Small power catamarans?

[Nojjan]

I might live in the wrong part of the world for this but I never see any "small power cats" (<20'). Can someone enlighten me of why this is?

[marshmat]

Few such boats are seen around here either.
A pontoon boat is technically a kind of catamaran and we do have plenty of them from 18' upwards. But the smaller ones kind of suck in terms of performance.
I think a big part of the reason why there are so few small power cats can be traced to simple physical realities. For a small craft to be capable of speeds more than a few knots, it has to be able to plane. Planing requires a large running surface area. It's hard to get a large planing surface in a catamaran, period, especially so when the vessel's dimensions are small. After all, you still need enough volume there to float the boat and crew. Larger cats tend to have a higher length/beam ratio on the individual hulls, often this ratio is high enough that the distinctions between displacement / semidisplacement / planing modes become blurred and decent performance can be achieved without having to depend entirely on dynamic lift from a large, flat underside.
Another factor, perhaps more important in the real world of economics-driven boatbuilding, is that in smaller sizes, the added labour cost of building two hulls, each of which has tight, tricky curves and limited space in which to work, probably becomes prohibitive when compared against a simpler monohull form.