VAN DE STADT DESIGN     

                                                            YACHT DESIGNERS & NAVAL ARCHITECTS                                      

Design 616  -  OPEN 40 "SYLLOGIC"

The SYLLOGIC has been especially designed for the Singlehanded Trans Atlantic Race in June 2000.Unlike the Round the World Races the STAR is an upwind race. The basis for the design is therefore an OPEN 40 with optimal close-hauled characteristics.

Canting mast
Rather than a canting keel the Syllogic features a canting mast. A keel canted to windward for more stability is undesirable in terms of hydrodynamics: the keel produces less leverage and, so close to the water surface, creates more resistance.

From an aerodynamic point of view a mast canted approximately 25 degrees to windward has many advantages. The propulsion force of the sail increases because of the larger projected area and the boat is lifted out of the water instead of being pushed into it (sailboard effect). The tendency for weather helm decreases because the sail forces remain inside the boat. Placing the weight of the mast and rigging further to windward also increases the righting moment, although to a lesser extent than in the case of a canting keel. This is compensated for by the use of more water ballast (approx. 1000 litres).

Rotating keel
The design of the hull is such that under a 20-degree heeling angle its shape under water remains virtually symmetrical, with a 6-degree angle rotation from the centre line of the boat. That is why, amongst other things, she features two rudders. When the boat heels, the leeward rudder is met by an optimal flow (see drawing no. 616.1.10).
The suspension of the bronze fin keel with lead bulb with its 3.40-metre draft is constructed in such a way that it can rotate around its vertical axis by 12 degrees, thus reducing the drift angle by 6 degrees. This results in a lower hull resistance and a wider slot between the mainsail and the jib (see drawing no. 616.13.20).

Construction
For the hull the Van de Stadt Woodcore method was selected. This time the Western Red Cedar planking is covered inside and out with two layers of U.D. Carbonfibre for optimal strength and stiffness.
This is not the lightest possible construction, but certainly a safe one because of the greater resistance to impact. In addition, the hull positively contributes to the righting moment (upwind characteristics) through the low position of the centre of gravity. However, much attention was given to saving weight when it came to the deck, since this lies much higher. The developable deck is made of prefab sandwich plates of Carbon/Nomex; extremely light and strong.

This also applies to the spars, which are made of High Modulus Carbonfibre.

Stability
The range of positive stability are a major safety aspect, and they were extensively studied for this design. Unique stability graphs were made with ballast tanks filled on one side and the mast canted to the same side. The graphs were made both for capsizing to windward and to leeward, and because of the asymmetrics for a complete 360-degree turn (see drawing no. 616.13.12 and 14).

These graphs show that the SYLLOGIC, with all movable weights on one side cannot remain upside down. The ballast tanks can also be filled after the boat has already capsized.

The stability calculations also brought out that the angle of vanishing stability increases with the mast canted, because the centre of gravity goes down. This in contrast with a canting keel, where the angle of vanishing stability considerably decrease.

Robot
Skipper Pieter Adriaans is one of the managing directors of the SYLLOGIC company, which specialises in self-learning computer systems. Not surprisingly, the yacht SYLLOGIC is equipped with a self-learning computer on the autopilot, which is fed by the many sensors on board.The "Robot", that thinks along with the skipper, must prove its ability.

Conclusion
The SYLLOGIC is a remarkable design with many new ideas. The canting of the stayed mast with the help of a hydraulic cylinder in the bottom of the boat is uniqe.