Ganged Sail

Motivation

Improvements to sailing vessels can be achieved by using higher aspect ratio airfoils (sails) and ganging multiple airfoils so that the cascade effect is realized. The cascade effect is noted in water and gas turbines where the flow from one surface helps to eliminate separation from the following one. My ganged sail system achieves both desirable features for potentially higher speed sailing for a given length vessel, particularly for catamarans, including personal watercraft.

The high aspect ratio (slim sail profile) leads to high aerodynamic efficiency because less wind energy is lost over the top of the sails.

Key Features

Using multiple sails with each sail on its own mast allows for high aspect ratio (six or more), without stays, as the multiple masts share wind loading, so the cantilevered masts are sufficient without stays to interfere with mast-sail rotation for alignment according the wind direction. A sketch of the sail concept is shown below in figure 1.

Figure 1: Sail.

Several of the high aspect ratio sails can be ganged together to maximize total sail area and can be overlapped somewhat to realize the cascade effect. Figure 2, below, shows a concept for a personal watercraft catamaran.

Figure 2: Catamaran personal watercraft.

Not shown in Figure 2, above, is the canvas trampoline for pilot and passengers. The craft is steered with the dual rudders at the aft end of the vessel, and the sail angle of attack is controlled by the pilot with the rope bridle ("control rope" in the figure). The masts rotate in greased sleeves (bearings) at their attachment point to the center structure, and are ganged together with control cables ("gang lines" in the figure) so they all move together. Because the sail profile is symmetrical, the force of the wind induces no torsion in the mast, so the control forces required are small.

Email Richard dot J dot Wagner at gmail dot com