I've done a little more research and playing around with my centerboard this year. I now know from other sources, it is the actual lift of the board that minimizes leeway. While our boards are not optimally shaped, the simple angle of attack, the same as putting your hand out a car window and tilting it until it lifts, creates "llift".
You may not feel this lift, but your boat does, I'm now convinced. I've spent more time sailing close hauled, board up, board down. It's hard to get a scientific reading, but the trend is quite obvious.
Close hauled, my wheel pilot will generally hold a tight course (it's an easy helm with any good boat) allowing me to concentrate on actual course via gps. I wait until the boat settles into a scallop pattern steering a range of degrees as it goes to windward. I don't pinch up as high as the boat will go, but a good combination of speed to weather. She'll show a course range swinging around 10 degrees on the gps.
After staying in that range, I'll lower the board. From there, the usual result after the boat settles for a while, is an increasingly weatherly course, over the ground. There's no real change in the boats magnetic bearing, on either magnetic compass or Fluxgate on the AP as the pilot is doing it's job holding a course. Sometimes this GPS course only changes a few degrees, hardly discernable. Other times, it grows to a clear 10 to 15 degrees. That's quite a bit. From there, I sometimes find I can increase the windward heading on the pilot as well which could be the result of increased apparent wind due to speed.
Another indicator is in all this raising and lowering. When the board is working, you need the extra force to "break" it from the flow which through lift, is causing the board to press against the centerboard slot. When there is no lift, there's no friction, and also likely little or no usefulness such as off the wind(and you may hear the board powerlessly clunking each side of the keel slot). If you want to check for lift going to windward, this is a convincing test. If you feel resistance, your board is working and giving your boat a more weatherly course.
Suffice to say, I haven't proven anything except to myself, but in doing a little research, there's no mystery to the effect of a centerboard to windward, as you would expect. It's just a little more mysterious with boats like ours compared to say the daggerboard in a dinghy. They work quite well. Boats like Finessterre winning 3 Bermuda races quickly proved this.
You may not feel this lift, but your boat does, I'm now convinced. I've spent more time sailing close hauled, board up, board down. It's hard to get a scientific reading, but the trend is quite obvious.
Close hauled, my wheel pilot will generally hold a tight course (it's an easy helm with any good boat) allowing me to concentrate on actual course via gps. I wait until the boat settles into a scallop pattern steering a range of degrees as it goes to windward. I don't pinch up as high as the boat will go, but a good combination of speed to weather. She'll show a course range swinging around 10 degrees on the gps.
After staying in that range, I'll lower the board. From there, the usual result after the boat settles for a while, is an increasingly weatherly course, over the ground. There's no real change in the boats magnetic bearing, on either magnetic compass or Fluxgate on the AP as the pilot is doing it's job holding a course. Sometimes this GPS course only changes a few degrees, hardly discernable. Other times, it grows to a clear 10 to 15 degrees. That's quite a bit. From there, I sometimes find I can increase the windward heading on the pilot as well which could be the result of increased apparent wind due to speed.
Another indicator is in all this raising and lowering. When the board is working, you need the extra force to "break" it from the flow which through lift, is causing the board to press against the centerboard slot. When there is no lift, there's no friction, and also likely little or no usefulness such as off the wind(and you may hear the board powerlessly clunking each side of the keel slot). If you want to check for lift going to windward, this is a convincing test. If you feel resistance, your board is working and giving your boat a more weatherly course.
Suffice to say, I haven't proven anything except to myself, but in doing a little research, there's no mystery to the effect of a centerboard to windward, as you would expect. It's just a little more mysterious with boats like ours compared to say the daggerboard in a dinghy. They work quite well. Boats like Finessterre winning 3 Bermuda races quickly proved this.