Analysis of 2008 Newport to Bermuda Race
Part One: Big Boat Analysis and Overview
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. The routing solution below for Blue Yankee (with our Advantage Racing Software) shows a slight preference for option 1 (red optimal route), which is some 17 minutes faster than the black route near the rhumbline (a small difference out of 64+ hours for either route). One unique feature of Advantage is that it simultaneously computes comparison routes (with times color-coded in the "Best Course Comparisons" box below). In situations such as this, it can be very helpful to know that a "non-optimal" route is almost as fast, especially when there may be other reasons to prefer it besides estimated time. All other software only computes the "optimal" route.
The graphic below shows more detail of the above solution 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 Blue Yankee 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, 1157 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 10 miles further from the finish than the more central (black and blue) comparison routes.
So why is the red route predicted to be slightly faster? The graphic below shows predicted wind (black vectors ranging to 12 knots) at the same time as the graphic above. The wind is coming from slightly east of south, which means that a boat on the red route has a better angle to sail than a boat on the black route. In part of the remaining distance to the finish, a boat on the red route may be able to sail on a reach while a boat on the black route has to tack. And, although the "red" boat is somewhat further away (graphic above), it is further south and hence its distance to windward is less than the "black" boat. The only problem is that the primary advantage of the red route depends on the details of the wind pattern 48 hours into the race, something which is often not easy to predict with great accuracy. Rather than depend on this to get a modest (17 minute) advantage, the more prudent choice is a route near the rhumbline. Most big boats made this choice. In contrast, for the smaller boats, the westerly course was much preferred and an easy choice (use link below for analysis).
Further down, a boat on the black (rhumbline) route is able to take advantage of the western edge of a cold eddy for a bit more speed. At this point, a boat on the red route is still some 8 miles further away from the finish. The reason why it is faster appears below.
Another Advantage feature reports the maximum and minimum wind predicted on the optimal and comparison routes (click T/W button to toggle to this view). In this case the minimum wind on the red route is 7.3 knots and max is 16.2. Generally, minimum wind of 4 knots or less may take the boat close to a "hole," and make the route more sensitive to the accuracy of the forecast. In this case it looks OK.