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post #3200 of Old 11-07-2012 Thread Starter
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Orc vpp

Very interesting information about a major alteration on the accuracy of their Velocity Prediction Program (VPP) to be implemented for the 2013 sailing season.

I hope that they get it right this time and that an unfair advantage is not given to heavy boats regarding light ones (I am talking of modern boats) as it was till know.

This is very important because this is what defines the shape/weight of many cruiser-racers that to be winners under the past formula would have to be lesser good sailboats. That would be a right step towards boat development.

They say:

the Offshore Racing Congress (ORC) is pleased to announce a major step forward in the accuracy of its Velocity Prediction Program (VPP) to be implemented for the 2013 sailing season. One of the principal elements of this program, the Residuary Resistance (Rr) formulation, has been revised to now be more accurate for a broader range of yacht types that race within the ORC fleet database.

This new innovation is the result of an extensive multi-year study conducted by the International Technical Committee (ITC) in which historical data derived from tank test results has been combined with new research using Computational Fluid Dynamic (CFD) tools to create the new formulation.

"This is a huge step forward in solving a difficult problem which has faced VPP research for many years," says Bruno Finzi, Chairman of ORC. "The Congress applauds the ITC for the completion of this major project that will benefit all boats racing in the ORC fleets around the world."

The new Rr formulation used in the new VPP is producing theoretical predictions which are much closer to the measured performance data taken from numerous boats in the ORC fleet.

"We looked at this carefully to help validate our results. The implied wind calculations are also much closer to that observed on the race course," says Alessandro Nazareth, Chairman of ITC.

The Rr project's new formulation was the result of collating the relevant Delft Systematic data, analyzed by ITC member Kay Enno Brink and the CFD results coming from ITC's Philippe Pallu's work at CRAIN and the Fine-marine code work performed by new ITC member Jason Ker. Another ITC member working on this project was Andy Claughton of Southampton University.

"Validation of this new formulation has been very important to ensure that all elements of the fleet are treated fairly," says Claughton. "Our tests indicate that if any race from the past is rescored using the new rule the spread of corrected times for the first 10 or 15 boats is reduced, sometimes by 20-30%. This is fantastic progress."


I guess this is really about lighter boats not to be unfairly penalized because designers were complaining about that and Jason Ker had a leading position on that complaint, probably because he is just one of the leading NA whose boats win, light or not

As they quote the work and contribution of Jason Ker for this new model, so I guess it is just the case.

This is a major step in what regards conditions for better sailing boats, a bigger than most would think. Shapes of sailing boats have been determined along the years by racing rules and the type of shapes/weight/draft they favor.


Last edited by PCP; 11-07-2012 at 11:27 AM.
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