Trim axis of planing boat.

About which axis or point does a boat trim when planing? Is it simply the CG or is it some other point?

And am I correct in stating that when the vessel is static, the axis about which it will trim when mass moves on the vessel is the centroid of the water-plane area?

 

It gets more complicated when planing. The dynamic lift is dependent of shape and speed. It shifts with speed as the boat rises up on a plane because the shape and total surface area submerged change.

 

When planing, the static trim will be determined by the equilibrium of all the external non-inertial forces (hydrostatic, hydrodynamic, aerodynamic, mass) and moments around the CoG.
I realize that the above is essentially a tautology, but is hard to say anything more than that without getting into the design details of the vessel.

 

That's right, but just a small trim changes the locus of the centroid of the water plane. So the next incremental trim motion has an slightly different axis and so on.