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post #21 of Old 04-03-2019
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Re: Generic Polars

Originally Posted by colemj View Post
You don't need highly calibrated instruments to show optimum VMG in relative terms. Ours are always calculating VMG, and we don't use them to know the exact VMG - just to trim and sail the boat to the maximum VMG they show. Whether that absolute number is real or not is inconsequential. This works well, unless one thinks that the instrument calibrations are constantly changing in short terms. If they are, then they aren't very useful for anything, let alone VMG.

Our autopilot has an upwind setting to sail at maximum VMG, where it constantly monitors boat speed and wind and adjusts course so that VMG is optimum. Like us, it doesn't care about the absolute VMG number - only that it sails at the highest VMG calculated.

Really does not work that way as the numbers need to be accurate on all the instruments to give you a VMG that is worth sailing . if the speeds are off on one instrument and not on the others then you will think you are sailing to best VMG. In reality you are sailing to what the instruments say is a best VMG but could be way off the mark. Garbage in Garbage out

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