The hull shape of the RZ96 derives from the proven efficient lines of the RZ85.
The waterline beam of the RZ96 is slightly greater, but not enough to reduce hull speed or to change the feeling of initial stability significantly.
The addition of sponsons, without reducing the beam of the frame in direct proportion, has increased the flare (the angle at which the sides of the hull spread outward) of the topsides. As a consequence the hull’s secondary stability is greatly increased. This means that the RZ96 will float over or through a head on or following wave on an even keel, but will also be predictably stable when leaned into a broadside wave or edged for directional control.
Furthermore, this configuration of beam allows the hull to carry a modern high aspect ratio 5 square meter sailing rig.
1 - The RZ96 has a length to beam ratio (measured at the waterline!), which ensures a relatively high hull speed potential, i.e., it is an efficient hull.
The fundamentals of hydrodynamics are such that waves of longer length (distance peak to peak) are faster than waves of shorter length. A boat’s hull speed is directly related to the distance between its bow and stern wake, the farther these are apart, the faster they are, the faster the hull can be propelled within their trough (simplification!). Longer hull length also allows a narrower beam for a given displacement and draft, thereby reducing the immersed cross-sectional area of the hull, reducing this particular drag component. In the RZ96 this reduction is carefully balanced against an increase in the drag component due to an increase in wetted hull surface area (as proven in the largely similar lines of the RZ86).
The RZ96 has a longitudinal distribution of immersed lateral area, which gives bow and stern a good measure of “bite” relative to the total area. This allows the RZ96 to oppose the turning forces of wind and waves and stay on course.
Dedicated control directional strokes can be effectively used to overcome the tendency of the RZ96 to track straight. “Edging” the hull purposefully enhances its ability to respond to changes of direction. Edging an RZ96 is comfortable and predictable ... see “secondary stability” under “beam” above.
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