Both IRC and ORC require flying headsails to be measured, but there are differences in descriptions and data that boats and measurers need to be aware of.

Equipment Rules of Sailing (ERS) definition of a flying head sail is any sail set with no edge attached to the rig (ERS G1.2). The IRC Rule overrides ERS G.1.3(d) by adding that it must also be set forward of the forestay. If the ratio of the half-width and foot measurements is greater than 75% the sail is classified as a spinnaker under IRC and ORC ratings, when less than 62.5% for IRC only it is classified as a headsail.

Both IRC and ORC require flying headsails to be measured. IRC only reports the largest flying sail. When getting your flying sails measured it is best to measure and confirm the mid-girth to foot ratio first this can save additional measurements. Where the sail less than 75% it will need to be measured and include the additional measurements for a headsail.

Where IRC only requires the largest sail to be measured. ORC requires all flying sails (spinnakers and headsails) be measured including those flown inside the forestay (staysails etc.). If the vessel has multiple tack points and hoist heights for the outside flying sail these measurements are also required and the sails used on these different points identified.
 

To find out more about ORC and IRC ratings click here.

By Chris Zonca https://www.sailing.org.au/about/ourstaff/