Syllogic is a remarkable Open 40 Sailboat designed by Van de Stadt Yacht Design. She focuses on the OSTAR (Observer Single Handed Trans Atlantic Race), She was designed to be a very fast and stable boat while sailing upwind. The OSTAR is all upwind, making it different from the other races that allow Open class boats. Syllogic breaks the mould and catches the eye because of her revolutionary cant mast, rotating keel and RoboSail a computer controlled set of winches and controls that can sail the boat without and interaction; in theory at least.

Cant Mast

Syllogic features a canting mast instead of a canting keel. Upwind a keel canted to windward for more stability isn’t the best option as the keel produces less leverage and since it’s closer to the surface it creates more resistance.

Aerodynamically a mast canted 25 degrees to windward has plenty of advantages. The sail becomes more efficient because of a larger projected area. The boat is also lifted out of the water. Most boats develop a weather helm as they heal over due to the sail forces moving outside the boat, the cant mast prevents that, keeping the forces inside the boat. By placing the weight of the mast and rigging further to windward you gain some righting moment, although not as much as a canting keel produces. Syllogic compensates by using more water ballast (about a 1000 liters).

Syllogic uses a stayed canting mast that is canted hydraulically. The stays are led below decks with blocks. The wire rope is then led to a vertical whipstaff that is canted. By canting the whipstaff you change the length of the stays, pulling and pushing the mast to windward or leeward.

Rotating Keel

Syllogic features a fixed keel that doesn’t cant but rotates along the vertical centerline about 6 degrees to either side. This rotating keel helps reduce drag by aligning the airfoil parallel to the water flow, thus reducing drag and unwanted lift. The design of the hull is such that under a 20 degree heeling angle its shape under water remains virtually symmetrical, with the keel rotated 6 degrees 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.

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.


Syllogic is equipped with a one of a kind robot autopilot that learns as the skipper sails the boat and adjusts accordingly. This really isn’t a surprise considering that skipper Peter Adriaans is one of the managing directors of Perot Systems. Basically the autopilot learns and thinks along with the skipper, getting information from a multitude of sensors.


Syllogic’s cant mast is a major stability factor. It provides lots of positive stability. Van de Stadt made extensive studies that plotted out the stability of this boat. Syllogic is designed to return upright from any position and cannot be left upside down with all the weight to one side. The canting mast provides enormous stability on its own. The water ballast and fixed keel make this boat even more stable and since it has righting moment to burn, the skipper can really push her to the limits of her construction and safely sail through some hellish conditions.

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.


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 center of gravity. However a lot of attention was turned toward making the deck lighter, 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.


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 unique.

After the first sea trials everyone agrees that the canting mast works. Peter Adriaans seemed to be very pleased with the performance of his new boat, especially since this was only a sea trial. He expects to push the boat even faster and before the start of the OSTAR. The boat is also considerably faster and she answers the helm better than similar fixed mast boats.


Length over all      12.19 m
Length waterline     12.00 m
Beam	                4.00 m
Draft                3.40 m
Displacement         4.5 metric tons
Ballast              1.7 metric tons
Water                1.0 metric tons
Main                 85 m2
Jib                  30 m2
Sail Area	           120 m2
Reacher              82 m2

1. Taken from emails with Van de Stadt Designs and Peter Adriaans

Sources: Myself
Van De Stadt Design
Professional Boat Builder issue 68

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