Use Of Portsmouth Yardstick Handicapping System
It must be emphasized that the Portsmouth Numbers System is based on the premise that all classes are rated equally, and that it is the ability of the skipper and crew that determines a boat's standing in a race. Race committees should require all participants to race under their one-design class rules or modify the ratings where deviations exist. When no class rules or class organization exists, race committees should establish that a particular entrant claiming a Portsmouth Number in the Tables conforms to descriptions as outlined in the Yardstick before racing begins.
Special Note to Race Committees: When the Notice of Race or Sailing Instructions specify the US SAILING Portsmouth Yardstick for scoring, a boat's D-PN constitutes a rating certificate, and owners and/or skippers are subject to the requirements of ISAF RRS 78 – Compliance with Class Rules; Certificates.
A. Portsmouth Yardstick Tables
1) Description of the Tables
The tables are divided into five types of classes – Centerboard, Sailboard, Multihull, Keelboat and Offshore. The tables consist of Class Identification, US SAILING Code, Basic Portsmouth Number
(D-PN), and Wind Velocity Handicap Factors (HC) for the BN ranges 0-1, 2-3, 4 and 5-9.
Parentheses "( )" around numbers indicate numbers based on a limited amount of race data (5 to 15 data points) and are suspect. Brackets "[ ]" around numbers indicate numbers based on estimates from less than 5 data points or calculated from other rating systems formulae. Bracketed numbers are highly suspect and individual clubs are urged to verify and modify them with their own race data (methods given in Section III C).
Brackets are converted to parentheses when the number of race data points available reaches 5 and parentheses are removed when the number of data points reaches 15.
Where Wind Velocity Handicap Factors are not listed, D-PN may be used or, preferably, a number calculated by methods described in Section III B.
The class listings refer to boats that are rigged and sailed according to their one-design class rules or organizations or, when rules or class organization do not exist, carry a racing complement of sails and gear. For classes with optional rigs, sails and equipment, the class listing normally refers to a primary version described below.
Sloop rig (over cat rig, yawl, tall mast, etc.);
Centerboard classes with jib, genoa and spinnaker, as allowed by one-design class rules;
Keelboats (over their centerboard counterparts);
Offshore classes with lightweight engines and folding or feathering props, 2-blade solid prop in aperture, or retractable outboard motor. When separate listings for a variation do not appear in the Tables, a D-PN or HC may be determined using appropriate modification factors (see Table VI).
Refer to factory literature to determine if certain classes of boats are standard from the factory with heavy inboard engines and folding or feathering props. Skippers requesting these allowances should supply factory literature showing such engines and props are supplied as standard from the factory.
2) Handicapping Methods
The Yardstick values listed in the Tables serve as handicaps when used in the handicapping system
defined by: CT = ET / HC X F
where CT = corrected time;
ET = elapsed time;
HC = D-PN, Wind Velocity Handicap Factor, or allowance modified HC;
F = 100
The Portsmouth Yardstick and Handicapping System is intended to include the use of Wind Velocity Handicaps. Allowance Modification Factors are always optional. Also, clubs may simplify the system according to their needs but should be aware that inequities can result.
The method of handicapping should be decided upon before the beginning of the racing season, series, regatta or individual race. Likewise, each participant should know his/her handicap before racing. Yacht/sailing clubs employing modified handicapping methods should so state in the Notice of Race or Sailing Instructions. Potentials and limitations of the various handicapping methods are:
D-PN only: Works well for classes with similar characteristics and rig (catamarans without trapeze, displacement hulls, etc.) where wind velocity is not a factor. D-PN may be used to separate handicap classes into fleets or to establish fleets for level class racing. Race committees faced with a large entry in mixed fleet racing on water where marked changes in wind conditions are common may find D-PN the preferred method for handicapping.
D-PN plus Wind Velocity Handicap Factors: Use of Wind Velocity Handicap Factors allows encompassing a wider variety of class characteristics and rig (catamarans with or without trapeze, planing centerboards with or without trapeze, planing and displacement hulls plus mixed fleets of these types of craft).
D-PN with or without Wind Velocity Handicap Factors plus Genoa Allowance Modification Factors: As the size of the genoa has the greater influence on performance, use of genoa modification factor alone may be desirable. Genoa modification should be made for centerboard classes when non-class genoas are substituted for class approved jibs.
D-PN with or without Wind Velocity Handicaps plus specified allowance modifications: Clubs may decide on specific allowances (restricted use of spinnakers or trapeze) to insure uniformity within a class. A single D-PN could then suffice for a class allowing use of optional equipment.
3) Determination of Handicaps for Classes Not Listed in the Tables
Methods for determining D-PN and Wind Velocity Handicaps are given in Section III. These should be determined before racing begins.
B. Beaufort Numbers
Beaufort Numbers (BNs) are used to characterize weather conditions. The appropriate BN must be assessed by the Race Committee based on average conditions during each race. Determinations of average wind velocity is the sole responsibility of the Race Committee whose decision is final.
Wind velocity should be determined near water level. The committee boat generally serves as the location for determination of wind velocity. If so used, care should be taken in observing that local wind strength approximates that of the race course. If the wind/wave height table (Table I) is utilized, the Race Committee should observe sea conditions at the start, during and at the finish of each race and determine an average BN for that race.
Other suitable methods for obtaining an average wind velocity are authorized at the discretion of the individual clubs and their race committees. If high masthead anemometers are used, readings should be corrected to near water level velocities. After determination of an average BN, the BN range is determined by rounding off the average to the nearest whole number.
We currently group:
BN 0-1 to represent drifting conditions,
BN 2-3 to represent light conditions,
BN 4 to represent fresh, and
BN 5-9 to represent strong conditions.
C. CALCULATION OF RACE RESULTS
Pre-race preparation by race committees for handicap racing is required in order to expedite scoring. Handicaps should be extracted from the Tables and listed on race handicapping sheets containing the following items: date, event, race number, course, race committee personnel, BNs, classes or class description, starting times and identity of each starting fleet and finishing times. Elapsed times (ET), handicaps (HC), corrected times (CT), and finish positions may be included. Examples of such race handicapping forms are shown in Figures II and III.
Corrected time is calculated from the equation: CT = ET / HC X F
Finish position is determined by lowest CT = 1st, etc.