When I left San Benedicto yesterday, I entered the coordinates of Hiva Oa into the chart plotter, the location in the Marquesas that I am sailing to. The question is, how do I measure my progress? There are basically four measurements:
1) The distance to the waypoint (Hiva Oa) as the crow flies (DWP), 2413 nm as of 9:00 yesterday.
2) The distance closer I am in a 24h period (DWP yesterday – DWP today). Since yesterday, I am 109 nm closer (i.e., the instrument now reads 2304).
3) The distance I sailed as the crow flies in the last 24h. Because of weather or strategic planning, I might not be sailing directly towards the Marquesas. In the last 24h, this distance is 110 nm.
4) The actual distance I sailed in the last 24h. I rarely sail in a straight line because the wind direction changes and the wind vane actually zigzags the boat. This is not a number that is easily arrived at, but was approximately 114 nm in the last 24h.
The second number effectively tells me how many days it will take to make the passage, assuming I make the same progress each day, which of course I won’t. 2304/109=21 days. Three weeks would be a good time for the passage.
The third number tells me what the average boat speed was over the 24h period. The “hull speed” of my boat is theoretically 7.5 kt. It rarely goes that fast. On occasion it will go faster if it is surfing on following waves. The reason the second and third number are the same is because in the last 24h I have in fact been (on average) steering a course towards the Marquesas. This will not always be the case.
The fourth number tells me something about the efficiency by which I am sailing. For example, how good I and/or the autopilot is keeping me on course. If you study the actual course I am taking, you will see it is more of a straight line during the parts of the day when I am awake and tending to the details of sailing. As a single-handed sailor, I can expect less efficiency than if other people were tending to the sailing when I was not. Basically, I sailed an extra 4 nm in the last 24h. Another way of thinking about this is I lost 45m. My actual average speed in the past 24h was 114/24=4.75 kt. Keep in mind there were periods during the last 24h where the winds were light and I could only make 2-3 kt speed, whereas other times I was close to hull speed. So, an average of 5 kt is pretty good.
1) The distance to the waypoint (Hiva Oa) as the crow flies (DWP), 2413 nm as of 9:00 yesterday.
2) The distance closer I am in a 24h period (DWP yesterday – DWP today). Since yesterday, I am 109 nm closer (i.e., the instrument now reads 2304).
3) The distance I sailed as the crow flies in the last 24h. Because of weather or strategic planning, I might not be sailing directly towards the Marquesas. In the last 24h, this distance is 110 nm.
4) The actual distance I sailed in the last 24h. I rarely sail in a straight line because the wind direction changes and the wind vane actually zigzags the boat. This is not a number that is easily arrived at, but was approximately 114 nm in the last 24h.
The second number effectively tells me how many days it will take to make the passage, assuming I make the same progress each day, which of course I won’t. 2304/109=21 days. Three weeks would be a good time for the passage.
The third number tells me what the average boat speed was over the 24h period. The “hull speed” of my boat is theoretically 7.5 kt. It rarely goes that fast. On occasion it will go faster if it is surfing on following waves. The reason the second and third number are the same is because in the last 24h I have in fact been (on average) steering a course towards the Marquesas. This will not always be the case.
The fourth number tells me something about the efficiency by which I am sailing. For example, how good I and/or the autopilot is keeping me on course. If you study the actual course I am taking, you will see it is more of a straight line during the parts of the day when I am awake and tending to the details of sailing. As a single-handed sailor, I can expect less efficiency than if other people were tending to the sailing when I was not. Basically, I sailed an extra 4 nm in the last 24h. Another way of thinking about this is I lost 45m. My actual average speed in the past 24h was 114/24=4.75 kt. Keep in mind there were periods during the last 24h where the winds were light and I could only make 2-3 kt speed, whereas other times I was close to hull speed. So, an average of 5 kt is pretty good.
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