Catamaran stability

Catamaran hulls are known to provide a reasonable metacentric height and hence a lower rolling period, but providing a catamaran hulls for passenger or pleasure crafts make the ship stiff and hence cause violent motions.So how is an ideal rolling period of 10-12 seconds achieved in a catamaran hull?

 

Same way as any hull...waterplane (i.e. Ixx) to weight (i.e. volume) and height of CG. That's why high speed passenger cats generally have lower beams and more decks than optimum for performance.

 

As JEH notes the key is the WPA.

This can be achieved in 2 different ways, increasing the volume or reducing the waterplane area. But increasing the volume means a vessel like the big RoRo types circa 5-1000 tonnes. Or if a vessel has a small waterplane area, what is it...a Swath. And it has roll periods that you seek but at much reduced size.

Take your pick....

More info here too