Introduction to Trim of ship and its variation .pptx
1. CANADIAN UNIVERSITY OF BANGLADESH
Course name: Fault Detection and Damage Prevention
Code: SME 4455
Lecture: 1
Ehamadul Haque Ani
Lecturer
Shipping and Maritime Science
2. TRIM
The trim of a ship is the difference between the forward and aft
draft. When the aft draft is greater the vessel is deemed to have a
positive trim, and it has a negative trim when the forward draft is the
greater.
Longitudinal stability also known as “Trim”
3. CONT’D TRIM
Trim is measured as the difference between draft forward and draft
aft.
CONDITIONS:
If difference is zero = Ship is on even keel
If forward draft is greater than aft draft = Trimming by bow
If aft draft is greater than forward draft = Trimming by stern
4. TRIMMING BY STERN OR AFT
It occurs when aft draft will be more than fwd draft.
6. TRIM BY ‘0’ OR EVEN KEEL
It occurs when fwd and aft draft will be same.
7. TRIM CAUSED OR CHANGE OF TRIM
Trim cause or change of trim is the difference between initial trim and
final trim.
8. CONT’D TRIM CAUSE
Here, Intial trim = 6-4= 2m by S
Final trim = 5.5-4.5 =1m by S
So, Trim cause = Initial trim – Final trim
= 2 -1
= 1m by fwd ( Fwd draft increase and aft draft
decrease)
9. TRIMMING MOMENT (TM)
Trimming moment: Trimming moment is the moment which will cause the
trim.
10. CALCULATION OF TM
Calculation:
Consider the added weight = w ton
d= The distance between the COF and pivot point of weight.
So, trimming moment TM = w*d t-m by bow or fwd or head
Similarly when weight will be added at aft side that time trimming
moment will be TM = w*d t-m by stern or aft
11. CONT’D CALCULATION
In case of unloading or discharge:
Consider the the same weight ‘w’ has discharged from forward. That time
trimming moment TM = w*d t-m by stern
Why stern? Because discharging ‘w’ weight from forward the aft draft
will increase, so trimming moment will be by stern.
WHOLE THING WILL BE OCCURRED IN VICE-VERSA CONDITION
DURING DISCHARGING FROM AFT.
13. IN CASE OF SHIFTING LOAD
DURING DISCHARGE “W” WEIGHT FROM FWD:
Weight = w ton
D1 = Distance between COF and pivot point of w
So, TM = w*d1 t-m by S
DURING LOAD “W” WEIGHT AT AFT:
TM = w*d2 t-m by S
Total TM= w*d1 + w*d2
= w (d1+d2)
=w* D t-m (D=total distance)
14. (MCTC)
For a particular draft, it is the longitudinal moment (about the LCF)
required to bring about a trim of 1 centimeter. This parameter plays
vital role especially when the crew on board requires to load cargo in
any one hold or ballast, or de-ballast, and predict the resultant trim
caused by the action.
MCTC is a very important hydrostatic parameter required for
stability calculation.
15. CONT’D MCTC
Moment to change the trim by 1 cm.
Consider we need 200 t-m of moment which creates a trim 1 cm.
So, 200 t-m (TM) = 1 cm (change in the trim)
2000 t-m (TM) = 10 cm (change in the trim)
TRIM CAUSED (Tc) = TM/MCTC = 2000/200 = 10 cm
TM= MCTC*Tc (cm)
