I'm glad you enjoyed the graphic Ed. The gps data is very interesting since it gives speed, heading, at various positions over time increments. I'll post more someday, since you like it. Perhaps I'll do a test to see how high I can point.
The method I described was really two different tests that you can do. One is to simply watch your average course heading to see what your tacking angle is. The gps is very good at this since not only does it make a record to later view, but you are not looking at where the boat is headed per the compass and having to deduct measured slip angle. Rather, the gps tells you your 'actual' heading.
The other test is for using the VMG to optimize trim. Using the VMG readout is a great thing to watch when you try to adjust your boat trim, either by sail trimming or by adjusting boards or your point of sail. But, simply knowing the wind direction does not allow you to project a way point that is equally centered between your tacks. First you must find your actual center of upwind resistance. (A phrase that I've coined.)
Once you've sailed the boat on each tack, you then know the center of the overall upwind resistance. The center of resistance moves away from the bearing of the wind's direction due to other forces including two big ones, current and waves. While your bow may be pointing 35º off of the apparent wind, your slip angle, current and waves reaction may have your boat moving in a course that is more like 50º off the actual wind. On the opposite tack, everything usually changes.
By averaging the boat's actual direction of travel on each of the two upwind tacks, you'll be able to form an imaginary target far enough away that the angle to the imaginary destination won't change measurably from one side of the course to the other side of the course. This will keep the bearing to the imaginary point, constant as you progress. All of this, of course, depends on some good steady wind direction!
On the rudder issue, I do believe you are beginning to enter apples vs. oranges territory. Sailing upwind is entirely different than downwind. I would expect optimum foil positions and angles to be different in each case. I was focusing on the upwind and weather helm stuff since Mark primarily had mast rake concerns. Sailing off the wind with a spinnaker gives so much lee helm that mast raking wouldn't touch it. Also, as you "heat it up" the CE moves aft and you often end up with Weather Helm. The changes are radical because the apparent wind angle changes are radical when downwinding. (When beating, your apparent may go from 40º to 10º at times. When downwinding, your apparent could move all the way from 180º to say 30º) To try to balance a boats helm for such radically changing conditions could prove to be impossible; you must steer with your sails.
Good point about the added sail area (in a square top) and how most of the influence is still at the draft pocket, not far from the mast. But I think what I was most concerned about was the fact that the area added aloft has more leverage from position changes (mast rake) due to its distance from the mast base. The top of the sail moves farther fore and aft than does the foot, when mast is raked.
GARY
