MJP68 said..
That seems to be the common theme, rig it till it looks right, but I just don't get out enough to be able to equate what the sail looks like on the beach with how it's feeling on the water.
And because I don't sail as much as I want to, the last thing I feel like doing is braving the shore break to tweak the settings by 5mm for a change that may or may not be better, or given the other 200 variables, noticeable!
So I'll always be a "numbers" guy, and I'm ok with that.
There are some very simple visible clues when rigging a sail.
Eg.
1) for rotational (i.e without cams) sails, apply downhaul until the front of the batten above the boom is parallel with the front of the mast.
2) for cammed sails, apply downhaul until the crease between the 2nd and 3rd batten from the top of the mast is about 80% across the sail towards the mast. Many sail brands have a mark on the sail of this location.
Then go sail and see how it feels. I use the Duotone XT extension. This allows easy adjustment of downhaul on the water. Make small adjustments ( one click up or down) and go sail and check. Using this method, it's surprising how quickly you can find optimum downhaul setting for a given wind condition. Downhaul adjustments for lighter or stronger wind are usually only about +- 1cm from optimum
Once downhaul is set, you can then, as Gestalt suggested, play with small adjustments of outhaul.
