ALGOR AROUND THE WORLD - Italy

Algor Software Helps Italian Boat Manufacturer Design Smoother Riding Catamaran

Foil design reduces the effect of rough seas on catamaran ride quality, increases comfort.

As just about any avid boater will tell you, catamarans are not the most comfortable craft to be in if the seas are rough. These twin-hulled boats are fast, efficient and can be fitted with virtually any creature comforts one could desire. However, they have a distinct tendency to pitch substantially when confronted with large waves. This can quickly turn a pleasure trip into a very unpleasant experience.

Adding Comfort and Safety

In an effort to improve this situation, Ing. (Engineer) E. Giannitto, of Rodriquez Cantieri Navali SPA, one of Italy's leading shipyards, used Algor software to design and analyze a component that could be added on to the firm's existing catamaran designs. "The object," said Ing. Giannitto, "was to control and reduce the angle, speed and acceleration of the pitching motion caused by rough seas. Our idea was to use foils, placed at the front of the craft, to develop upward and downward lift forces in the opposite direction of the vertical movement of the ship's bow."

Ing. (Engineer) E. Giannitto working on the Algor model for the catamaran foil and strut.

Multiple Materials

The company's engineers needed to know the stress and deformation levels for the entire structure, including the foil, the strut that attaches the foil to the bow of the ship and the ship's hull. The problem was further complicated by the fact that the structure uses steel, light alloy and composite materials.

Here we see a stress analysis of the final model. The contour is also deflected.

Multiple Analyses

"First, we built a model using beam elements to represent the foil, an attached flap and the strut," said Ing. Giannitto. "Then, we built a more complex model using brick and shell elements that represented the strut and the area of the boat's hull where the strut was to be attached. Lift and drag forces were applied to the lower end of the strut based on the results of the analysis of the beam model. In this way, we avoided having to build a complex model that included the foil with its trailing flap.

"The initial analysis results indicated some high stress areas," continued Ing. Giannitto. "The design was modified and additional analyses were run. Once we had a workable design, we determined that just two foils, one for each hull, placed forward of midships and away from the center of gravity, would develop the necessary upward and downward forces to control and slow the pitching action caused by the waves. This design has been incorporated into our catamaran models and is making sailing in rough seas much more comfortable for both passengers and crew members."

The completed foil is shown mounted on one of the company's catamarans.

A closer view of the foil and attaching strut during construction.

About Algor

"Since we began using Algor software in 1989," said Ing. Giannitto, "We have utilized both the design and analysis capabilities in the creation of all foils for our many hydrofoil craft designs. We typically test for stress, deflection and natural frequencies. I appreciate Algor software's ease-of-use and the ability to configure the workstation according to our needs. I also am happy with the fact that the software is constantly updated."