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CSA Multihull Rating Rule

February 2017

The CSA Multihull Rating Rule belongs to the Caribbean Sailing Association (CSA). This Rule shall not be used, copied or otherwise distributed without the permission of the owner.

  1. General Items

    1. Administration of the rule - The CSA will appoint a Chief Measurer, Senior Measurers, Measurers and Trainee Measurers to administer this rule. In order to obtain a Rating under this Rule a yacht’s owner or captain can contact one of the Measurers listed on the Caribbean Rule Website WWW.CARIBBEAN-SAILING.COM and arrange to have the yacht measured. In addition to measuring yachts Measurers provide the services outlined in this document.

    2. Intent - The intent of this Rule is to handicap fairly the broad variety of multihull yachts which race within the Caribbean region. The rule will compute a RATING for each yacht which is intended to be representative of its true speed potential.

    3. Time on Time Handicapping - This Rule is a “Time on Time” rule – Each yachts RATING will be converted to a TIME CORRECTION FACTOR (TCF) which will be used to convert her Elapsed Time (ET) for the Race to a Corrected Time (CT). (CT = ET x TCF). Hereinafter the terms “Rating” and “TCF” shall mean one and the same thing.

    4. Standard and Light TCFThe standard TCF shall be applied, by default, to all races taking place under normal Caribbean conditions. The light TCF can be applied when the forecast conditions for a race indicate that wind speeds are expected to be consistently below 12 knots for the expected duration of the race.

      1. If the Light TCF is to be applied, competitors should be advised no later than 5 minutes before the warning signal for their class.

      2. The decision to apply the Light TCF will be taken at the sole discresion of the Race Committee.

    5. Ownership of the rule - The measurements used, formulae and calculations are the property of the CSA. The CSA may change these at any time.

    6. Measurement Rule - The rule is based on actual measurements. Formulae used to calculate the rating will be applied ‘across the board’ and not to a particular individual yacht in isolation.

    7. Not a Development Rule - This rule is not a development rule and it is not anticipated that owners or designers will deliberately seek to exploit the rule so as to artificially reduce the yacht’s rating relative to her true speed potential. Where this appears to have been done, the Chief Measurer will take appropriate action to negate any unfair advantage.

    8. Safety Guidelines - The CSA does not offer safety guidelines.

    9. Paperless Rule - This Rule is a ‘paperless rule’ and a yacht’s only official TCF can be found on the latest computer database. Any paper issued to the yacht is purely a measurement record.

    10. Measurement process- The CSA Multihull Rule comprises an “in the water” measurement part as well as the requirement for a certified displacement. Inspection of the underwater appendages may be required, especially in the case of foils that are designed to provide vertical lift.

  1. Regatta Rules

    1. Regatta Measurer - Any regatta using the CSA RULE may, in consultation with the CSA Chief Measurer (CM), appoint and bear the cost of a CSA Measurer as Regatta Measurer to serve on the Technical Committee. Duties shall include:

a) Advise the Organising Authority and Race Committee on class assignment.

b) Review ratings of all entered boats and notify the owner, organizers and the Protest Committee of any errors found.

c) Be the “authority responsible” referred to in RRS 64.3 and perform any services required under this article from such an authority, provided that the CM has issued the necessary permission for the Regatta Measurer to perform this role.

d) Correct errors found as permitted under the CSA RULE and as agreed by the Protest Committee.

e) Prepare and submit a detailed Measurer’s Report on the regatta.

f) Any other duties requested by the Organisers that are appropriate to be done by a Regatta Measurer.

    1. Correcting Ratings during RegattaTechnical Errors

When the Technical Committee is satisfied that there is a technical error (i.e. typographical, calculation, measuring error, incorrect TCF /sail combination, etc.) in a boat’s current rating at any time during the regatta, the Technical Committee shall notify the relevant authorities including the protest committee. If the protest committee is satisfied that the rating is in error, the Measurer shall make the necessary corrections and the scoring shall be adjusted to the new TCF for all races in the regatta including those already sailed.

    1. Rating Protest

When a rating protest is submitted to the protest committee that committee will be responsible to ensure that both the protesting and the protested yachts deposit measurement fees as described under CSA Rule 3.1 (see below). RRS 64.3(d) shall be used to determine which party will pay any measurement fees incurred and which party shall have the measurement fee refunded.

If, as result of a protest on rating, or as a requirement from the race committee a yacht is re-measured to confirm her rating handicap, the following tolerances to confirm her TCF shall apply.

If the protest is solely in relation to the use of incorrect sails, then only the sails need to be measured. If as a result of this measurement the TCF of the yacht changes by ‘more’ than +/- 0.001 then the protest is considered to be upheld and then yacht’s TCF will be adjusted accordingly.

If the protest is of a more general nature and the entire yacht requires to be re-measured then the protest shall be considered to be upheld if the yacht’s TCF differs by ‘more’ than +/- 0.003 from the current TCF and the database will record the new rating.

    1. The Chief Measurer is the final authority for interpretation of this rule.

In resolving disputes the CM will be guided by the intention of the rule (to provide a fair TCF as stated in para A1.2 above) rather than by the precise wording of any clause or statement. This authority can be delegated to a Regatta Measurer or other senior Measurer if necessary.

    1. Un-measurable Yachts

If a yacht, arriving at a regatta to race, cannot be given a measurement rating because of some abnormality in its dimensions which results in the calculated rating being inapplicable, or which has essential equipment which is not allowed under the rule, the matter shall be referred to the Regatta Measurer (if there is no regatta Measurer this shall be referred to the Chief Measurer). The RM/CM shall use his best efforts to arrive at a fair rating for the yacht and may suggest to the regatta organizer that this yacht be given a provisional rating (for this regatta only) to allow it to race. The RM/CM shall have the authority to alter the rating of the yacht during the regatta if, in his subsequent opinion, the initial rating allocated does not truly represent the speed of the yacht.

    1. Standard Dimensions

Some common classes may be given standarised hull and rig dimensions which are recorded in the database as an average of many measurements for that particular type of yacht. In this case only the sails, factors, and miscellaneous information, need to be recorded uniquely in the database, the hull and rig dimensions being the standards. If the Measurer suspects that the boat may not be a substantially standard production version, (for example if it has been modified, or stripped out, etc.) he shall measure the boat in the normal way and it will race with the TCF for that specific yacht rather than the TCF assigned to the class.

The CM shall determine which designs may have standard measurements. The CM’s approval is required for all boats with standard dimensions. From time to time the standard measurements may be modified as more information is collected.

    1. One Design Class Rating

Certain classes may be designated as ”one-design” and each yacht in the class can be given the same CSA rating after it is determined that the yacht is ‘Class Legal’ by a Measurer who is qualified to determine this for that class of yacht. The CM shall determine which Measurers can issue one design certificates and the TCF for each one-design class.

    1. Minimum Dimensions

Regatta Organisers have the right to stipulate minimum sizes of yacht which will be accepted into the class and regatta as a whole. Establishment and control of these minimums is outside the scope of this rule.

  1. Yacht Owners Rules

A CSA Measurer shall advise on preparing the yacht to be measured, advise on how to obtain an optimal rating, measure the yacht and enter the data into the rating program. This program will compute the rating of the yacht and also compute several TCFs for varying sail combinations. The Measurer shall charge a fee for this service.

    1. Fees

The measurement fee is made up of two parts: (a) a fee for the administration of this Rule and, (b) a fee to reimburse the measure for the service provided. These fees are charged based on the overall length of the yacht. Fees will be collected as specified by the CSA from time to time and may be collected by the individual Measurer who Measures the yacht and who will pass on the administrative portion of the fee to the CSA.

Fees, for year 2017

Complete measurement (a) US$ 2 per ft t plus (b) US$ 2.00 per ft

Partial measurement (a) US$ 2.00 per ft plus (b) Measurer’s hourly rate.

Annual Update involving no measurement (a) US$ 2.00 per ft (b) US$ 25 flat rate.

Each Measurer’s hourly rate may differ according to which island he/she is based in.

    1. Ratings

The measurements taken for the yacht shall be entered in the CSA Multihull Rating Program. The TCFs shown by this software is the current Rating for the yacht. A yacht may only have one current rating.

    1. Rating and Measurement Validation

      1. Ratings are valid for one complete calendar year Jan/01 – Dec/31 (Note – Yachts which carry out a first measurement or a change update after 01/Dec of any year will consider to have been measured / certified in the next full calendar year), unless this rating becomes invalid as indicated below.

      2. Measurements are valid for five calendar years from first measurement – including the year of measurement - unless they become invalid as detailed in 3.3.3 below. Invalid measurements result in an invalid rating.

      3. Measurements become invalid when

The boat is sold to a new owner

Five calendar years elapse, including the year of first measurement

The boat is significantly modified since last measured

The boat acquires new sails

If the CM determines that a Rating is invalid

If the Rating Rule is changed to require different measurements or different ways of measuring

      1. Re-validation - When a Rating becomes invalid the owner or agent shall request a re-measurement of the yacht. When requested to do this a Measurer shall carry out such checks or re-measurement as necessary and shall update the database as appropriate.

    1. Updating Ratings

When asked to update a rating a Measurer shall carry out whatever checks – up to and including a full re-measurement – that he/she think are appropriate to comply with 1.2. There is an obligation on the yacht’s owner / captain to point out any modifications made or other reason why the boat’s rating should not be automatically updated. Deliberate failure to do so may result in the yacht’s Rating being invalidated by the CM.

A yacht’s rating may be updated at any time to accommodate changes made to the yacht, but its rating shall not be updated more than three times in a calendar year without approval from the CM.

    1. Rating Changes Prior to an Event

There are several alternate TCF’s (for different sail combinations) for each rated yacht. A yacht may elect to race with any one of these TCF’s, but must declare which TCF/sail combination it intends to use by the deadline set by the Regatta Organizers. The TCF elected to be used cannot then be changed during that specific regatta.

Any request to alter a rating immediately prior to a regatta, after that yacht’s initial registration but before close of registration, shall be put to the RM/CM who shall adjudicate on this matter. Late measurement changes are to be discouraged.

    1. Re-measurement

A full re-measurement of a yacht shall be undertaken every 5 years or if the current measurements become invalid for any reason (See .3.4 and .3.5 above.)

This may also be done at the request of the CM if he/she suspects that the rating may be incorrect, It may also be done at the request of a protest committee as a result of a valid protest.

The owner of the yacht may not request re-measurement by a different Measurer in a different territory within the existing rating’s measurements validity period (5 years) without specific reason being given and the specific approval of the CM obtained. (i.e. ‘shopping around’ for best measurement is not allowed.)

    1. Temporary Ratings

Temporary ratings may be issued only for a single regatta and only and as a last resort. The Measurer must be confident that the rating so issued will stand up to a measurement protest. The rating must be clearly marked as “TEMPORARY” in the database and should include the circumstances requiring its issue in the notes. A Temporary Rating cannot be updated without a full measurement of the yacht.

    1. Power Assisted Operations

Yachts racing under the CSA Multihull Rule may use power assisted winches and may use power activated auto steering systems, if they wish. This changes ISAF RRS 52.

    1. Owner – Measurer Responsibilities

      1. The OWNER shall be responsible for presenting his yacht for measurement as specified in 3.13 and in a location (Note – a location at a dock is normally preferable) where the water is sufficiently calm to ensure an accurate measurement. The Owner (or his agent) must be in attendance to assist as necessary. The Owner must ensure that there is a suitable dinghy available. The Owner must make available all sails requiring measurement – or provide appropriate certified data for these sails (from a reputable sailmaker or another internationally recognized certificate).

      2. The MEASURER shall ensure the yacht is in a proper condition for measurement as specified below. The yacht is to be measured Empty so the Measurer shall personally check the whole boat from stem to stern including sounding all tanks and bilges to ensure the conditions for Empty are adhered to. Shortcomings shall be brought to the attention of the owner who shall remove, relocate, or fix all items as required by the Measurer in accordance with Rule 3.13.

    2. Preparation of a Yacht for Measurement

      1. Measuring Trim - A yacht will be presented for measuring in an empty state as follows:

        All items needed for racing may be left on board, including racing sails, sheets and halyards and racing anchor. In addition, all normal furnishings may be left in place, including drawers, doors, tables, cabin soles and bunk mattresses.

        All other items such as food, drinks, stores, tools, safety equipment, additional lines and personal belongings must be removed and all bilges must be empty.

        All tanks will be empty, except for the fuel tank, which may contain a measured amount of fuel.

        The underwater surfaces must be clean and free of marine growth.

      2. Information - The following information must be readily available for the Measurer:

Owner’s Name and Address

Owner’s (or ship’s) Email address

Captain’s Email address

Sail Numbers

Design Class or Type

Year of First Launch

Maximum Draft – from ship’s plans or other recognized data sheet

Minimum Draft – for yacht equipped with daggerboards

Accurate drawings showing underwater profile of yacht and any foils that may be present.

Propeller / drive – number and type

Copies of any existing rating certificates, from any recognized rating authority, including the CSA.

      1. Measurement Location - To ensure accuracy of measurement, yachts shall move into a sheltered location as designated by the Measurer with minimal wind and water disturbance (and a clear space all around the yacht of 1.5m.

      2. Representative in attendance - The Owner, Captain, or their representative shall be in attendance to give assistance as needed.

      3. Dinghy Required - The Owner, Captain or their representative shall provide a small tender or dinghy for the Measurer to take the Freeboard and Overhang measurements.

      4. Mainsail and mizzen measurement - the owner must have available the main and mizzen sails that he intends to use for racing.

      5. Headsail Measurements - the Owner must have available the largest area headsail he proposes to use for racing. He must be aware that he cannot race with a larger headsail than that declared. If he has stamped and signed sails from a previous measurement these markings must be available for scrutiny.

      6. Spinnaker Measurements – the Owner must have available all spinnakers and screachers that he intends to use for racing.

      7. Sail Measurements – sails will be measured in accordance with the current measurer's guidelines. If a measurement certificate from a recogised sail loft or other institution exists, these measurements may be used in place of physical measurements where applicable.

      8. Displacement certificate – the owner must provide a recent weight certificate for his yacht. The certificate must be prepared from measurements taken from a direct single point load cell or from multiple load cells on a travel lift that have been calibrated to eliminate the horizontal load component. The yacht must be weighed in measuring trim.

      9. Production Displacement – in some cases, where it is impractical to weigh the yacht, a specified displacement from the manufacturer may be allowed in place of the measured displacement. The lightest published displacement for the particular model will be used.

      10. Measurement Definitions – Measurements defined as follows will be taken in order to calculate a particular yacht’s rating:


        1. DM Measured displacement of boat

        2. DD Declared displacement of boat


        3. LOA Length overall

        4. FOH Forward overhang – 0 for plumb or reverse bow

        5. FF Forward freeboard – enter 1 for plumb or reverse bow

        6. AOH Aft overhang – 0 unless aft most point occurs more than 2% of LOA above waterline

        7. AF Aft freeboard – enter 1 unless aft most point occurs more than 2% of LOA above waterline

        8. DS Distance between stems

        9. UF Propeller correction factor - none = 1, One fold = 0.98, One fixed = 0.97, Two Fold = 0.975, Two fixed = 0.964

        10. V Draft to underside of hull or fixed keel if present

        11. TH Hull type – Catamaran = C, Trimaran = T

          Daggerboards and Foils

        12. TB Board type – None=N, Standard=S, Asymmetric=A, C-Board=C, L or T-Board=L

        13. BV1, 2, 3, 4 Board /Foil 1, 2, 3, 4 maximum exposed vertical length

        14. BH1, 2, 3, 4 Board /Foil 1, 2, 3, 4 maximum exposed horizontal length

        15. BC1, 2, 3, 4 Board/Foil 1, 2, 3, 4 maximum cord


        16. PCR Mast control – Rotating = R, Fixed = F

        17. PCC Mast control – Canting = C, fixed = F

        18. MPC Circumference of rotating mast

        19. ZPC Circumference of rotating mizzen mast


        20. MPU Vertical distance between the top of the mainsail hoist and the clew

        21. MPL +/- Vertical distance of mainsail clew above or below tack

        22. ME Maximum outhaul distance perpendicular to mast

        23. MGT Top width

        24. MGU ¾ width

        25. MGM ½ width

        26. MGL ¼ width

        27. MAD Mainsail declared area (for info only, not to be used in rating calculation)

          Mizzen / 2nd main

        28. ZPU Mizzen hoist

        29. ZPL +/- Vertical distance of mizzen clew below or above tack

        30. ZE Maximum outhaul distance perpendicular to mast

        31. ZGT Top width

        32. ZGU ¾ width

        33. ZGM ½ width

        34. ZGL ¼ width

        35. ZAD Mizzen declared area (for info only, not to be used in rating calculation)

          Headsail (Most forward sail flown from a fixed stay)

        36. I Forestay height

        37. J Foretriangle base

        38. JL Headsail luff length

        39. JH Top width

        40. JGT 7/8 width

        41. JHU ¾ width

        42. JGM ½ width

        43. JHL ¼ width

        44. LPG Perpendicular distance from clew to luff

        45. HAD Declared headsail area (for info only, not to be used in rating calculation)


        46. SLU Length of spinnaker luff

        47. SLE Length of spinnaker leach

        48. SF Length of spinnaker foot

        49. SMG Distance between mid points of spinnaker luff and leach

        50. SAD Declared spinnaker area (for info only, not to be used in rating calculation)


        51. CLU Length of screacher luff

        52. CLE Length of screacher leach

        53. CF Length of screacher foot

        54. CMG Distance between mid points of screacher luff and leach

        55. CAD Declared screacher area (for info only, not to be used in rating calculation)