by GreenLake » Mon Oct 05, 2015 3:44 pm
@interim: don't mind when people revive older topics to add to the discussion there, but you seem to want to branch out, so I gave you a new topic for all questions about using GPS to monitor performance.
Now, to estimating.
Just sail at different speeds and observe your wake. How visible is it, does it looks like a "powerboat wake" behind the transom, and so on. I did "measure" some of the slower speed using a "dutch log", that is, timing how long it took a bit of flotsam to pass down the length of the hull. Done a few times to give me a baseline, then correlated to the wake (also the sound the boat makes going through the water).
Now, with a GPS, you can do an estimate, then have another person tell you whether you got it right. I think you'll improve quickly.
The tacking angles are not that atypical I would say.
Waves can make a big difference. I sailed in a 14ft dinghy a while back in waves and they were not perpendicular to the wind, instead they were perpendicular to one tack and parallel (more or less) to the other. The result was really interesting. The boat felt like there was something wrong with the trim because it never really made speed against the waves while in the other direction it was as if everything had come together, because as far as the boat was concerned it was seeing super flat water. The DS is a bit heavier that what I sailed in that day, but if the waves were really 2' you'd be getting there.
On the DS, in the right conditions (more moderate than what you report) you can improve pointing with Barber haulers.
~ green ~ lake ~ ~