Monday, August 4, 2014

The Long Curve



We usually think of going from point A to point B in a Cartesian manner: a straight line. Sailboats are not so linear even with all of their electronic navigation gear. As Beth and I set out for Washington  Island, WI from Beaver Island, MI we'd hoped for a Southeast wind and a beam reach. What we got was wind that was slightly west of south, which put Speakeasy on a very close haul, which it does poorly and with our regret due to the uncomfortable ride.

I determined from a wind map based on NOAA data that the wind would become more southerly as the day wore on so after a conference with the sleepy crew, we decided to set the auto helm to 30 degrees apparent and let the boat follow the changing wind. When locked into the wind rather than a compass point, the auto helm keeps the boat pointed toward a particular angle to the wind direction. If the wind did not change for the better, we would end up on the shore of the Garden Peninsula rather than Rock Island and Washington Island, which are south of it. 

Fortunately, NOAA had predicted the wind shift accurately and our track followed this bow curve toward our intended destination. In the following image, the blue triangle represents Speakeasy current location and direction. The grey dashed lines behind the triangle represent the actual locations in the past. Notice that this dashed line has curved toward the southwest as NOAA predicted.

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