Kirby 25 Class Rules Effective January 1, 2010



  1. To maintain the K-25 as a one-design class with the object of providing fair competition between equal boats as well as providing a boat suitable for handicap racing and cruising.
  2. To protect the owner’s investment and keep the cost of ownership as low as possible.
  3. To maintain the high performance characteristics of the K-25 by permitting improvements to be adopted by the procedure for changing Class Rules as specified in the Class


To have clear and precise rules this will be essentially self-controlling.

Section 1 – Construction

1.1 – The standard K-25 as supplied by MIRAGE YACHTS LIMITED or another authorized builder constitutes the K-25 one-design. Except where variations are specifically permitted by these rules, the K-25 class yachts shall be alike in hull, deck, keel, rudder and mast, construction, weight and weight distribution, sail plan and equipment. When possible design drawings will be used to determine whether a particular boat meets this requirement. When no design drawings are available, the class executive and/or the class measurer shall make that determination.

1.2 – The Builder agrees to produce a consistent, uniform K-25 and will provide drawings and specifications of what constitutes the currently supplied standard K-25 to the class measurer when requested.

1.3 – The basic weight of the standard K-25 as supplied by the manufacturer shall be a minimum of 1430 kg. Yachts found to be below this minimum will add the appropriate ballast to their bow and stern only.

1.4 – The keel may be smoothed to maximize its original shape, or, if faired, will be faired to within a reasonable tolerance of the accepted Kirby 25 aluminium templates.

1.5 – Antifouling paint is permitted, but not required.

1.6 – All deck fittings shall remain as located by the builder except as specifically permitted by these class rules. The type, size, or manufacturer may vary provided they serve the same function.

1.7 – The basic minimum weight of a Kirby 25 rudder is 7.7 kg. Yachts having rudders weighing less than the minimum will add the appropriate ballast in their stern at approximately the same location as the rudderpost.

1.8 –  Repairs that inherently result in slight deviations from the design are permitted only when those repairs are required for the seaworthiness of the yacht, they do no result in any performance advantage, and it is impracticable to return the yacht to its original condition.


1.9.1 Stanchions and Lifelines – There shall be at least two stanchions placed on       each side of the boat in the original builder’s location.At least one life line of any material(s) and sufficient strength (i.e. steel wire, Aramid Fiber or webbing) shall be fitted to run through the stanchions on each side of the boat from the bow pulpit to the stern pushpit. The bottom of the holes in the stanchions and stern pushpit to which the top lifeline is attached shall be no lower than 450 mm above the deck at that location. The lifeline may attach to the bow pulpit at any height. Stanchions must be made of at least 7/8″ inch diameter steel tube.

1.9.2 Stern Push Pit and Bow Pulpit – The pulpit or pushpit design may be altered if it accomplishes the same basic function as the original. Replacement or modified pulpit and pushpit(s) must be structurally sound and offer as much support as the original components. It must be fabricated of minimum 7/8″ diameter steel tube. Two separate Push Pits may replace the original single Stern Pushpit on the transom. The original factory supplied Stern Pushpit may be modified as long as it meets the criteria stated herein. For any stern pushpit, original, replacement or modified, the bottom of the attachment point for the top lifeline that runs along the side of the boat must be minimum 450 mm above the sheer line at that location. The top horizontal rail of the bow pulpit must be a minimum of 500 mm above the sheer line at that location. There must be at least four vertical supports for the bow pulpit.

Section 2 – Sails

2.1 – Sail Measurement

2.1.1 – The IYRU international sail measurement rules shall apply unless specifically modified by these class rules.

2.1.2 – For any class regatta only one mainsail, one genoa, 4140 mm < LP> 2830 mm, one jib LP < 2830 mm and one spinnaker may be used. Local fleets may opt for additional sails to suit local conditions.

2.1.3 – Reinforcement or stiffening is permitted within 600 mm from each sail corner or reefing cringle.

2.2 – Mainsail

2.2.1 – The mainsail shall be of any weight, and made of any woven or laminated material up to and including the use of Kevlar. No sail material more advanced than Kevlar may be used (Dacron, Mylar, Pentex and Kevlar are all permitted). Sails not complying with this rule, and purchased prior to May 11, 2001 will be permitted.

2.2.2 – Principle measurements:

Mainsail height, (P) = 9220 mm

Foot of mainsail, (E) = 3430 mm

Leech length maximum = 9800 mm

Width at ½ leech length max = 2200 mm

Width at ¾ leech length max = 1320 mm

2.2.3 – The mainsail may have a maximum of four battens positioned so as to divide the leech in approximately equal parts. The top 2 battens may be full length.

2.2.4 – Headboard width, measured perpendicular to the luff = 125 mm ± 10 mm

2.2.5 – The boltrope on the foot of the mainsail may slide into a track on the boom.

2.2.6 – A flattening and two additional reef points are permitted.

2.3 – Headsails

2.3.1 – Headsails shall be of any weight, and made of any woven or laminated material up to and including the use of Kevlar. No sail material more advanced than Kevlar may be used (Dacron, Mylar, Pentex and Kevlar are all permitted). Sails not complying with this rule, and purchased prior to May 11, 2001 will be permitted.

2.3.2 – Genoa – L.P. max = 4140 mm

2.3.3 – Jib – L.P. max = 2830 mm

2.3.4 – A maximum of three battens are permitted in the jib leech. Battens are to divide the jib leech in approximately equal parts. Maximum batten length is full; maximum batten width is 50 mm.

2.4 – Principle Measurements

2.4.1 -Height of foretriangle (I) max = 8150 mm; Base of foretriangle (J) max = 2745 mm

2.5 – Spinnaker

2.5.1 – The spinnaker shall be of any weight, and made of nylon.

2.5.2 – The spinnaker shall be symmetrical in shape.

2.5.3 – Girth measurement max = 4930 mm; Leech measurement max = 8200 mm

Section 3 – Spars and Standing Rigging

3.1 – Material and Modifications

3.1.1 – Spars shall be of aluminium extrusion.

3.1.2 – No alterations or modifications to the spar extrusions are permitted except to facilitate the attachment of rigging and fittings as specified in these rules.

3.2 – Location and Measurement

3.2.1 – The mast shall be mounted on the deck. The forward edge of the mast at the deck shall not be more than 2745 mm (J) from the bow.

3.2.2 – Contrasting coloured measurements bands of a minimum width of 20 mm shall encircle the mast. The distance from the upper edge of the lower band to the lower edge of the upper band shall not be more than 9220 mm (P). The top edge of the lower measurement band shall be 810 mm ± 5 mm above the foot of the mast.

3.3 – Standing Rigging

3.3.1 – The standing rigging shall only consist of one forestay, one standing backstay, two upper shrouds and two lower shrouds.

3.3.2 – The location of the attachment point of standing rigging on the mast and decks and the location of the spreaders shall remain as supplied by the builder. The spreader length from the mast surface to the shroud bearing point shall be 710 mm (28”) minimum.

3.3.3 – The forestay length shall be 8585 mm ± 25 mm. The forestay lower attachment point shall be 75 mm ± 5 mm above the deck.

3.3.4 – The intersection point of the forestay with the mast shall not be more than 8150 mm (I) from the deck.

3.4 – Main Boom

3.4.1 – The main boom may only be fitted with attachment points for: an adjustable outhaul, one main sheet fiddle block, a vang, reefing equipment and spinnaker boom storage hangers.

3.4.2 – A contrasting coloured measurement band of minimum width 20 mm shall encircle the boom. The forward edge of the band shall be no more than 3430 mm (E) from the aft surface of the mast, when the boom is held at right angles to the mast.

3.5 – Spinnaker Pole

3.5.1 – The overall length of the spinnaker pole including fittings, shall not be more than 2745 mm.

3.5.2 – The spinnaker pole and fittings shall be of the same style as supplied by the licensed builder.

3.5.3 – Spinnaker pole launcher and retriever systems are not permitted.

Section 4 – Running Rigging

4.1 – Halyards

4.1.1 – Only two foresail halyards are permitted, one of which shall be used as a spinnaker halyard. The double sheave box for the halyards will be located below the attachment point of the forestay.

4.1.2 – A double luff-groove headstay is permitted.

4.1.3 – Mast halyard locks on the main or foresail halyards are not permitted.

4.2 – Boom Vang

4.2.1 – The boom vang shall have a maximum mechanical advantage of 8:1. Boom kickers are allowed.

4.3 – Outhaul and Reefing Tackle

4.3.1 – The mainsail outhaul, flattening reef and clew reefing controls shall be mounted on or in the boom only and shall not be connected to any other part of the boat. The tack reefing control shall be mounted on the mast.

4.4 – Other Sail Controls

4.4.1 – A single mainsail cunningham, with maximum mechanical advantage of 4:1 is permitted.

4.4.2 – Barber haulers and twings are permitted.

4.5 – Sheet Locations

4.5.1 – The location and lengths of the foresail sheet tracks and mainsail traveler track shall be as specified on the K-25 design drawings.

4.6 – Winches

4.6.1 – Only 3 winches of 8:1 maximum power ratio, are permitted. Multi speed and self tailing winches are not permitted. All winches are to be mounted on the cabin top in the position specified in the design drawings.

4.7 – Furling

4.7.1 – Roller sail furling gear is prohibited.

4.8 – Miscellaneous

4.8.1 – No through deck, cockpit, hull or transom holes are permitted for sail control lines.

4.8.2 – Mechanical advantage of the mainsheet is optional.

4.8.3 -The mainsheet cleating system is optional.

4.8.4 – The type of mainsheet traveller track, car and control arrangement are optional.

4.8.5 – The cleats for the three halyards, jib sheets, vang, cunningham, spinnaker pole up-haul and down-haul are to be mounted on the cabin top. The type and location of blocks and cleats for the barber hauler, twings, spinnaker sheet and guy controls are optional.

4.8.6 – The standing backstay tensioning control lines shall have a maximum mechanical advantage of 24:1. The two running backstay tensioning control lines shall have a maximum mechanical advantage of 24:1.

4.8.7 – Only two running backstays are permitted. The running backstay anchor points at the deck shall be no further forward than the first stanchion base from the stern. The running backstays shall remain operational at all times. Shock cord lifters and/or retractors are permitted.

4.8.8 – Replacement and relocation of halyard cleats with clutches is permitted providing they remain on the cabin top.

Section 5 – Equipment Required on Board for Class Racing

5.1 – Notwithstanding anything in these rules, all safety equipment as prescribed by local or national authorities must be carried on board.

5.2 – An outboard motor 3.3 hp minimum, a minimum weight of 10 kg and an approved fuel container of minimum capacity of 2 litres.

5.3 – The outboard motor must remain on its motor mount, on the transom, at all times.

5.4 – An approved fire extinguisher.

5.5 – One steel anchor 6 kg minimum weight or one aluminium anchor 3.5 kg minimum weight as rated by the manufacturer.

5.6 – 30m of 9 mm non-floating anchor line.

5.7 – The self-contained recirculating marine toilet may be removed for racing.

5.8 – A 12V wet cell battery sufficient to power required navigation equipment; weight optional.

5.9 – A bucket minimum capacity of 9 litres.

5.10 – Bilge pumps may be removed for racing.

5.11 – Two fenders

5.12 – A first aid kit.

5.13 – An approved life jacket for each member of the crew.

5.14 – 1 tool kit.

5.15 – Cushions and hatch covers may be removed. Wash boards must remain.

Section 6 – Crew

6.1 – The crew, including helmsman, shall consist of a minimum of three to a maximum of five persons while racing.

Section 7 – Optional Equipment Permitted While Class Racing

7.1 – Two compasses (of any type), 1 knot meter-log,1 depth sounder 1 weather radio, 1 windex with light, 1 hand bearing compass, 1 GPS receiver.

7.2 – A tiller extension, length optional.