Description:ARRANGEMENT FOR LAUNCHING OF SHIPS FROM SLIPWAY BY FLOATING OUT USING NATURALTIDE

FIELD OF INVENTION
The present invention belongs to the field of ship launching. More particularly, the present invention discloses arrangement, design and process of execution for launching of ship constructed on inclined slipway by floating out in natural tide.

BACKGROUND ART
Traditionally, ships constructed on inclined slipways are launched by gravity launching. The gravity launching arrangement requires an elaborate set-up such as fixed ground ways, sliding ways, hanging shores, tie beam, fore poppet, wax coat, trigger locks, spun shores, etc. This arrangement is time consuming and commercially uneconomical as compared to floating out of the vessel using natural tide. Construction of the vessel and its launching by floating out from the slipway have some practical difficulties which have been mitigated for safe launching in present innovation.

Launching of a ship is generally carried out by four different methods. These methods are:
a) Gravitational type launching from inclined slipway.
b) Floating-out type launching from dry dock.
c) Mechanical type launching from inclined slipway. (d) Air bag launching from inclined slipway.
The present launching relates to vessel constructed on inclined slipway and innovatively launched by floating out the vessel in natural tide thus saving cost & time required for undertaking gravity launching on the inclined slipway. Present method of launching the vessel by floating out from inclined slipway can be used when the available natural tide height is higher than the drafts of vessel required for floating-out. Thus it can be applicable in construction and launching by floating out of smaller size vessels (Approx 45 M Long) from inclined slipway. Further this innovation will allow shipbuilders to use available slipway for construction and launching without expending time and cost involved for gravity launching arrangements.

OBJECT OF INVENTION
In shipyard many vessels are built simultaneously. Depending on availability of the facilities such as dry dock and inclined slipway, the place for construction of the vessel is planned. In case, if smaller vessel (Around 45M long) is to be constructed & launched, then it is always preferred and easier to build the same in dry dock and float-out, however, before this innovative launching could happen, the inclined slipway was only available for construction of 45M long vessel on slipway, then as per traditional practice gravity launching was to take place. However, for gravity launching, the cost involved for elaborate arrangement and time were the two factors which resulted in innovative steps towards constructing and floating out in natural tide. Further in requirement of simultaneous construction of sister vessels, two different time slots and efforts shall be required for gravity launching of the vessel. Hence comparatively easier and cost-effective method of construction in slipway but launching by floating out is invented.

SUMMARY OF INVENTION
The present innovation relates to the innovative process adopted for launching of the ship constructed on inclined slipway by floating-out the vessel in natural tide.

Traditionally, ships constructed on slipways are launched by gravity launching however, since the cost involved and the time required for gravity launching was undesired for this project, innovative and unprecedented option to construct vessel on inclined slipway was developed and launched under natural tide.
Following steps for this innovative float-out in natural tide from inclined slipway were undertaken, viz, positioning the vessel as near as possible to the dock gate for getting essential tide height for floating and towing the vessel out of inclined slipway, orienting the vessel with forward facing the gate and aft side of vessel away from river end (Refer to Fig-1) enabling shafting work on aft area, maintaining a slope of1:40 on a dock floor of 1:20 with requisite arrangement on dock blocks and utilising the width of inclined slipway to position two vessel simultaneously side by side with reasonable clearance (Refer to Fig-2).

Therefore such as herein described there is provided an arrangement for launching of ship constructed on inclined slipway by floating out in natural tide comprising of an inclined slipway, along which the said ship being launched at designed location and orientation, a supporting system, preferably wooden, consisting of dock blocks, shore supports, additional supports at pivot point, through which ship can be erected with its keel at slope 1:40 the said inclined slipway have a slope gradient of 1:20, a supporting system, preferably of concrete blocks for supporting wooden dock blocks; and an essential natural tide height for floating and towing the vessel out of inclined slipway for launching of a ship to water by floating out.

In an embodiment, the aft of the ship is oriented away from the river end in order to resist the knuckle reaction at aft blocks which were secured with extra bracketing support to avoid slipping thus enabling access for shafting work.

In another embodiment, the slope of the ship keel is optimized, to achieve the stable dock block arrangement and wherein at any stage from starting of the operation to bow lift and float off, the frictional force is well above the sliding force.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 illustrates profile view for erection orientation of ship with slope in present innovation;

Fig. 2 illustrates plan view for twin launching of ships placed side wise in accordance with the present invention;

Fig. 3 & 4 illustrates actual view of blocks erection laid for erection of ship in accordance with the present invention;

Fig. 5 illustrates ships getting built on blocks before float-out;

Fig. 6 illustrates two ships erected and ready for launch in accordance with the present invention;

DETAILED DESCRIPTION
Traditionally, ships constructed on inclined slipways are launched by gravity launching however, since the cost involved and the time required for gravity launching was undesired for this project, innovative and unprecedented option to construct vessel on inclined slipway was developed and launched under natural tide.

Conventionally the slope in the inclined slipway is steep and maintained at 1:20 and the available tide height on inclined slipway is gradually reduced from river end to another end of the inclined slipway. Hence, for this innovation, the ship was erected on incline slipway just near the lock gate of slipway so that required tide height for floating of the vessel is available faster (Refer to Fig-1).

In contrary to general practise of Gravity launching from Inclined slipway, the vessel was innovatively positioned such that, forward of vessel oriented towards lock gate. This arrangement yielded twin advantages, viz, the aft of vessel which was away from lock gate was appropriate for undertaking shafting work and the draft corrections could be conveniently managed during natural float-out.

The dock block arrangement for a vessel with horizontal keel on inclined slipway of slope gradient of 1:20 is considered steep and would lead to sliding due to weight component shifting forward during construction or during float-out. To mitigate this problem, the slope of dock block for keel of vessel on incline slipway was decided at1:40 considering the coefficient of friction of wood vis-a-vis steel hull and another major factor such as side dock blocks on forward. In Fig 1 profile view, orientation and position of ship is shown in accordance with the innovation. It can be seen that by this orientation optimum slope and requirement for space in aft of ship, lower height of aft and fore dock block is achieved.

During launching operation i.e water inflow in natural tide and subsequent bow lift, dock blocks at aft of the ship are under high load due to the suing/knuckle reaction and would result in forward sliding due to weight component. As planned in the present innovation, orientation of aft of the ship away from the river end was considered and to counter the knuckle reaction, aft blocks were secured with extra bracketing support to avoid slipping.

Further in this present innovation since slope of the ship keel is optimized where sliding force is well within friction between ship bottom surface and dock block. It is also checked in any stage from starting of the operation to bow lift and float off, the friction force is well above the sliding force. Sufficient number of dock blocks specially suing dock blocks is also provided with support for withstanding horizontal forces.

Further the present method of launching can be used for construction of two ships side by side and launch them together. Since the requirement of tide height for launching to both vessels will be same if they are kept at same longitudinal location, present method is suitable for the simultaneous construction and the twin launching. This will also enable a shipyard to use the slipway facility and simpler launching procedure.

Refer fig 2 plan view showing erection of vessel for twin construction and twin launching as per present innovation.

In the present innovation underwater appendage in the bottom shell were clearly avoided to foul with the dock block arrangement such that after floating out the dock block arrangement were not in way of vessel being towed out of incline slipway, further in some dock blocks were fastened with the rope and blocks are removed/toppled on dock floor as soon as vessel is clear of wooden dock block during float out.

In present innovation, launching by floating out of the vessel build on inclined slipway was achieved successfully by planning & mitigating all possible issues envisaged for safe launching. Refer fig 3 & 4 where actual dock layout is shown for twin ship erection and launching and in fig 5 erected ships are shown for twin launching in accordance with present innovation.

ADVANTAGES AND INDUSTRIAL APPLICATION OF INVENTION
The concept, design and method of launching of ship which is built on inclined building berth by floating out in natural tide can be applied as comparatively simple and cost saving method than conventional gravity launching. Present method of launching by floating out from slipway can be used for slipways where available natural tide height is greater than the water level required for floating the vessel. Thus, it can be applicable in construction and launching by floating out of smaller size vessels from inclined slipway.

The Slope of Vessel baseline with respect to horizontal is 1:40; accordingly, the dock blocks are positioned on inclined berth with declivity of 1:20.

Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration by way of examples and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims:WE CLAIM :

1. An arrangement for launching of ship constructed on inclined slipway by floating out in natural tide comprising of:

? an inclined slipway, along which the said ship being launched at designed location and orientation,

? a supporting system, preferably wooden, consisting of dock blocks, shore supports, additional supports at pivot point, through which ship can be erected with its keel at slope 1:40 the said inclined slipway have a slope gradient of 1:20;

? a supporting system, preferably of concrete blocks for supporting wooden dock blocks; and

? an essential natural tide height for floating and towing the vessel out of inclined slipway for launching of a ship to water by floating out.

2. The arrangement as claimed in claim 1wherein the aft of the ship is oriented away from the river end in order to resist the knuckle reaction at aft blocks which were secured with extra bracketing support to avoid slipping thus enabling access for shafting work.

3. The arrangement as claimed in claim 1 to 2, wherein the said slope of the ship keel is optimized, to achieve the stable dock block arrangement.

4. The arrangement as claimed in claim 1 to 3, wherein at any stage from starting of the operation to bow lift and float off, the frictional force is well above the sliding force.

5. The arrangement as claimed in claim 1 to 4, wherein dock block arrangement has been provided for withstanding vertical forces as well as horizontal forces.

6. The arrangement as claimed in claim 1 to 6, wherein the said arrangement is configured for launching of two ships, side by side and launch them together, since the requirement of tide height for launching of both the vessels is same and are kept at same longitudinal location.

7. The arrangement as claimed in claim 1 to 6, wherein the said dock blocks are placed/ removed such that after floating, the dock block arrangement were not in way of ship being towed out of incline slipway.

8. The arrangement as claimed in claim 1 to 7, wherein the said dock blocks were operably fastened with rope and blocks are removed / toppled on dock floor as soon as ship is clear of wooden dock block during float out.

9. A process of launching of ships from slipway by floating out using natural tide employing the arrangement as claimed in any of the preceding claims.