Background -- Maximizing Speed to Windward

Without Fancy Instruments

Accuracy and Sensitivity

I am sure there will be a ton of things that are more important than the mathematical accuracy of this method. For example, the wind will change as I try and make measurement, I will not be able to sail the boat in a constant direction to the apparent wind. Perhaps I have made some fundamental error in my calculations or my boat is too different than a Cal-40 and everything changes. I have no idea. What I do know is that I used a vastly inferior and significantly flawed version of this method to decide to fall off about 5 degrees on a beat and turned two losses on Saturday into a decisive win on Sunday. Point too high and you just are stopping the boat. I was in a one design race and the boat I was racing against just pointed higher. Trying to point as high as he was just didn't work. His aluminum mast just allowed more forestay pressure than I am willing to put on my wood mast. Falling off and pointing considerably lower and we put many boat lengths on him on the last leg.

The math does say that this method is sensitive to how you drive but not overly sensitive. To determine how sensitive it was I needed a measure of "close enough". What I picked was the equivalent of 1 PHRF rating difference which is 3 seconds per mile. I figured that for me that was 0.3%. Thus I would call 0.3% change in VMG to Wind perfect. Roughly, that is a 4 degree range in true wind angle or a 2 degree range in apparent wind. That is pretty close and may be hard to do. Target boat speed has a range of about 0.4 knots and that certainly can be done. Thus, if you come up with good measurements you should be able to come up with a target boat speed that you can hold. I also looked at how accurate the boat speed and wind speed measurements needed to be and found that a 30% error was tolerable. We then need to make sure we can calibrate our wind meter and knot meter to better than 30% of each other. Remember again that they don't have to be accurate, they just have to read the same.

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