America's Cup

[jyl]

I know zip about this. Avg windspeed 20 kmh, how do the boats go 40 kmh?

[svandamme]

The wind does not simply push the boat

The boat converts wind into power
The sail diverts the wind, that exerts a force
It's that force that is used and it's no different then a regular engine that produces force:
It will keep accelerating the boat until the drag in the water becomes to much..

[Bill Douglas]

Originally Posted by svandamme

It will keep accelerating the boat until the drag in the water becomes to much..

Yup, it's all about reducing drag.

[jyl]

So can the boats go faster with wind from a rear quarter than from directly astern? I don't understand how it works.

I have an unrelated question about boats. Assuming a boat is sailing with its hull in the water (not up on the foils), would it be faster if the hull were flexible? My logic is that wind means bumpy water (I think these are called "waves") and vehicles on bumpy surfaces are faster with suspension.

[nota]

Originally Posted by jyl

So can the boats go faster with wind from a rear quarter than from directly astern? I don't understand how it works.

I have an unrelated question about boats. Assuming a boat is sailing with its hull in the water (not up on the foils), would it be faster if the hull were flexible? My logic is that wind means bumpy water (I think these are called "waves") and vehicles on bumpy surfaces are faster with suspension.

ever see an iceboat ?
with low drag on ice they can go 100mph in 20 to 30 mph wind speed
lift is the force giving the speed
dead down wind is all drag no lift and slow

a whale can flex some but most are faster under water then at the surface
do to drag from surface waves the moving body produces aka wake

even rubber boats add hard bottoms to go fast as flex is drag

[tevake]

The boat exceeding the true speed, has to do with apparent wind speed on the sails.

Sailing close to or across the wind you can add the boats speed to the true wind speed to determine what wind the sails are experiencing.
Going straight downwind the boats speed is subtracted from the true wind speed, so no way to get extra power to the sails

Looking closely at the sails on the foil cats the sails are sheeted in close to the centerline of the boat on most points of sail because as the boat accelerates the apparent wind direction moves more forward relitive to the boats heading, further enhancing the apparent wind speed.

Cheers Richard

[Kraftwerk]

Going to watch these foiling masters in NYC harbor again. Saw them 2 years ago, was thrilling, kind of crazy. Looked slightly out of control, although those sailors are very skilled. The foiling -cat's do have more to do with dingy's like 420 's than single hull, lead keel, in that they can completely wipe themselves out. In a keel boat that takes a big storm usually.