Remember that, as winds increase through that range, we change sails six or seven times. The goal is to keep the right amount of sail up. Not too little, and especially not too much. Fortunately for our boat—and us—it usually sails better in strong winds with smaller sails than you'd imagine.

Part of the reason the boat is fastest with wind from the beam is that, when the wind is from more aft, the sails start to blanket one another. The curved shape of the sails creates low pressure in front of each sail and high pressure behind—that's what makes the boat go, and that's why the wind angle is so important. When you're sailing far off the wind, the sails work like a “barn door” held up in the wind, and they're not as efficient, since they don't produce the pressure differential like when the wind flows over them.

This brings us to Question 3, Which sails do you use in which conditions? We have a chart (below) that represents all of the sails and graphically depicts the range of wind speeds and wind angles at which we deploy them. This is called the SAILECT chart.  Clever name huh?
 

Click image for larger version.

Here are all the sails and their colors, with a little description:

Full Mainsail: Blue outline, bottom third of graph, 170 Sq. Meters
Mainsail, 1 reef: Dashed green outline, bottom middle of graph, approx. 138 Sq. Meters
Mainsail, 2 reefs: Dashed yellow line, upper middle of graph, approx. 112 Sq. Meters
Mainsail, 3 reefs: Dashed red line, top third of graph, approx 85 Sq Meters
Code 0: Orange, light-wind sail for all angles, 170 Sq. Meters
Genoa: Brown, light to medium air, upwind and reaching, 130 Sq. Meters
Solent: Purple, medium to strong air, upwind and reaching, strong downwind, 87 Sq Meters
Trinquette: Red, heavy air, upwind, reaching, and super strong downwind, 47 Sq. Meters
Storm Jib: Yellow, storm conditions, up or down, rarely used, 29 sq. Meters
Big Spinnaker: Grey, light to medium air, downwind conditions, 425 Sq. Meters
Small Spinnaker: Dark purple, heavy air or bad waves, downwind, 330 Sq. Meters
Big gennaker: Pink, broad reaching and heavy air, downwind, 270 Sq. Meters
Small gennaker: Green, 110-130 degrees reaching, very heavy downwind, 180 Sq meters
Staysail: Blue overlapping area, using the Solent or trinquette at the same time as another sail on the bowsprit to gain speed, usually the big spinnaker or one of the gennakers.

The wave conditions influence the choice of sails. In big waves downwind, it's usually necessary to change to a smaller spinnaker or gennaker earlier. In order to prevent nosediving when reaching in wavy conditions, the reef is often taken sooner, as it reduces the height of the sail plan.