Planing Boat Power Profile

From what I read in the literatures, the towing power (P = drag"velocity) rises speedily from displacement mode and drops when drops when it reaches planing fully (imagine reduced drag forces). Therefore, I would expect such power vs speed curve to resemble Fig. (a) attached. Contrary to this, most of the profile take the form in Fig. (b).

Can someone please explain to me why and probably refer me to free resources (papers, etc) where I can see different towing power ves speed prifiles?

Apologies if my question looks stupid, I am very new in boat design.

 

I have seen Resistance vs Speed curves with the shape of you first graph (a), but not Power vs Speed curves. If a Power vs Speed curve has that shape then at a constant throttle setting the speed of a boat may be unstable at speeds where the power needed decreases with increasing speed.
Are you a student?

 

I'm not a student but not an expert in boat design.

Anyways, what's then the advantage when the power keeps rising based on Fig. (b)?

 

Any naval architecture book with an emphasis on resistance and propulsion will cover the topic.

What you can see below is the total resistance being broken down into: residuary resistance...wave making...and the frictional resistance being separated out from the total resistance.
There are other elements to the resistance, but I wont go into that for now...it may confuse matters, but these have been allocated into the 2 curves.



This form is "typical" for most vessel that go beyond the prismatic hump.

 

.......and, since the question was about "Power", which equals "Drag times Speed", you get the power curve by multiplying the drag values with the corresponding speed values. That will result in a more "stretched" curve shape; reminding of the "b" curve in the first note.