This is because boats with waterline length to beam ratios greater than 81 are not limited by hydrodynamic drag factors whereas smaller boats need to plane to do so planing requires enormous amounts of power for displacement hulls.

Catamaran hull ratio. Typically this will be 8-101 for a slow cruising catamaran or the main hull of most trimarans 12-141 for a performance cruiser and 201 for an extreme racer. For this a set of catamaran hull forms with the main hull length of 40 m and with a different separation ratios sL generated by using standard modelling software. So by and large faster boats have finer hulls.

Good catamaran cruisers have values from 8-12 racers from 12 to significantly higher. Many years ago a client of mine informed me of his invention of what he called the S Number S which is a way to rate the performance of all sailboats on a scale of 1 to 10 using the Sail AreaDisplacement ratio SAD and the. Since the hull generated by the student is aimed at being a representative hull of sailing catamarans produced in South Africa it was named Representative Hull 1 or RH1.

Beam WL Hull Fineness Ratio Max. Hull Fineness Ratio HFR The Hull Fineness Ratio known as the hulls beam-to-length ratio is an interesting number. See figure 26 242 Discussing hull shape.

My 28 trimaran has been up to 15 knots without planing or surfing. And if I bring the aft end width down to 16 inches the hulls then have a LB ratio of 301. With explanations of the various design ratios publishing one a week.

The Prismatic Coefficient Cp is a measure of the fullness of the ends of a boat the higher the number the fatter the ends and - surprisingly - the more efficient at high speeds. Hull length-to-beam ratio LwlBh This ratio is the measure of hull slimness at the waterline which is significant for performance. With such wide aft hull ends the boat will have a lot more buoyancy than I need.

What its used for Performance Larger LB indicates a slimmer hull. A twin-hull is exactly what it sounds like- it means that the boat has more than one hull. The values of SL considered were 02 04 10 and infinite ie the monohull case.