data for drag increase in different sea states

[singleprop]

Are there any data available that describes hull drag changes with different sea-states, i.e horsepower required in different sea-states

It is obviously dependent on hull shape.

Singleprop

[Leo Lazauskas]

Originally Posted by singleprop

Are there any data available that describes hull drag changes with different sea-states, i.e horsepower required in different sea-states

It is obviously dependent on hull shape.

Singleprop

It also depends on where the waves are coming from, (e.g. head, quartering, or beam etc), the spectrum of the waves, whether they are long-crested or short...

I'm not sure if there are any tables that might help you, but some old free(ish) codes like SMP (Ship Motion Program) can give rough estimates. A search for "added resistance", "ship motions" and authors names such as Salvesen, Tuck, Faltinsen, Joosen, and Sclavounos might turn up something of use.

Leo.