Page 160 - statbility for masters and mates

148 Ship Stability for Masters and Mates
Weight Distance from C.F.
ve x 50 ±
Moments
ve
1200 30 600 20 2000 x 45 360 5
50x
± 36000
12000 ±
90 000 45x ±
102 000 45x
± 1800
37 800 50x
Trimming moment required Change of trim MCT 1 cm 25 100 2500
Trimming moment required 2500 tonnes m by the head
Resultant moment Moment to change trim by head MCT by stern
or
and
; 2500 102000 45x 37800 50x 102 000 45x 37 800 50 x
64 200 95x 95x 61 700
x=649.5 tonnes 2000 x 1350:5 tonnes
Ans. Discharge 649.5 tonnes from No. 1 hold and 1350.5 tonnes from No. 4 hold.
Using trim to ®nd the position of the centre of ¯otation
Example
A ship arrives in port ¯oating at drafts of 4.50 m A and 3.80 m F. The following cargo is then loaded:
100 tonnes in a position 24 m aft of amidships
30 tonnes in a position 30 m forward of amidships 60 tonnes in a position 15 m forward of amidships
The drafts are then found to be 5.10 m A and 4.40 m F. Find the position of the longitudinal centre of ¯otation aft of amidships.
Original drafts 4.50 m A 3.80 m F give 0.70 m trim by the stern, i.e. 70 cm. New drafts 5.10m A 4.40m F give 0.70m trim by the stern, i.e. 70cm. Therefore there has been no change in trim, which means that