DE68906787T2 - RO-RO FERRY WITH ENLARGED SURVIVAL POSSIBILITIES FOR WATER INLET AND UNHANDLED LOADING AND UNLOADING OF THE SHIP. - Google Patents

Description

The invention relates to a car ferry in which the risk of flooding has been improved in conjunction with the easier flow of unloading and loading traffic.

It is known that the ferry must be provided with a continuous main deck which is some distance above the water surface in terms of freeboard, to which deck all the watertight bulkheads of the lower hull extend. In order to comply with the International Coastal Organization regulations, the ferry must not sink lower and/or lean to port or starboard by more than seven degrees if damage leads to flooding of one or more compartments between the divided bulkheads. At a slope of not more than seven degrees, the edge limit, which is 75 millimeters below the main deck, should not be submerged. Stern doors, comparable to stern or bow doors, should provide quick access with minimal obstruction for entire rows of traffic. This is a necessary feature for efficient unloading and silting of car ferries. The combination between the existing International Coastal Organization regulations and the provision for unobstructed traffic rows naturally lead to the design of the traffic deck clearance, which is an open space or walk-through deck extending from the stern to the bow doors. Although ferries are built in accordance with the International Coastal Organization regulations, and the requirements for the flow of through traffic are satisfactory in an undamaged or undamped ferry, there are serious deficiencies when the main deck is flooded by a side collision, damage to the stern or bow door or other causes. The ingress of seawater, especially during major floods, creates the appearance of a "free surface" which can destroy the horizontal stability of the ferry and therefore cause the ferry to sink.

A clear solution of extending the watertight bulkheads upwards to the upper deck to break the main deck and aligning the provision for watertight passages in the bulkheads with the rows of unloading and loading traffic results in time delays during loading and unloading of the ferry. They also result in a large loss of usable length of the roadway due to interruptions in the flow of traffic. Such delays and space losses seriously affect the economic handling of loading traffic.

The present invention seeks a way to provide the car ferry with improved stability against capsizing without compromising the uninterrupted length of the car lane, which is so necessary for an efficient unloading and loading operation.

Accordingly, the invention provides that a car ferry has a double side housing extending lengthwise in the main deck, and that the housings have large watertight doors at the forward and rear extreme ends and are capable of being closed by engine manipulation to seal the gaps between the ends of the housing and the structure of the ship's side adjacent the stern and bow doors. The housings, which are permanent watertight structures, in conjunction with the longitudinally closing doors, effectively divide the ferry into three longitudinal watertight compartments with minimal effect on unloading and loading traffic. While effectively reducing the deck area susceptible to flooding and thereby causing damage or other causes.

An increase in freeboard is achieved by extending the top of the bulkhead upwards into the stepped "U" formation so that it is high in the outboard and deep inboard. The depth of the "U" formation can be either shallow, at one meter intervals, or deep, at two and a quarter meter intervals. The main deck extends forward or aft over the top of the bulkhead, which raises the side decks of the outboard housing and which lowers the middle deck between the housings. Since a loss of height of a vehicle in the track of the outboard housing is inevitable, such cars can be placed in the upper superstructure. This is not unusual. The stepped, deep "U" formation provides useful cabin and storage space below the raised side deck. It also greatly increases the space boundary, doubling the angle of inclination before the deck edge is submerged and the flooding of the vehicle deck begins. The space below the side deck on the starboard and port sides can not only provide use for additional cabin and storage space, but is also an ideal location for one or more motor-operated lock gates, which would be placed adjacent to the bulkheads. The outboard lock gates, in the form of a single side, rise vertically to act as a water barrier, thus dividing the fore and aft outboard compartments into two or more areas. The central lock gate, or lock gates, encloses a single side each, moving horizontally from starboard to port inboard to couple with a column in the centerline. It rises vertically from the main deck and thus divides the flooding area of the longitudinal central compartments.

With the invention of this ferry, the freeboard is increased and the space limit raised; it has greatly reduced the "free surface" of overwatering; it has large reserves of outboard buoyancy to keep a ferry at a straight angle; it has additional hull structure to reduce the depth of penetration by a side collision; and the effects of vehicle lag at large angles of inclination are reduced.

A vehicle ferry of the old design normally has a longitudinal housing in its vehicle deck, placed transversely, or approximately so, across the centre of the ferry. This serves, among other things, to accommodate the exhaust pipe of the propulsion engine to the funnel; it includes a stairwell for passengers and crew; and it provides support for hoisted vehicle decks. As an alternative, it is known to have a double housing on the starboard and port sides, instead of a single centre housing.

Previous ferries having single and double hulls, respectively on sheets 1/8 and 2/8, together with vehicle ferries of the invention on sheets 3/8 to 8/8, are shown in the accompanying drawings. Therein the main deck 1 extends from the bow 2 to the stern doors 3. The hulls 4 extend upwards from the main vehicle deck 1 to, and through, the upper vehicle deck 5, which in large vehicle ferries normally has a vehicle deck with watertight access doors at the fore and aft ends, respectively 6 and 7.

In the preferred embodiment of the invention, the raised side decks 8 of the main vehicle deck 1 slope in the form of fixed ramps at the end. The ferry is equipped with large doors 10. They are designed to roll or fold essentially alongside and to close watertight to the ship's side structure, adjacent to the bow 2 and stern doors 3.

Similarly large watertight doors 11 on large vehicle ferries with upper vehicle decks close watertight to the superstructure adjacent to the forward door 6 and the aft door 7. Each ramp, shown here lowered 12, is fitted with hinges mounted outside the doors. This facilitates the flow of traffic over the ramps leading to and from the raised side decks.

The space under the raised side decks of a stepped ferry accommodates one or more lock gates. Each of the lock gate pairs is surrounded by vertically arranged individual fields 15 in order to divide the flood-prone areas of the outboard vehicle deck 8 into smaller areas 8a and 8f. They are also surrounded horizontally by inner fields 16 together with center posts 17 in order to divide the flood-prone areas of the center vehicle deck 1 into smaller areas 1a and 1f. The height of the center lock gates does not, however, hinder the lifting mechanism for the car deck.

The foregoing benefits were achieved with little, if any, increase in the ferry’s center of gravity; with minimal impact on conventional ship structures; and without interference with existing lifesaving exercises.

A preferred embodiment of the invention will now be described with reference to the accompanying drawings, although by way of illustration only:

Figure 1 is a cross-section of an earlier model of a ferry with a center housing.

Figures 2 and 3 are floor plans of the main deck and upper vehicle deck of the ferry, as already shown in figure 1.

Figure 4 is a cross-section of an earlier model with two hulls, which are separated dwarf ship.

Paragraphs 5 and 6 show floor plans of the main deck and upper vehicle deck of the ferry, as already shown in paragraph 4.

Figures 7 and 8 are accordingly floor plans of the main deck and upper vehicle deck of the ferry, as already shown in figures 4, 5 and 6, with the housing extended at the front and rear and with the additional larger, watertight doors to divide the vehicle deck into three watertight compartments.

Figure 9 is a cross-section of a double hull ferry with a main vehicle deck in a stepped shallow "U" formation forming the upper of the lower hull watertight bulkheads.

Figure 10 is a cross-section of a ferry with double hull and main vehicle deck in stepped, deep "U" formation.

Paragraphs 11 and 12 are accordingly floor plans of the main deck and upper vehicle deck of the ferry, as already shown in paragraph 10.

Figure 13 is a diagram showing the side casings in perspective and an arrangement of priority watertight doors.

Number 14 is the same cross-section as number 10, but with lock gates.

Figures 15 and 16 are floor plans of the main deck and upper vehicle deck of the ferry, as shown in figure 14, but with lock gates and all longitudinal doors closed.

Figure 17 is a cross-section of a medium-sized ferry with a single deck in a stepped, deep "U" formation.

Figure 18 is a cross-section of a small ferry with a single deck in a stepped, deep "U" formation.

Claims (4)

1. A car ferry with bow and/or stern doors (2,3) and with double side casing (4) arranged watertight astern and moored along the port and starboard sides of the ship's midships; with two or four large watertight doors (10) of approximately the same height as the casing; each door long enough to bridge the gap when closed between the fore and/or aft deck at the outermost end of the casing (4); the front and/or rear of the ship's side casing adjoins the bow and/or stern door. 2. On a vessel equipped with a double side casing (4) as in point 1., and with stern doors but without bow doors, or vice versa; two large watertight doors (10) fitted at the extreme end of the side casing, adjacent to the stern or bow door, avoiding any gaps astern by structurally extending the opposite sides of the casing forward or aft so that the sides of the vessel join. 3. A vessel as mentioned in items 1 and 2, in which most of the watertight sections of the lower hull terminate at the upper end in a stepped "U" formation, which may be shallow or deep; the height level (8) is on the vessel's side at the outer side casing and the depth level (1) inside the longitudinal casing; this step must, if possible, be deep enough to allow space for cabins and storerooms outside the longitudinal casing. 4. A vessel as mentioned in the procedures in which the higher sides of the stepped "U" formation (8) surround one or more places along the vessel, at one or more bulkheads: a system on which watertight sluice gates (16,16,17) are arranged, which can be closed inwards and upwards, in order to cause a minimum of obstruction during the unloading and loading of the vessels.