Naval arch incline test

1. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytechnic
Inclining Test
Kalyan Chatterjea

2. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytech
Inclining Test: Problem
 A ship of 2 500 t displacement (as inclined) and KM
6.6 m, was heeled by moving inclining weights 12 m
across the deck giving the deflections on a 6 m
plumb line as given in the table (shown in next slide).
 We need to find the ship’s metacentric height GM (as
inclined).

3. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytech
Inclining Test: Process
ShiftShift MassMass MovedMoved Deflection from originalDeflection from original
positionposition
11 3 t3 t S --> PS --> P 50 mm (P)50 mm (P)
22 3 t3 t S --> PS --> P 110 mm (P)110 mm (P)
33 6 t6 t P --> SP --> S 12 mm (P)12 mm (P)
44 3 t3 t P --> SP --> S 37 mm (S)37 mm (S)
55 3 t3 t P --> SP --> S 88 mm (S)88 mm (S)

4. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytech
The Inclining Experiment
 Carried out to obtain
Lightship weight
Lightship KG
A
B
C
D
Weights are each 3 t
12 m
Length = L m
Deflection = x m
tanθ = x/L

5. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytech
A
B
C
D
50 mm Port
3t
Shift1. Deflection 50 mm for 36 tm
B 6m length
∆LT = 2500 t
The Inclining Experiment

6. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytech
A
B
C
D
110 mm Port
6t
Shift1. Deflection 50 mm for 36tm
Shift2. Deflection 60 mm for 36tm
B
The Inclining Experiment

7. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytech
A
B
C
D
6t
12 mm port
Shift1. Deflection 50 mm for 36tm
Shift2. Deflection 60 mm for 36tm
Shift3. Deflection 98 mm for 72tm
A
B
The Inclining Experiment

8. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytech
A
B
C
D
9t
37mm Stb
Shift1. Deflection 50 mm for 36tm
Shift2. Deflection 60 mm for 36tm
Shift3. Deflection 98 mm for 72tm
Shift4. Deflection 49 mm for 36tm
D
The Inclining Experiment

9. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytech
A
B
C
D
12t
88 mm Stb
Shift1. Deflection 50 mm for 36tm
Shift2. Deflection 60 mm for 36tm
Shift3. Deflection 98 mm for 72tm
Shift4. Deflection 49 mm for 36tm
Shift5. Deflection 51 mm for 36tm
Total 308 mm 216tmTotal 308 mm 216tm
Deflection/tm = 0.308/216 m/tmDeflection/tm = 0.308/216 m/tm
= 0.001426 m/tm= 0.001426 m/tm
C
The Inclining Experiment

10. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytech
W
W
d
Go
G1
M
W.d = ∆.GM.tanθ
= ∆.GM. (x/L)
or, GM = --------
W.d
∆. (x/L)
or, GM = --------
L
x . ∆
------
W.d
m/tm
Or, GMLT = ------------------
6
0.0014 x 2500
= 1.68 mAs Inclined
The Inclining Experiment: Calculations

11. K Chatterjea Feb'03 Singapore Maritime Academy Singapore Polytech
Theory underlying an inclining test is simple but unless following
precautions are taken the results obtained will not be reliable.
 Ship should be as nearly complete as possible.
 Experiment should be carried out in calm weather with no wind and
current and level keel condition.
 All mooring ropes should be slack.
 All weights capable of moving transversely should be secured.
 All tanks should either full or completely empty (as far as
practicable).
 There should be minimum number of people on board and those
present should have restricted movements.
 Draughts of ship should be measured at aft, midship & forward
 Density of water around the ship should be measured at several
positions round the ship
The Inclining Experiment: Precautions