pacific Northwest of North America to the Mediterranean. Each year regional, continental, and World Championship regattas are held using the ORC International rating system, and each year the ITC meets to further refine and improve the ORC VPP.

For more information about ORC, ORC rating systems, ORC regattas and events, and to download the 2009 ORC VPP Documentation in pdf form, visit the ORC website at www.orc.org.