The ORC VPP or Velocity Prediction Program, is the core of the ORC International and ORC Club Rating Systems. The ORC Designer’s suite (DVP) consists of the ORC Manager appication (includes measurement data editing, hull offset file editing and other utilities) and the VPP executable. the input data (DXT and OFF file formats) are processed by the VPP, which produces hydrostatic data and velocity predictions for 6 to 24 knots of true wind speed at true angles of optimum beat, 52,60,75,90,110,120,135,150 and optimum run.
It is objective of any rating system to give a boat rating which depends on her characteristics in order to equalize her with other boats of different size and characteristics. Characteristics that are positive for boat speed, like length of the water line or sail area, and those that are negative, like beam, displacement and wetted surface, are the most common influences in any rating system. Establishing which of these characteristics influences boat speed is therefore the problem that has to be resolved. Thanks to the developments in modern science and technology, ORC gives the most accurate solution to this problem, and establishes important principles of boat measurement and calculation of corrected times.
The only possible way to rate boat fairly is to tell how fast she can sail in certain wind conditions or to predict her speeds. To do so, ORC has developed with continuous research and update an ORC Velocity Prediction Program (VPP) as mathematical model which calculates boat’s performance from the set of measurements and gives rating which is then applied for race scoring. ORC VPP is calculating boat’s theoretical speeds for various conditions: wind strength of 4, 6, 8, 10, 12, 14, 16 and 20 knots, direction of true wind from the close-hauled to 52, 60, 75, 90, 110, 120, 135, 150 and 180 degrees. VPP program creates a computer simulation of the boat’s performance based on scientific research of boat hulls in hydrodynamic basins, sails in aerodynamic tunnels and measurements taken on real boats as well as computer fluid dynamics (CFD) tools available nowadays.
The VPP has a two-part structure comprised of the solution algorithm and the boat model. The solution algorithm must find an equilibrium condition for each point of sailing, where it balances the driving force from the sails with the hull and aerodynamic drag, and the heeling moment from the rig with the righting moment from the hull.
For more information on VPP and VPP documentation, please click this link:
https://orc.org/for-designers/orc-vpp
