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You understand alot of physics that I couldn't hope to.


First concept is that a sail is sucking you forward. The wind isnt necessarily pushing you, the lift created by the differiences in pressure as it goes around the mast and over the sail suck you forward. This is called lift and its how we all go upwind so well.

Now to create more lift you need a rounder sail shape. Once the wind speed increases you need less power and you flatten your sail by having less rotation and more sheet on.

Wings do all that better and allow for slots and other mechanisms that allow the airflow to attach to the surface better, and create a more efficient sucking or lift. This also allows for the wing to operate at higher angles of attack (more round sail shape) than a soft sail can get to.

Acat go upwind really well because the sail is very efficient. Downwind Acats need to gybe down the course at very hot angles because they dont have spins. When an Acat is going downwind the travelor is all the way out, the mast rotator is off (all the way out) and the outhaul an downhaul are also off. This gives you a very full, round sail shape and creates more power or lift downwind.

The wing sail does this better because it can be basically turned sideways on the boat. This allows Ben to go downwind deeper and faster, while the rest of us mortals need to go less deep and probably less fast. Our vmg isnt as good as Ben's.

If you are having trouble picturing whats going on think about what happens on an airplane wing. The the plane is taking off and landing the flaps are down (high angle of attack) and extended aft. This creates more lift and power. The path the air has to travel to get over the top of the wing is very round.

When the plane is up to speed the flaps are moved up and into the wing. Since you dont want to fly around at take off speed, the wing needs to change its shape to allow the plane to go faster. The flaps are moved forward and up and this is a less round path the air needs to take (lower angle of attack)

Next time you are on a plane get a window seat by the wing.

Now go re-read Wouters post and then you'll be ready to read the posts on sailinganarchy.

Bill