Structural Design of Ships-1 SHELL EXPANSION DRAWING 12/16/2011 Department of Ship Technology Kurian Joseph (17)

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INDEX

1. Aim...........................................................................................................................................Pg.No.2

.

2. Procedure.................................................................................................................................Pg.No.3

3. Selected Ship……………………......................................................................................................Pg.No.4

4. SED ..........................................................................................................................................Pg.No.8

5. Conclusion................................................................................................................................Pg.No.9

6. Reference...............................................................................................................................Pg.No.10

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1. AIM

The Assignment is to prepare the shell expansion of any ship on a drawing sheet. To avoid complications

the bow and aft part are not drawn.

Shell Expansion

Shell expansion is a two-dimensional drawing showing the arrangement of the shell plates, stiffening

members, all butts, seams, fillets welds etc. The drawing shows the various plate strakes and their

identification number. The purpose of the drawing is to assist in the plate development and subsequently

the cutting of the strakes prior to fabrication and erection.

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2. PROCEDURE

The shell is expanded in the transverse plane, where longitudinal distances are measured relative to the

centreline axis. All vertical dimensions in this drawing are taken around the girth of the vessel rather than

their being a direct vertical projection. This technique illustrates both the side and bottom plating as a

continuous whole. The girth of the main deck, tween deck, double bottom etc. is taken at each station

and the ordinates are plotted to get the profile of the shell expansion. Bulkheads are fixed vertically and

after that the strakes are decided.

Strakes of steel plating are distinguished by letters from the keel onwards, the garboard strake being ‘A’.

The plates in each strake are numbered from aft to forward. The girth of the ship decreases towards the

ends and so the width of the plate must be decreased in these parts. To save making the plates too

narrow, at the ends of the ship, a number of pairs of adjacent strakes are run in to one. This is done by

means of a stealer plate.

The strakes taken from the midship and primary members are also plotted. The maximum size of the

plate is 10m x 3 m and other checks which are done on shell expansion are given below.

The minimum distance between two butt welds is 200mm.

The minimum distance between any other two welds is 100mm.

The angle between two seams at the joint should be greater than 600.

Butts or seams at the position of stiffening member should be avoided.

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3. SELECTED SHIP & OTHER DETAILS

The selected ship is a Multipurpose General Cargo Vessel designed under the Lloyd’s Register of Shipping rules and regulations. The ship has a deadweight of about 22000dwt. The vessel should run at a speed of 14.5 knots and its area of operation is from Mumbai– Mombasa – Toamasina – Mumbai. Multipurpose General Cargo Carrier as the name indicates is a ship, which should be able to handle multiple requirements such as the ability to carry general cargo (cargo in granular form, bale form, sacks, etc), palletised cargo (containers or any other similar packing) and heavy loads in general.

LOA 163.7 m

LBP 158.4 m

B (mld) 24.2 m

D (mld) 14.75 m

T (mld) 10.2 m

Deadweight 22000 t

Speed 16 kn

Radius of

Action 6100 nm

The attached body plan has dimensions.

24.2cm x 14.75cm ( the y axis of sed has a scaling of 1:100)

& the shell expansion drawing dimensions are estimated to be.

105.6cm x 26.2cm(the x axis of sed has a scaling of 1:150)

Table of girth length :

stn 0 8.9 cm

stn 0.5 10 cm

stn 1 14.67 cm

stn 1.5 17.9 cm

stn 2 18.5 cm

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stn 3 19.83 cm

stn 4 21.06 cm

stn 5 22.7 cm

stn 6 24.15 cm

stn 7 25 cm

stn 8 25.75 cm

stn 9 0 cm

stn 10 26.2 cm

stn 11 0 cm

stn 12 26.11 cm

stn 13 25.8 cm

stn 14 25.47 cm

stn 15 24.5 cm

stn 16 23.43 cm

stn 17 21.36 cm

stn 18 19.07 cm

stn 18.5 17.41 cm

stn 19 16.7 cm

stn 19.5 16.25 cm

stn 20 15.8 cm

The standard plate dimensions taken are :

Keel Strake - 1m x 6m

Garboard Strake – 2m x 6m

Bilge Strake – 2.5m x 6m

Sheer Strake – 2.2 x 6m

Other plates are cut keeping in mind the need for minimizing the cutting of plates and the need for

continuity or continuous seam length.

Table showing bilge length for drawing the bilge strake :

Aft

stn 10 11.87 cm

stn 9 - cm

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stn 8 11.5 cm

stn 7 11.3 cm

stn 6 10.68 cm

stn 5 9.825 cm

stn 4 9.136 cm

stn 3 8.6935 cm

stn 2 - cm

stn 1.5 - cm

stn 1 - cm

stn 0.5 - cm

stn 0 - cm

Fore

stn 11 - cm

stn 12 11.79 cm

stn 13 11.5536 cm

stn 14 11.384 cm

stn 15 10.767 cm

stn 16 10.4132 cm

stn 17 9.4184 cm

stn 18 8.797 cm

stn 18.5 8.233 cm

stn 19 - cm

stn 19.5 - cm

stn 20 - cm

cm

General Arrangement plan & Body Plan :

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4. SED

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5. CONCLUSION

Body plan was obtained plotting spline curves in Autocad. Necessary scaling was done. The outline for

the ship girthwise was drawn and thus finally the shell expansion was drawn.

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6. REFERENCE

a. Ship Construction – D.J.Eyres

b. Project Report, MV Veera - CUSAT

c. Merchant Ship Construction – Pursey