Originally Posted by Stumble
As mentioned above it really depends on the boat.
But typically a #2 (say 115-135) is the worst possible sail for any conditions. If you coukd ignore the spreaders and stay you could get a decent sheeting angle on them, but obviously you can't. This requires you to move the lead well outboard of the ideal sheeting angle. A 155 by comparison while having to go just as far outboard, also gets to come much further aft. So the angle between the centerline of the boat, and the line made from the tack to the clew is much smaller.
This is why most racing boats go from a 155 to the largest inside overlapping sail they can fly (typically a 115 or so). Not because reducing sail area isn't desirable, but because when you reduce area you also increase the sheet angle to such a point that it kills your pointing ability. And for most boats it is faster to be slightly over powered than to have to give up the pointing ability. Though there are boats this isn't true on, particularly very narrow for the leingth boats like an Olson 30, or Hobie 33.
That's not necessarily correct. In the area I race in, most boats have a #2 and they will shift down to that before they go with a #3. Perhaps it is because we are in a light to moderate wind area. There are many times when the #1 is too much power, but the #3 is not enough.
Tight sheeting angles on the headsail is not always what you are looking for, and the slot effect of overlapping sails should not be discounted.