Tuesday 14 September 2010

AC vs A-cat

From the America's Cup site:

AC72 approximate dimensions:

LOA - 22.0 meters (72 feet)

Beam - 14.0 meters (46 feet)

Displacement - 7,000 kilograms (15,500 pounds)

Wingsail area – 300 square meters (3,229 square feet)

The catamaran will be able to fly a hull in 5 to 6 knots true windspeed. The target boatspeeds in winds under 10 knots were set at 1.2 times the true windspeed upwind and 1.6 times true windspeed downwind.
This performance is pretty close to a modern A-cat. In 10 knots we do 12 knots and downwind 16 knots. (or are the target speeds maybe in VMG?, in winds above 10 knots the AC will be faster and we will see speedbursts opver 30 knots (one of the design parameter))
The wingsail area is not that big. To have the same sailarea/weight ratio as an A-cat you have to double the sailarea by adding jibs and gennakers.
The whole thing is pretty straight forward and certainly not a an Alinghi style lake racer. The design issues are; who builds the most powerful hulls and who builds the thinnest wing.
My predictions: The winning hulls will be closer to a DNA than to the latest C-class designs. The best wing will not be the most powerful wing but the most efficient wing. (VMG is king not sheer power)
In medium to strong breeze conventional rigs might be competitive too.
The balance issue Alinghi had will not be that big this time because in this boxrule we will not see hulls with overhang.

If big boats do not outperform small boats, I prefer smaller boats.
Though would really like to see a Dutch Challenge. We can build it.

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