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MANUAL

KattegattDesign

PROJECT NO. P1114-00

DOC. NO. P1114-00-040-MA-001

CLIENT:

Chalmers Tekniska Hgskola

PROJECT NAME:

MMA136 Ship Geometry and Hydrostatics

SUBJECT:

Design Assignment Guidance

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Project: MMA136 - Ship Geometry and Hydrostatics

Subject: Design Assignment Guidance

Issued By: Jan Bergholtz

Proj: P1114-00

Date: 31 Aug 11

Page: 2

Author: JBz

CONTENTS

1 INTRODUCTION .............................................................................................................. 3

1.1 Objective ....................................................................................................................... 3

1.2 Purpose ......................................................................................................................... 3

1.3 Hull Modelling and Stability Analysis Exercise in General ................................................ 3

2 BASIC SHIP GEOMETRY ................................................................................................... 4

2.1 Ships Lines .................................................................................................................... 4

2.1.1 Lines and Body Plan ..................................................................................................................4

2.1.2 Reference System .....................................................................................................................7

2.2 Main Particulars ............................................................................................................. 82.2.1 Datum Points ............................................................................................................................8

2.2.2 Moulded Dimensions ................................................................................................................8

2.3 Freeboard and WT Integrity ............................................................................................ 9

2.3.1 Buoyant Hull ..............................................................................................................................9

2.3.2 WT Subdivision ....................................................................................................................... 10

3 COMPUTER AIDED NAVAL ARCHITECTURAL DESIGN WORK ............................................ 11

3.1 Hull Modelling Basics using Autoship ............................................................................. 11

3.1.1 General ................................................................................................................................... 11

3.1.2 Control Points ........................................................................................................................ 11

3.1.3 Edit Points .............................................................................................................................. 123.1.4 Surfaces .................................................................................................................................. 13

3.1.5 Rows and Columns ................................................................................................................. 13

3.1.6 Knuckles and Chines ............................................................................................................... 14

3.1.7 Degree of Curvature............................................................................................................... 14

3.1.8 Direction ................................................................................................................................. 14

3.1.9 Ship Hull Assembly and Analyses ........................................................................................... 15

3.2 Subdivision and Compartment definition in Modelmaker............................................... 16

3.2.1 General ................................................................................................................................... 16

3.2.2 Parts, Components and Shapes ............................................................................................. 16

3.2.3 Command Script Files ............................................................................................................ 17

3.2.4 ModelmakerCmd-File Example ............................................................................................. 19

3.3 Hydrostatic and Stability Analyses in Autohydro ............................................................ 22

3.3.1 General ................................................................................................................................... 22

3.3.2 Run Script Files for Hydrostactics .......................................................................................... 22

3.3.3 Run Script Files for Intact Stability Analysis ........................................................................... 23

3.3.4 Autohydro Hydrostatics Example ........................................................................................... 25

3.3.5 Autohydro Loading Condition Stability Evaluation Example.................................................. 27

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1 INTRODUCTION

1.1 Objective

Objective The course of Ship Geometry and Hydrostatics includes one exercise in Hull Modelling

and Stability Analysis. The objective is to provide understanding of and some

experience in using modern computer software in naval architectural design work.

1.2 Purpose

Purpose The purpose of this document is to constitute guidance to the execution of a Hull

Modelling and Stability Analysis task, using the naval architectural computer softwaretools Autoship, Modelmaker and Autohydro. Furthermore, this document presents

specifications of the Vessels to be modelled and analysed within the exercise.

1.3 Hull Modelling and Stability Analysis Exercise in General

Supervision The design workshop classes will be in the Ritsalen according to schedule, and will be

supervised by:

Jan Bergholtz Kattegatt Design AB

[email protected]

Ana Sanz Kattegatt Design AB

[email protected]

Exercise

moments

The exercise will be carried out as five moments:

1. Hull Modelling Autoship

2. Verification of Hydrostatic Properties Autoship & Autohydro

3. Modelling of Compartments Modelmaker

4. Intact Stability Analysis, two Loading Conditions Autohydro

5.

Damage Stability Probabilistic Assessment Autohydro / MS Excel

For approval all five tasks must be fulfilled, a written report shall be established

comprising Hydrostatic Tables, Tank Capacities and Stability Analyses of two Loading

Conditions, e.g. Full Load Departure and Ballast Condition Departure, and finally an

adequate documentation of the Probabilistic Damage Stability Assessment.

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2 BASIC SHIP GEOMETRY

2.1 Ships Lines

2.1.1 Lines and Body Plan

The exterior shape of a ships hull is a curved surface defined by the Ships Lines.

Precise and unambiguous means are needed to describe this surface, as the ships

form must be configured to accommodate all internal volumes, must meet buoyancy

and stability constraints, must show acceptable speed power, seakeeping and

manoeuvring characteristics and finally must be buildable.

Lines Hence, the Lines consist of orthographic projections of the intersections of the hullform with three mutually perpendicular sets of planes, seeFigure 2.1.1.

Figure 2.1.1 Ship Lines Plan

Normally ships have only one plane of symmetry, the centreplane, which constitutes a

principal vertical plane of reference. The shape of a ship cut by this plane is known as

the profile, see Figure 2.1.2. Vertical sections parallel to the centreplane, spaced for

convenient definition of the hull form and identified by their distance to the

centreplane, are called buttocks.

Centreplan,

Profile

Figure 2.1.2 Centreplane, Profile

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A waterline plane is a plane perpendicular to the centreplane, selected as a principal

horizontal reference plane, Figure 2.1.3.

Waterline

Plane

Figure 2.1.3 Waterline plane

The Design Water Line, DWL, represents the waterline near which the fully loaded ship

is intended to float. The waterlines are defined by their height over the base line.

A Plane perpendicular to both the centreplane and the waterline plane is defined as a

transverse plane, which normally exhibits symmetry around the Centre Line, Figure

2.1.4.

Transverse

Plane

Figure 2.1.4 Transverse Plane

Frames The transverse sections are often referred to as the frames. The distance between the

frames is depending on what purpose the frames are intended to fulfill. For hydrostatic

calculations the length between perpendiculars divided into a set of 21 equidistant

frames, #0 - #20, and a more dense spacing towards the forward and aft ends are

normally considered to be sufficient. During the production phase, however, each

building frame must of course be defined.

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Body Plan A drawing comprising a set of frames is often referred to as the Body Plan where the

Fore Body is represented on the right hand side of the centre line and the After Body on

the left hand side,Figure 2.1.5.

Figure 2.1.5 Body Plan

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2.1.2 Reference System

CoordinateSystem The coordinate system, most commonly used, has its datum point, origo, at theintersection between the centreplane, the Base Line which is the longitudinal horizontal

line parallel to the waterline plane at the upper surface of the keel plating and the

transverse plane through the axis of the rudder stock, see Figure 2.1.6.

Positive

Directions

The longitudinal axis is positive from stern towards bow, the transverse axis is positive

from centre line, CL, towards the starboard side, SB, and the vertical axis is positive

from base line, BL, and upwards.

Figure 2.1.6 Coordinate System

AP

FP

X

Y

Z

LPP

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2.2 Main Particulars

2.2.1 Datum Points

For practical reasons the waterlines, buttocks and frames are evenly spaced and datum

points are needed to start from. A longitudinal reference point at the fore end of the

ship is provided by the intersection of the Design Water Line, DWL, and the bow

contour. The line through this point, perpendicular to the DWL, is called the Forward

Perpendicular, FP. The Aft Perpendicular is often taken as the axis through the rudder

stock or the intersection of the DWL and the transom profile,Figure 2.2.1.

Fwd and Aft

Perpendic.

Figure 2.2.1 Forward and Aft Perpendiculars

The distance between these two reference lines is referred to as the Length between

Perpendiculars, LPP.

2.2.2 Moulded Dimensions

Moulded

Draught

The Moulded Draught is the perpendicular distance in a transverse plane from the top

of the keel plate to the Design Water Line, if unspecified it refers to amidships.

Moulded

Depth

The Moulded Depth is the perpendicular distance in a transverse plane from the top of

the keel plate to the underside of the deck plating at the ships side, if unspecified it

refers to amidships.

Moulded

Breadth

The Moulded Breadth extreme is the maximum horizontal breadth of any frame

section. The terms Breadth and Beam are synonymous.

AP FP

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2.3 Freeboard and WT Integrity

2.3.1 Buoyant Hull

For all ships a required freeboard is determined in accordance with the IMO Load Lines

resulting in a minimum allowable distance between the load water line and the deck to

which the watertight (WT) integrity is maintained. The freeboard grants a minimum

amount of reserve buoyancy as composed by the buoyant hull limited by the freeboard

deck, seeFigure 2.3.1.

Buoyant Hull

Figure 2.3.1 Freeboard and Buoyant Hull

Flooding

Points

Any opening leading into the buoyant hull must terminate at a minimum threshold

distance above the freeboard deck or be fitted with an adequate closing appliance.

o A Watertight, WT, closing appliance must withstand a specified hydrostaticpressure and is then considered to be a part of the WT-integrity.

o A Weathertight, WeT, closing appliance is considered closed for the purpose of

righting arm calculations but can not withstand any hydrostatic pressure and

may thus not be submerged at equilibrium.

o An Unprotected Opening is considered as a flooding point through which

progressive flooding may occur if the opening is immersed. Hence, stability

calculations, e.g. righting arm curves, shall terminate as soon a flooding point is

reached. A typical unprotected flooding point is represented by the Engine

Room ventilation.

AP FP

Main Deck / Freeboard Deck

ER-Vent

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2.3.2 WT Subdivision

WT

Subdivision

Below the freeboard deck the ship is subdivided in an adequate number of

compartments separated by WT-bulkheads. The compartments may be arranged as

machinery spaces, void spaces, cargo spaces or tanks containing consumables or ballast

etc.

The subdivision is arranged such as to provide reserve buoyancy and residual stability

also after suffering a stipulated damage to the hull shell.

Permeability In order to account for un-floodable volumes inside a compartment, such as structural

steel members and various equipment a volumetric filling rate, permeability, is

required. For the purpose of the subdivision and damage stability calculations in

accordance with regulations the permeability for general compartments shall be

applied as follows:

o Stores 0.60

o Accommodation and Public Spaces 0.95

o Machinery Room 0.85

o Void Spaces 0.95

o Tanks intended for Liquids 0 or 0.95*)

*) which ever results in more sever requirements

However, when establishing various load conditions a more deterministic approach for

calculating a true permeability of e.g. Tanks is applied. The deduction for structural

members inside a Tank can in general be set to 1.5% of the gross volume, hence a

permeability for Tanks of 0.985 can normally be applied.

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3 COMPUTER AIDED NAVAL ARCHITECTURAL DESIGN WORK

3.1 Hull Modelling Basics using Autoship

3.1.1 General

NURBS Autoship is a 3D hull modelling software using non-uniform rational B-splines (NURBS)

curves and NURBS-surfaces for the representation of the hull. The B-spline curves are

made up of continuous end-to-end segments, joined at knots or knot vectors. This

means that hull surface is defined and controlled by a number of mathematical entities

called control points in the 3D space surrounding the object.

3.1.2 Control Points

Control

Points

The control points can be compared to polynomial coefficients. Hence, when defining a

curve or a surface, the order, degree, of the polynomial must first be determined, i.e.

how many control point must be used in order to provide a good representation of the

shape. The control points are organised in rows and columns, each of which having a

positive direction. This means that all surfaces have a positive and a negative side,

which must be considered when calculating an enclosed volume. Figure 3.1.1 shows

how Autoship control points are represented on the screen.

Figure 3.1.1 Control Points along a curve

Control Points

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Control point can be moved, deleted, added to a curve, and manipulated using the

software Select and Edit mode tools. Autoship bends the curve towards a control point,

but does not make the curve to coincide with a control point. When one control point is

moved, no other control points of the entity are moved. Figure 3.1.2 shows the effect

of moving two control points governing the curve.

Figure 3.1.2 Effect of moving Control Points

3.1.3 Edit Points

Edit Points Autoship also provides edit points for shaping curves. Edit points are shown as small,

unfilled squares on the curve, see Figure 3.1.3. If an edit point is moved, its

neighbouring points also move, and the curve is redrawn through the new location of

the edit points, see Figure 3.1.4.

Figure 3.1.3 Edit Points on a curve

Figure 3.1.4 Moving Edit Points

Edit point are derived from control points, there is one edit point for each control point.

When moving an edit point it is actually the control point which is being relocated.

Edit Points

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3.1.4 Surfaces

Surfaces One frequently used method of creating a surface in Autoship is to, based on a curve,extrude the surface in one direction or along another curve. Often one fore body

surface and one after body surface are extruded from the midship section curve, see

Figure 3.1.5, and then modified in order to represent the intended shape of the forward

and aft parts of the hull.

Figure 3.1.5 Extruded Surface based on a Midship curve

3.1.5 Rows and Columns

In Autoship, a surface is built-up by a mesh of i x j control (or edit) points, a matrix

having i rows, Figure 3.1.6 and j columns, Figure 3.1.7. Hence, the number of Columns

must be the same on every Row and vice versa, the number of Rows must be the same

on every Column along a surface.Rows

Figure 3.1.6 RowsColumns

Figure 3.1.7 Columns

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3.1.6 Knuckles and Chines

Knuckle A Knuckle is a sharp discontinuity on a curve, e.g. the tangent-point at the transitionfrom a bilge radius to a flat bottom or flat side on a midship curve, Figure 3.1.8.

Figure 3.1.8 Knuckle Point on a midship curve

Chine Turning a control point into a Knuckle point will result in turning the complete row or

column, which ever is activated, into a discontinuity, a Chine, along the surface.

3.1.7 Degree of Curvature

Degree of

Curvature

When creating a curve in Autoship, you must specify its maximum degree. The degree

of a curve is the order, power, of the polynomial used to define the entity. Degree 1 is

linear, degree 2 uses a quadratic polynomial and degree 3 uses a cubic polynomial.

Autoship allows up to degree 5.

Number of

Control

Points

The degree of curvature is related to how many control points are needed to define a

curve. There is always one control point more than the degree of curvature. Thus, a 1

degree curve is a straight line between two control points, a degree 2 curve is

composed of at least three control points, etc. A degree 5 curve composed of at least

six control points can be used to create smooth and very complex surfaces. However, a

high degree surface is very difficult to manipulate locally in a controlled way.

3.1.8 Direction

Direction All Autoship curves, rows and columns have a positive direction. On a curve this

direction is indicated by a small arrow at the beginning of the curve, Figure 3.1.9.

Figure 3.1.9 Positive Direction of Curve

Knuckle Points

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Surface In-

and Outside

The existence of a positive or negative direction of a curve results in a defined inside

and a defined outside of a surface. This must be considered when executing analyses of

an enclosed volume, ship hull. If not, strange hydrostatic properties will be generated.

3.1.9 Ship Hull Assembly and Analyses

Hull Group When all surfaces required to describe the hull are created a group is assembled. This

hull group can now be immersed and analysed with regard to basic hydrostatic

properties such as displacement, geometrical coefficients, centre of buoyancy and

flotation etc.

Calculation

Frames

Autoship is also used to define the number, the location and spacing of frames used for

hydrostatic calculations. Furthermore frames, buttocks and waterlines used for

visualisation of the hull shape can be defined.

Project File The modelling work in Autoship is stored as a project file, *.pr3.

Geometry

File

*.gf#

The hull surface created in Autoship is exported to Modelmakerand Autohydro through

a geometry-file (*.gf#; # = any arbitrary number for identification of file version). Note

that the *.gf# does not comprise the surface but only a numerical representation of the

defined frames.

File Adm. An administrative rule of thumb is to separately define the ships moulded bare hull and

save the geometry file as *.gf0, and then define the appended hull and save it as *.gf1,

etc.

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3.2 Subdivision and Compartment definition in Modelmaker

3.2.1 General

Subdivision The hull geometry, i.e. the outer boundary of the vessel, represented by the frames as

defined in Autoship is imported into Modelmaker for further definition of the

subdivision into compartments such as tanks, cargo holds, machinery spaces,

accommodation etc.

Cleaning of

Frames

When importing the hull geometry by loading a *.gf# file the frames may have to be

cleaned from excessive coordinate points which are not needed. As mentioned

above, the hull shape is only represented by frames, i.e. a surface is no longer available

at this stage. The cleaned bare hull geometry-file should then be saved, preferably by

overwriting the old bare hull geometry file.

Script Files

*.cmd

The subdivision can be created by using the application menus and commands or by

writing a script file (*.cmd). It is strongly recommended to apply the script writing

method, even though this method requires knowledge about application specific

commands and may seem time consuming, since script are easy to duplicate e.g. for

starboard and port tanks etc. Furthermore, checking and / or modification of

compartment coordinates are much quicker when using the script method. Finally,

alterations in compartmentation can easily be done by just introduce the desired

changes in the Command File and re-run the commands.

3.2.2 Parts, Components and Shapes

In order to handle the complexity of a vessel geometry model, a hierarchical data

structure is used. The model is broken up into Parts, Components and Shapes. The

vessel, with its buoyant appendages and superstructure, normally consists of one Part.

Each Part is made up of one or more Components (e.g. HULL = hull + skeg +

superstructure) and each Component is composed of a Shape.

Parts A Part is a group of one or more Components. Each Part is identified by a name, has a

description and a class designation of either:

o Hull

o Appendage

o Superstructure

o Sail

o Tank

Tank parts have, in addition, a side designation, a substance name and specific gravity,

a capacity and optional sounding tube definitions.

More than one component may refer to the same shape. This saves computer memory

and disk space when identical shapes are involved (as in port and starboard tanks).

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Components Each component is identified by a name (which may be unique only within the

referencing part) refers to one shape by name. Side specifies whether the shape is to

be reflected about its own centerplane to the opposite side. Also included are the

permeability (for containers) or effectiveness factor (for displacer) and a flag indicating

whether the component adds to or deducts from the part volume.

Finally, the component gives the shape a specific location on the vessel by means of

the shift vector, although this is frequently 0,0,0, indicating that the shape is defined in

Ship Coordinates.

3.2.3 Command Script Files

The Script Files comprises various Commands of which the most commonly used are

defined below.

Clear Every Command Script File should start with the Clearcommand, ensuring that any

previous geometries, settings and commands are cleared prior to running an updated

command file.

Read read *.gf#. The geometry file which is currently located in modelmaker will be

removed and the specified geometry file, *.gf#, will be loaded.

Create create [Part Name/]Component Name Marks the start of a block of component

creation information and provides the name of the component and part to be created.

The part name can be used to identify an existing part or if the name does not exist, anew part will be created.

The component name should not identify an existing component. If only a component

name is given, modelmaker will assume that the part and component have the same

name. The component creation information is terminated and a component is created

at either a forward slash of a component parameter.

Contents cont Description Is used to set the default contents of a tank and the specific

gravity of the specified liquid.

ModelMakerand Autohydro recognizes the following abbreviations:

DO DIESEL OIL

FO FUEL OIL

FW FRESH WATER

GAS GASOLINE

HO HYDR OIL

KER KEROSENE

LO LUBE OIL

SEW SEWAGE

SW SEA WATER

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Permeability perm

Specifies the permeability factor between 0 and 1.0 of a container

component (it will also set the effectiveness factor of a displacer component). Default

value is: 0.985 (1.0 for displacers) or the same as the first component of the part.

Ends ends L1, L2 Defines the longitudinal locations of the forward and aft boundary L1 and

L2 of the components.

Top top V1 [@ L1, V2 @ L2]Defines the height of the top of a box shaped compartment.

The top may be sloped by specifying differing heights at 2 different longitudinal

locations.

Bot bot V1 [@ L1, V2 @ L2] Defines the height of the bottom of a box shaped

compartment. The bottom may be sloped by specifying differing heights at 2 different

longitudinal locations.

Inboard in T1 [@ L1, T2 @ L2] The Inboard command specified the inboard side location of a

box shaped compartment. This side may be sloped by specifying different half-

breadths at different longitudinal locations.

Outboard out T1 [@ L1, T2 @ L2]The Outboard command specifies the outboard side location of

a box shaped compartment. This side may be sloped by specifying different half-

breadths at different longitudinal locations.

Locus loc @ L [=T1,V1, T2,V2, ....., Tn,Vn] Results in an explicit section curve at the shape

longitudinal location L. The curve is represented by transverse-vertical coordinate pairs

running in the counterclockwise direction looking forward. The first point isconsidered to follow the last point. If only the L parameter is given, a section is

interpolated at that location from the other shape data given. One Locus statement is

needed for each section. The final shape is the intersection of the shape defined by

the Locus statements and the volume bounded by the Top, Bottom, Inboard and

Outboardstatements.

Fit fit [Component Name] The fit command uses the current component creation

information and fits this new component to the specified part. The most common use

of this command is the case where a tank is fit to the hull.

Opposite opp [Part Name] The opposite command generates a new Part and copies all of theexisting components from the original part into the newly created part. The opposite

command is used after the create command. The create command identifies the part

to be created and the original part is identified by the opposite parameter. The part

name should therefore be the name of an existing part.

Write write [*.gf#]Writes the geometry file out to disk. A drive and path specification may

be included in the filespec. If the path is not specified, the file will be written to the

current modelmaker directory.

NB!!! NB! The Hull including the defined compartments and tanks shall preferably be saved

under a new file name, e.g. *.gf2, in order not to overwrite the bare hull geometry file

*.gf1

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3.2.4 ModelmakerCmd-File Example

Clear

Read Test.gf1

create HULL\Rudder.c

ends 1.6a, 0.8f

top 5.0 @ 1.6a, 5.0 @ 0.8f

bot 0.3

out 0.2

/

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create Forepeak.c

cont SW

perm = 0.975

ends 152f, 165f

top 7.5

bot -1

fit Hull

/

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create Fuel_Tk.s

cont FO

perm = 0.975

ends 80f, 89.6f

locus @ 80f = 15, 7.5, 10, 7.5, 10, 4.75, 8, 4.75, 8, 2, 15, 2

locus @ 89.6f = 15, 7.5, 10, 7.5, 10, 4.75, 8, 4.75, 8, 2, 15, 2

fit Hull

/

create Fuel_Tk.p

opposite Fuel_Tk.s

/

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3.3 Hydrostatic and Stability Analyses in Autohydro

3.3.1 General

Hydrostatic

and Stability

Analyses

The application Autohydro is used for hydrostatic and stability analyses of hull shapes

and associated compartment definitions. Hence, analyses are performed on the loaded

geometry file *.gf# (in our case *.gf2 which comprises bare hull and compartments).

The application includes a report generator used for the establishing of stability

booklets.

Accuracy Autohydro works as a true floating simulator solving the condition equilibrium

including the effect of free surfaces etc. However, the hull shape and the compartment

definition are only represented by frames. Hence, the accuracy of the results is highly

dependent on the quality and resolution (number of calculation frames) of thegeometry file.

Script Files

*.run

The analyses can be executed by using the application menus and commands or by

writing a script file (*.run). Again, it is strongly recommended to apply the script writing

method, even though this method requires knowledge about application specific

commands and may seem time consuming, since script are easy to duplicate e.g. for

multiple Loading Conditions and various Damage Cases etc. Furthermore, checking and

/ or modification of Conditions, Damage Cases and Criteria etc are much quicker when

using the script method.

In order to limit the computing time, it may be wise to write separate run file forvarious purposes, e.g. one file for the Hydrostatics HS.run, one file for Intact Stability

Analysis INTACT.run and one file for Damage Stability Analysis DAM.run etc.

The Run Files comprises various Commands of which the most commonly used are

defined below.

3.3.2 Run Script Files for Hydrostactics

Read Read *.gf#. The geometry file which is currently located in Auto hydro will be removed

and the specified geometry file, *.gf#, will be loaded.

Units Units MTSets the units to metric units (meters and tonnes).

Clear Report Every Run File should start with the Clear Reportcommand, ensuring that previously

executed calculations are cleared and a blank report is started prior to running an

updated command file.

Report

Header /

Footer

Report Header [Header Text]and Report Footer [Footer Text]creates a report header

and footer including the stated texts respectively.

Water Water Sets the ambient water specific gravity to specified value, in general

1.025 for seawater and 1.000 for freshwater.

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LBP LBP L1, L2 Sets the longitudinal position of the forward and aft termination to be

considered when calculating trim, coefficients etc. If FP and AP are used then the

Length between Perpendiculars will be used as reference length. If no calculation

length is defined Autohydro uses the LWL and specifies the trim in degrees.

ghs ghs draft @ L = d1, d2, , dn calculates the General Hydrostatic Properties on the

specified drafts d1, d2, , dn using a constant draft increment corresponding to d2 -

d1.

Disk Disk [File Name.rtf] Saves the current report in the current computer folder. The

extension *.rtf provides a MS Word Rich Text Format which can be edited and printed

using MS Word.

3.3.3 Run Script Files for Intact Stability Analysis

Read Read *.gf#. The geometry file which is currently located in Auto hydro will be removed

and the specified geometry file, *.gf#, will be loaded.

Units Units MTSets the units to metric units (meters and tonnes).

Clear Report Every Run File should start with the Clear Reportcommand, ensuring that previously

executed calculations are cleared and a blank report is started prior to running an

updated command file.

Header /

Footer

Report Header [Header Text]and Report Footer [Footer Text]creates a report header

and footer including the stated texts respectively.

Limit off Limit OffClears any activated Stability Evaluation Criteria.

Water Water Sets the ambient water specific gravity to specified value, in general

1.025 for seawater and 1.000 for freshwater.

LBP LBP L1, L2 Sets the longitudinal position of the forward and aft termination to be

considered when calculating trim, coefficients etc. If FP and AP are used then the

Length between Perpendiculars will be used as reference length.

FldPtFldPt (n) [Description] L, T, Vdefines the location of a Flooding Point through whichprogressive down flooding can occur. An arbitrary number of Flooding Points can be

defined.

Limit Limit Title [Name] defines a Title of a set of Stability Evaluation Criteria as defined

below (IMO A167):

Limit (1) area from 0 to 30 > .055

Limit (2) area from 0 to 40 or Fld > .09


Limit (4) RA at 30 or Max > .2

Limit (5) Angle from 0 to Max > 25

Limit (6) GM at Equil > .15

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Note Note [Text]Sets a title of the forthcoming calculations, e.g. note Light Ship will set the

title Light Ship for the Loading Condition.

Delete Del All Weights Command, deletes all previously defined Fixed Weights except the

Light Ship Weight.

Type Type (*) IntactSets all Tanks to Intact Condition.

Load Load (*) 0Sets the Contents in all Tanks to zero, making sure that any previously Tank

Loads are reset prior to running a Stability Evaluation of the Condition.

Weight Weight [Mass, L, T, V] Sets the Light Ship Weight and defines the Centre of Gravity

longitudinal, transverse and vertical for the Light Ship Weight.

Add Add [Name, Mass, L, T, V] Adds a Fixed Weight at a defined Centre of Gravity. An

arbitrary number of Fixed Weights can be added.

Load Load (Tank) Sets the Contents in the specified Tank to the specified

filling percentage. This command is repeated for all Tanks used in the requested

Loading Condition.

Solve Solve Finds the equilibrium floating status for the defined Loading Condition.

Status Status Provides the status of the current Loading Condition with regard to Floating

Status, Fixed Weights Status, Tank Status etc.

Status

Cartoon

Status Cartoon Provides a graphical presentation of the Tank Status.

Ra Ra /Lim /Notes Computes righting arms and produces tabular and graphical output at

one or more heel angles and evaluates the stability against the current stability

criteria, displaying limit margins. The extension /Notes turns on an extra column that

identifies key angles such as the equilibrium point, maxRA, second intercept, etc

Page Page Forces a page break to separate the current Loading Condition from the following

Condition.

The next and following Loading Conditions are defined and evaluated by repeating the

Commands from the Command Note.

Disk Disk [File Name.rtf] Saves the current report in the current computer folder. The

extension *.rtf provides a MS Word Rich Text Format which can be edited and printed

using MS Word.

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3.3.4 Autohydro Hydrostatics Example

delete all weightsload(*) 0

ghs draft @ MS = 0.5,1.0,...,5.0

Hydrostatic Properties

Draft is from Baseline.

No Trim, No heel, VCG = 0.000

Draft at

1.834f(m)

Displ

(MT)

LCB

(m)

VCB

(m)

LCF

(m)

TPcm

(MT/cm)

MTcm

(MT-m/deg)

KML

(m)

KMT

(m)

0.500 210.793 2.552a 0.279 1.466a 5.23 1688.67 458.951 24.240

1.000 493.328 1.786a 0.552 0.995a 5.97 2266.91 263.255 13.056

1.500 803.803 1.441a 0.823 0.825a 6.43 2685.93 191.436 9.424

2.000 1135.400 1.256a 1.095 0.837a 6.83 3089.52 155.891 7.785

2.500 1486.664 1.174a 1.369 1.017a 7.22 3537.90 136.336 6.940

3.000 1858.041 1.173a 1.646 1.342a 7.63 4064.57 125.325 6.484

3.500 2250.598 1.240a 1.926 1.797a 8.07 4690.66 119.403 6.243

4.000 2665.385 1.366a 2.211 2.322a 8.51 5415.27 116.396 6.132

4.500 3102.474 1.541a 2.499 2.849a 8.96 6213.96 114.746 6.108

5.000 3560.214 1.728a 2.789 3.106a 9.34 6924.16 111.422 6.144

Water Specific Gravity = 1.025.

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Hydrostatic Properties at Trim = 0.00, Heel = 0.00

Long. Location in m

Draft

@1.834f

5.0a 4.0a 3.0a 2.0a 1.0a

1.0

2.0

3.0

4.0

5.0LCB m

LCF m

VCB m

Displ.MT

MT/cm Imm.

Mom/Deg Trim

KML

KMT

VCB m x 1 0.0 1.0 2.0 3.0

Displ.MT x 1000 0.0 1.0 2.0 3.0 4.0

MT/cm Imm. x 1 5.0 6.0 7.0 8.0 9.0 10.0

Mom/Deg Trim x 1000 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0

KML x 100 1.0 2.0 3.0 4.0 5.0

KMT x 10 1.0 2.0

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3.3.5 Autohydro Loading Condition Stability Evaluation Example

clear report

Fldpt (1) "Opening No1 Stb" 29f 7s 23

Limit title IMO A.167

Limit (1) area from 0 to 30 > .055



Limit (4) RA at 30 or Max > .2

Limit (5) Angle from 0 to Max > 25

Limit (6) GM at Equil > .15

Weight 1200, 1.173a, 0, 4.23

note Full Load Condition

Add "Crew and Effects" 2 15f 0 12

Add "Stores" 3.2 12f 0 5

Add "Pay Load" 1.4 0.5a 0 3.3

Load (FRESHW.S) 1

Load (FRESHW.P) 1

Load (DB#3.C) .98

Load (DB#3.S) .98

Load (DB#3.P) .98

Load (DB#4.C) .98

Load (SETTLING.S) .98

Load (SETTLING.P) .98

so

statusstatus cartoon

ra /lim /notes

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Full Load Condition

Floating Status

Draft FP 2.386 m Heel zero GM(Solid) 3.277 m

Draft MS 2.498 m Equil Yes F/S Corr. 0.248 m

Draft AP 2.609 m Wind 0.0 kn GM(Fluid) 3.029 m

Trim aft 0.15 deg. Wave No KMT 6.945 m

LCG 1.514a m VCG 3.668 m TPcm 7.24

Loading Summary

Item Weight

(MT)

LCG

(m)

TCG

(m)

VCG

(m)

Light Ship 1 200.00 1.173a 0.000 4.230

Deadweight 290.26 2.921a 0.000 1.346

Displacement 1 490.26 1.514a 0.000 3.668

Fixed Weight Status

Item Weight

(MT)

LCG

(m)

TCG

(m)

VCG

(m)

LIGHT SHIP 1 200.00 1.173a 0.000 4.230u

CREW AND EFFECTS 2.00 15.000f 0.000 12.000u

PAY LOAD 1.40 0.500a 0.000 3.300u

STORES 3.20 12.000f 0.000 5.000u

Total Fixed: 1 206.60 1.110a 0.000 4.244u

Tank Status

FRESH WATER (SpGr 1.000)

Tank

Name

Load

(%)

Weight

(MT)

LCG

(m)

TCG

(m)

VCG

(m)

Perm

FRESHW.P 100.00% 27.42 16.808a 4.616p 2.830 0.950

FRESHW.S 100.00% 27.42 16.808a 4.616s 2.830 0.950

Subtotals: 100.00% 54.85 16.808a 0.000 2.830

FUEL OIL (SpGr 0.870)

Tank

Name

Load

(%)

Weight

(MT)

LCG

(m)

TCG

(m)

VCG

(m)

Perm

SETTLING.P 98.00% 9.31 20.178a 3.869p 2.949 0.950SETTLING.S 98.00% 9.31 20.178a 3.869s 2.949 0.950

DB 3.C 98.00% 66.53 5.963f 0.000 0.625 0.950

DB 3.P 98.00% 37.82 5.370f 4.486p 0.697 0.950

DB 3.S 98.00% 37.82 5.370f 4.486s 0.697 0.950

DB 4.C 98.00% 68.03 6.190a 0.000 0.612 0.950

Subtotals: 66.41% 228.81 0.027f 0.000 0.834

Displacer Status

Item Status Spgr Displ

(MT)

LCB

(m)

TCB

(m)

VCB

(m)

Eff

/Perm

HULL Intact 1.025 1 490.64 1.519a 0.000 1.372 1.000

SubTotals: 1 490.64 1.519a 0.000 1.372

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Fluid Legend

Fluid Name Legend Weight

(MT)

Load%

FRESH WATER 54.85 100.00%

FUEL OIL 228.81 66.41%

Righting Arms vs Heel Angle

Heel Angle

(deg)

Trim Angle

(deg)

Origin Depth

(m)

Righting Arm

(m)

Area

(m-Rad)

Flood Pt Height

(m)

Notes

0.00 0.15a 2.503 0.000 0.000 20.572 (1) Equil

5.00s 0.14a 2.485 0.281 0.012 19.887 (1)

10.00s 0.11a 2.435 0.574 0.050 19.058 (1)

15.00s 0.08a 2.351 0.878 0.113 18.093 (1)

20.00s 0.03a 2.230 1.190 0.203 17.005 (1)

25.00s 0.02f 2.053 1.455 0.319 15.825 (1)

30.00s 0.07f 1.815 1.663 0.455 14.568 (1)35.00s 0.13f 1.534 1.805 0.607 13.225 (1)

40.00s 0.22f 1.232 1.863 0.768 11.778 (1)

45.00s 0.30f 0.896 1.890 0.932 10.267 (1)

47.44s 0.33f 0.719 1.895 1.012 9.515 (1) MaxRa

50.00s 0.36f 0.529 1.889 1.097 8.712 (1)

55.00s 0.39f 0.147 1.850 1.260 7.116 (1)

60.00s 0.38f -0.252 1.779 1.419 5.495 (1)

Unprotected Flood Point

Name L,T,V (m) Height (m)

(1) Opening No1 Stb 29.000f, 7.000s, 23.000 20.572

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IMO A.167

Limit Min/Max Actual Margin Pass

(1) Area from 0.00 deg to 30.00 >0.0550 m-R 0.455 0.400 Yes(2) Area from 0.00 deg to 40.00 or Flood >0.0900 m-R 0.768 0.678 Yes

(3) Area from 30.00 deg to 40.00 or Flood >0.0300 m-R 0.312 0.282 Yes

(4) Righting Arm at 30.00 deg or MaxRA >0.200 m 1.895 1.695 Yes

(5) Angle from 0.00 deg to MaxRA >25.00 deg 47.44 22.44 Yes

(6) GM at Equilibrium >0.150 m 3.029 2.879 Yes

Righting Arms vs. Heel

Heel angle (Degrees)

Armsinm

0.0s 10.0s 20.0s 30.0s 40.0s 50.0s 60.0s

0.0

0.5

1.0

1.5

2.0Righting Arm

R. Area

Equilibrium

GMt

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