Originally Posted by sandy stone
Assuming you have telltales on the jib luff - sail upwind with the jib sheeted in and all telltales streaming aft. Slowly turn upwind until the telltales start to flutter. If the top windward or bottom leeward telltale flutters first, move the car forward a little. If the top leeward or bottom windward goes first, car goes back a little. Goal is for all windward telltales to flutter at the same time.
Once you get that, you have a base position and you can make minor (couple of inches) adjustments for wind speed like you were talking about.
The point being to have the shape of the foot about the same as the shape of the leech.
You can also do that by eye, or by the method Gansett mentions.
All my headsails have lines drawn from the clew which lets you set it at a glance.
Headsail trim is much less interesting than mainsail
trim. I adjust the clews of both my jib and staysail with barber haulers, inboard and outboard
, to have some modicum of control over the angle of attack, but it's a very meagre effort compared to what you can do with the mainsail
on a boom, where you can make the sail fatter or flatter, and feather it, or bite it into the wind. Headsails, unlike mainsails, are basically "on", or "off".