Compilation of North American Portsmouth Numbers and Wind Dependent Handicap Factors
A Service for Sailors with online access provided by US Sailing The North American Portsmouth Yardstick for centerboard boats, multihulls, keelboats and offshore classes are posted here. 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 derived from actual records boat classes 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 is 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 e-mail to PortsmouthNA@att.net or by mail to Carl Reigart, 962 Diane Street, Leeds, AL 35094, or via mail to US Sailing, Attn. Portsmouth Committee, P.O. Box 1260, Portsmouth, RI 02871. 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. Copyright © 2011 by N. E. Richards and J. F. Spinnler Reprint permission by the authors is required for material in the Portsmouth Yardstick Please contact the Portsmouth Numbers Committee at PortsmouthNA@att.net for permission.