Small waterplane area twin hull (SWATH) is a twin-hull ship design that minimizes hull volume in the surface area of the sea. By minimizing hull volume in the sea's surface, where wave energy is located, the vessel becomes very stable, even in high seas and at high speeds. The bulk of the displacement necessary to keep the ship afloat is located beneath the waves, where it is less affected by wave action, as wave excitation drops exponentially with depth. Placing the majority of the ship's displacement under the waves is similar in concept to submarines, which are also not affected by wave action.
The twin-hull design provides large, broad decks and a stable platform. The main disadvantages to the SWATH hull form are that they have a deeper draft than catamarans and mono-hulled ships. Furthermore, SWATH vessels can use up to 80% more power than an equivalent catamaran because of increased hull surface and more friction.
The SWATH design gives exceptional stability in high seas. This is accomplished by placing most of the ship's displacement below the level of the waves (like a submarine) where all the kinetic energy of the sea surface is located. Conversely, ships with traditional hull designs have most of their displacement in the wave level of the sea, causing them to roll and pitch in the waves.
Abeking & Rasmussen shipyards can refer to their elementary experience in the building of SWATH ships. The specific characteristics of this type of ship offer such space and comfort in the field of mega-yacht that they can satisfy the most extravagant owner's desires and open totally new dimensions.
Besides the generous areas on each deck, one is impressed by the operation ability which is independent of the seastate and enables unspoilt enjoyment of maritime lifestyle. Salons with unprecedented areal space, free balconies and generously dimensioned free zones enable a pleasant stay of board even in rough seas and opens up adventurous worlds, which conventional yachts have nothing to set against. with a wide range of shops, which fulfil very specific demands and have to guarantee a high technological standard.
The buoyancy of a SWATH ship is provided by two submarine hulls connected to the upper platform by twin narrow struts from each of the submarine hulls. This mature technology used by the military and for deep-sea research ships. Very simply the hull form reduces the upward forces on the vessel as the wave passes through. The biggest advantage comes in a beam sea because the technology significantly reduces the vessel's vertical movement and totally eliminates the quick jarring movements. The idea of SWATH was taken from the principle of submarines at periscope depht, which has been shown to have minimal or no motion, placing most of the ship's displacement under the waves.
The Small Waterplane Area Twin Hull is a twin-hull ship design that minimizes hull volume in the surface area of the sea. By minimizing hull volume in the sea's surface, where wave energy is located, the vessel becomes very stable, even in high seas and at high speeds. The bulk of the displacement necessary to keep the ship afloat is located beneath the waves, where it is less affected by wave action, as wave excitation drops exponentially with depth.
Advantages are: (1) ability to deliver big-ship platform steadiness and ride quality in a smaller vessel and (2) ability to sustain a high proportion of its normal cruising speed in rough head seas. SWATH ships typically have two submarine-like lower hulls completely submerged below the water surface. Above water, a SWATH resembles a catamaran.
However, the purpose for a balanced Small Waterplane Twin Hull ship design is not to minimize ship motions at the expense of speed-power or payload capabilities. During the design process, if the total amount of strut waterplane area is decreased, the transverse spacing between the hulls must be increased to regain adequate transverse stability to resist heeling over moments as a result of wind or movement of all passengers to one side of the ship.
Adequate clearance to the underside of the connecting structure is also essential to allow the Small Waterplane Twin Hull ship to ride over surface waves that are typically present in coastal waters. This type of operating mode results in the smallest vertical motions and is called platforming. For rough seas, with wave heights exceeding the amount of cross-structure clearance, SWATH ships are designed to have a sufficiently short heave period to provide inherent contouring behavior at low speeds.
30 % more TEU
A wider and rectangular platform increase the TEU capacity with more than 30 % and make a significantly lowered gravity point.