Fuente info AC34
GETTING TECHNICAL: THE DEATH ZONE
PUBLICADO EL 18 AGOSTO 2011
For the novice sailor, learning to sail on a ‘reach’ is one of the first things they learn to do. Reaching - sailing in a direction with the wind blowing at right angles to the boat - is one of the most basic, predictable aspects of sailing.
In a normal boat, that is.
In a high-powered ultra-fast multihull like the AC45, reaching is one of the most hazardous points of sailing. Because they are so efficient, the boats start to generate their own wind, known to sailors as apparent wind. You know the wind you feel on your face when you’re riding a bike? That’s apparent wind. A sailing boat doesn’t tell the difference between the wind that blows naturally, and the wind that it generates by moving forwards - apparent wind.
Apparent wind is why AC45s can travel faster than the natural wind. In fact sometimes more than three times the speed of the wind. This is a good thing, most of the time. But not necessarily on a windy day when you’re trying to sail down a reach. Like the first minute of the race, when the boats set out on a reaching start.
In strong winds, it’s going to be very tricky for the boats to sail in a straight line from the start to mark one, because there is a risk they will generate too much apparent wind, too much power. In these conditions, the straight line course becomes a ‘death zone’. That’s what the sailors call it.
As the boat accelerates and the apparent wind builds, the power rapidly increases and exceeds the righting moment available. Either you capsize, or you change direction. You either need to sail below the direct line, or above it, or a combination of the two. So to stay upright and in control, you actually end up sailing a zigzag course to the mark.
Communication between the crew is key, as Glenn Ashby of Emirates Team New Zealand explains: “We have a constant conversation on board whether we’re going to head up or down [from the straight line route] and we try to keep the hammer down as much as we can [going as fast as we can]. We’re aiming to keep the boat sailing at a constant angle of heel. Powered up is the key to get down to that first mark in good shape.”
Whether you are in high or low mode, it is all about sailing as close to the death zone as you can without becoming overpowered. Get it right, and you’ll lead the race. Get it wrong, and you’re swimming. Welcome to the Death Zone.