You're right Mary - I was a bit soft. I should clarify:

I meant that I don't doubt his calculations that it takes 1.8 times more power to pull a cat from 20 knots to 27 knots. However, that says nothing about whether or not a catamaran can acquire, control, or manipulate that additional power requirement...The previous statment by Frenchie only says that it takes more force to go 27 knots than 20 - that's pretty basic. When you consider some of the variables like the angle of the sail plan and relative angle of forces relative to the direction of travel, the design of the sail plan, sailor weight & skill, surfing waves and such, it doesn't surprise me in the least to see cats achieve 30k.

Mathmatical models are great for evaluating differences in hull shapes, foils, etc against other similar models. However, they are not always real world. A mathmatical model is for comparing hulls and foils because if it is 20% off from real world, the next analysis of the next system, although also 20% off, still shows an increase or decrease between the two that allows you to evaluate the benefits of one system over the other.

I'm not calling Frenchie a liar either - his models are likely well designed, sound, and thouroughly tested - It sounds like he has the technical background to analyze the results - but I gotta go with real world experience on this one.