High speed craft

High speed crafts are improving to a vital component of the international transportation industry. Successful commercial High speed crafts have been operating internationally since the late 1950s. Examples including monohulls, hydrofoils, and surface effect vessels. No specific standard is provided to define the term “ High speed craft.” The International Maritime Organization (IMO) has a definition, but this is only for vessels engaged in international routes. To provide a definition, High speed crafts are quick commercial service providers that can approach the speed of 25 knots or even higher, and capable of carrying a minimum of 35 passengers and/or commercial cargo.

A High speed craft is defined as a craft with maximum operating speed higher than 30 knots, as a result it could be use Froude number larger than 0.4 to characterize a fast vessel supported by the submerged hull, such as monohulls and catamarans. Submerged hull supported vessels with maximum operating speed in Froude number less than 0.4, are called displacement vessels. If Froude number is greater than 1.0, the hydrodynamic force mainly carries the weight, and this type of vessel is called a planing vessel. Vessels operating with maximum speed in the range, greater than 0.4 and less than 1.0, are called semi-displacement vessels.

There is a wide variety of High speed crafts in use, with very different physical features. The vessels differ in the way the weight is supported. The vessel weight can be supported by:

  • Submerged hulls;
  • Foils; and
  • Air cushions

Submerged hull-supported High speed crafts

This type of High speed crafts is categorized into three main types. These types are:

  • Multi-hull (including catamarans, trimarans, …)
  • Planing
  • SWATH

The most common type of High speed craft is the catamaran. The catamaran designs include the wave-piercing and semi-SWATH types of hulls. Trimarans and pentamarans with one large hull in center and combined with small hulls are other types of multihull vessels.

Planning vessels are typically smaller vessels which used as patrol boats, in order to sport competitions and usually used for the military purposes.

A SWATH (small water plane area twin hull) vessel, is defined by a small waterplane area and two demi-hulls. A SWATH has higher natural periods in heave and pitch than a similarly sized catamaran.

Submerged hull-supported High speed craft
Foil-supported High speed crafts

Foil-supported High speed craft

This type of vessel is fully submerged or free-surface piercing foils. The first commercial High speed crafts were the monohull hydrofoil boats with free-surface piercing foils. and some hydrofoils are installed under the hull, where it could remain either fully submerged or floating on the surface, while speed increases. These foils generate a force into the up direction, in such a way that waterplane area of the hull could be decreased.

Air cushion-supported High speed craft

Surface effect ships (SES) or air-cushion catamarans of lengths less than 40 m were frequently built for commercial use until the mid-1990s. An air cushion is located between two side hulls and by a flexible rubber in the bow and aft end. The pressure in the air cushion is produced by a fan system that produces a force which lifts the vessel. This force carry about 80% of the weight of vessel.

The first type of air cushion supported vessel in an High speed crafts, is the air-cushion vehicle (ACV). The ACV is amphibious, because a flexible rubber seal system is used for the air cushion in this type of vessels.

An air cushion vehicle can be characterized by generating forces in airborne condition. The examples of this type are Ekranoplans or wing-in-ground (WIG) vehicles (Figure 10). The WIG flies close to the water surface, which gives an extra lift. It cruises at a speed of 180 km/hour (90 knots) and is claimed to have high maneuverability and short stopping distance.

Figure 11 illustrates a conceptual High speed craft which air cushion, submerged hulls and foils are used to support the vessel weight. The air cushion is located between the side hulls and by flexible rubber in the forward and aft end of the vessel.

Air cushion-supported High speed craft

Comparison of High speed crafts hulls

There are some advantages and disadvantages on different types of High speed crafts.

  • Planing catamarans:
    • Less trim angle in comparison to planing monohul
    • Better transverse static and dynamic stability in comparison to monohulls
    • Increasing deck area
  • Monohull vessel:
    • Good seakeeping
    • Good Maneuverability and course stability
    • Less speed reduction with respect to its hull shape
    • Less production cost in comparison to multihulls
  • SWATH:
    • Good operability
    • High deck area
    • Good maneuverability and course keeping
    • Efficient propulsion system
    • High frictional drag due to high wetted surface
    • Low longitudinal stability
    • High draft
    • Sensitive to weight distribution
    • Complicated power transmission system
  • Catamarans and multihull vessels:
    • Low wave resistance due to the high length to beam ratio
    • Good transverse stability
    • High deck area
    • Good maneuverability and course stability
    • Reduction in forces due to slamming
    • High damage stability due to the number of compartments it has
  • Surface piercing hydrofoils:
    • Designing for speed above 40 knots
    • Wave making reduction at high speeds
    • Having trouble while docking or berthing, due to high width in hydrofoils
    • Making cavitation at high speeds
    • Bad seakeeping due to presence of foils
    • Selecting propulsion system with high efficiency is difficult, because the entire hull is out of water
  • Trimaran:
    • Low wave resistance at high speeds
    • Good transverse stability
    • High deck area
    • Efficient operability at high heading angle
    • Complex hull structural design
    • Difficult docking operation
  • Wave piercing catamarans:
    • Higher speed with respect to the traditional catamarans
    • Less speed reduction against waves

Marinnor Company in accordance with its expert and experience on high speed crafts, focuses on under 24m length. Marrinor Company has able to design, build and delivery these kind of crafts, such as patrol vessels, ambulance boats, crew boats, search and rescue boats, catamarans and etc.

Design steps start with customer requisition and complete with requirement of any local or international classification society. In concept design, Marinnor R&D department provides general arrangement plans, catalogues, maker list, technical specification, Gantt chart and 3D model according to customer requisition. This step may take 1-2 weeks according to the vessel complexity. Marinnor is able to design high speed crafts operating in different weather condition according to any operational area by simulating and analyzing using CFD software for hydrodynamic and hydrostatic performance. The validation and verification of the designs may be done with CFD software or towing tank test, if necessary.

Marinnor High speed craft

8.5m Ambulance Boat

Hull Material: Marine Aluminum 5083

Length O.A: 8.5 m

Beam O.A: 3 m

Max. Draft: 0.65 m

Main Engines: 1×200 hp(Outboard)

12m Patrol Boat

Hull Material: Marine Aluminum 5083

Length O.A: 12 m

Beam O.A: 3.8 m

Max. Draft: 0.85 m

Main Engines: 2×500 hpDiesel

Information

Address: Cennetoğlu Mah.Yeşillik Cad – No.230/514 35110 – Karabağlar-izmir Türkiye
Phone: +90-23 2237 7778
Email: [email protected]

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