Multi-hulls: new options and scientific developments

Abstract

The widespread development of multi-hull ships began in the second half of the twentieth century, and today many hundreds of such ships of various designs are being built. This intensive development can be explained by the characteristics of various multi-hull ships. Any multi-hull ship type differs both from mono-hulls and from other multi-hull types because of their individual characteristics. The main characteristics of multi-hull ships are examined briefly here. Their larger deck area relative to mono-hull ships means that they are more economical for most types of ‘volume’ cargoes including passengers, cars and other wheeled vehicles, light containers, laboratories, weapons, aircraft and helicopters and so on. Similarly, in comparison with their mono-hull counterparts, multi-hulls are safer because of their larger and more simply achieved transverse stability and bigger above-water volumes. The larger permissible aspect ratio of these hulls also makes them more energy efficient at higher speeds. All multi-hull ships are, in general, more seaworthy than their mono-hull counterparts, and ships with small water-plane area (SWA ships) have the best performance characteristics with regard to seakeeping. The strength specificity of multi-hulls is the leading role in determining transverse loads and the need for avoiding wet bottom slamming. Despite their applied significant advantages, the author believes that the main characteristics of multi-hull ships can be further improved. A general picture of his proposals is given below: • New level feature: Super-fast, triple-hulled vessels with sufficient airborne unloading capacity – for the doubling of achievable speeds in smooth water and relatively small wave conditions. • New level feature: New shape for fast ships with SWA – for higher speeds in waves. • New level feature: Special options for container-carriers (for transatlantic routes or for island service by gas-carrying containers) – for small-draft harbours with no reduction in seaworthiness. • New level feature: Twin-hull escort tugs – for 10 times greater transverse stability, i.e. sufficiently less likelihood of being over-heeled by the tow rope. • New service feature: Outrigger SWA carrier for unmanned aircraft – for minimal displacement and sufficient seaworthiness. • New service feature: Outrigger SWA passenger liners with one to two helicopters – to avoid entry into harbours. • New safety feature: Inexpensive modernisation of existing small- and medium-sized passenger ferries through the addition of outriggers without docking the ship