Stamford - Vineyard Race 2000 (Sept. 1 -3) 
| We build detailed models to predict
currents in race venues worldwide. Our PC programs enable you to study current in advance
and plan race strategy. This year we expanded our coverage of east coast waters to include
special workups of the Gulf Stream - digital current prediction models at a new level of
detail and accuracy which our tactical programs utilize for best-course routing. (For
details on use in the recent Bermuda Race, see www.goflow.com/bermuda.htm). Last year we introduced our tidal-current models of Long Island Sound a month or so prior to the 1999 Stamford-Vineyard Race, and our programs were used by several boats in that race, including the winner, Lora Ann. Racers experienced light winds, which emphasized the importance of good current information, and also the need for more accurate and detailed wind forecasting. For this year's race, our tactical "Force 3" program will include a FREE wind forecast model to use in routing computations. If you are computer-phobic or short-handed, we can locate a navigator for you to operate the program. Our users in LI Sound are very enthusiastic about the accuracy of our current predictions. Unlike every other program, we compute current point by point, not just at scattered NOAA sites, and our laylines, headings, routes, etc. take current into account moment by moment along each leg. Our "Force 2" entry-level program is just $175, including data for LI Sound (add $85 for BI to Nantucket, including Narragansett Bay and Buzzard's Bay). The examples below are taken from last year's Stamford-Vineyard Race, which began 15:00 on September 3, 1999. The graphic below shows current on the approach to
Orient Point at 10:00 p.m., 9/3, about 20 minutes after max ebb at The Race. The current
points shown in yellow are added at the user's option, at any location, to provide more
detail in the race venue. Currents of this magnitude can have a significant effect on the
position of laylines, course selection and race strategy. In the graphic, the solid blue
lines are the laylines in the absence of current at the mark labelled "OP,"
northwest of Orient Point, assuming wind of 10 knots from 225 degT. Due to the variable
current, the actual laylines are shown by the magenta dots (if you sail at the optimal
tacking angle on a jibe and make the target speed, you will sail this corrected, curved,
course to the mark). The "best tack" tactical solution shows that a port jibe to
the upper layline, followed by an approach along it, is 5.5 MINUTES faster than the
starboard jibe solution. |
 |
The graphics and tactical results on this page 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 chart. This is the only program which can do this, and the only one which can be calibrated to actual sensor data from real-time NOAA sensors. Our programs integrate the current model with a full range of navigational and tactical functions. There are many functions for strategic planning. We set up a
series of waypoints defining two alternative courses of equal length from Stamford to just
north of Orient Point, and "solved" these courses for current-corrected headings
and times for various wind assumptions. The "south" course runs closer to
the Long Island shore, passing north of Smithtown and Wading River, while the
"north" course passes south of Stratford and Bridgeport. For a start at 15:00 on
9/3, and assuming constant wind speed and direction over the course, the "south"
course was consistently favored for all wind assumptions, ranging from a difference of
only 6 minutes for wind from the due south, to a difference of 26 minutes for wind from
the SW (all wind speeds were taken to be 10 knots). At this hour, one might expect more
breeze along the southern route, so this should be an easy choice. [The results depend on
the day and time of the start, so in some scenarios, the northern route would be favored,
assuming equally good wind.] Speeds in the table below are the average speed on the
leg, based on wind angles and boat polars (we used J120 polars). |
| Optimum Course Computation for SV (South Course) Begin Time: 15:00 Wind: 10 from 225 ST
TO S1 at 7.61 knots: 9.5 nm 95 deg 1 hr, 22 min 16:21.9 Total Distance: 56.3 nm Total Time: 7 hr, 33 min Optimum Course Computation for SV (North Course) ST TO N1 at 6.5 knots: 7.7 nm 82 deg 1 hr, 18 min
16:18.1 Total Distance: 56.3 nm Total Time: 7 hr, 59 min |
| Our tactical program's "best
course" routing calculation goes even further. Given assumed (or instrument-measured)
wind speed and direction, and your boat polars, it searches all possible routes to find
the quickest, and plots alternatives for comparison. The graphic below shows routes from N
of Orient Pt enroute to N of Block Island, at 11:00 p.m. on 9/3, again assuming wind out
of the southwest at 10 knots. (Polars are J120's). The fastest course is always shown in
red, and comparison courses in other colors. The corresponding times are shown in the box
at the upper left. In this example the time differences range as high as 27 minutes, for a
leg which can take at little at 89 minutes. In this example, a route along the rhumbline
is favored (which would require jibing back and forth to stay along the red line), but
this is often not the case. Note that the router takes into account islands and other
obstacles, as shown by the yellow course. These calculations should be done live, on the
spot, as the results are highly dependent on exact time and location, and on wind
conditions. |
 |
| Our standard "Force Two" program is just
$175, 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" and "best course"
routing functions shown above, plus it reads and interprets wind files, all boat
instrument data and boat polars. We also have add-on current modules for Deckman and OS3. For details on our programs, see the details on this site; to order, go to http://www.goflow.com/order.htm. Or call us at 415-332-8507. NOTE: You can now purchase an effective, sunlight-readable PC repeater screen for the cockpit at a reasonable price. Ask about our "Tactical Racing Package" with OceanPC. We also provide program-certified navigators for major races. AND, if you are sailing elsewhere, check out our editions for San Francisco Bay, the Chesapeake, Puget Sound, the San Juan's, Tampa Bay, etc. For details on our offshore "Atlantic Packages," see www.goflow.com/atlantic.htm. |
