Design Goals For A Catamaran

A Catamaran is designed to do three things:

1. Provide a stable ride in moderately rough water
2. Travel in a straight line through the water
3. Reduce the amount of water drag

Thinking it through

Double pontoons create stability and aid straight-line travel. They especially give resistance to side-to-side tipping. Because they are much longer than wide, they also act as rudders.

Water drag is reduced by shaping the pontoons "aerodynamically" and placing the balance point so that the nose-up floating angle is brought down horizontally when blown. The dynamics of the interaction between nose angle and sail force produces a design-limited speed for the boat. In general you can design a faster breath blown catamaran by increasing the nose angle and blowing harder.

The deck is best placed on top of the pontoons with one pontoon at each side of the deck. If the pontoons are made tall enough, about 3/4 inches and 1/2 inch wide, the deck will keep from dipping into the water and will remain dry during a race. If the deck tips into the water, more drag will be created and the boat will slow down dramatically.

As with any regatta boat with a sail, the sail is best placed right on the rear of the deck. In this position, the tendency to tip forward when blown hard is minimized. Blowing technique can reduce this tendency further and allow for some steering also.