J105 North American's

If you will be competing in the 1999 North American's in San Francisco, you will need a good knowledge of local currents to be competitive. During the period 8/13 - 8/15 the flood will range to 4.1 knots in the central Bay. This can dramatically affect the position of laylines, course selection and overall strategy. The graphic below shows max flood on 8/13 (approx 1248 pm). The solid blue lines are the laylines in the absence of current at the mark labelled "9," assuming a typical wind of 18 knots at 250 deg T and J105 polars. 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 a starboard tack to the lower layline, followed by an approach along it, is 4.5 MINUTES faster than the port tack to the upper 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, including the top of the local J105 fleet. 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 is just $169.95, and the advanced tactical "Force Three" program is $1,500. With Force Two you get all the 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. Force Three adds a long list of tactical computations, such as the "best tack" feature shown in the graphic and a complete "best course" routing function, plus it reads and interprets all boat instrument data and boat polars.

For details on our programs, see the information on this site; to order, go to http://www.goflow.com/order.htm.

Note: if you are sailing elsewhere, check out our editions for Long Island Sound, Narragansett Bay, the Chesapeake, Puget Sound, the San Juan's, etc. We are rapidly expanding our inventory of current models, the latest being a custom model for Cowes Race Week and the Fastnet for Ted Turner, Gary Jobson and Larry Ellison to use on Sayonara.