Changes

Roll acceleration is the force of gravity (G force) you experience during a roll. High rates of acceleration are very uncomfortable, stress the body, and make it impossible to sleep. Marchaj <ref> Marchaj, Seaworthiness, The Forgotten Factor, chapter 4, "Boat Motions in a Seaway"</ref> has proposed four physiological states: Imperceptible, Tolerable, Threshold of Malaise, and Intolerable. Malaise starts at 0.1 G, Intolerable starts at 0.18 G.

Hull Speed = 1.34 * LWL^1/2

Maximum hull speed of a displacement boat in knots is 1.34 times the square root of the length of the hull at the water line. Maximum speed is attained when the length of the bow wave is the same as the waterline length. Maximum hull speed is really the maximum efficient hull speed. You can drive a boat faster than its hull speed but it will take increasing gobs of power to do so.

=== Speed/Length Ratio ===

The Speed/Length Ratio (SLR) is the boat’s maximum velocity in knots divided by the square root of the LWL in feet. For example, with an LWL of 54 ft 04 in and a maximum speed of 9 knots, a boat's SLR is 1.22. Typically a boat is at its most fuel efficient at an S/L between 1.1 and 1.2. SLR is closely related to the Prismatic Coefficient.