US3690281A

US3690281A - Stern construction for icebreaking vessels

Info

Publication number: US3690281A
Application number: US100171A
Authority: US
Inventors: William O Gray
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1970-12-21
Filing date: 1970-12-21
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12
Also published as: GB1374311A; CA954389A

Abstract

A construction for the stern of an icebreaking vessel wherein the stern is constructed and arranged to have a shape such that the vessel as it backs into its own broken channel filled with previously broken ice, effectively will shovel the ice pieces up and to the sides of the vessel, thereby clearing the channel so as to facilitate backing and simultaneously keep the ice away from the vessel''s screw(s).

Description

United States Patent Gray Sept. 12, 1972 [54] STERN CONSTRUCTION FOR 998,278 7/1911 Clifford ..l14/57 X ICEBREAKING VESSELS 3,521,590 7/1970 German et al. ..1 14/41 [72] lnvmon wllham Primary Examiner-Trygve M. Blix Asslgneer Essn Research and Engineering, Attorney-Manahan & Wohlers and F. Donald Paris Company 22 Filed: Dec.2l, 1910 [57] ABSTRACT A construction for the stern of an icebreaking vessel [21] Appl' l00l71 wherein the stem is constructed and arranged to have a shape such that the vessel as it backs into its own [52] Cl ..1l4/41 broken channel filled with previously broken ice, ef- [51] Int. Cl. ..B63b 35/08 fectively will shovel the ice pieces up and to the sides [58] Field of Search 114/4042, 57 of the vessel, thereby clearing the channel so as to facilitate backing and simultaneously keep the ice [56] References Cited away from the vessels screw(s).

. UNITED STATES PATENTS 6 Claims, 5

PATENTEDsEP 12 1912 SHEET 10F 2- Y 4 M m N M m WM MO Q w WJ/ Y B STERN CONSTRUCTION FOR ICEBREAKING VESSELS BACKGROUND on THE INVENTION With the relatively recent discovery of vast resources, such as oil, in such inaccessible areas as the frozen north slope of Alaska, there exists a very urgent need for providing a suitable means for transporting these resources through remotely situated areas to commercially desirable market areas, as typified by the heavily commercialized East Coast of the United States and its various population centers. To transport these resources in the most economical manner, serious consideration has been given to moving the resources through the heavily ice-laden passages in the Arctic, with the hope that these passages could be opened as commercial year-round trade routes. Consequently, various designs and constructions for icebreaking ships that would be sufficiently large and powerful to be able to operate in these ice-infested waters on ayear-round basis have been investigated. One such ship construction that appears capable of obtaining the foregoing results incorporates a stern constructed and arranged in accordance with the present invention. Despite the various obstacles, it is generally agreed and has been shown .from an operational viewpoint that a ship can be constructed and operated successfully in the ice. Although it has been shown to solve the problem of the ship breaking the ice when traveling in a forward direction, this still leaves the problem of providing a suitable stern construction to readily allow the ship to back into its own broken channel filled with the previously broken ice while preventing the same broken pieces of ice from damaging the ships screws. Further, by providing a ship that easily can back into its own broken channel of ice, this substantially contributes to the efficiency of the ship when ramming ahead in ice thicker than can be continuously broken and also provides a significant reduction in the backing power required.

DESCRIPTION OF THE PRIOR ART Known stern constructions for icebreakers, generally have been characterized by section shapes sloping SUMMARY OF THE INVENTION The present invention relates to icebreaking ships, and more particularly to an icebreaking ship having a novel and improved stern construction.

In accordance with the present invention there is provided an icebreaking ship having a stern construction for enabling ships to break ice and to allow the ship, when backing into its own broken channel filled with previously broken ice, to shovel the ice pieces up and to the sides of the ship thereby clearing the channel so as to facilitate backing and simultaneously to keep the ice away from the ships screws. According to the present invention, the longitudinal sections and profiles of the stern slop downwardly and aft in the vicinity of the in-ice-operating or load waterline to a distance sufficiently below that waterline so that it is below the level of the floating pieces of broken ice. By designing a ship to have a stern shape as disclosed herein, there is provided means whereby the stern can shovel pieces of ice up and to the sides as the ship proceeds astem in a previously broken channel so that the channel is cleared to facilitate backing. Further, this type of stem construction provides substantially improved protection to the propellers and rudders while the ship is backing and provides additional protection to the screws and rudders while moving ahead from any ice that may be present at the sides of the broken channel. The results obtained by utilizing a stern construction in accordance with the present invention contributes greatly to the efficiency of an icebreaking ship when ramming and further, provides a reduction in the required backing power in comparison to previously known prior art icebreakers having conventional shaped stems.

Accordingly, it is a primary object of the present invention to provide a novel and improved icebreaking ship having a stern shape that will result in facilitating the backing of the ship into its own broken channel filled with previously broken ice.

Another object of the present invention is to provide a novel and improved icebreaking ship wherein the stem is capable of clearing a channel as the ship moves astern and providing protection for the ships components located at the stern.

Another object of the present invention is to provide a novel and improved icebreaking ship having a stern shape wherein the hull forming the stern slopes down and aft in the vicinity of the waterline to a distance below the waterline sufficient to enable the stern to shovel the broken pieces of ice up to the sides of the ship as the ship proceeds the stern in its previously broken channel.

A further object of this invention is to provide a novel and improved stern shape for an icebreakingship which improves the ramming efficiency of an icebreaker and provides for a reduction in the required backing power thereof.

Having in mind the above and other objects that will be evident from an understanding of this disclosure, the invention comprises the construction and arrangements as illustrated in the presently preferred embodiment of the invention which is hereinafter set forth in such detail as to enable those skilled in the art readily to understand the function, operation, construction and advantages of it when read in conjunction with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic outline of the top plan view of an icebreaking ship incorpoating the novel and improved stem shape of the present invention;

FIG. 2 is an enlarged perspective view of the stern constructed and arranged in accordance with the teachings of the present invention;

FIG. 3 is a side elevation view of the stern of FIG. 1;

FIG. 4 is a half breadth view of the stern of FIG. 1; and

FIG. 5 is a body view of the stern of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Having reference to the drawings, FIGS. 1 through 5 illustrate in detail a preferred embodiment of the present invention. InFIG. 1 the novel and improved stern constructed in accordance with the teachings of the present invention is shown as incorporated in an icebreaking ship 11 having a bow portion 12, which typically may be constructed and arranged so that the ships beam, that is, the widest part of the load waterline, is situated in the bow of the ship as illustrated in FIG. 1, references being made to copending U.S. Pat. Application Ser. No. 48,326 (Case RM-590), filed June 22, 1970, for specific details regarding the bow construction. Although the novel stern of the present invention has been disclosed incorporated-in a ship having a bowconstruction as disclosed in the aforementioned patent application, it is to be understood that this stern would be suitable for use with various other designs for icebreaking ships including the absence of a wide beam bow..

As best illustrated in FIG. 2 the stern, generally designated 13, comprises concave-

like hull sides

14 and 15 which slope down from the deck 16 and extend outwardly a distance below the load or in-ice-operating waterline (LWL), which typically may be 80 feet as indicated in FIGS. 3 and 5, terminating at a distance sufficiently below the load waterline, for example, 60 foot, so that the outwardly extending portion of the stem is below the level of the floating pieces of broken ice in the channel. The outward downwardly sloping nature of the hull in the vicinity of the stern provides for a shape which effectively is shovel-like in configuration so that the stern is capable of shoveling pieces of ice up onto its

hull sides

14, 15 and thence onto adjacent unbroken ice as the'ship proceeds-astern in its previously broken channel thereby clearing the channel and facilitating backing. Further, as is apparent from thedrawings, the stern shape according to the present invention provides protection for the conventionally arranged propellers 17 and l8,'as well as the

rudders

19 and 20 while the ship is backing and also provides additional protection for the propellers and the rudders from any ice that may be present at the sides of the broken channel while the ship proceeds in a forward direction. Since the stern slope terminates below the level of the floating pieces of broken ice, any of the broken ice that may come in contact with the ships hull in the vicinity of the stern will be caused to be scooped up and thrown laterally outward of the

ships sides

14, 15.

The actual shape and construction of the stern shown in FIG. 1 is illustrated in the usual manner in FIGS. 3, 4, and. 5 by passing a plurality of horizontal and vertical planes at spaced waterlines (WL) and stations, respectively, on the ship and plotting the resulting lines on the coordinate systems as shown. FIG. 3 shows as side elevation of the stern portion of the ship of FIG. 1, that is, the fore and aft curvature from the stern toward the bow of the ships deck as shown in side elevation. The base line coordinates define the stations at which vertical cuts of the ship are taken including a zero reference line AP (aft perpendicular). Although normally 2] (including the zero station) stations are employed, only those necessary to fully disclose the ships stern in a clear manner are shown. The vertical coordinates define waterlines (WL) (feet) taken at different elevations of the ship. The stem lines (20, 40, .etc.) shown in FIG. 4 illustrate a half-breadth plan view of the stern portion of the ship, while the stern lines in FIG. 5 illustrate a body plan of the sterns shape at various stations along the base line. Since the stem is symmetrical about its centerline (CL) only one-half of the stern lines are illustrated in each instance.

Typical lines of a preferred embodiment of a stern constructed and arranged in accordance with the present invention are illustrated in FIGS. 3 through 5. Thus, as shown in these figures, the hull in the vicinity of the stern begins to slopedownwardly and outward of the ships sides at the deck or 100 foot waterline and effectively has a concave configuration such that the slope of the sides approaches a substantially horizontal plane, that is, the slope decreases as the sides extend .outward from the deck toward their point of termination, so as to form a construction that will enable the stem to shove] the pieces of broken ic'e up onto the sides of the ship as it proceeds astern. The sloping stern sides may terminate, for example, at the 60 foot waterline which, as illustrated, is well below the load or inice-operating waterline, which occurs at foot. At the terminating point or the 60 foot waterline, the hull portion of the ship below that point comprises a substantially conventional configuration. Although the stern lines illustrated in FIG. 3 have a generally smooth continuous curvature, it also is within the scope of this invention to employ straight sections (as indicated by 20A and 35A in broken lines) to comprise the required shape.

As shown in FIGS. 3 to 5, the preferred embodiment of the heretofore described stern shape extends aft from between Stations 8% and 9 /2 to the rearmost point on the ship. As illustrated, the lateral outward extension of the ships sides at the stern extends substantially to, but just short of the 80 foot waterline, but preferably the stern sides extend laterally to a waterline substantially 60 to 80 per cent of loaded draft.

Various alterations of the structure herein disclosed will suggest themselves to those skilled in the art. The present disclosure sets forth a preferred embodiment of the invention which is for the'purpose of illustration only and is not to be construed as a limitation of the invention. All modifications of the invention which employ the novel features herein disclosed are intended to be included in the scope of the appended claims.

Having thus set forth the nature of the invention, what is claimed herein is:

1. An icebreaking ship having a main deck, a load waterline WL, and a hull including a stern portion of symmetrical shape about the longitudinal center-line of said ship, said stern portion having lateral and rear sides of substantially concavelike configuration, said sides terminating in a common plane disposed parallel to and located vertically below said main deck, said sides constructed and arranged to slope downward and outward from said deck and terminating outboard of said stem at a predetermined distance below said load waterline WL, whereby said ship, when backing in its own broken channel filled with previously broken ice, is adapted to shovel the ice pieces up and dispose them laterally of the sides of the ship.

2. A hull construction according claim 1 wherein said stern sides extend longitudinally between a Station 8% and the rearward most point of said ship.

3. A hull construction according to claim 1 wherein the slope of said sides decreases as said side approach their termination point below said load waterline WL.

4. A hull construction according to claim 1 wherein said stern sides extend longitudinally between a Station 8% and the rearward most point of said ship and extend laterally outward of said ship terminating at a waterline substantially 60 to per cent of loaded draft.

5. A hull construction according to claim 1 wherein said sides terminate in a substantially continuous curvature as seen in horizontal section at the waterline defining the tennination of said sides.

6. A hull construction according to claim 1 wherein said stern portion is constructed and arranged to pro tect any propellers and rudders associated with said ship from damage when said ship is proceeding in the aft direction, as well as from any ice that may be present at the sides of the broken channel in which said ship is preceeding in a forward direction.

Claims

1. An icebreaking ship having a main deck, a load waterline WL, and a hull including a stern portion of symmetrical shape about the longitudinal center-line of said ship, said stern portion having lateral and rear sides of substantially concave-like configuration, said sides terminating in a common plane disposed parallel to and located vertically below said main deck, said sides constructed and arranged to slope downward and outward from said deck and terminating outboard of said stern at a predetermined distance below said load waterline WL, whereby said ship, when backing in its own broken channel filled with previously broken ice, is adapted to shovel the ice pieces up and dispose them laterally of the sides of the ship.

2. A hull construction according claim 1 wherein said stern sides extend longitudinally between a Station 8 1/2 and the rearward most point of said ship.

4. A hull construction according to claim 1 wherein said stern sides extend longitudinally between a Station 8 1/2 and the rearward most point of said ship and extend laterally outward of said ship terminating at a waterline substantially 60 to 80 per cent of loaded draft.

5. A hull construction according to claim 1 wherein said sides terminate in a substantially continuous curvature as seen in horizontal section at the waterline defining the termination of said sides.

6. A hull construction according to claim 1 wherein said stern portion is constructed and arranged to protect any propellers and rudders associated with said ship from damage when said ship is proceeding in the aft direction, as well as from any ice that may be present at the sides of the broken channel in which said ship is preceeding in a forward direction.