US3831540A - Catamaran and method of making - Google Patents

Abstract

There is disclosed a method for converting conventional ships hulls into catamarans, comprising the longitudinal and vertical division of the hull into two halves. The two halves are then connected by a bridging member to define a deck, and the open inner sides of the two halves are completed to make them watertight. In a preferred construction, to compensate for increased lightship weight and allow for greater capacity, a section is added to the centre of each of the longitudinal halves, thus increasing the length of the vessel. By this means, a hull that has marginal stability or is unstable or otherwise unsuitable for use can be given increased stability and carrying capacity and to take advantage of other unique features which catamarans possess. The result is a catamaran of much lower cost than a new ship.

Description

United States Patent [191 Case [111 3,831,540 Aug. 27, 1974 CATAMARAN AND METHOD OF MAKING [76] Inventor: John N. Case, 783 Cave St.,

Victoria, BC, Canada 22 Filed: Jan. 31, 1972 21 App]. No.: 221,943

Catamarizing the Island Princess; Case; Ocean Industry; Oct. 1971.

Primary Examiner-Trygve M. Hlix Assistant Examiner-Stuart M. Gioldstein ABSTRACT There is disclosed a method for converting conventional ships hulls into catamarans, comprising the longitudinal and vertical division of the hull into two halves. The two halves are then connected by a bridging member to define a deck, and the open inner sides of the two halves are completed to make them watertight. In a preferred construction, to compensate for increased lightship weight and allow for greater capacity, a section is added to the centre of each of the longitudinal halves, thus increasing the length of the vessel. By this means, a hull that has marginal stability or is unstable or otherwise unsuitable for use can be given increased stability and carrying capacity and to take advantage of other unique features which catamarans possess. The result is a catamaran of much lower cost than a new ship.

4 Claims, 7 Drawing Figures 1 CATAMARAN AND METHOD OF MAKING BACKGROUND OF THE INVENTION This invention relates to methodsfor the construction of catamarans, and more particularly to methods for the reconstruction of ships of conventional type, using the hull to form a catamaran.

It occasionally happens that for some reason, a ship is unstable or marginally so for certain valuable loaded conditions or otherwise unsuitable for use for reasons such as insufficient capacity, insufficient deck area, or insufficient sea keeping ability. The normal procedure in such cases, if the ship has not foundered before the instability problem is noted, is to decrease her carrying capacity by restricting her carrying capability, to decrease her range by carrying permanent ballast to improve her stability, to restrict her service conditions, or a combination of all three. Whether her insufficiency is any of those above, very often a new vessel is considered necessary before the inadequate vessel has reached her normal useable life span.

SUMMARY OF THE INVENTION It has been discovered that use can be made of the hulls of such vessels, to provide a stable ship with increased carrying capacity the cost of which is far less than the construction of a new ship. According to the present invention, a hull is longitudinally divided into two halves, and then the two halves are connected together by spacing members to form a deck. The inner sides of the two hulls are completed by filling the two openings resulting from the longitudinal division. Preferably, since the finished vessel has increased lightship weight from the completion of the hulls and from the provision of the bridging members, sections are added to the centre of each half of the vessel to provide, not only increased buoyancy, but increased storage capacity and deck area.

It will be immediately obvious that the work involved in carrying out the above procedure is less than the work involved in constructing a new ship. Further, the vessel resulting from the catamarizing process will have increased stability and deck area compared with the original ship. The cost of conversion is considerably less than the cost of new construction.

BRIEF DESCRIPTION OF THE DRAWINGS In the attached drawings, which illustrate schematically the method of the present invention:

FIG. I is an end elevation of a ships hull;

FIG. 2 is a side elevation of such a hull;

FIG. 3 is an end elevation of the hull, longitudinally divided;

FIG. 4 is a side elevation ofa hull, cut into two amidships;

FIG. 5 is a front elevation showing the two halves of the hull of FIG. 3 connected by a bridging member;

FIG. 6 is a side elevation of a hull showing a centre section added; and

FIG. 7 is an end elevation similar to FIG. 5, of a modified form of hull.

DESCRIPTION OF THE PREFERRED EMBODIMENT There are several ways of carrying out the methodof the present invention. The ship that it is desired to convert into a catamaran can be, for example,

l. Placed in a dry dock for cutting.

2. Cut in pieces and lifted onto a building way.

3. Placed in a floating dock.

Other means may be used depending upon the facilities available. It is, of course, necessary to utilize a space which has sufficient width that the two halves of the hull, when cut, can be moved apart the desired distance. By any suitable technique, the vessel is then divided, from bow to stem, along the keel.

In FIG. 1, the two halves .of the hull in section are identified as 10 and 11. In FIG. 2, which is an elevation in the direction of the arrow 12 in FIG. 1, the line 13 shows a dividing point between the bow section 10 and the stern section 10". In the preferred construction, after the longitudinal division of the hull into sections 10 and 11 has been completed, the two halves are each divided at 13 to provide .fore and aft quarter sections e.g. I0 and 10 as illustrated.

As mentioned above, the addition of a deck to connect the two halves l0 and 11, such deck being illustrated at 14 in FIG. 5, adds to the lightship weight of the vessel. Similarly, the completion of the two halves of the hulls to form water-tight compartments by forming walls at 15 and 16 in the halves l0 and I1 adds to the lightship weight of the vessel and freeboard is therefore reduced. If the catamaran is to have adequate freeboard, it is therefore necessary to increase buoyancy. This is best done, a illustrated in FIG. 6, by adding a mid-section 17 between the bow and stem portions of each half 10 and 11. Thus, referring to FIG. 6, each half of the completed catamaran will have added buoyancy and the length of the section 17 in relation to its weight will determine the amount of buoyancy added. Of course, the structural adequacy of ends 10', 10" can be a limiting factor in lengthening them, but the ends can be modified to add strength.

The two inner sides 15 and I6 ofeach hull l0, 11, of course, need not be flat as illustrated but can be suitably shaped so that they partially or completely match the shape of the outer portions I8, 19 respectively.

In some cases, it is possible to use the old deck of the original ship plus the bridging member between the two halves of the catamaran, covering the bridging member between the two halves 10 and 11 and possibly the old deck, with a new deck. This depends upon the water clearance required, and length that it is possible to add for increased buoyancy. It is also possible to provide deck 14 in the form of a skin only, the skin forming the apparent cross structure, plus cross frames 14a. This is accomplished by making the deck houses 20 (FIG. 7) take the load between the hulls. This could be done on forming the catamaran if sufficient extent of deck houses were required for the specific conversion to provide adequate strength.

Twin screw ships lend themselves particularly to the above conversion but single screw ships can also be adapted by adding an additional propulsion system or leaving the vessel as a single screw catamaran by taking advantage of a unique feature of properly designed catamarans whereby the manouvrability with one screw from either hull, plus two rudders, one in each hull, is sufficient manouvrability for some tasks.

It is believed that the above description while in schematic form, is sufficient for a person skilled in the art to make the invention in that the steps taken to carry out the method once the inventive concept is under 2. The method defined in claim 1 further comprising the steps of:

a. dividing each half into bow and stem sections and adding a hull portion between said sections to increase buoyancy.

3. The method defined in claim 1, wherein the two separated hulls are connected by a deck.

4. The method defined in claim 3, wherein the deck is a skin and the two halves are held in their spaced relationship by a deck house.

Claims (4)

1. A method for making a catamaran from a conventional ship''s hull comprising the steps of a. dividing a hull longitudinally and vertically from bow to stern; b. forming two separate hulls from the two halves so formed by completing the open inner sides of the two halves; c. completing the catamaran by connecting the two separated hulls.

2. The method defined in claim 1 further comprising the steps of: a. dividing each half into bow and stern sections and adding a hull portion between said sections to increase buoyancy.

3. The method defined in claim 1, wherein the two separated hulls are connected by a deck.

4. The method defined in claim 3, wherein the deck is a skin and the two halves are held in their spaced relationship by a deck house.

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