ORC’s Technological Advances Are Shaping the Future of Sailing

05. Nov 2024

5 November 2024 - Singapore - The strength of the ORC system is in its ability to use the latest scientific and technical tools to provide what’s needed for fair racing among racing sailboats of dissimilar design. With continual investment in research and updated analyses of the fleet, this approach to handicapping is more consistent and objective than other approaches since it can use these tools to more fairly rate boat types that range widely among Monohulls, Multihulls, Superyachts and now J Class yachts too.

Taking the lead in this endeavour is the ORC’s International Technical Committee (ITC), a group of dedicated yacht designers, experts in aerodynamics, hydrodynamics, and other technical fields who are led by chairman Andy Claughton (formerly of the Wolfson Unit at University of Southampton) and vice-chairman Alessandro Nazareth (of Vallicelli Yacht Design). The other current members of ITC and ITC’s Research Associates are mentioned here.

This group receives input and feedback from ORC users around the world (sailors, race organizers, rating officers, project managers, sailmakers, riggers, etc), along with their own observations on how to improve the core tool for ORC - the Velocity Prediction Program (VPP) - as well as other technical elements of measurement and scoring that forms the foundational elements of the ORC system.

ORC actually uses 4 VPP’s developed by ITC: the ORCi VPP that is used for the vast majority of Monohull certificates issued; the ORC Superyacht VPP used for these yachts >30 m in length; the ORC Multihull VPP; and the VPP tailored for use with the J Class.

ITC made recommendations for improvements to the 2025 ORCi VPP based on Submissions it received this year and its research on the following topics:

Non-Manual Power: After input from industry experts and race organizers, ITC proposes the following revision of the non-manual power penalty, so that the penalty is sensitive to the boat length. Total penalty amount:

- 0.3% for 10 m LOA and below
- ⁠10-18 m LOA computed linearly between 0.3% and 0.6%
- 0.6% for 18 m LOA and above

The total is divided 35% for non-manual power rig adjustment, and 65% for sail sheets. The crew weight no longer affects the penalty.

Headsail Furlers: The LP restriction on the allowance for using a furling headsail, when it is the only working headsail on the boat, will be removed. The new allowance will be based on the area of the headsail at each wind speed. The REEF parameter in the VPP will be used to determine the allowance, with a larger sail to be awarded a larger allowance.

Upwind effect of keel width: The residuary resistance of long keel hulls, which have no separate rudder, will be reviewed in 2025 with an ambition to update the force model for the 2026 VPP. This work is also pertinent to the development of the ORC J Class VPP.

VPP sensitivity to small changes in keel area: During the meeting ITC ran a test to explore the changes to predicted speeds arising from a 10% change to the keel lateral area. The committee concluded that whilst it was possible for an increase in keel area to make the boat better balanced, or more tolerant, and therefore faster, the VPP was behaving as it should. There was no method by which the VPP could predict that an increase in keel area would increase the predicted speed.

The committee also discussed whether the introduction of an age allowance related to the appendages might address the problem. It concluded that the complexity of devising and managing such a process outweighed any potential benefit. The committee also noted its policy to ensure that the use of age allowance did not offer boats unwarranted handicap benefits.

4 knot wind speed in the VPP: A submission asked that the VPP wind speed matrix be expanded to include 4 knots, and ITC supports this expansion. This prompted a wider discussion about the definition of the sec/mile polar speed curves at each TWA. This curve needs to be unambiguously defined throughout the sailing wind speed range so that PCS and WRS calculations are consistently applied.

The committee agreed to test the VPP running at four knots and if this proved viable then it should be considered for inclusion in the 2025 VPP.

Other progress was made on these topics in response to bothSubmissions and ongoing basic research:

Offwind aero force coefficients: Based on observations made in the submissions of a perceived bias in rated speed of Asymmetric versus Symmetric spinnakers, a study was made of the aerodynamic force coefficients for offwind sails, with the following recommendations:

- small adjustments will be made to the force coefficients to produce results that better match observations from the ORC Performance Database
- small adjustments are required to the 78% mid-width ordinal HSF coefficients to maintain smooth transition along the entire mid-width range (50% to 85%)

Heel Limit: ITC looked at the predicted heel angles when running and reaching in strong winds, and whether introducing a heel limit would be beneficial. They concluded that a single fixed limit would not improve the handicapping. But the matter was added to the 2025 research agenda to investigate a more sophisticated approach which would not involve introducing a yaw moment balance into the VPP.

In summary, the following changes are proposed for the 2025 ORCi VPP:

Adjustment to off wind sail coefficients to improve TWA predictions.
Revised credit for furling headsails based on REEF parameter and remove LP limit.
Improved force model for yachts fitted with lifting foils.
Use of non-manual power revised penalty.
Introduction of 4 kts TWS.
Life raft position.

The test runs of the new proposed VPP with these changes indicate a small increase in the APH ratings by approximately 0.4 % on average among the 1800 designs in the test fleet:

For details of the research conducted and improvements for the ORC Superyacht, Multihull and J Class VPP’s, consult the full version of the ITC Minutes at this link here.

Weather Routing Scoring:

The ORC WRS system, powered by PredictWind, has been used to score or shadow score 50 regattas during 2024. The process is handled from within the ORC Scoere software and can now offers the ability to select from the grib files available in the area. Making this selection is not mandatory as the PredictWind API has access to the complete online method that chooses the best forecast and current model available for each locale.

Whilst the handicapping process starts with a simulated race for every boat using her scoring polar table, the input to the scoring system is a distribution of TWS and TWA experienced during the race. This is then used to create a PCScs and is then used to calculate a Predicted Elapsed Time, and a scratch sheet based on the average PET for the division.

To date the ratio of PET/ET has been used as the KPI, and on this metric the WRS system always outperforms the APH. A better metric would be the comparison of the TWA TWS matrix from the WRS and that observed onboard. This data is much more time consuming to a gather as it needs the boat’s log data.

Our analysis of the race results from some logged data shows that when the weather forecast matches the race conditions the WRS system is very effective. Boats that finish the course several hours apart are handicapped for the wind they see throughout the race, so the cases where the breeze drops or builds for the later finishers is captured - this is something that a single number can never do.

The process of capturing the predicted wind conditions from the race simulations, and creating the pre-start handicap tables has proven to be a very fast and reliable process.

WRS Web App Development:

Whilst ORC will continue to offer WRS as a remote service for race organisers, ORC wishes to make the system available via a machine-agnostic Web App. During 2024, the ORC has developed a Web App, which is close to being available as a beta product.

The web app will give the user the ability to use a laptop or tablet with an internet connection to: