Tobbera:
I am puzzled by your statement that the telltales are not entirely affected by the apparent wind direction. Yes sure, the sails "disturb" the wind around the tell tales etc, but the original source is the apparent wind that blows on the boat/sails. The same apparent wind that will blow on the wind vane. I If the apparent wind shifts 5 degrees to port, the starboard telltale is going to indicate. If the apparent wind shifts 5 degrees to starboard, the port telltale will indicate. The only information I'm getting from the steering telltales in the jib, is wind direction (wind shifts). Or am I missing something regarding wind direction versus beating upwind?
You are correctly describing how you (and other sailors) use tell tales. But since you can't see the wind direction upwind of the sail you don't see just how much the sail is affecting it. You need to look at wind tunnel pictures using smoke plumes to show wind direction. Think about it this way - if the sail didn't affect the wind how would it generate any force?
If you would not like to spend a lot of time on a failed project I suggest you find some quick and dirty way to test my allegations before going much further.
Of course I can quite see how you might wish to pursue it anyway just to see what happens. My original concern was that you were focused on issues of PID fine tuning without thinking about the external "mechanical" issues.
...R