J24 Nationals 2001

If you will be competing in the 2001 J24 Nationals in San Francisco, you will need a good knowledge of local currents to be competitive. During the period 8/9 - 8/12 the ebb and flood will exceed 3 knots in the central Bay. While not as strong, current in the TI race venue varies dramatically in direction from one side of the course to the other, leading to differential currents of up to 1.5 knots. This can dramatically affect the position of laylines and overall strategy. The graphic below shows currents north of Treasure Island at 1330 hours on the afternoon of 8/9, an hour before max flood. The solid blue lines are the laylines in the absence of current at upwind mark "61", assuming a typical wind of 12 knots at 250 deg T. Due to the strong and variable current, the actual laylines are shown by the magenta dots (if you sail at the optimal tacking angle and make the target speed, you will sail this corrected, curved, course to the mark). The "best tack" tactical solution shows that, even for this short leg (about 25 minutes to the mark) a port tack to the upper layline, followed by an approach along it, is almost 2 MINUTES faster than an approach via the starboard tack to the lower layline.

This graphic and tactical results are based on the PC program we have developed and refined for San Francisco Bay over the past few years, which has become a standard tool for most of the top Bay racers. This computes currents at any day and time, and at every point on the Bay (the current points shown in yellow are added to the chart at the user's option; you can add as many as you like, anywhere you like, to provide more detail in the racing venue). This is the only program which can do this, and the only one which can be calibrated to actual sensor data from the real-time NOAA sensors. Our standard "Force Two" program for the PC is just $175.00, is self-contained with charts, and provides a broad spectrum of current prediction and display features, boat simulation functions, layline calculations and our utility to quickly build and solve courses for current-corrected headings, times, etc.; plus you can hook live to a GPS. You can plan ahead by setting the display for any day and time of the year, and make printouts to take along on the boat.

For details on our programs, check the information on this website; to order, go to ORDER FORM. Or call us at 415-332-8507. We have a range of tactical programs for all racers.

AND, if you are sailing elsewhere, check out our editions for Long Island Sound, Block Island Sound, Narragansett Bay, the Chesapeake, Puget Sound, Tampa Bay, Auckland, the San Juan's, English Chanel, etc. We are rapidly expanding our inventory of current models, and also provide short-term ocean models for the Gulf Stream.