More seriously , they consider that a ship above 80 m long.(so 1500 tons) is sea worthiness (for high sea).

But if you want to have an helicoptere platform you need a 16 meter beam (because of the roll) with means 4000/5000 tons.

Moreover if you want to be able to follow a carrier, you need at least a 5000/6000 tons ship close to 150 meter long.

It is linked to Froude number.

h*tp://en.wikipedia.org/wiki/Froude_number

h*tp://en.wikipedia.org/wiki/Wave_making_resistance

 

 

Herald, yes they may be able to cross an ocean, but most likely only in relatively calm weather.

Herald is right.I have seen a French who have done world circumnavigation alone going in the south pacific in the roaring 40° with wave of 20 meters on a ...6 meter sail boat.

Now if we speak of a war ship which have to travel at a minimum speed and still be able to use its weapons or sensor , 80 m seems a minimum.Big wave could damage sensor and weapons when the bow goes under water.

Sea worthy frigate are above 3000/4000 tons.ANd today navies prefer even 5000/6000 tons.

Fair enough - so no real minimum size for seaworthiness applies, but practical matters do apply minimums on the sizes of sea-worthy warships.

Here's a link showing comparisons of different hull forms.

 

 

Really depends what type of ship or armament you need to put on it. The height and size of the superstructure will have an effect on key properties. Even for VLS type systems, the wieght of the missles could affect how much of your hull is immersed. Key thing though especially for monohull vessels , you will need a lot of power to get past the 40 knot threshold. Fuel, machinery space needed will play key in whatever design you need.  

As long as it floats, what's the problem?