US SAILING

Portsmouth Yardstick Text - Section V



PORTSMOUTH YARDSTICK
 Section V
MODIFICATION FACTORS AND CODING SYSTEM
FOR DEVIATORS FROM NORMAL CLASS RACING DESIGN

1) Introduction

All boats proposing to compete on a handicap basis should be encouraged to carry the full complement of sails permitted by class rules, or, where such rules do not exist, a racing complement of sails (genoas, spin­nakers, traps, etc.). Such racing equipped boats are the primary versions of classes as defined in Section II A. The PN Committee recognizes that this is an ideal situa­tion and that individuals do not always race in properly outfitted boats due to cost, desire to experi­ment, lack of crew, etc. Multiplicity in design and rigs contributes to the problem.

A system of allowances modifying the D-PN and HC has been devised, along with a coding system, so that these boats may be handicapped equitably. It is hoped that the system will contribute to the encouragement of race participation, especially in small club fleets where each boat may be one-of-a-kind. Also, it should aid clubs in reporting their handicap data to US SAILING where proper identification of boats with deviations is of prime importance.

As stated previously, these modifications, or others, are at the discretion of individual clubs. Each club should decide either before each race, or before the racing season begins, whether modifications are desired and which ones will be used.

Modification factors have been derived from rating formulae rather than from race data. If a sufficient number of clubs continue to partici­pate and supply the required data in proper form (coded), empirical numbers may be derived in the future.

2)  Coding System for Portsmouth Classes

The coding system for the Yardstick classes allows the Portsmouth Numbers Committee to keep track of data for classes deviating from normal class racing design, class model changes, lack of crew, etc.

This subsection is intended for those clubs interested in supporting the development of allowance modification factors from race data.

Details of the coding system:
It is based on an eight character alpha-numeric field;
Offshore classes, with a few exceptions, and some classes in the other class groups, are identified by three alpha characters followed by two numeric characters for length. Remaining classes are identified by two to six alpha-numeric characters;
The remaining two characters of the eight character field are used to designate variations in class design and sail plan;
Meter classes normally will have three numeric characters following the alpha characters;
Level rating classes will have a special field of three alpha with three numeric codes;
Certain class variations (Mk #, masthead rig, tall mast, yawl, ketch, etc.) require separate listings in the Yardstick Tables.
Numbers located in character #6 normally designates these;
A number in character #7 designates crew, engine, and propeller allowances;
Genoa allowance is designated by the letter "G" in character #7 or #8 (genoa of undetermined size for centerboard classes) or by a number located in character #8 (% overlap known for keelboat and offshore classes). The letter "J" is used in special circumstances when allowance for use of jib only is claimed;
Other class variations (trapeze, spinnaker, etc.) are designated by letter codes interspersed among numbers as required in characters #7 or #8.
3)  Examples of classes with variations coded under the Portsmouth Number Coding System:
    US SAILING Code
Class

Variation 1

 1 2 3 4 5 6 7 8
Fox Cat rig F O X     C    
Sunfish One crew with wt. over 225 lbs. S F         3  
Sidewinder Cat rig, 2 crew with wt. over 225 lbs. S W N D   C 3  
Morgan 28 Light engine, folding prop, 180% genoa M O R 2 8     1
Morgan 28 Heavy engine, 3 blade prop, 155% genoa M O R 2 8   8 2
Morgan 28 Mk III, heavy engine, 3 blade prop, 133% genoa, tall rig M O R 2 8 M 8 3
Ranger 23 Retractable outboard motor R N G 2 3      
Ranger 23 1/4 ton 2 R N G 1 / 4    
Ranger 23 1/4 ton, Mk II 2 R N G 1 - 4    
Ranger 35 1 ton R N G 1 / 1    
Ranger 35 2 ton R N G 2 / 1    
San Juan 7.7   S J - 7 . 7    
Thistle Single handed, no spin (hypothetically) 1 T H         * 0
                   
1 Class rules prevail                
2 Will require separate listing in Portsmouth Yardstick Tables                

4)  Alpha-Numeric Codes
Letter codes for variations that require separate listings in the Portsmouth Yardstick Tables should generally be placed in character location #6 of the eight character field. Any class requiring one of these letter codes will require a separate listing in the Tables. The code becomes a fixed code associated with that class only.

In the Tables, primary versions of classes having variations for these separate listings are considered to be sloop rigs and keelboat versions. When the primary version is described as one of these variations, the let­ter codes are not used. Example: Butterfly is a cat rig and code is BUT. Freedom 21 Deep Keel is both sloop and cat rigged and codes are FDM21 and FDM21C, respectively.

A = Gaff rig
M = Masthead rig
B = Centerboard version of keelboat N = Wing keel
C = Cat rig R = Cutter
E = Keel-centerboard version U = Unirig
F = Fin keelboat version W = Swing or retractable keel version
H = High or tall rig X = Special, unique or custom design
K = Ketch Y = Yawl
L = Keelboat version where standard is another type (i.e., shoal draft)

Alpha-numeric codes for variations for which modification factors are employed (sails, crew, propeller, and weight allowances) are interspersed in character locations #7 or #8 of the eight character field, if needed.

5)  Application of Modification Factors
Table VI contains a list of deviations for which allowances may be made, plus modification factors for D-PN and HC as a function of BN Range. Allowances may either increase or decrease these basic numbers. The modification factors (MF) are multipliers. Modified D-PN or HC are found by multiplying the D-PN or HC by the appropriate MFs from the Table.

Modification formulae:    
      D-PN modified = (D-PN)(MF) 
If two or more modifications are desired,
D-PN modified is given by:
      D-PN modified = (D-PN)(MF)1(MF)2

Similarly, wind handicap factors (HC) may be modified.