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2001 Fastnet Race  - August 12 -   Cowes, GB
Congratulations to:  Force 4 User

Morning Glory (2nd to Rock, 3rd overall)  IRC Class Overall

This year there were essentially two different races: one out to the Rock in strong winds, mostly on the beam, and back, in dying winds which made it very tough on the smaller boats who got to the Rock late ...

Going out, MG took 33.5 hours and corrected to 2nd behind Loco, which reached the Rock some 5.5 hours later. Coming back in decreasing wind, MG took 29 hours to cover the considerably shorter distance to Plymouth, and corrected to third behind Tonnerre de Breskens (almost a day behind), and Zaraffa (6 hours behind), taking second to Zaraffa in IRC Super Zero.
This year the Fastnet race will begin at Cowes at 1600 hrs on August 12, to the Fastnet Rock off the south coast of Ireland, and back to a finish at Plymouth, a distance of 608 miles. Over the several days of the race, there is likely to be significant variation in the wind experienced by a boat at any given location, and obviously there will be many tidal cycles. Our "Local Knowledge" current model of the Solent and English Channel (extending all the way to the Fastnet Rock) provides a very accurate prediction of currents during the race, and at least twice the resolution of any other source. Our routing software applies the current model, factors in wind prediction files and the boat's performance characteristics (polars) to find the fastest possible route. It also produces several alternative routes for comparison and enables modification of wind files enroute if actual conditions experienced differ from the prerace forecast.

The examples below illustrate routing computations, wind and current for the Fastnet route had it been started in midday on April 20, 2001. At this time there was a very substantial change in wind along the outgoing route alone (to the Fastnet), and the router had to find the best overall strategy to cope with this.

 

Sample routing computation West Cowes to Needles (assuming wind of 10 knots from 250T deg) just after low water at Portsmouth. The "red" route is the fastest, and hugs the Cowes coastline to avoid the early flood. This optimal route is some 4 minutes quicker (out of 78 minutes) than the "yellow" route along the opposite shore, but just a minute quicker than the "blue" route which stays out of the shallows. All computations below are for Volvo 60 polars, and current effects will be greater for a slower boat.
wpe1E.gif (65087 bytes)

 

Routing solution from south of Needles to the Fastnet Rock, beginning on 4/20 at 1400 hours. The black wind vectors are computed from a public-access grib file and show the original wind from slightly west of north. The blue streamers show current (current flows away from circle in direction of blue line), and indicate an ebb at the start of the route. With current from behind and wind on the beam, the original part of the route is pretty much the rhumbline. The zigs and zags further along reflect changes in wind and current (see below).
wpe13.gif (57570 bytes)

 

Further along the same route (4/20 at 2000 hrs), the boat has reached the position shown by the magenta circle. Note that wind near the Fastnet Rock has backed to the northwest, and currents back at the start are now at flood.
temp.bmp (828718 bytes)

 

Still further along the route (4/21 at 0400 hrs), the wind approaching the Fastnet Rock is now slightly north of due west, and the boat has deviated from the rhumbline to head almost due west. The reason for this is not evident at this time, but becomes apparent in the next figure.
temp2.bmp (828718 bytes)

 

The boat is now approaching the Fastnet Rock from the SE on 4/21 at 1200 hrs. At this point the wind has lightened considerably to the north of the route, which was anticipated by the router and occasioned the earlier move to the west.
temp3.bmp (828718 bytes)

 

The router is used most effectively by recalculating the optimal route as the race progresses, and by computing alternative routes for comparison. The solution below is computed from a point west of Land's End, and shows boat positions (black dots) on 4/21 at 0851. The "red" route is the quickest. The other routes are constrained to different sectors for the first half of the distance, and are optimal thereafter (e.g.,the "yellow" route is initially restricted to the far right of the course). Times for each route are shown in the box, and are color-coded to match the route. There is relatively little difference in the southerly routes, in which increased windspeed compensates for extra distance, but sharply slower times to the north. Distances from boat position to the mark (Fastnet Rock) are shown in the last column.
wpe1C.gif (56771 bytes)

 

Same calculation with boat positions (black dots) on 4/21 at 1149 hrs.
wpe1D.gif (58848 bytes)

 

If you will be sailing in the Fastnet 2001 or the Jubilee (or anywhere in the Solent or English Channel), our LK current modules and programs can greatly assist your tactical planning. We have programs at different levels, and can also provide current modules and interpretive software (a "DLL") to augment third-party tactical programs and enable them to read our current values.

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