The Type 054A frigate is a monohull and also a war ship.
You gave me an example of a catamaran that is a ferry. How is this related to the topic?
Why don't you give me an example of a piston engine powered, monohull, warship that can sustain 30 knots, I'd appreciate it.
We're talking about propeller driven. Let's stay on topic please.
What about the Karakurt class?
Once again, the Iver Huitfeldt class.
Back in WW2, the Z51, which blows through at 36 knots.
Type 23 frigates are in excess of 28 knots. These are diesel electric ships used with ASW.
Here is a transport vessel that can max at 30 knots.