Newport-Bermuda 2008

Routing for the Newport-Bermuda Race always is a balance between optimal wind and optimal current in the Gulf Stream. In 2008, these factors combined to give the larger (faster) boats a choice of two options: (1) taking advantage of the south-flowing eastern edge of a warm eddy, north of the main Gulf Stream and west of the rhumbline, or (2) sailing the rhumbline to minimize distance sailed. For the larger boats it was a close call, but for the smaller the first option was clearly the best. The routing solution below (using our Advantage Racing Software) for Aurora, a Tartan 41, shows a substantial preference for option 1 (red optimal route), which is some 2 hours minutes faster than the comparison black route near the rhumbline.

CONGRATULATIONS TO AURORA ... rated the second-slowest boat in Class 2, which arrived ahead of all but one boat in the class, finishing first in SDL-2 and 5th overall in the race (see routing details below).

The graphic below shows more detail of the routing in the vicinity of the warm eddy and main Gulf Stream (the blue streamers show the Gulf Stream current predicted by "Local Knowledge" and used by Aurora and many others in this race). The black dots on each colored route show predicted boat position at the time shown in the "Best Course" box (in this case, 2104 on 6/21), and the right-hand "DTG" column shows distance to the finish from each black dot. At this point, although the red route utilizes the warm (clockwise) eddy for more speed, a boat on this route is still some 18 miles further from the finish than the more central (black and blue) comparison routes. As shown below, the advantage of this route is not the warm eddy per se, but the fact that this compensates for the extra distance sailed to the west, where the boat will pick up the strongest wind and best angle to sail to Bermuda.

Further down, after crossing the main Gulf Stream, a boat on the optimal red route benefits from a SW flow of current along the eastern edge of a cold eddy, and is now just 6 nm behind (in DTG) a boat sailing the black (rhumbline) route.

The graphic below shows the same intermediate timepoint as the one above, but this time it displays the wind distribution (black vectors, ranging to 20 knots). Compared to boats further east (black dots), the boat on the red optimal route is closer to windward, and has a better angle and stronger windspeed to sail to the finish in Bermuda. Although only some 6 miles closer at this point, the red boat is predicted to arrive at the finish 2 full hours before the black (rhumbline) boat. Compared to the faster boats (see link below), the benefits of the westerly route are enhanced for the smaller boats because they arrive at this point later, at a time when the stronger winds are filling in nicely from the west. In our analysis for the faster boats (with Blue Yankee polars), the wind at this point ranged only to about 12 knots.

The benefits of routing software! Aurora, a Tartan 41, was rated second-slowest in the 16 boat SDL-2 class, but found the right route to finish before all but one boat in her class (and corrected almost 2 hours ahead). The graphic below shows Aurora's actual reported track to Bermuda (black line), compared to her routing solution at the start (blue line) and a recomputed solution midway (green line). The difference between the initial and recomputed routes in the final part of the race illustrate the importance of getting updated wind forecasts during the race. These are now permitted from public sources, and enable racers to correct for changes in the forecast while underway. While the Gulf Stream current is pretty stable, winds are often difficult to predict for the full time period of this race. This is just one more reason why it is important to recompute routing solutions as you go, from actual boat position and with the latest wind forecast.