I am starting this thread for information about the ORA ORC and EZ Rating Systems.
The formula used by EZ (and ORR & ORC) to measure a spinnaker is: Area = SLU x (SFL + (4 x SHW)) / 6
NOTE: For an Asym spinnaker, SLU is replaced with ASL, where ASL = (SLU + SLE) / 2
CoPilot AI suggests the formula is a ✅ World Sailing / IYRU Sail Measurement System (ERS) standard. Historically called IYRU (International Yacht Racing Union), now World Sailing Formalized in the Equipment Rules of Sailing (ERS)
This measurement system defines how sails (including spinnakers) are measured and gives standard formulas for area.
A classic spinnaker area formula like:
Area = SF × SL / 2 + 2 × (SMG − SF/2) × SL / 3
comes directly from IYRU / World Sailing measurement instructions for spinnakers. [f18-intern...tional.org]
SF = foot width
SL = leech length
SMG = mid‑girth
Copilot by defaults uses a different measurement system.
Area=2SL×(SHW+SFL)
Where:
SL = luff length
SHW = half-width
SFL = foot length
I have attached a copy of my EZ certificate. Class rules suggest the max area on a J/30 spinnaker 704 ft². My actual spinnaker measured in at 633.3 ft²
https://www.regattaman.com/cert_form.php?sku=h-73-2026-2314-10472-0-430 I will post additional information as I learn EZ. Jim Teeters is our
US Sailing representative and contact for EZ related questions.
Dave@j30.us
