I ran across this article (http://members.shaw.ca/taonui/windvane.html) outlining one solo circumnavigator's tests between windvane and electronic autopilot. In short, his results showed the autopilot steered a straighter course, but the windvane yielded more miles made good (by as much as 10% !! )
One point from the article.
Quote
The objective when passage making is to maximize the number of miles made good toward a selected point.
That is, he is not considering power consumption or mechanical simplicity issues; the ONLY basis for his test is which method yields a quicker passage.
This is the test with Otto vs. the Albert?? I love that article... and it says quite a bit. However, it may not be fully applicable to all boats, as different hull designs will react to each slightly differently. I noticed that the windvane seems to really come into its own when sailing close to the wind or on running down wind... the autopilot seems to be more efficient on the beam reach. This makes sense, since sailing close on the wind and running dead downwind can both be very sensitive to slight changes in the boat angle.
One thing I would have liked to have seen is how well Otto did on a apparent wind angle based setting, rather than a compass-based setting. Would the autopilot be able to gain back the small increments of efficiency sailng close hauled or not? Of course, not all autopilots are setup to be able to steer to apparent wind angles, and the apparent wind at the top of the mast is going to be slightly different than that seen by a windvane at the deck level of the boat.
It also reminds me of another story about a sailor who was constantly feathering the boat to follow lifts and headers. His captain had told him to just steer the compass course laid out... but the sailor just wouldn't ignore the headers and lifts. Then, about a week into the passage, the captain pulled the sailor aside and asked him if he could teach the others how to do what he had been doing...since the captain had realized that the boat was making about 6% more miles made good when he was at the helm, following the lifts and headers.
Needless to say on a vessel that is powered by the wind the straightest course is generally not the most efficient.
Quote from: AdriftAtSea on March 01, 2007, 05:56:49 PM
One thing I would have liked to have seen is how well Otto did on a apparent wind angle based setting, rather than a compass-based setting.
He did that. All of his courses higher than 90 degrees were witht the AP following apparent wind.
I guess I have to go read it, since it's been over a year since I first read that...