It's all based around the formula and the basic fact that waterline length equals speed. Like in the Meter classes, the IAC boats are built around a formula where each boat can be different because the ratio is all that matters. If you have so much waterline and so much displacement and so much sail area, the toatal must equal the same thing.....lose some of this and you gainsome of that. Waterline length is critical which has led to the odd bow designs and various stern configurations. The "snap-on" hull idea effectively changes the rating but also keeps the yacht within the formula and allows a better flow at the stern as well.

In both the IAC boats and the previously used 12 Meters, everyone is trying to gain that tiny fraction of speed through mods like this. The old saw that a boat that looks fast generally is, is still pretty true however. Back in '74 there was a 12 Meter of radical design named Mariner which was skippered by Ted Turner (prior to Courageous) that was very blunt at both ends and arguably the ugliest 12 ever built....also one of the slowest. Turner couldn't get any speed out of it and there was a constant argument over the design which Ted blamed for the slow speed (he was right). Turner capped the months long argument with a line that became infamous....."Hell, even a turd is tapered at both ends!"

Spaw