...Perhaps I should have emphasized the wave-piercing
aspect rather than make mention of SWATH. ...

A narrow water plane and light weight are key to high speed in
catamarans. The A class cats have been leading the way in very low
volume, very fine hull shapes. They are very much wave piercing
designs. The new C class "Object 2" by Steve Killing is a good example
of the current state of the art in this. Many cruising cats have been
designed with very fine bows and narrow water planes often expanding at
a distinct chine to get reasonable volume in the living spaces. Some
have even had wave true wave-piercing bows extending beyond the main
hulls. However, the trend in dedicated cruising boats has been to
towards wider, simpler hulls. When Alexander Simonis was designing the
Moorings 4500 he did a study and found that Fn's rarely exceeded 0.6 in
the cruising fleet and concluded that ideal cruising cat hulls should
place more emphasis on wetted surface and load carrying and less on
wave drag. His hulls ended up being around 1:8 length to beam and
quite full and round. The advantages of simple tooling, high volume
and good load carrying are hard to argue against in a dedicated
cruiser. In the racing fleet very light, slender, wave piercing hulls
have proven themselves. Sadly, there seems to be comparatively little
demand for cat designs that take the middle ground.

-- Tom.