IRC Notice on Spinnaker Definition

The IRC Technical Committee has issued the following notice:

It has come to our attention recently that several sailmakers have developed spinnakers which may be flown with the luff as presented for measurement being there solely for measurement purposes, and when the sail is set with the luff folded back presenting a section of the body of the sail as the leading edge when set.

This effectively produces a sail which has a far flatter and shorter mid width, enabling the sail to be flown at tighter angles than when set with the luff as the leading edge of the sail. Whilst the sail is not reefed, it is behaving exactly as one with a reef applied to the leading edge of the sail.

It is considered that this circumvents the reefing element of the IRC definition of a spinnaker, which states:

RRS 50.4 shall not apply. A spinnaker is defined as a sail set forward of the foremost mast with half width (measured as a spinnaker) equal to or greater than 75% of foot length and without battens. A spinnaker may be set reefed by any means while racing under IRC provided that when measured in any reefed condition it continues to satisfy the IRC definition of a spinnaker.

It is recognised that the definition of “reefed” may or may not apply to this arrangement. However, the IRC Technical Committee agrees that such an arrangement may also be considered as double luff sail, due to the physical luff of the sail as presented for measurement not being the same as the effective luff of the sail when set. It is noted that IRC rule 21.2.2 does not use “luff” in the ERS defined sense in this respect.

The intention of the notice below is to ensure that Fundamental Policy Rules 2.2, 2.4 and 2.8 are respected and complied with by all competitors, and that a sail measured as a spinnaker complies with that definition when in use.

The following shall therefore apply with immediate effect:
Any spinnaker which may be set with tension applied between the head point and the tack point in a way that effectively introduces a secondary leading edge to the sail may be considered to have a double luff for the purposes of IRC rule 21.2.2 and if so shall have Rig Factor adjusted accordingly. Any such sail shall be declared with photographs prior to use, and additional measurement data may be required.

Source: IRC Technical Committee – 8 December 2016