Faster Than the Wind

All:
I was reading in my catamaran book that cats can go "faster than the wind" but it does not go into detail on how this is possible.
Does anyone know if this is possible and explain how that happens?
Thanks!

_________________
Eric Weller
2006 F18 Capricorn
1980 H16
Keep the pointy side up!

The way it happens is due to the affects of true wind, boat wind, and apparent wind.
When your standing still and you feel the wind you are feeling the true wind,
but when you move the wind direction seems to change. This is the apparent wind and what you sail by.
Boat wind is the "wind" your boat creates by movement. There is a diagram calculation showing how to see it but basically to go fast than the wind you need a apparent wind that is faster than the true wind and a fast boat to get there.

It's definintely possible. If you watched the 33rd America's cup earlier this year you saw cats occasionally going up to three times the true windspeed.

These days, there are quite a few different sailcraft that can sail faster than the true windspeed...catamarans, windsurfers, high-performance dinghys, ice boats, and land sailers. It basically boils down to having a high lift-to-drag ratio. You need a powerful yet 'slippery' rig, a low drag hull, and adequate righting moment to balance the power of the rig.

sm

Yes its possible.

Boat sails operate more like wings than like parachutes. So, if you are sailing downwind, with your sail working like a parachute. When you are going the speed of the wind, the apparent wind, as others have mentioned, would be zero, and so no force would be placed on on the sail, and so you would not accelerate any more.

However, say you are going 90 degrees to the wind. The wind blows past the sail, and generates lift, perpendicular to the direction of the wind. You can get moving faster and faster, but the apparent wind will continue blowing past the sail, and will continue exerting a force on the sail. Once the force on the sail equals the resistence from the water, the boat stops accelerating.

When you have something like an iceboat, with very little moving resistence, the boat can be going many many times the speed of the wind, but at an angle to it, and so the apparent wind blowing past the sail will continue to be present, pushing the boat along.