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Understanding Ship and Boat Trim
(Stability & Trim - Part 2)
By: Brian Trenhaile, P. E., Naval Architect & Marine Engineer, Hawaii Marine Company, 2004
There are basically only two types of trimming calculations. Other trimming calculations are just variations of
these two fundamental types. In Case I you know the vessel's weight and center of gravity (CG) location and you
seek to find the forward and after drafts. In Case II you know the forward and after drafts and desire to know the
vessel's weight and center of gravity (CG) location. The simple approach that is presented here should be readily
understandable by anyone with a basic understanding of algebra and geometry.
This article should benefit anyone involved with designing or operating any type of floating vessel. Regulatory
agents and classification society employees also need to understand these methods in order to check various
designs for compliance. This article is also designed to give a good theoretical understanding of the calculative
methodology utilized in the trim and stability sheets sold on this site.
The vessel's "Curves of Form" are needed to perform these calculations. No attempt is made to describe the
theory behind or how to construct the "Curves of Form." This article is only concerned with application of "Curves
of Form" data.
Vessel Geometry and Sign Conventions Adopted
Vessel geometry is defined in figure below. All items are drawn to show the positive sign conventions adopted for
this method.
Some important characteristics of this picture are:
•
B is the Buoyancy Force provided by the vessel with level trim. Usually obtained from a "Curves of Form"
plot. In this procedure B is numerically equal to the vessel's displacement (i. e. B = ).
•
W is the total weight applied to the vessel. Usually obtained from a "Weights and Moments" analysis.
•
L is the length between the forward and after draft marks
•
LCG is the Longitudinal Center of Gravity location, normally obtained from a "Weights and Moments"
analysis.
•
LCB is the Longitudinal Center of Buoyancy location, usually obtained from a "Curves of Form" plot.
•
LCF is the Longitudinal Center of Floatation, normally obtained from a "Curves of Form" plot.
•
TA is the draft and the Aft Draft marks
•
TF is the draft at the Forward Draft marks
•
TM is the Draft Amidships, located midway between forward and aft draft marks
•
TLCF is the draft located at the Longitudinal Center of Floatation.
The sign conventions adopted for this presentation are:
•
Distances Aft of Amidships are Positive, applies to LCG and LCB
•
Trim by the stern is defined as Positive
•
Trim Moment causing trim by the stern is Positive
•
Trim Lever that causes trim by the stern is Positive
Now that the geometry is defined and the sign conventions are stated, we can proceed with the two basic
trimming cases.
Case I - Displacement & CG Location Known Find Forward & Aft Drafts
This option is utilized over and over again in design and operational stages to determine a vessel's responses to
various loading conditions.
Step 1 - Obtain Equilibrium
•
For equilibrium the vessel weight must equal the vessel's displacement, W = .
•
With this displacement enter the "Curves of Form" and obtain a draft. This draft (TLCF) obtained is the
draft present at the LCF location.
Step 2 - In the "Curves of Form" at this LCF draft obtain the following:
•
Moment to Trim
o
MTI Moment to Trim one Inch, for English Units of long tonsfeet/inch or
o
MTC Moment to change Trim one Centimeter, for Metric Units of
metric tonsmeters/cm.
•
Longitudinal Center of Buoyancy, LCB, feet or meters, with aft of amidships defined as positive
•
Longitudinal Center of Floatation, LCF, feet or meters, with aft of amidships defined as positive
Step 4 - Find the Trim.
•
First the trim lever is defined mathematically as Trim Lever = LCG - LCB, in either feet or meters. If this
value is positive trim by the stern should be produced. If it is negative the vessel should trim by the
bow. Sign convention consistency is extremely important. For instance if the LCG is 5 feet aft of
amidships and the LCB is 2 foot forward, the trimming lever would be equal to 5 - (-2) = positive 7
feet. Since the numerical value is positive this scenario will cause trim by the stern.
•
The applied trimming moment is defined mathematically as TM = (LCG - LCB)
•
The hydrostatic response trimming moment is defined mathematically as:
o
TM = TRIMMTI for English units
o
•
TM=TRIMMTC for metric units.
For equilibrium to occur, the applied trimming moment must equal the response trimming moment. The
previous defined equations are combined, algebraically rearranged with the following expressions for trim
obtained:
o
TRIM = (LCG-LCB)/MTI for English units of inches, the value obtained must be converted to feet,
by dividing by 12, prior to applying it in the formulas which follow.
o
TRIM = (LCG-LCB)/MTC for metric units of centimeters, the value obtained must be converted to
meters, by dividing by 100, prior to applying it in the formulas which follow.
o
When the above expressions are satisfied, there is corresponding subtle hydrostatic physical
reality for the trimmed vessel condition. This reality is that the LCB has moved to a new location
that is either directly above or below the LCG location. However, the initial LCB that must be
applied in these trim calculations correspond to the vessel in a level condition (i. e. obtained from
"Curves of Form" values).
Step 5 - Find the Forward and After Draft Via Geometry
•
This method involves the use of similar triangles and the position of the LCF.
•
For the forward draft the similar triangles present yield the following expression TRIM/L = TF/(LCF+L/2),
solve this for TF to obtain TF = (TRIM/L)(L/2+LCF) = TRIM(1/2+LCF/L), then apply the following
formula from geometry to obtain the forward draft TF = TLCF - TF = TLCF - TRIM(1/2+LCF/L).
•
For the aft draft the similar triangles present yield the following expression TRIM/L = TA/(L/2-LCF), solve
this for TA to obtain TA = (TRIM/L)(L/2-LCF) = TRIM(1/2-LCF/L), then apply the following formula from
geometry to obtain the forward draft TA = TLCF + TA = TLCF + TRIM(1/2-LCF/L).
•
Alternatively, based on geometry, the after draft may be more simply computed as follows:
TA = TF + TRIM.
•
With the forward and aft drafts known the mean draft can be quickly computed as follows:
TM = (TF + TA)/2.
Step 6 - Important Points to Remember
•
If the LCB is aft of the LCG the vessel will trim by the bow. If the LCB is forward of the LCG then the vessel
will trim by the stern. These principles apply regardless of the position of the LCF.
•
Sign convention consistency is extremely important. If they are not followed the formulas presented here
will not work properly.
Step 7 - Improvements Made to this site's Trim and Stability Sheets
•
The MTI or MTC values that are presented in the "Curves of Form" are based on the assumption that
metacentric radius in the longitudinal direction is equal to the metacentric height in the longitudinal
direction (i. e. BML = GML). This assumption yields approximations for moment to trim values. These
approximations are normally adequate since in most cases there is not much difference between the
BML and GML values. Furthermore the approximations must be made because the VCG values are not
known at the time that the "Curves of Form" are made.
•
However in the "Trim and Stability Sheets," that are available on this website, the VCG values are known
for the conditions at hand, so the moment to trim values are computed accurately. Three basic formulas
are applied. First, by definition, the restoring moment = GMLTan. Second geometry present requires
that Tan = Opposite/Adjacent = TRIM/L. Three, by definition GML = KML - VCG, where KML is obtained
from the "Curves of Form" instead of MTI or MTC. All three of these equations are combined and
rearranged yielding: MTF = (KML - VCG)/L. MTF in this case is moment to trim one foot, where TRIM
equals one foot. Note that ML can be obtained from the following formula: KML = BML + VCB. The "Curves
of Form" may just give BML and VCB, but this is alright since these can be summed to obtain the
KML value. Another article in this website, "Understanding Stability" explains the theory discussed in this
paragraph. However, a little adaptation is required by the reader because that article applies to stability
in the transverse direction and this article applies to stability in the longitudinal direction.
Case II - Forward & Aft Drafts Known, Find Displacement & LCG Location
This option is used by naval architects, yacht and boat designers, marine surveyors, marine inspectors and others
for deadweight surveys and for stability tests. It is also used by dock masters, by captains, mates, fisherman and
others who may want to determine a vessel's weight and center of gravity location.
The first goal of this analysis is to find the LCF draft. This draft is needed because the "Curves of Form" are based
on the LCF draft and not the mean draft. After this draft is determined, the primary goals of obtaining a
displacement and the LCG location are easily determined through the use of the "Curves of Form" data.
Step 1 - Calculate the Mean Draft & Trim Present
•
Compute the mean draft present, where TM = 1/2(TF + TA). Remember the "Curves of Form" are not based
on this mean draft but on the LCF draft. However this mean draft serves its purpose as a close estimate
for the LCF draft and is initially used to retrieve preliminary data from the "Curves of Form."
•
Compute the trim present, with this formula TRIM = TA - TF.
•
These values of draft and trim are now used to help determine the LCF draft (TLCF).
Step 2 - Obtain the LCF Draft Through Iteration
•
At TM go into the Curves of Form and obtain a initial value for LCF.
•
An expression for the LCF draft needs to be derived. Fortuitously the waterline slope (or
Tan =TRIML) and the ship length (L between forward and aft draft marks) are known. From similar
triangles we have TLCF / TRIM = LCF / L. From geometry we have TLCF = TM + TLCF. Combining the
preceding two equations we have: TLCF = TM + (TRIM)LCF / L
•
Compute the initial guess for LCF draft through application of TLCF = TM + (TRIM)LCF / L
•
Go back to the "Curves of Form" with initial TLCF just computed and obtain a new value for LCF.
•
Recompute the LCF draft, by using the LCF value just obtained into the following formula: TLCF = TM +
(TRIM)LCF / L.
•
The LCF just obtained should be close to the one previously calculated. If not, repeat this process using
the most recent LCF draft value to enter the "Curves of Form" to get a new LCF value. Recompute another
LCF draft using the formula TLCF = TM + (TRIM)LCF / L and compare it with the preceding LCF draft
computed, they now should be very close. Usually only need to iterate once. The last value for LCF draft
is the considered the actual LCF draft and it is applied in the rest of this analysis.
Step 3 - Obtain "Curves of Form" Data Based on the LCF Draft
•
With the last TLCF value enter the "Curves of Form" and obtain the following:
•
Displacement, 
•
Longitudinal Center of Buoyancy, LCB
•
Moment to Trim, MTI or MTC. Which term depends on applicable units system.
o
MTI for English units of inches, the value obtained from "Curves of Form" must be converted to
feet, by dividing by 12, prior to applying it in the formulas which follow.
o
MTC for metric units of centimeters, the value obtained from "Curves of Form" must be converted
to meters, by dividing by 100, prior to applying it in the formulas which follow.
Step 4 - Derive Relationships Between Trim and LCG
•
Two relationships for trimming are presented and then equated to each other, the combined result is then
manipulated to give an expression for computing LCG.
•
First the applied trimming moment is defined as TM = (LCG - LCB).
•
Second the hydrostatic response moment is defined as TM = MTITRIM.
•
These equations are equated to each other and solved for LCG to obtain the following result:
LCG = LCB + MTI TRIM /
Step 5 - Calculate the LCG Value
•
With the LCB, TRIM, MTI (converted to per foot or meter) and displacement compute the LCG using the
formula just derived in Step 4.
Step 6 - Important Points to Remember
•
It trim value is positive, the vessel is has trim by the stern (the stern is submerged deeper than the bow)
then the LCG must be located aft of the LCB.
•
If trim value is negative, the vessel has trim by the bow (the bow is submerged deeper than the stern),
then the LCG must be located forward of the LCB.
•
Sign convention consistency remains extremely important! If they are not followed exactly the formulas
presented here will not work properly.
Update: Another article on this website, "Understanding Ship and Boat Stability (Stability & Trim - Part 1)" is
meant to be a prelude to this article. This article apples to stability in the longitudinal direction, whereas the
prelude article applies to stability that is in the transverse direction.
Simple box barges also present an interesting and quick way to learn about stability, trim, list, weights and
moments. There is an article entitled "Barge Trim, List and Initial Stability (GM - metacentric heights)" that should
be helpful.
Understanding the parallel axis theorem is also very useful for both stability and structural analysis. This subject is
comprehensively discussed in an article entitled "Parallel Axis Theorem."
Application: The concepts described in this article are utilized in the following templates:
•
•
•
Trim and Stability Sheet, English Units
Trim and Stability Sheet, Metric Units
Quick Box Barge Calculations, English Units
Articles in this website are provided for education purposes only. It is understood and agreed that nothing expressed in the
articles contained in this website is intended or shall be construed to give any person, firm, or corporation any right, remedy
or claim against Hawaii Marine Company or any of its owners, officers, or employees.
Trimming calculations and procedures on bulk carriers | Maritime
Statistics
11
0
0
This post states the trimming calculations and procedures on board the bulk carriers. In
relation to Bulk carriers, the word ‘trimming’ has two meanings. The first meaning is the
process of making the cargo level in the Ship’s holds. This procedure is something to do with
utilizing the maximum space in the cargo holds.
The second meaning of trimming is to bring the ship to a certain draft [or trim] to be specific
while carrying out the completion of cargo. In simplistic terms, the procedure of distributing a
certain quantity of cargo into certain holds so that on completion the ship comes to a certain
draft and trim is called the trimming procedure on bulk carrier.
In this tutorial we shall check out how the calculations are done and why it is important for the
ship’s officers’ to familiarize themselves with these trimming calculations and procedures.
So, let us begin.
Prior carrying the trimming calculations, it is important that you take account of the following 3
things1. Be fully aware of the limiting draft of the ship. The limiting draft of the ship could be
dependent upon restrictions at load port, discharge port, load line zones, intermediate
port such as bunkering port or canal transit etc. The point is that the ship’s officer must
be fully conversant with the limiting draft of the ship.
2. Always take into account few centimeters of sag allowance esp for ship’s of larger size
and/or loading high density cargoes. Note that a prudent Chief Mate will always take
into account sag allowance in order to prevent overloading of ship. Overloading can
lead to numerous problems for a ship.
3. Always take penultimate holds (and not the extreme holds) for trimming esp for
Panamax and above size. For ships having 5 holds, end holds shall be used. Although,
this rule is not fixed and any hold can be used for carrying out trimming operations –
depending upon the final trim requirement and/or space available in the holds.
Having said above, sufficient amount of trimming quantity shall be kept in hand for final
trimming. This quantity shall be increased especially while loading in ports where the shore
scale is not frequent calibrated and the wrong calibration might result in reduction in planned
trimming quantity (as due to error the shore may load excess cargo).
Let us assume the case of Panamax Bulk carrier having 7 cargo holds. The intermediate Draft
Survey is done and vessel has arrived at the trimming stage.
The drafts obtained are –
Ford: 13.00 mtrs
Aft: 13.40 mtrs
Mid: 13.22 mtrs
The ship has trim of 0.40 mtrs and SAG of 2 cms.
The limiting draft of the ship is 13.482 mtrs and ship needs to finish loading on an Even Keel.
Step 1: Calculate the Cargo which can be loaded by calculating the Sinkage
Sinkage means how much more the ship can be submerged in the water by loading cargo such
that it comes to the limiting draft.
Sinkage has a simple formula –
Sinkage Available = Limiting draft – Current Midship draft – Sag allowance
Note that the Current Midship draft is the VISUAL draft being noted and not the Mean draft of
the ship. In this case, it is 13.22 mtrs.
Hence Sinkage Available = 13.482 – 13.220 = 0.262 mtrs or 26.2 cms.
I have not taken any SAG allowance, but if in your experience particularly when loading High
Density Cargoes always take few cms of Sag allowance. It will aid you to not to overload the
ship.
After calculating the sinkage, let us calculate how much cargo which will result in that sinkage.
Cargo to load = Sinkage Available (in cms) x TPC
= 26.2 x 68.30 = 1789.46 tonnes ~ 1790 tonnes of cargo.
The TPC value used is the one specified for your hydrostatic draft.
Now it’s time to know what are Trimming Tables
Trimming Tables
Trimming tables gives effect on ship’s fore and aft draft when 100 MT of cargo is loaded into a
certain compartment. Trimming tables can be a part of Trim and Stability Booklet or can be
provided separately. Ship officers shall well familiarize themselves with usage of trimming
tables as different shipyards can present the data in such tables in different formats.
Once such format is specified below belonging to a bulk carrier. Note that Cargo Hold 1~5 are
not mentioned explicitly but instead they are named R.1.01 ~ R.1.05.
However we shall keep things simple and use proper names for the compartment. In this
problem I intend to use Cargo Hold 2 and 6 for trimming so this is how the data for the same
will look like –
Above data shows the effect on forward drafts when 100 mt of cargo is loaded into a cargo
hold no 2 and 6. The words TF and TA states the correction for Forward and Aft draft
respectively. While the numbers following 11,12,13,14 is the mean draft of the ship which is
used to enter the tables.
As per the table if 100 tonnes of Cargo is loaded in Cargo Hold No 2 for ship at mean draft of
11.00 mtrs the Forward draft will increase by 0.056 mtrs and Aft draft will decrease by -0.022
mtrs. Similarly, for mean draft of 12 mtrs if 100 tonnes of cargo is loaded in Hold No 6 the
Forward draft will decrease by 0.011 mtrs and Aft draft will increase by 0.041. The negative
sign means that the correction shall be subtracted (draft is reduced) and positive sign means
correction shall be added (draft is increased).
Moving on, the ship has a mean draft of 13.20 mtrs ((13.00 + 13.40)/2 = 13.20) and therefore
we need to interpolate between the values of 13 and 14 mtrs as shown –
On interpolation we get the following values –
So let us move on to our next step.
Step 2: Calculate total trim change caused by the holds in which cargo is being loaded
This is done by making a simple table as follows –
In this table we are finding out the change of trim – obtained by taking a difference of the ford
and aft sinkage values. The important thing to note here is we have to KEEP the signs active.
Note in the case of Cargo Hold No 2 – the corrections are actually added when the difference is
taken and similar case is with the values of Cargo hold No 6. The total change of trim is
obtained by ADDING values for both holds as shown in red box.
Step No 3: Calculating cargo to load in 1st Hold (Hold No 2)
Now we have to calculate the quantity we shall load in Cargo Hold no 2. The ship presently has
a trim of 0.40 mtrs by stern. Our first aim is to bring the ship to Even Keel. This can be achieved
only by loading certain quantity of cargo in Hold 2 such that it causes a trim change of 0.40
mtrs by head and brings the ship to even keel. This can be calculated by using the following
formula –
So as you can see we need to load 526 tonnes of cargo in Hold No 2 in order to bring the ship
to even keel.
Step 4: Calculate the cargo to be loaded in Second Hold (Hold No 6)
From above we know that 526 tonnes is to be loaded in Hold 2. So the balance cargo to load is
1790 – 526 = 1264 tonnes
Now this cargo needs to be distributed in Hold 2 and Hold 6 such that the ship is loaded to her
limiting draft and NO TRIM CHANGE IS CAUSED (as we need the ship to finish loading on an
even keel). Let us first calculate the cargo which can be loaded into HOLD NO 2.
This can be calculated by the following formula –
Alternatively you can calculate the Cargo to load in Hold No 6 by using the same formula only
but replacing the “Change of trim caused by #6” with “Change in trim caused by cargo hold #2”.
Going by above; if say 508 tonnes of cargo is to be loaded in Hold No 2, then balance cargo to
be loaded in Hold No 6 is –
1264 – 508 = 756 tonnes (to be loaded in Hold 6)
Summarizing above results –
Cargo Hold No 2 needs to load 508 tonnes to bring the ship to even keel. Thereafter, Hold No 2
and Hold No 6 needs to load 526 tonnes and 756 tonnes respectively in order to bring the ship
to her draft while keeping the trim same ie Even Keel. This calculation needs to be done prior
carrying out the Trimming and therefore the calculations shall always be checked and rechecked. Keeping these formulas in mind will save you a lot of time.
For better understanding you can watch the video hereJust in case you want to get your free copy of a Trimming Program you can write to us
at ask@funnel2tunnel.com and we shall be happy to provide you with a sheet which can be
used on any ship after making few minor changes to the data elements.
For exciting tutorial videos follow our youtube channel here.
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Do share your thoughts in the comment section below.
Fair Seas and Bonn Voyage!
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0 Trimming calculations and procedures on bulk carriers 4 Published by marinetales
11 0 0 This post states the trimming calculations and procedures on board the bulk carriers.
In relation to Bulk carriers, the word ‘trimming’ has two meanings. The first meaning is the
process of making the cargo level in the Ship’s holds. This procedure is something to do with
utilizing the maximum space in the cargo holds. The second meaning of trimming is to bring
the ship to a certain draft [or trim] to be specific while carrying out the completion of cargo. In
simplistic terms, the procedure of distributing a certain quantity of cargo into certain holds so
that on completion the ship comes to a certain draft and trim is called the trimming procedure
on bulk carrier. In this tutorial we shall check out how the calculations are done and why it is
important for the ship’s officers’ to familiarize themselves with these trimming calculations and
procedures. So, let us begin. Prior carrying the trimming calculations, it is important that you
take account of the following 3 things- Be fully aware of the limiting draft of the ship. The
limiting draft of the ship could be dependent upon restrictions at load port, discharge port, load
line zones, intermediate port such as bunkering port or canal transit etc. The point is that the
ship’s officer must be fully conversant with the limiting draft of the ship. Always take into
account few centimeters of sag allowance esp for ship’s of larger size and/or loading high
density cargoes. Note that a prudent Chief Mate will always take into account sag allowance in
order to prevent overloading of ship. Overloading can lead to numerous problems for a
ship. Always take penultimate holds (and not the extreme holds) for trimming esp for
Panamax and above size. For ships having 5 holds, end holds shall be used. Although, this rule
is not fixed and any hold can be used for carrying out trimming operations – depending upon
the final trim requirement and/or space available in the holds. Having said above, sufficient
amount of trimming quantity shall be kept in hand for final trimming. This quantity shall be
increased especially while loading in ports where the shore scale is not frequent calibrated and
the wrong calibration might result in reduction in planned trimming quantity (as due to error the
shore may load excess cargo). Let us assume the case of Panamax Bulk carrier having 7 cargo
holds. The intermediate Draft Survey is done and vessel has arrived at the trimming stage. The
drafts obtained are – Ford: 13.00 mtrs Aft: 13.40 mtrs Mid: 13.22 mtrs The ship has trim of
0.40 mtrs and SAG of 2 cms. The limiting draft of the ship is 13.482 mtrs and ship needs to
finish loading on an Even Keel. Step 1: Calculate the Cargo which can be loaded by calculating
the Sinkage Sinkage means how much more the ship can be submerged in the water by loading
cargo such that it comes to the limiting draft. Sinkage has a simple formula – Sinkage
Available = Limiting draft – Current Midship draft – Sag allowance Note that the Current
Midship draft is the VISUAL draft being noted and not the Mean draft of the ship. In this case, it
is 13.22 mtrs. Hence Sinkage Available = 13.482 – 13.220 = 0.262 mtrs or 26.2 cms. I have
not taken any SAG allowance, but if in your experience particularly when loading High Density
Cargoes always take few cms of Sag allowance. It will aid you to not to overload the ship. After
calculating the sinkage, let us calculate how much cargo which will result in that
sinkage. Cargo to load = Sinkage Available (in cms) x TPC = 26.2 x 68.30 = 1789.46 tonnes ~
1790 tonnes of cargo. The TPC value used is the one specified for your hydrostatic draft. Now
it’s time to know what are Trimming Tables Trimming Tables Trimming tables gives effect on
ship’s fore and aft draft when 100 MT of cargo is loaded into a certain compartment. Trimming
tables can be a part of Trim and Stability Booklet or can be provided separately. Ship officers
shall well familiarize themselves with usage of trimming tables as different shipyards can
present the data in such tables in different formats. Once such format is specified below
belonging to a bulk carrier. Note that Cargo Hold 1~5 are not mentioned explicitly but instead
they are named R.1.01 ~ R.1.05. However we shall keep things simple and use proper names
for the compartment. In this problem I intend to use Cargo Hold 2 and 6 for trimming so this is
how the data for the same will look like – Above data shows the effect on forward drafts when
100 mt of cargo is loaded into a cargo hold no 2 and 6. The words TF and TA states the
correction for Forward and Aft draft respectively. While the numbers following 11,12,13,14 is
the mean draft of the ship which is used to enter the tables. As per the table if 100 tonnes of
Cargo is loaded in Cargo Hold No 2 for ship at mean draft of 11.00 mtrs the Forward draft will
increase by 0.056 mtrs and Aft draft will decrease by -0.022 mtrs. Similarly, for mean draft of
12 mtrs if 100 tonnes of cargo is loaded in Hold No 6 the Forward draft will decrease by 0.011
mtrs and Aft draft will increase by 0.041. The negative sign means that the correction shall be
subtracted (draft is reduced) and positive sign means correction shall be added (draft is
increased). Moving on, the ship has a mean draft of 13.20 mtrs ((13.00 + 13.40)/2 = 13.20) and
therefore we need to interpolate between the values of 13 and 14 mtrs as shown – On
interpolation we get the following values – So let us move on to our next step. Step 2:
Calculate total trim change caused by the holds in which cargo is being loaded This is done by
making a simple table as follows – In this table we are finding out the change of trim –
obtained by taking a difference of the ford and aft sinkage values. The important thing to note
here is we have to KEEP the signs active. Note in the case of Cargo Hold No 2 – the
corrections are actually added when the difference is taken and similar case is with the values
of Cargo hold No 6. The total change of trim is obtained by ADDING values for both holds as
shown in red box. Step No 3: Calculating cargo to load in 1st Hold (Hold No 2) Now we have to
calculate the quantity we shall load in Cargo Hold no 2. The ship presently has a trim of 0.40
mtrs by stern. Our first aim is to bring the ship to Even Keel. This can be achieved only by
loading certain quantity of cargo in Hold 2 such that it causes a trim change of 0.40 mtrs by
head and brings the ship to even keel. This can be calculated by using the following formula
– So as you can see we need to load 526 tonnes of cargo in Hold No 2 in order to bring the
ship to even keel. Step 4: Calculate the cargo to be loaded in Second Hold (Hold No 6) From
above we know that 526 tonnes is to be loaded in Hold 2. So the balance cargo to load is 1790
– 526 = 1264 tonnes Now this cargo needs to be distributed in Hold 2 and Hold 6 such that the
ship is loaded to her limiting draft and NO TRIM CHANGE IS CAUSED (as we need the ship to
finish loading on an even keel). Let us first calculate the cargo which can be loaded into HOLD
NO 2. This can be calculated by the following formula – Alternatively you can calculate the
Cargo to load in Hold No 6 by using the same formula only but replacing the “Change of trim
caused by #6” with “Change in trim caused by cargo hold #2”. Going by above; if say 508
tonnes of cargo is to be loaded in Hold No 2, then balance cargo to be loaded in Hold No 6 is
– 1264 – 508 = 756 tonnes (to be loaded in Hold 6) Summarizing above results – Cargo Hold
No 2 needs to load 508 tonnes to bring the ship to even keel. Thereafter, Hold No 2 and Hold
No 6 needs to load 526 tonnes and 756 tonnes respectively in order to bring the ship to her
draft while keeping the trim same ie Even Keel. This calculation needs to be done prior carrying
out the Trimming and therefore the calculations shall always be checked and re-checked.
Keeping these formulas in mind will save you a lot of time. For better understanding you can
watch the video here- Just in case you want to get your free copy of a Trimming Program you
can write to us at ask@funnel2tunnel.com and we shall be happy to provide you with a sheet
which can be used on any ship after making few minor changes to the data elements. For
exciting tutorial videos follow our youtube channel here. Follow us on various other platforms –
Twitter: https://twitter.com/funnel2tunnel Facebook:
https://www.facebook.com/funnel2tunnel/ Instagram:
https://www.instagram.com/funnel2tunnel/ Linkedin:
https://www.linkedin.com/company/funn… Do share your thoughts in the comment section
below. Fair Seas and Bonn Voyage! 24 Comments Skip Estipona says: May 27, 2021 at 9:23
am Thank you,much appreciated if you send trimming programs. Log in to Reply seawizard
says: June 1, 2021 at 4:32 pm We have replied to you! Log in to Reply Rolan Lapshyn says: May
19, 2021 at 1:37 pm Good day, I will be very appreciate if You will help me and send trimming
program for bulker Panamax on my e-mail: rolanlapshyn@gmail.com Log in to Reply seawizard
says: June 1, 2021 at 4:32 pm We have replied to you! Log in to Reply Stanley says: April 11,
2021 at 4:32 pm Nice presentation. Could you please send me a copy of your excel sheet?
Thanks in advance. Log in to Reply seawizard says: June 1, 2021 at 4:33 pm We have replied to
you! Log in to Reply Nazrul says: January 28, 2021 at 2:54 am Is trimming table provide the
draft change at the draft mark or draft at the perpendicular? Log in to Reply name says: April
20, 2021 at 5:03 pm The trimming table provides change of drafts fwd and aft upon
loading/discharging certain quantity of cargo. Such changes of draft can be applied to draft
marks. Log in to Reply Anonymous says: May 2, 2021 at 7:35 am Do you have a program for 9
cargo holds. Sometimes trimming holds are 3 holds. If you have please send it to me my email
add LOY1228@YAHOO.COM.PH Log in to Reply Anonymous says: May 2, 2021 at 7:32 am Do
you have a program for 9 cargo holds. Sometimes trimming holds are 3 holds. If you have
please send it to me my email add LOY1228@YAHOO.COM.PH Log in to Reply Althaff says:
December 24, 2020 at 7:16 pm Requested to send trimming program Log in to Reply
marinetales says: January 11, 2021 at 9:39 pm please write to us at ask@funnel2tunnel.com
and we shall send you the copy. Log in to Reply Anonymous says: December 15, 2020 at 7:57
am I’m in the process of making my own excel form draft survey & trimming using table, lcg, lcf
template. If you could share an excel form of this trimming calculation, plz send it to my email
wilfrid.ang@gmail.com This will be a great help for me. Thanks Log in to Reply Ömer Gürsoy
says: November 25, 2020 at 9:49 am Very helpfull information. I will be very pleased if you
share the trimming program with me. Log in to Reply Amit Sood says: November 9, 2020 at
2:41 pm Kindly requesting you to share the trimming program to my mail id. Log in to Reply
marinetales says: November 10, 2020 at 2:49 pm Hi Amit … we have replied to your mail. Plz
check. Log in to Reply seawizard says: June 1, 2021 at 4:34 pm We have replied to you! Log in
to Reply james says: October 29, 2020 at 12:33 pm can you share the copy of trimming
program on my email i.d : rebello75hotmail.com Log in to Reply marinetales says: November 1,
2020 at 12:19 am Hi James we have shared it to you! Log in to Reply Roselito Salomon
Ventures says: October 16, 2020 at 2:18 am Thank You very much Very useful really apprecite
your presentation More Power Log in to Reply marinetales says: November 1, 2020 at 12:20 am
Thanks Roselito. Glad you liked it. Keep following. Log in to Reply marinetales says: November
10, 2020 at 2:50 pm Thanks Roselito…. glad you liked it. Log in to Reply Sarpreet singh says:
May 20, 2020 at 10:28 am Nice demostration sir Log in to Reply marinetales says: May 20,
2020 at 11:50 am Thanks Sarpreet. Glad it helped you. Log in to Reply Leave a Reply You must
be logged in to post a comment. What’s New? → In Maritime Technology → Shipping News →
New Regulations → Maritime Facts Name* Email* Useful links → Sailor's Corner → Learn →
Ask → Free Books → Free Notes Our mission An effort to bring the Maritime Community
together. This is for all the sailors, shipping enthusiasts, dreamers of the sea, and the would be
sailors. Keep yourself up-to-date with the Maritime World. 0 Hold cleaning standards you
should know about June 28, 2021 0 Everything you need to know about Grain Loading | Pre
loading preparations | Part II June 16, 2021 Copyright @ funnel2tunnel 2021. All Rights
Reserved. 0 Home Learn Ask Shop What’s New? Sailor’s Corner User Account 0 Trimming
calculations and procedures on bulk carriers 4 Published by marinetales 11 0 0 This post
states the trimming calculations and procedures on board the bulk carriers. In relation to Bulk
carriers, the word ‘trimming’ has two meanings. The first meaning is the process of making the
cargo level in the Ship’s holds. This procedure is something to do with utilizing the maximum
space in the cargo holds. The second meaning of trimming is to bring the ship to a certain draft
[or trim] to be specific while carrying out the completion of cargo. In simplistic terms, the
procedure of distributing a certain quantity of cargo into certain holds so that on completion
the ship comes to a certain draft and trim is called the trimming procedure on bulk carrier. In
this tutorial we shall check out how the calculations are done and why it is important for the
ship’s officers’ to familiarize themselves with these trimming calculations and procedures. So,
let us begin. Prior carrying the trimming calculations, it is important that you take account of
the following 3 things- Be fully aware of the limiting draft of the ship. The limiting draft of the
ship could be dependent upon restrictions at load port, discharge port, load line zones,
intermediate port such as bunkering port or canal transit etc. The point is that the ship’s officer
must be fully conversant with the limiting draft of the ship. Always take into account few
centimeters of sag allowance esp for ship’s of larger size and/or loading high density
cargoes. Note that a prudent Chief Mate will always take into account sag allowance in order
to prevent overloading of ship. Overloading can lead to numerous problems for a ship. Always
take penultimate holds (and not the extreme holds) for trimming esp for Panamax and above
size. For ships having 5 holds, end holds shall be used. Although, this rule is not fixed and any
hold can be used for carrying out trimming operations – depending upon the final trim
requirement and/or space available in the holds. Having said above, sufficient amount of
trimming quantity shall be kept in hand for final trimming. This quantity shall be increased
especially while loading in ports where the shore scale is not frequent calibrated and the wrong
calibration might result in reduction in planned trimming quantity (as due to error the shore
may load excess cargo). Let us assume the case of Panamax Bulk carrier having 7 cargo
holds. The intermediate Draft Survey is done and vessel has arrived at the trimming stage. The
drafts obtained are – Ford: 13.00 mtrs Aft: 13.40 mtrs Mid: 13.22 mtrs The ship has trim of
0.40 mtrs and SAG of 2 cms. The limiting draft of the ship is 13.482 mtrs and ship needs to
finish loading on an Even Keel. Step 1: Calculate the Cargo which can be loaded by calculating
the Sinkage Sinkage means how much more the ship can be submerged in the water by loading
cargo such that it comes to the limiting draft. Sinkage has a simple formula – Sinkage
Available = Limiting draft – Current Midship draft – Sag allowance Note that the Current
Midship draft is the VISUAL draft being noted and not the Mean draft of the ship. In this case, it
is 13.22 mtrs. Hence Sinkage Available = 13.482 – 13.220 = 0.262 mtrs or 26.2 cms. I have
not taken any SAG allowance, but if in your experience particularly when loading High Density
Cargoes always take few cms of Sag allowance. It will aid you to not to overload the ship. After
calculating the sinkage, let us calculate how much cargo which will result in that
sinkage. Cargo to load = Sinkage Available (in cms) x TPC = 26.2 x 68.30 = 1789.46 tonnes ~
1790 tonnes of cargo. The TPC value used is the one specified for your hydrostatic draft. Now
it’s time to know what are Trimming Tables Trimming Tables Trimming tables gives effect on
ship’s fore and aft draft when 100 MT of cargo is loaded into a certain compartment. Trimming
tables can be a part of Trim and Stability Booklet or can be provided separately. Ship officers
shall well familiarize themselves with usage of trimming tables as different shipyards can
present the data in such tables in different formats. Once such format is specified below
belonging to a bulk carrier. Note that Cargo Hold 1~5 are not mentioned explicitly but instead
they are named R.1.01 ~ R.1.05. However we shall keep things simple and use proper names
for the compartment. In this problem I intend to use Cargo Hold 2 and 6 for trimming so this is
how the data for the same will look like – Above data shows the effect on forward drafts when
100 mt of cargo is loaded into a cargo hold no 2 and 6. The words TF and TA states the
correction for Forward and Aft draft respectively. While the numbers following 11,12,13,14 is
the mean draft of the ship which is used to enter the tables. As per the table if 100 tonnes of
Cargo is loaded in Cargo Hold No 2 for ship at mean draft of 11.00 mtrs the Forward draft will
increase by 0.056 mtrs and Aft draft will decrease by -0.022 mtrs. Similarly, for mean draft of
12 mtrs if 100 tonnes of cargo is loaded in Hold No 6 the Forward draft will decrease by 0.011
mtrs and Aft draft will increase by 0.041. The negative sign means that the correction shall be
subtracted (draft is reduced) and positive sign means correction shall be added (draft is
increased). Moving on, the ship has a mean draft of 13.20 mtrs ((13.00 + 13.40)/2 = 13.20) and
therefore we need to interpolate between the values of 13 and 14 mtrs as shown – On
interpolation we get the following values – So let us move on to our next step. Step 2:
Calculate total trim change caused by the holds in which cargo is being loaded This is done by
making a simple table as follows – In this table we are finding out the change of trim –
obtained by taking a difference of the ford and aft sinkage values. The important thing to note
here is we have to KEEP the signs active. Note in the case of Cargo Hold No 2 – the
corrections are actually added when the difference is taken and similar case is with the values
of Cargo hold No 6. The total change of trim is obtained by ADDING values for both holds as
shown in red box. Step No 3: Calculating cargo to load in 1st Hold (Hold No 2) Now we have to
calculate the quantity we shall load in Cargo Hold no 2. The ship presently has a trim of 0.40
mtrs by stern. Our first aim is to bring the ship to Even Keel. This can be achieved only by
loading certain quantity of cargo in Hold 2 such that it causes a trim change of 0.40 mtrs by
head and brings the ship to even keel. This can be calculated by using the following formula
– So as you can see we need to load 526 tonnes of cargo in Hold No 2 in order to bring the
ship to even keel. Step 4: Calculate the cargo to be loaded in Second Hold (Hold No 6) From
above we know that 526 tonnes is to be loaded in Hold 2. So the balance cargo to load is 1790
– 526 = 1264 tonnes Now this cargo needs to be distributed in Hold 2 and Hold 6 such that the
ship is loaded to her limiting draft and NO TRIM CHANGE IS CAUSED (as we need the ship to
finish loading on an even keel). Let us first calculate the cargo which can be loaded into HOLD
NO 2. This can be calculated by the following formula – Alternatively you can calculate the
Cargo to load in Hold No 6 by using the same formula only but replacing the “Change of trim
caused by #6” with “Change in trim caused by cargo hold #2”. Going by above; if say 508
tonnes of cargo is to be loaded in Hold No 2, then balance cargo to be loaded in Hold No 6 is
– 1264 – 508 = 756 tonnes (to be loaded in Hold 6) Summarizing above results – Cargo Hold
No 2 needs to load 508 tonnes to bring the ship to even keel. Thereafter, Hold No 2 and Hold
No 6 needs to load 526 tonnes and 756 tonnes respectively in order to bring the ship to her
draft while keeping the trim same ie Even Keel. This calculation needs to be done prior carrying
out the Trimming and therefore the calculations shall always be checked and re-checked.
Keeping these formulas in mind will save you a lot of time. For better understanding you can
watch the video here- Just in case you want to get your free copy of a Trimming Program you
can write to us at ask@funnel2tunnel.com and we shall be happy to provide you with a sheet
which can be used on any ship after making few minor changes to the data elements. For
exciting tutorial videos follow our youtube channel here. Follow us on various other platforms –
Twitter: https://twitter.com/funnel2tunnel Facebook:
https://www.facebook.com/funnel2tunnel/ Instagram:
https://www.instagram.com/funnel2tunnel/ Linkedin:
https://www.linkedin.com/company/funn… Do share your thoughts in the comment section
below. Fair Seas and Bonn Voyage! 24 Comments Skip Estipona says: May 27, 2021 at 9:23
am Thank you,much appreciated if you send trimming programs. Log in to Reply seawizard
says: June 1, 2021 at 4:32 pm We have replied to you! Log in to Reply Rolan Lapshyn says: May
19, 2021 at 1:37 pm Good day, I will be very appreciate if You will help me and send trimming
program for bulker Panamax on my e-mail: rolanlapshyn@gmail.com Log in to Reply seawizard
says: June 1, 2021 at 4:32 pm We have replied to you! Log in to Reply Stanley says: April 11,
2021 at 4:32 pm Nice presentation. Could you please send me a copy of your excel sheet?
Thanks in advance. Log in to Reply seawizard says: June 1, 2021 at 4:33 pm We have replied to
you! Log in to Reply Nazrul says: January 28, 2021 at 2:54 am Is trimming table provide the
draft change at the draft mark or draft at the perpendicular? Log in to Reply name says: April
20, 2021 at 5:03 pm The trimming table provides change of drafts fwd and aft upon
loading/discharging certain quantity of cargo. Such changes of draft can be applied to draft
marks. Log in to Reply Anonymous says: May 2, 2021 at 7:35 am Do you have a program for 9
cargo holds. Sometimes trimming holds are 3 holds. If you have please send it to me my email
add LOY1228@YAHOO.COM.PH Log in to Reply Anonymous says: May 2, 2021 at 7:32 am Do
you have a program for 9 cargo holds. Sometimes trimming holds are 3 holds. If you have
please send it to me my email add LOY1228@YAHOO.COM.PH Log in to Reply Althaff says:
December 24, 2020 at 7:16 pm Requested to send trimming program Log in to Reply
marinetales says: January 11, 2021 at 9:39 pm please write to us at ask@funnel2tunnel.com
and we shall send you the copy. Log in to Reply Anonymous says: December 15, 2020 at 7:57
am I’m in the process of making my own excel form draft survey & trimming using table, lcg, lcf
template. If you could share an excel form of this trimming calculation, plz send it to my email
wilfrid.ang@gmail.com This will be a great help for me. Thanks Log in to Reply Ömer Gürsoy
says: November 25, 2020 at 9:49 am Very helpfull information. I will be very pleased if you
share the trimming program with me. Log in to Reply Amit Sood says: November 9, 2020 at
2:41 pm Kindly requesting you to share the trimming program to my mail id. Log in to Reply
marinetales says: November 10, 2020 at 2:49 pm Hi Amit … we have replied to your mail. Plz
check. Log in to Reply seawizard says: June 1, 2021 at 4:34 pm We have replied to you! Log in
to Reply james says: October 29, 2020 at 12:33 pm can you share the copy of trimming
program on my email i.d : rebello75hotmail.com Log in to Reply marinetales says: November 1,
2020 at 12:19 am Hi James we have shared it to you! Log in to Reply Roselito Salomon
Ventures says: October 16, 2020 at 2:18 am Thank You very much Very useful really apprecite
your presentation More Power Log in to Reply marinetales says: November 1, 2020 at 12:20 am
Thanks Roselito. Glad you liked it. Keep following. Log in to Reply marinetales says: November
10, 2020 at 2:50 pm Thanks Roselito…. glad you liked it. Log in to Reply Sarpreet singh says:
May 20, 2020 at 10:28 am Nice demostration sir Log in to Reply marinetales says: May 20,
2020 at 11:50 am Thanks Sarpreet. Glad it helped you. Log in to Reply Leave a Reply You must
be logged in to post a comment. What’s New? → In Maritime Technology → Shipping News →
New Regulations → Maritime Facts Name* Email* Useful links → Sailor's Corner → Learn →
Ask → Free Books → Free Notes Our mission An effort to bring the Maritime Community
together. This is for all the sailors, shipping enthusiasts, dreamers of the sea, and the would be
sailors. Keep yourself up-to-date with the Maritime World. 0 Hold cleaning standards you
should know about June 28, 2021 0 Everything you need to know about Grain Loading | Pre
loading preparations | Part II June 16, 2021 Copyright @ funnel2tunnel 2021. All Rights
Reserved. 0 Home Learn Ask Shop What’s New? Sailor’s Corner User Account ShareThis Copy
and Paste