05.01.00 General
5.01.01 As stated in ISAF Equipment Rules of Sailing (ERS) all Sails shall be measured on a flat surface with sufficient tension to remove wrinkles across the line of measurement and shall include the fabric length between measurement points.
Definitions of the ERS shall apply
No limit is defined for primary and secondary reinforcement.
05.01.02 Only single-masted Boats are allowed.
05.01.03 Double luffed Sails, rotating Masts, permanently or mechanically bent spars (or any similar devices) are prohibited.
Normal adjustment of Rigging in order to bent a Mast or spar whilst sailing is allowed.
05.01.04 Adjustment Eyes (formerly named Cunningham holes) in Headsails and Mainsails are allowed.
05.01.05 a. The Maximum Sail Area of a Mainsail or a Headsail shall not exceed 18,50 square metres.
b. Sail Areas of a Mainsail or a Headsail shall not exceed 12 square metres. 05.01.06 RRS 54 shall not apply.
05.02.00 Measurement of Mainsail (see figure 3).
05.02.01 Sail Area of the Mainsail (SMGV) is given by:
SMGV = P*(HB+2*MGT+3*MGU+4*MGM+4*MGL+2*E)/16
05.02.02Hoist (P)

P shall be measured between the inner edge of the Lower Limit Mark and the Upper Limit Mark on the Mast (this changes ERS F.6). MArks are 25-millimetre Limit Marks painted on the Mast. The lower edge of the Upper Limit Mark corresponds to the top of the Mainsail headboard. The upper edge of the Lower Limit Mark corresponds to a fair extension of the top of the boom in case of Mainsails fully secured at the Foot, or to a fair extension of the straight line joining the Clew Point to the Tack Point in case of loose footed Mainsails.
Only one pair of Limit Marks is allowed on a Mast.
if the Mainsail is loose-footed, the inner edge of the Lower Limit Mark may be higher than the fair extension of the boom.
05.02.03Widths

* HB is the maximum fore and aft dimension of the headboard of the Mainsail (see figure 4).
* MGT, MGU and MGL are the Quarter Width (ERS G.7.4), Half Width (ERS G.7.5) and Three-Quarter Width (ERS G.7.6).
MGT is the Upper Width (ERS G.7.7), the Upper Leech Point being a point, equidistant from the Three-Quarter Leech Point and the Head Point (see figure 3).
All these measurement points shall be at the extreme outside of rope or fabric of the sail's edge, with the Sail laid flat.
* E is the Outer Point Distance (ERS F.12.1), mesured from the aft side of the Mast to the inner edge of a 25-millimeter measurement mark painted on the boom.
When a rounded Leech allows a gain is sail area, the measurer shall extend the measurements of the nearest measurement points, in order to include the rounded Leech in the measured area.
05.02.04 The points on the Leech from which the cross measurements are taken shall be determined bridging any hollows in the Leech with straight lines joining the aft extremities of the battens or the points at which they emerge from the fabric of the Sail.
05.02.05 The Foot roach shall not be greater than 0,15 metre. It shall be measured from the straight line joining the Clew Point to the Tack Point. 05.02.06 Battens
The number of battens in the Mainsail shall be limited to three, with following restrictions:
* The top batten length shall not be greater than 45% E.
* The distance between the Head Point and the nearest point of the Top Inside Edge of the batten pocket (BLP) shall not be less than 20% P.
* The medium and lowest battens shall not be greater than 33% E and their position is free.
05.02.07 Reefing
Reefs in the Mainsail are permitted along the Foot only.
Except for roller reefed Mainsails, Mainsails shall have at least two reefs.
The reefs shall be reinforced to support the same constraints as the Foot of the Mainsail. This applies to the eyes and the reinforcement cloth. They shall be of similar size, strength and dimension.
The Boat equipment shall include equipment, necessary to tuck the reefs up to the highest one, operational in navigation. 05.02.08 Old mainsails
Mainsails made according to the former Measurement Rules (edition 1988) are allowed, but they may no longer be made since January 1st, 2001, unless the Boat is a Racer or Cruiser and the owners association doesn't allow the Mainsails made in accordance with the current Class Rules. A copy of the 1988 rule can be found in Appendix 3.
05.03.00 Headsails (see figure 5. For a test period of four years beginning January 1st, battens are allowed according to test rules in Appendix 4 - Section 3

05.03.01
A Headsail is defined as a triangular Sail set in the Half Width (HW) measured from the Half Leech Point to the nearest point on Luff shall not exceed 50% of the Luff perpendicular (LP). 05.03.02 Where the Top Width is greater than 40 millimetres, the Corrected Luff length (JL) shall be measured between the Tack Point and a point where the projections of Luff and Leech is no more than 40 millimetres. Otherwise, JL is the Luff Length. 05.03.03 Sail area of Headsail (SMF) is given by:
SMF = 0,5*JL*LP
05.03.04 The Foot roach shall not be greater than 0,10 metre.
05.03.05 No boards nor battens may be used in Headsails.
05.03.06 The area of the Storm jib shall not be greater than 3,00 square metres, nor be smaller than 2,00 square metres.
05.03.07 The Storm Jib shall be made of non-laminated polyester cloth (Dacron) and have a thickness of no less than 0,240 millimetre.
05.04.00 Spinnaker (see figure 6)

05.04.01 Click on figure for a full-size copySpinnaker Leech Length(SL): is the distance from Head Pointto Clew Point.
Spinnaker Half Width (SMG): is the distance between the Half Leech Points
Spinnaker Foot Length (SF): is the distance between the Clew Points. 05.04.02 For measurement as a Spinnaker a Sail shall have the following characteristics: a. Leeches are of equal length. b. The Sail is symmetrical about a line joining the Head Point to the centre of the Foot. 05.04.03 The Half Width (SMG) shall not be taken as less than 75% of the Foot Length (SF). 05.04.04 Sail Area of Spinnaker (SMS) is given by:
SMS = SL * (4 * SMG + SF) /6
05.04.05 SMS shall not be greater than 19,60 square metres.
05.04.06 No angle shall be greater than 110 degrees.
05.04.07 The distance the Headsail halyard and the spinnaker halyard, or between one of these halyards and the forestay Rigging Point shall not be larger than 0,20 metre. The measurement of the halyards is taken between the centrelines of the halyards, held perpendicular to the front of the mast.
05.04.08 For a test period of five years beginning January 1st, 2005, asymmetrical spinnakers are admitted according to provisional rules, published in Appendix 4 (A4.01 and A4.02).
These rules may be modified yearly.
05.04.09 Spinnakers made according to the former Measurement Rules (edition 2002 or earlier) are allowed, they may no longer be made since January 1st, 2005. A copy of the 2002 rule can be found in Appendix 3. 05.05.00 Spinnaker Pole 05.05.01 A spare Spinnaker Pole may be carried on board and used as a replacement of a broken pole whilst racing.
05.05.02 The Spinnaker Pole Extension (SPL) shall be measured from the forward side of the Mast to the extreme outboard end of the Spinnaker Pole, set on its fitting on the Mast in a horizontal position on the centre line of the Boat. This changes ERS F.14.1.
An automatic Spinnaker Pole shall be set from the cockpit in its outermost position and measured with no other tension applied. 05.05.03 The Spinnaker Pole extension (SPL) shall not be taken as greater than 2,25 metres. 05.06.00 Forestay
05.06.01 A permanent forestay, with strength no less than the Boat Weight, is mandatory
05.07.00 Sail Number Limitation 05.07.01 Sails aboard a yacht in a race shall be limited to not more than:
* One Mainsail
* Two large Headsails
* One storm jib
* One spinnaker
05.07.02 Prior to a race, only one from each type of Sails (two large Headsails) shall be submitted from each boat for inspection. Only Sails that have been stamped shall be on board.
05.07.03 The Storm Jib shall be on board when racing.