Hi Wouter,

I think that it is not so simple as some hulls are cutters (meaning they slice through the water in a displacement fashion) and some hulls are planers (meaning they ride atop the water like a power boat). We both know it's not that simple, and I don't want any newcomers to catsailing to be misled. The line between the two categories is very blurry. For example, the Stealth and I17R both have flat-bottomed but very narrow sterns while the Taipan 4.9 has rounded bottom but wide, voluminous sterns. The upshot is that both types of sterns can allow planing in certain points of sail and with crew weight in the right place. Upwind and downwind the "cutters" and "planers" (I like your term "hopper" better; and I would call them "slappers") each have different characteristics, but the fact is cats sail most of the time in displacement mode with occasions of planing. Cats easily exceed the dogma of "hull speed" due to the narrow, fine hulls and low wetted surface (esp flying a hull). I'm not telling you anything you don't know, I just thought we ought to get the info out so others aren't mislead into thinking one type of hull planes like a jet ski and other type cuts through like a tanker. It's kind of like the wave piercer discussion--all cats pierce through wave, but where volume in the hull is distributed determines the hull's response when piercing a wave. Cutters, slappers, hoppers, piercers...when you get out on the water, it's amazing how comparable the performance is between the categories. They may behave differently, but big differences have not been seen in speed.

As a side bar, I've noticed that hull design may be a surprisingly small piece of the performance puzzle. Look at how well the Tornado hull shape still performs (incidentally, the T4.9 is very similar to a mini Tornado hull shape except for the plumb bow). I don't know much about the Tornado, but from what I've heard, rig devolopment, light weight, and the best sailors are what keep it on top. I'm not a great sailor and I'm a novice at setting up my rig. But at least I got a light boat going for me. The Australians have, over the years, approached cat design differently than here in the States. Go back to the early 80s--in the States we were sailing Hobie 16s and the Aussies were sailing Mosquitos and Cobras. Goodall told me they tried to make light weight boats with very refined rigs--that's how they get speed; whereas the nacra/inter and hobie design m.o. appears to be more of a heavy boat, big rig, brute force approach to speed. Both approaches work, just different underlying philosophy, and that philosophy comes through in the differences between the designs. The I17R is a big boat (for a single hander) with a big rig; the F16s are smaller, lighter and have smaller rigs. So here's another way to categorize single handers--the brute force and the finesse groups. Every one of the boats in either category that I've been has been fun to sail. I guess that's really what matters.