My post did not at all mention max hull speed. Please, read the posts carefully before criticizing!
I assume that almost all readers of this forum understand quote marks in the sentence: “….”fool” the stern wave into assuming a much longer waterline length”.
Froude number: Froude developed his formula from boat-model experiments. The Froude number says something about the wave generated by a hull moving in water.
There are several versions of the formula (dimensionless, densimetric, etc), so stating that “Froude’s REAL law is …” is a simplification at best. For a ship, the Froude number is defined as: Fr = V/square root of(g*L) where V is the velocity of the ship, g is the acceleration due to gravity, and L is the length of the ship. See JIMI’s previous post.
The Froude number relates to the fact that wave velocity is related to wave length.
A displacement boat generates waves. A displacement boat travelling faster than the velocity of the waves it generates, is subjected to large resistance against its movement (wave drag). Hence, a large amount of power is needed to increase the speed further.
With very slender hulls, wave drag is a relatively small component of total drag.
There are ways of altering the stern of a boat to move the stern wave to behind the boat (“fool” the stern wave): - the vertical sharply cut stern which allow the water to detach from the stern, - the horizontal wings of the International 14s just beneath the water surface, - the appendix of the New Zealand’s boat for America’s cup 2003 (the Hula).
Almost all small cats have vertical sharply cut sterns that allow the water to detach from the stern.
