hoz,
In that most of the boats (but not all,) discussed on this Forum have very symmetrical hulls, I'd think that the CLR should be at 50% of the waterline length. When that isn't the case, the easy way to determine the CLR is to make a cardboard cutout of the underwater profile and see where it will balance on a ruler. (Not a neat, scientific formula, but it works!)
That's why I've been thinking that it might be better to place the mast much further back than the one in Chuck's picture. (Sorry Chuck!)
If the lee-board was placed pretty much at the center (half the hull length,) the mast placement would then depend upon the sail's Center of Effort.
To find that, the CE, all you need to do is to draw a line perpendicular to each side of the sail, starting at the center of each side, and where they call cross would be the Center of Effort.
If those lines don't cross at a single point, then they will form a small shape, and the center of that shape will be your CE.
Place the mast so that newly-found point is just ahead (10% of the waterline length) of the middle of the boat, and it should balance nicely.
Now that you've got me thinking about all this, I guess I'm going to have to work something up for my Southwind build. . .
Mike S.
Spring Hill, FL