2025 ORC Rating Rules and Superyacht Rules update

In accordance with the IMS Rule A6 and ORC Rating Systems Introduction, ORC Rating Systems Rule 208 is corrected by adding:

208.5 Headsails shall be sheeted from only one point of the sail at a given time.

In accordance with the ORC Superyacht 104, ORC Superyacht Rule is corrected by adding:

204.10 Headsails shall be sheeted from only one point of the sail at a given time.

Background

ORC Rating systems (ORC International and ORC Club) use the International Measurement System (IMS) as a measurement platform and the ORC Velocity Prediction Program (VPP) to rate boats of different characteristics in calculating their ratings (time allowances) for different wind speeds and wind directions.

Sail measurements following WS Equipment Rules of Sailing (ERS) definition attempt to get sail area calculations as close as possible to the actual sail area as well as definition of the sail as a headsail or as a spinnaker and allow for the ORC VPP to properly assess a sail’s performance in different true wind angles depending upon its mid-width.

A headsail is defined as a sail set forward of the mast with the half width of less than 75% of the foot length. A spinnaker is defined as sail with the half width of 75% or more of the foot length. Decreasing the foot length and increasing the half width by adding additional roach to the headsail changes the applicable aerodynamic coefficients (that are based upon mid-width for HSF). In certain extreme circumstances, this can result in a sail being rated as being most efficient at wind angles significantly different than the VPP predicts. Such a sail will often require multiple simultaneous sheeting points to effectively sheet the sail. By limiting headsails to be sheeted from only one point of the sail, the intention is that headsails shall remain measured, used, and rated as intended.

In addition, it should be noted that an ORC rule already exists restricting sheeting points for the spinnaker (ORC 209.5) and IRC restricts multiple sheet points for headsails and spinnakers. Following the desirable UMS concept, this correction also improves standardization for the use of sails between different rating systems.

ORC Chief Measurer

Zoran Grubiša

13 May 2025

In accordance with IMS Rule A6 and ORC Superyacht Rule 104 this correction is published and taken with immediate effect. It shall be deemed final unless and until overruled by the ORC Management Committee and Congress. If not objected, it will be included in the next rule revision as well.