Quote:
Originally Posted by Zanshin
Y... I was using a log wheel, which is forward of the keel and only about 4 inches off the centreline (it is to port).
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My log wheel is also offset and I get different readings on opposite tacks, though not as much as you are seeing. I theorise that, as the boat is (what's the word?) crabbing sideways while close hauled, especially in a seaway, the flow over the log wheel will be affected by the hull shape differently on either tack. GPS will give a good comparison but for any accuracy you really need recordings. Both the GSP and the log wheel electronics are averaging a series of measurements and pitching particularly introduces a different variation to both.
I think SD had a good point about the accuracy of the wind instrument, the head to wind setting has to match both the aerodynamic and hydrodynamic centre lines and the boat's centreline.