Talador,

I don’t recall your views on the definition of a displacement hull, I merely conform to the industry standard for the meaning and use of the word. This may be boring and unadventurous, but is facilitates communication. It would help in this communication if you use the word in the same way. Just in case you misinterpret my usage, I use the term to refer to any hull which is not significantly supported by hydrodynamic forces in its designed speed range.

A flat bottomed displacement hull will generally have slightly larger wetted surface than the closest equivalent round bottomed hull, so will have slightly more frictional drag, wave drag will also differ slightly depending on the general distribution of volume along the length and other factors. If the hull does not squat at speed, it will be relatively efficient – low wave drag, and will be very similar in power requirement to a round bottomed hull of similar form which also does not squat.

You may assume that I am currently unable to provide accurate numbers, as this would require me to research data on hull resistance not currently in my possession, which I have no pressing need to do. Particularly since others on this forum have already offered you good advice, which you choose to dispute.

Cheers,

Peter