BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates in general to a FRP hull structure of a ship, and more particularly to an improvement of a FRP hull structure of a multi-hull type ship to achieve a desired strength and a desired high speed of the ship.

Description of the Prior Art

It is apparent that the land transportation will be faced with a limitation at no distant date in accordance with continuous increase in population as well as in vehicles. This limitation of the land transportation should be partially overcome by marine transportation. In recent, several types of sea transport ships, such as high-speed passenger ships, have been thus developed and wide used. Especially, in accordance with remarkable increase of the standard of living, the passengers as well as the goods holders prefer a safe high-speed ship which is also improved in its quality. In this regard, a high-speed ship, which can run at a high speed to an extent of about 50 knots, conventionally required by a sports boat or by a military ship, is wide used in varieties of fields.

Conventionally, the aforementioned high-speed ships are classified, in accordance with the lower structure of the hull, into several types, such as a mono-hull type ship, a catamaran, a hydrofoil craft, a surface effect ship (SES). Fig. 1 is a side view of a conventional SES. Each of the conventional multi-hull ship, otherwise stated, catamaran, and the conventional surface effect ship (SES) has the similar outer appearance as that of the ship of Fig. 1. Here, the multi-hull ship or the catamaran means a ship having a twin hull structure of which the two box-shaped hulls are spaced apart from each other and submerged under water. In this catamaran, the over-deck structure, which

includes the passengers quarters, a steering house and the like, is placed on a deck which is spanned between the two box-shaped hulls and connects the hulls together. On the other hand, the surface effect ship (SES) has a hull structure section which is basically equal to that of the above catamaran but has seals provided on the front and rear sections of the twin hull, respectively. When this surface effect ship runs, its twin hull rises to the surface of the water and slides on the water surface at a high speed by air under high pressure which is injected into a space defined by the twin hull, the seals and the water surface. As represented in Fig. 3 which is a sectional view of a high¬ speed passenger ship taken along the sectional line A-A of Fig. 1, the lower hull structure under a main deck 1 comprises a twin hull part and a wet deck part D extended between the twin hull part. The twin hull part comprises a side plate section A, a bottom plate section B, an inner plate section C.

In the prior art for FRP multi-hull type ship, the lower hull structure, including the plate sections A, B and C and the wet deck part D, may have a laminated single skin structure which is prepared by lamination of a plurality of laminated FRP panels as shown in Fig. 2A. In another embodiment of the prior art, the lower hull structure may have a sandwich structure which has a PVC foam substrate of a predetermined thickness reinforced by laminated FRP panels bonded to the inner and outer surfaces of the PVC foam substrate, respectively, as shown in Fig. 2B.

When the ship having the laminated single skin structure for all of the plate sections A, B and C, and the wet deck part D, the hull structure has a desired strength. Thus, when the ship having the hull structure of the laminated single skin structure unfortunately collides with a floating material or runs on a reef during a high speed running or at anchor, it is reliably prevented from being damaged and wrecked, thus to guarantee the safety of the passengers. However, this single skin hull structure also

has a problem that it inevitably causes a difficulty in its preparation due to the stiffener 4 which should be added to the single skin hull structure. Another problem of this single skin hull structure is resided in that it can not achieve the lightness of the structure, regarded as the most important point of the high speed ship, thus to scarcely achieve a desired high speed of the ship.

On the other hand, when all of the hull structure, including all of the plate sections A, B and C and the wet deck part D, are the sandwich structure, the ship reduces its weight, thus to achieve the desired high speed as well as reduction of the manufacturing cost. However, since the laminated FRP panel on the outer surface of the PVC foam substrate of this hull structure is relatively thinner than the laminated single skin structure above described, this sandwich structure is apt to be damaged and wrecked when the ship unfortunately collides with a floating material or runs on a reef during a high speed running or at anchor. In this regard, this sandwich structure does not guarantee the safety of the passengers. In addition, even when a portion of the lower section of the hull structure is damaged, the damaged portion can not be easily checked only by observation of the laminated panel on the inner surface of the PVC foam substrate. Hence, unfortunate partial separation of the damaged portion of the lower laminated panel from the outer surface of the PVC foam substrate may be passed over without repairing and this may cause a serious shipwreck.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a combined FRP hull structure of a multi-hull type ship in which the aforementioned problems of the known hull structures can be overcome and which comprises a twin hull part having a laminated single skin structure prepared by lamination of a plurality of laminated FRP panels, and a wet

deck having a sandwich structure prepared by bonding laminated FRP panels to upper and lower surfaces of a PVC foam substrate of a predetermined thickness, respectively, thus to reliably prevent a partial damage of the twin hull part even when the twin hull part unfortunately collides with a floating material or runs on a reef during a high speed running or at anchor, to guarantee the safety of the passengers, to lengthen the life of the hull structure and to achieve the lightness of the hull structure, the most important point of the high speed ship.

It is another object of the present invention to provide a combined FRP hull structure of a multi-hull type ship of which the twin hull part has the laminated single skin structure prepared by lamination of the plurality of FRP panels, thus to easily check a partial damage of the twin hull part and to guarantee the safety of the passengers.

In order to accomplish the above objects, a combined FRP hull structure of a multi-hull type ship in accordance with the present invention comprises: at least two hulls and a wet deck extending between the hulls, each of the hulls having a laminated single skin structure, the laminated single skin structure being prepared by lamination of a plurality of laminated FRP (fiberglass reinforced plastic) panels, each of the laminated FRP panels being prepared using a fiber material laden with a resin; and the wet deck having a sandwich structure, the sandwich structure being prepared by bonding the laminated FRP panel, comprising the fiber material laden with the resin, to each of upper and lower surfaces of a PVC foam substrate having a predetermined thickness.

The fiber material of the laminated FRP panel is selected from an aramid fiber material and a glass fiber material and the resin of the laminated FRP panel is an isophthalic type resin.

The bonding of the laminated FRP panels of the sandwich structure of the wet deck to the upper and lower surfaces of

the PVC foam substrate is achieved by a vacuum bagging, using an unsaturated acrylate resin as a bonding agent applied to interfaces between the laminated FRP panels and the upper and lower surfaces of the PVC foam substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a side view of a surface effect ship (SES); Figs. 2A and 2B are partial cross sectional views of conventional hull structures, respectively, in which: Fig. 2A shows a conventional laminated single skin structure; and

Fig. 2B shows a conventional sandwich structure; Fig. 3 is a schematic cross sectional view of SES having a combined FRP hull structure in accordance with a preferred embodiment of the present invention; and

Figs. 4A and 4B are partial enlarged sectional views of two parts of the combined FRP hull structure of the ship of Fig. 3, respectively, in which:

Fig. 4A shows a laminated single skin structure of a twin hull part; and

Fig. 4B shows a sandwich structure of a wet deck part.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the accompanying drawings, Fig. 3 schematically shows a combined FRP hull structure of a surface effect ship (SES) according to a preferred embodiment of the present invention, Fig. 4A shows a laminated single skin structure of a twin hull part, and Fig. 4B shows a sandwich structure of a wet deck part. In the same manner as a conventional multi-hull type passenger ship, the lower hull structure of this high speed passenger

ship includes a twin hull part and a wet deck part D. The twin hull part comprises three plate sections, that is, a side plate section A, a bottom plate section B and an inner plate section C. In accordance with the present invention, the twin hull part, including the side plate section A, the bottom plate section B and the inner plate section C, has a laminated single skin structure which is prepared by lamination of a plurality of FRP (fiberglass reinforced plastic) panels 2. Here, each of the FRP panels 2 is prepared using an aramid fiber mat or a glass fiber mat, the two types of fiber mats being laden with an isophthalic type resin. In the present invention, examples of the raw materials used in preparation of the laminated single skin structure of the twin hull part are a surface mat, a chopped strand mat, an uni-di rectional tape, a bi-axial mat, an aramid fiber, an urethane foam, gel coat, an isophthalic resin, an urethane acrylate resin and etc..

On the other hand, the wet deck part D, which is extended between the both hulls of the twin part under the main deck 1 and stretched over the water, has a sandwich structure. In order to prepare the sandwich structure, a laminated FRP panel 2' , comprising a fiber mat laden with an isophthalic type resin, is bonded to each of the upper and lower surfaces of a PVC foam substrate 3 by vacuum bagging. In this bonding process by the vacuum bagging, an unsaturated acrylate resin as a bonding agent is applied to the interfaces between the laminated FRP panels 2' and the upper and lower surfaces of the PVC foam substrate 3. In the present invention, examples of the raw materials used in preparation of the sandwich structure of the wet deck part D are a glass fiber, an aramid fiber, a PVC foam, an isophthalic type resin, an unsaturated acrylate resin and etc.. The operational effect of the above combined hull structure comprising the laminated single skin structure of the twin hull part and the sandwich structure of the wet

deck part will be given hereinbelow.

Since the side plate section A, the bottom plate section B and the inner plate section C, which constitute the twin hull part, comprise the laminated single skin structure which is prepared by lamination of the plurality of FRP panels 2, each of the FRP panels 2 being prepared using the fiber mat laden with the isophthalic type resin. The structure of the twin hull part is thus remarkably increased in its thickness in comparison with the known twin hull structure comprising the sandwich structure. Hence, this twin hull part having the laminated single skin structure reliably prevents its partial damage even when it is unfortunately imparted with a local impact load, such as caused by collision with a floating material or running on a reef during a high speed running or at anchor. As a result, this twin hull part having the laminated single skin structure guarantees the safety of the passengers.

On the other hand, since the wet deck part D has the sandwich structure prepared by bonding the laminated FRP panels 2, each comprising the fiber mat laden with the isophthalic type resin, to the upper and lower surfaces of the PVC foam substrate 3, respectively. Thanking for such a sandwich structure, the wet deck part D has a sufficient shear strength for resisting a slamming pressure conventionally acting thereon when the high speed ship rises to the water surface and slides on the water surface at a high speed. In addition, this wet deck part D having the sandwich structure is reduced in the thickness of the laminated panels 2' in comparison with the known wet deck part having the laminated single skin structure, thus to reduce the weight and to achieve the lightness of the ship, the most important point of the high speed ship.

As described above, in a combined FRP hull structure of a multi-hull type high speed ship of the present invention, the twin hull part has a laminated single skin structure and the wet deck part has a sandwich structure. Here, the laminated single skin structure of the twin hull part is

prepared by lamination of a plurality of FRP panels, each being prepared using a fiber mat laden with an isophthalic type resin. The sandwich structure of the wet deck part is prepared by bonding the laminated FRP panel, comprising the fiber mat laden with the isophthalic type resin, to each of the upper and lower surfaces of a PVC foam substrate by vacuum bagging. Thus, the twin hull part having the laminated single skin structure reliably prevents its partial damage even when it is unfortunately imparted with a local impact load, such as caused by collision with a floating material or running on a reef during a high speed running or at anchor, so that it guarantees the safety of the passengers. On the other hand, the wet deck part having the sandwich structure has a sufficient shearing strength for resisting a slamming pressure and is reduced in the thickness of the laminated panels, thus to achieve the lightness of the ship and a desired high speed. This sandwich structure of the wet deck part also simplifies the manufacturing process and reduces the manufacturing cost since it requires no additional reinforcement, such as εtiffeners.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.