Reading: Sailing optimization for Macs

[DaveC426913]

The data:

[Jimmyt]

In future explorations of the polars, I would suggest using the apparent wind speed and apparent wind angle, rather than "estimating" the true wind and angle. That way, you can use a handheld or boat-mounted instrument to get real-time wind data while sailing. You can easily solve for the true wind speed and angle graphically, or build a mechanical "slide-rule" style calculator device.

I say that based on my sailing experience, which consists of pretty inconsistent true wind speed (and often varying true wind angle). Your experience in your area may indicate true wind data to be consistent enough to use.

As you pointed out earlier, having a buddy aboard (or two) to gather and record data would be really helpful.

[DaveC426913]

In future explorations of the polars, I would suggest using the apparent wind speed and apparent wind angle, rather than "estimating" the true wind and angle.

I don't have any electronic instruments that give me AWA. So I would be estimating AWA by looking at the wind vane at the mast head.

So the tack-and-halve is pretty much the best precision I have.

I do have an electronic compass on my GPS, but I chose to use the boat compass. There seems like there might be a discrepancy of about 20 degrees between them, but I haven't sorted that out yet.

That way, you can use a handheld or boat-mounted instrument to get real-time wind data while sailing.

I've tried a handheld wind finder. Not an electronic one - a manual one. I am very disappointed with the results.

But yeah. I really need one. I had no idea they were so cheap. Thanks for pointing me at that.

[DaveC426913]

Here is another visualization of the data. For a while there, I thought my numbers drifted off along the imaginary axis, but I'm pleased to see my data verified.

This is not a trip log; it is a schematic. The arrows are vectors, not legs: their length is proportional to boat speed.
It's kind of cool to see how the vectors incrementally shorten in magnitude as I head up into the wind.

[Jimmyt]

Very interesting. Thanks for posting this.

[DaveC426913]

I finally managed to get out for a few hours with my old genny on and do some data collection.

Here's a question: when one says a "90 degree tack", does that means it has to happen in one trim from tack-to-tack? Or do we get to count tacking to a close reach and heading up to a close haul (which is how I was taught to do it when racing)?

Here's my latest run:

With my 150 genny, in an estimated 4 knots of wind, I managed to do two tacks with a no-sail zone of only 75 and 80 degrees respectively. I didn't believe it the first time, which is why I did another one, more carefully.






And this was in a very light wind. (If I had not seen my speed readings, I would have estimated this was a 3 knot wind, I only say it's a 4 knot wind because I managed to reach 3.8 knots for a bit!)

I would not have believed my numbers but I used my camera this time to capture my heading, my speed and my path all in a series of irrefutable photos:

These two pics are time-stamped 4 minutes apart:

[DaveC426913]

Here's the polar chart.

As before, the faded points are just port and starboard duplicated and flipped to generate more data points. I think this might be a mistake, since the first leg of the run on a port tack was in a 4 knot wind, whereas the 2nd, starboard leg was more like 3 knots.

But even without duplicating the data, it's still a mess - look at that 33% difference on the starboard close reach (2.8-3.8 knots between 62 and 67 degrees).