Come with me on a little journey because you and I are going to design an America’s Cup catamaran. Since neither of us are experts we won’t be too technical or get bogged down with too much detail but concentrate on getting some basic concepts right.
So let’s get started; we know the new America’s Cup cat is 72ft long, that is in the rule. Also it can be 46ft wide. Width means righting moment in cats and we want all we can get, so we push to the maximum dimensions. All pretty easy so far. Now the decisions, let’s start at the pointy end.
How full do we make the bows? In basic terms the finer the front 30 per cent the faster you go. Unfortunately against that is the tendency of fine bows to dig in and submerge, stopping the boat. At that point momentum takes over and you pitchpole. If you have not seen Torvar Mirsky on YouTube executing a perfect end-over-end in China last year, it is worth a look. Let me put it another way. Cycle down a hill at speed. Now lean forward and lock up the front brake. That same free-flight panic as you go over the handlebars is what every cat sailor lives in fear of. A fine bow looks like the Extreme 40s where a fuller bow is more like the AC45. In terms of fullness, if the X40 is a one and the AC45 is a 10...
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