A year ago I also tried to make some tracklog analysis in excel.


What I found:

1. It toke a lot of time until my boat reached the speed she had before the tack. t = 60 sec.

2. the acceleration is not continuous, poor helming...

3. My speed went down dramatically (21km/h --> 4km/h)ds = 17km/h = 4.7 m/s

4. This tack cost me (measure the blue area, just approximately ) ds x t / 2 = 4.7 m/s * 60 s / 2 = +- 140m.

5. So If I make an unwind leg with 5 tack instead only 3, it cost me nearly 300m. So I really need a good reason to do this.


Of course all of this depend on the wind/wave conditions, and just one tack is not representative. Based my practice the loosing should be much less. I hope...

Interesting. I will add some charting to my program.

I identify when the tack has begun (combination of drop in average speed and/or change in lat/long) to when the tack "ends" (increase in average speed). Two of my metrics are time to reduce speed or decelerate and time to accelerate.

Given your input, I think I will add distance covered on tack as well. Maybe I can work the math to show angle or arc of the tack as well.

Given comments on this board, I have begun doing more wide tacks. This increases deceleration time, but reduces acceleration time.

My guess is you will find technique even more important on the lighter boat. It is awfully easy to make an atrocious tack. Don't ask me how I know.