Apparent wind

In a Laser, or similar speed of boat, the affects of apparent wind is limited to the way the wind appears to come from more ahead due to your movement through the air.  So when you are beating at about 45 deg to the wind you need to trim your sail as if the wind was coming from about 30 deg ahead.

"Apparent Wind Sailing" occurs in boats which are fast enough downwind to make the wind appear to come from some angle in front.  In that situation the wind gets stronger the faster you go and so you can find yourself sailng maybe only 30 deg off of dead downwind but the wind appearing to come from some angle in front.  Boats with a PY of somewhere around 950 or lower encounter this quite a bit and it enables them to get downwind faster by zig zaging downwind rather than running dead.  It can be provoked by luffing a bit after hoisting, building up speed, and bearing away as the pressure increases.  It turns the runs into the sort of challenge of the beat where you have to choose the right compromise between speed and pointing closer to the mark.

My Laser4000 is often sailed best downwind with the main sheeted at much the same angle as when I'm sailing upwind.  In a medium breeze, if I didn't luff a bit after hoisting I would go downwind at about the same speed and angle as a Laser2000.  If I luff I accelerate and the apparent wind pressure is then enough to require me to get the crew on the wire.  The pressure is such that I have to bear away to keep the boat upright and I'm then sailing the same sort of angle as the Laser2000 - but at about twice the speed. Apparent Wind Sailing.