Anonymous wrote:
Does anyone know the rule of thumb for wetted surface area? If the hull
stays exactly the same same size and form yet the wetted surface area is
increased in what proportion does the speed decrease for a fixed power
input?


There is no simple "rule of thumb" for this. How do you increase
surface area and keep hull size & form the same? Is displacement held
constant? Have you already factored out wave-making drag?

(signed) Injun Ear (formerly known as Eagle Eye)