Quick analysis 24uurs zeilrace

In the weekend of the third week of August traditionally the 24 hours sailing race is held in the Netherlands.  This year for the 45th time.

We participated this race this year for the first time with a crew of 6 and a X-372. Four experienced with sailing races (steering, main sail, foresail and tactics) and 2 (including me) for their positive influence on the overall team efforts (sandwiches, enjoying the sun, the insights of a toursailor on racing and some tweets off course) and I think mainly responsible for the good results.

The rules of the race are quite simple. Just sail as much miles as possible within 24 hours. The winner is the one which has sailed most miles compared to his theoretical distance based on the length of his ship. For the race only a certain amount of tracks are allowed (see picture), which makes it a more strategic game as you have to think about the wind shifts of the next (up to 24) hours and where to go.

We raced the tour-classwith around 500 boats participating and we finished 11th.  We sailed officially 149.67 nautical miles in total, which sums up to an average speed of 6.24 knots in 24 hours.

And off course the route has been deeply analyzed…


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Click here for a full screen view

1) GPS Visualizer

Above the analysis of the GPS data based on the online tool supplied by GPS Visualizer.com. The output of this and the different bouys I combined in Google Earth.

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In this map you see the bouys we have rounded, the ideal tracks and the actually sailed route. The pixel-color of the route tells the actual speed off that moment, see for an explanation the legend.

2) Ocean Pilot

I have further analyzed the GPS data using the online GPS analyzer called OceanPilot.com and it showed we had sailed in total 313.9 miles (which makes me think you have to divide it by 2) and an average speed of knots.  The only thing is that the heist of changing sails sometimes killed the GPS (in total about 1 hour of which about 40 minutes in the lock) so the data is just not 100% reliable. Furthermore the GPS log started earlier then the race itself. In total it has logged 156.95 nM and a top speed of 9.2 knots.

Track Speed Polar Speed VMG

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3) Good Old Excel

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Not being completely happy with the different analyses above, I could just not withstand the temptation to build my own Excel model. As a starting point I used the explanation and the geometric formula’s kindly provided by Chip Pearson (website) and the finetuning of the formula as provided by BlueMM (website).

The analysis showed that the average speed (over ground) was 6.42 knots (median of 6.61 knots) with a maximum of 9.18 knots. The speed or distance sailed (no currents on the IJsselmeer) during the race is presenterd in the graph above.

Some remarks are in place. Around 2 AM (the 8th hour) we crossed the lock of Enkhuizen and you can notice the drop in distance sailed. Furthermore around this time the GPS got hit by something, crashed and for 38 minutes it was out of order. Furthermore, we finished at 19:15:43 hours so the 25th hour consists of 15 minutes sailing time. My estimate is that compared to the official distance of 149.7 nMiles, we have sailed 160 nMiles actually. And finally, just for the statistics, I had in total 2,935 measurements with an average timespan of 29.76 seconds and for the Excel techies, the formula I used:

=ACOS(COS(RADIANS(90-lat1)) *COS(RADIANS(90-lat2)) +SIN(RADIANS(90-lat1))
*SIN(RADIANS(90-lat2)) *COS(RADIANS(long1-long2))) *3440,065

4) Final Thoughts

  • If you sail 24 hours in a race, it is most likely that you sail almost the same as touring a week in Croatia / Adriatica.
  • If you would have  sailed only the IJsselmeer, you could tweet everywhere during the race. Most likely the same accounts for the Waddenzee.
  • Sleeping is overrated when sailing, sun is not.
  • I am not convinced by the value added of such a deep analyses of GPS data but at least it does provide a lot of numbers, graphs and (interactive) figures.

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