[Robert A Cook PE]

SWATH is OK for smaller (frigate-sized) flat-topped hulls, like you pointed out. A small ship sees good advantages in stability, but at a higher cost to build, more water resistance (you need more fuel to go the same distance = more displacement = more weight = even more drag) and with a depth penalty: again, bearable if you have a small ship.

SWATH isn' effective for larger ships, mainly for the displacement answer I gave above, but also because the very large carrier sized ships don't get an advantage from SWATH in sea-keeping. Worse, they pay an extreme penalty in hull weight and complexity and expense of manufacturing and difficulty of construction for limited benefit.

[John O]

Thanks. It's been a while since I worked with hull forms at all (and I never worked with them in depth anyway) so I appreciate the info.