Updated 8-13-09

Compilation of North American Portsmouth Numbers
and
Wind Dependent Handicap Factors

Copyright © 2008 by N. E. Richards and J. F. Spinnler
Reprint permission by the authors is required for material in the Portsmouth Yardstick
Please contact hobockd@aol.com for permission

A Service for Sailors
with online access provided by
United States Sailing Association

INDEX FOR 2008 PORTSMOUTH YARDSTICK 
 

The 2008 North American Portsmouth Yardstick for centerboard boats, multihulls, keelboats and offshore classes are posted herein. The Yardstick is a widely used method of rating boats of different classes sailing the same courses and is used by clubs and fleets across the country. It is a time-on-time handicapping system and is derived from actual records of classes of boats with thoroughly documented ratings. Portsmouth Numbers are defined as the length of time boats would take to sail a common but unspecified distance. The formula is easy to use:
                         CT (Corrected Time) = ET (Elapsed Time) X 100 / HC (Handicap)

Annual changes in ratings are modest. The elapsed time for each boat in a race is measured against the primary and secondary yardstick classes in the race and a handicap calculated for each boat. These are stored in the database by Beaufort number. When there are new data, the previous ratings are adjusted by 25% of the difference between the old ratings and new history.

Assumptions made in generating Portsmouth Yardsticks (D-PN) include:

• That each boat placing first in each class was sailed to its true potential by a perfect crew according to flawless strategy;

• That all boats sailed the same course, experienced the same wind/water conditions and degree of interference of clear air;

• That all one-design boats conform to class specifications and rules, and use sails specified by the class; and

• That boats with multiple sail inventories (genoas, spinnakers, etc.) utilize the proper sails for the wind conditions and legs of the course. 

Clubs are invited to supply their race results annually via mail to US SAILING, Attn. Portsmouth Committee, P O Box 1260, Portsmouth, RI 02871, or via email to Darline Hobock. Race information required: Class Code, Average Wind Speed, Elapsed times and Corrected Times. Various reporting formats are usable including Excel, Word, HTML, text, Sailwave and other popular scoring programs. Please share your club or fleet's race results to improve the validity of the Yardstick. We are grateful to the many clubs who continue to support this Service to Sailors and to US SAILING for providing online access for its publication.

Thank you for your interest in and use of the North American Portsmouth Yardstick.

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