modelcrazy
I.E. close to shore. They are more or less very large patrol boats.....with helo's. Kinda take the Coast Guards duty but under DOT instead of Homeland Security.
The working theory was that you could buils a hollow ship, and fit in various modules to optimize it for whatever the needed mission was. And, since that covered all sorts of things like armaments and the like, the things would be cheap and eay to build. Also, since they were largely "empty space" they'd be fast, too.
Those last bits have been sticky wickets.
Also, having "mission modules" means having to have them all over the expected areas you are meant to employ the craft. And, there's the issue of it's never just the one mission at a time. The whole "we'll bolt on what we actually need, later" is why they went with only a 57mm deck gun.
So, yes, unloaded they can go pretty fast, except when their powerplants break down. which has been more frequent than expected (they expected the one powerplant to be all things at all times). Also, fully loaded with a given mission module, they are quite heavier, and not quite as fast.
The tri-hull design would have been an excellent one to have used two powerplants, one for cruise, and the other for speed. But, no, that was not politle to the monohull design.
It will likely become the F-35 of the surface fleet.