FreeCAD-Ship s60 tutorial (II)/de: Difference between revisions

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{{VeryImportantMessage|'''WARNING''': The Ship Workbench is currently unmaintained and is not functioning correctly due to that fact.<br/>
If you would like to help maintain this workbench, the source code is at https://github.com/FreeCAD/freecad.ship}}


== Overview ==
Before starting this tutorial, please ensure that you have already performed [[FreeCAD-Ship_s60_tutorial|the first part]].


Before starting this tutorial, please ensure that you have already performed [[FreeCAD-Ship_s60_tutorial|the first part]].
You can learn more about [[Ship_Workbench|FreeCAD-Ship here]]


Learn more about the Ship workbench from it's dedicated wiki page: [[Ship Workbench]]
{{VeryImportantMessage|<center>'''Windows users'''</center>
<center>FreeCAD-Ship have been recently integrated into FreeCAD package, so some bugs can be detected.</center>
<center>If your Ship module have icons lost, please rename '''ShipIcons''' folder at</center>
<center>C:\Program Files (x86)\FreeCAD0.13\Mod\Ship</center>
<center>path as '''Icons''' folder, and then restart FreeCAD.</center>}}


== Introduction ==
== Introduction ==
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* Area involved by ''GZ'' curve from 30 to 40 degrees of roll angle must be at least 0.030 m · rad.
* Area involved by ''GZ'' curve from 30 to 40 degrees of roll angle must be at least 0.030 m · rad.


In this tutorial we will set weights and tanks for our series 60 ship, in a unreal situation.
In this tutorial we will set weights and tanks for our series 60 ship, in a simulated situation.


== Ship weights ==
== Ship weights ==
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* Tanks, where fluid shape changes with the angle, needing center of gravity computation at each position.
* Tanks, where fluid shape changes with the angle, needing center of gravity computation at each position.


FreeCAD-Ship provides two different tools to generate each instance.
The Ship workbench provides two different tools to generate each instance.


[[Image:FreeCAD-Ship-WeightIco.png|center|Weights definition tool icon.]]
[[Image:FreeCAD-Ship-WeightIco.png|center|Weights definition tool icon.]]
<center><span style="font-variant:small-caps">Weights definition tool icon.</span></center>
<center><span style="font-variant:small-caps">Weights definition tool icon.</span></center>


Weights definition tool can be used to set first category of weights. When you launch the tool for first time (with ship instance selected), FreeCAD-Ship initialize ship weights with Lightweight ship (equal to ship displacement) that is placed on ship geometry centre of gravity X coordinate, and at design draft height. Usually you have at least, 2 relevant weights:
Weights definition tool can be used to set first category of weights. When you launch the tool for first time (with ship instance selected), the Ship workbench initializes ship weights with Lightweight ship (equal to ship displacement) that is placed on the ship geometry center of gravity X coordinate, and at design draft height. Usually there are at least 2 relevant weights:
* Structure.
* Structure.
* Main engine (or several of them).
* Main engine (or several of them).


So we will change it. Doing double click over each cell we can edit the value, seting this weights:
So we will change it. Double-click over each cell we can edit the value, setting weights:
* Structure, 15000 kg, (-0.1, 0, 1.25) m
* Structure, 15000 kg, (-0.1, 0, 1.25) m
* Starboard engine, 5000 kg, (-6.5, -0.65, 0.5) m
* Starboard engine, 5000 kg, (-6.5, -0.65, 0.5) m
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<center><span style="font-variant:small-caps">Weights definition 3D preview.</span></center>
<center><span style="font-variant:small-caps">Weights definition 3D preview.</span></center>


Weights position are shown at 3D screen view. This annotations will be removed when you ends with the tool, so don't take care about this. When you press '''Accept''' weights will stored at your ship instance.
Weights position are shown in the [[3D view]]. Note: the annotations will be removed when the tool is closed. When you press {{Button|Accept}} weights will be stored in your ship instance.


== Tanks ==
== Tanks ==
Tanks must be created on top of solid geometry, as the ship instance, so first step is create two bow tanks (one per ship side) solid geometries that we will consider (Ussually ships have a lot of tanks for fuel, fresh water, salt water, load, etc).
Tanks must be created on top of solid geometry, as the ship instance, so first step is create two bow tanks (one per ship side) solid geometries that we will consider (usually ships have a lot of tanks for fuel, fresh water, salt water, load, etc).


=== Geometry generation ===
=== Geometry generation ===
In order to generate tanks we load [[Part_Workbench|Part module]], and create a box solid.
In order to generate tanks we load [[Part_Workbench|Part module]], and create a box solid.


We need to edit the box, so we select it at '''Atributes and tags''' tree, and change from view to data tab. Uncollapse Placement, and into them Position, and set ''x'' to 1.5, and z to -1. We want to change box lenght too changing it for 5.0 (note that units can be in mm, don't take care about this).
We need to edit the box, so we select it at '''Attributes and tags''' tree, and change from view to data tab. Expand Placement, and into them Position, and set ''x'' to 1.5, and z to -1. We want to change box length too changing it for 5.0 (note that units can be in mm, don't take care about this).


Tank geometry will be common part of created box and ship geometry, so we can hide '''Ship''' instance, and show '''s60_IowaUniversity''' geometry. Selecting box and '''s60_IowaUniversity''' we can use Common operation generating our starboard tank geometry.
Tank geometry will be common part of created box and ship geometry, so we can hide '''Ship''' instance, and show '''s60_IowaUniversity''' geometry. Selecting box and '''s60_IowaUniversity''' we can use Common operation generating our starboard tank geometry.
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<center><span style="font-variant:small-caps">Tank instance generation tool icon.</span></center>
<center><span style="font-variant:small-caps">Tank instance generation tool icon.</span></center>


Now we can select '''StarboardTankGeom''' and execute tank instnace generation tool, where some data must be provided. We will set 40% of filling level, and 925 kg/m<math>\mathrm{m}^{3}</math> (fuel approach). When '''Accept''' is clicked a new tank instance called '''Tank''' is generated. We can rename it as '''StarboardTank''', and hide '''StarboardTankGeom'''.
Now we can select '''StarboardTankGeom''' and execute tank instance generation tool, where some data must be provided. We will set 40% of filling level, and 925 kg/m<math>\mathrm{m}^{3}</math> (fuel approach). When '''Accept''' is clicked a new tank instance called '''Tank''' is generated. We can rename it as '''StarboardTank''', and hide '''StarboardTankGeom'''.


We can repeat the same process in order to generate '''PortTank'''.
We can repeat the same process in order to generate '''PortTank'''.
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=== GZ curve computation ===
=== GZ curve computation ===
FreeCAD-Ship provide a tool to easily compute a ''GZ'' curve.
The Ship workbench provide a tool to easily compute a ''GZ'' curve.


[[Image:Ship_GZ.svg|center|128px|GZ curve computation tool icon.]]
[[Image:Ship_GZ.svg|center|128px|GZ curve computation tool icon.]]
<center><span style="font-variant:small-caps">GZ curve computation tool icon.</span></center>
<center><span style="font-variant:small-caps">GZ curve computation tool icon.</span></center>


With '''Ship''' instance selected, we can run the tool. The first thing that we can see at opened dialog is a list with all tank instances found at active document. We want to use both of them, so we click over the tanks that are remarked with a diferent background.
With '''Ship''' instance selected, we can run the tool. The first thing that we can see at opened dialog is a list with all tank instances found at active document. We want to use both of them, so we click over the tanks that are remarked with a different background.


In order to know the resultant ship displacement and draft we can press '''Update displacement and draft''', taking some time for the computation. We receive following data:
In order to know the resultant ship displacement and draft we can press '''Update displacement and draft''', taking some time for the computation. We receive following data:
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* Draft = 0.818664 m
* Draft = 0.818664 m


So we are in a unloaded situation, where draft are sightly lower than design draft. Ussually lower drafts imply lower ship stability, the draft depends on loading condition, so if we really expect than ship can be operated in this loading condition we can consider implement ballast tanks.
So we are in a unloaded situation, where draft are sightly lower than design draft. Usually lower drafts imply lower ship stability, the draft depends on loading condition, so if we really expect than ship can be operated in this loading condition we can consider implement ballast tanks.


We can also automatically compute ship trim, operation that can take around one minute, retrieving that our ship have 0.95 degrees of trim angle (positive by stern). In this example we will work without trim angle (0 degrees).
We can also automatically compute ship trim, operation that can take around one minute, retrieving that our ship have 0.95 degrees of trim angle (positive by stern). In this example we will work without trim angle (0 degrees).
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* 46 points. One for each 2 degrees. GZ computation can take some time, so take care about the number of points requested.
* 46 points. One for each 2 degrees. GZ computation can take some time, so take care about the number of points requested.


When we press '''Accept''' tool starts the computation. If you runs FreeCAD from terminal you can see work progress. In a couple of seconds we will receive GZ curve.
When we press '''Accept''' tool starts the computation. If you run FreeCAD from the terminal you can see work progress. In a couple of seconds we will receive GZ curve.


This tool use [http://www.pyxplot.org.uk/ pyxplot] and [http://www.ghostscript.com/ ghostscript] too. You can see where '''gz.dat''' output file has been placed at the report view (View/Views/Report view), and load it with datasheet software (for example [http://www.libreoffice.org libreOffice]). Nearby data file several auxiliary files has been created too:
This tool use [http://www.pyxplot.org.uk/ pyxplot] and [http://www.ghostscript.com/ ghostscript] too. You can see where '''gz.dat''' output file has been placed at the report view (View/Views/Report view), and load it with datasheet software (for example [http://www.libreoffice.org libreOffice]). Nearby data file several auxiliary files has been created too:
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<center><span style="font-variant:small-caps">Resultant GZ curve.</span></center>
<center><span style="font-variant:small-caps">Resultant GZ curve.</span></center>


''GZ'' maximum value is placed over 30 degrees (45 degrees), getting 0.25 m at 30 degrees (0.2 m is the minimum). Up to 30 degrees the area below ''GZ'' curve is 0.065 m·rad, up to 40 degrees we have 0.092 m·rad, being the area between 30 and 40 degrees of 0.027 m·rad. So our ship don't meets the IMO requeriments. The solution is place ballast tanks.
''GZ'' maximum value is placed over 30 degrees (45 degrees), getting 0.25 m at 30 degrees (0.2 m is the minimum). Up to 30 degrees the area below ''GZ'' curve is 0.065 m·rad, up to 40 degrees we have 0.092 m·rad, being the area between 30 and 40 degrees of 0.027 m·rad. So our ship don't meets the IMO requirements. The solution is place ballast tanks.

At the other hand the ship, in this bad condition, has positive ''GZ'' values up to 95 degrees roll angle, but has not been enoguht for IMO stability requirements, showing the hard cirteria imposed about this item.

Of course this example is not real (first for all fuel tanks cannot be placed in the double bottom structure, or using hull side as structure), but is a good example in order to learn to use [[Ship_Workbench|FreeCAD-Ship]].


At the other hand, the ship in this bad condition has positive ''GZ'' values up to 95 degrees roll angle, but has not been enough for IMO stability requirements, showing the hard criteria imposed about this item.


Of course this example is not real (first for all fuel tanks cannot be placed in the double bottom structure, or using hull side as structure), but is a good example in order to learn to use [[Ship Workbench]].


{{Ship Tools navi{{#translation:}}}}
{{clear}}
[[Category:Unmaintained{{#translation:}}]]

Revision as of 14:34, 22 February 2020

Tutorium
Thema
{{{Topic}}}
Niveau
Beginner
Zeit zum Abschluss
Autoren
FreeCAD-Version
Beispieldateien
Siehe auch
None

WARNING: The Ship Workbench is currently unmaintained and is not functioning correctly due to that fact.
If you would like to help maintain this workbench, the source code is at https://github.com/FreeCAD/freecad.ship

Overview

Before starting this tutorial, please ensure that you have already performed the first part.

Learn more about the Ship workbench from it's dedicated wiki page: Ship Workbench

Introduction

In this tutorial we will work with weights and tanks in order to compute GZ curve, the most important hydrostatic stability parameter. GZ is the static moment generated when the ship takes roll angle, of course, since the GZ arm is positive, the ship has a positive moment, and will try to recover upright position, but when GZ turns on negative numbers ship has not anymore stability, reaching a critical situation.

IMO (International Maritime Organization) set following criteria:

  • GM >= 0.15 m. GM (metacentric height) is the initial tangent of the GZ curve.
  • Maximum GZ value must be placed over 30 degrees of roll angle.
  • With 30 degrees roll angle, GZ value must be 0.2 m at least.
  • Area involved by GZ curve up to 40 degrees of roll angle must be at least 0.090 m · rad.
  • Area involved by GZ curve up to 30 degrees of roll angle must be at least 0.055 m · rad.
  • Area involved by GZ curve from 30 to 40 degrees of roll angle must be at least 0.030 m · rad.

In this tutorial we will set weights and tanks for our series 60 ship, in a simulated situation.

Ship weights

In order to can compute GZ curve we need to know ship weights, and their position at each roll angle, so weights will be divided in two categories:

  • Fixed weights, that are fully linked to ship movements.
  • Tanks, where fluid shape changes with the angle, needing center of gravity computation at each position.

The Ship workbench provides two different tools to generate each instance.

Weights definition tool icon.
Weights definition tool icon.
Weights definition tool icon.

Weights definition tool can be used to set first category of weights. When you launch the tool for first time (with ship instance selected), the Ship workbench initializes ship weights with Lightweight ship (equal to ship displacement) that is placed on the ship geometry center of gravity X coordinate, and at design draft height. Usually there are at least 2 relevant weights:

  • Structure.
  • Main engine (or several of them).

So we will change it. Double-click over each cell we can edit the value, setting weights:

  • Structure, 15000 kg, (-0.1, 0, 1.25) m
  • Starboard engine, 5000 kg, (-6.5, -0.65, 0.5) m
  • Port side engine, 5000 kg, (-6.5, 0.65, 0.5) m
  • Emergency engine, 2500 kg, (0.2, 0, 2.5) m
Weights definition 3D preview.
Weights definition 3D preview.
Weights definition 3D preview.

Weights position are shown in the 3D view. Note: the annotations will be removed when the tool is closed. When you press Accept weights will be stored in your ship instance.

Tanks

Tanks must be created on top of solid geometry, as the ship instance, so first step is create two bow tanks (one per ship side) solid geometries that we will consider (usually ships have a lot of tanks for fuel, fresh water, salt water, load, etc).

Geometry generation

In order to generate tanks we load Part module, and create a box solid.

We need to edit the box, so we select it at Attributes and tags tree, and change from view to data tab. Expand Placement, and into them Position, and set x to 1.5, and z to -1. We want to change box length too changing it for 5.0 (note that units can be in mm, don't take care about this).

Tank geometry will be common part of created box and ship geometry, so we can hide Ship instance, and show s60_IowaUniversity geometry. Selecting box and s60_IowaUniversity we can use Common operation generating our starboard tank geometry.

Generated tank geometry.
Generated tank geometry.
Generated tank geometry.

We can perform port side tank selecting our starboard geometry and executing mirror tool, selecting XZ as mirror plane.

In order to convert geometry into a ussual solid shape our tanks, and recover our s60_IowaUniversity geometry, we can load Draft module, and with starboard tank geometry selected execute Upgrade, and repeat with port side tank geometry. We can rename geometries as:

  • StarboardTankGeom
  • PortTankGeom

We can delete created Box, that we don't need anymore.

Tank intances generation

If reload FreeCAD-Ship module another time, we can find tank instances generator tool.

Tank instance generation tool icon.
Tank instance generation tool icon.
Tank instance generation tool icon.

Now we can select StarboardTankGeom and execute tank instance generation tool, where some data must be provided. We will set 40% of filling level, and 925 kg/m (fuel approach). When Accept is clicked a new tank instance called Tank is generated. We can rename it as StarboardTank, and hide StarboardTankGeom.

We can repeat the same process in order to generate PortTank.

View of generated weights.
View of generated weights.
View of generated weights.

Figure shown our ship result that we will compute.

GZ curve computation

The Ship workbench provide a tool to easily compute a GZ curve.

GZ curve computation tool icon.
GZ curve computation tool icon.
GZ curve computation tool icon.

With Ship instance selected, we can run the tool. The first thing that we can see at opened dialog is a list with all tank instances found at active document. We want to use both of them, so we click over the tanks that are remarked with a different background.

In order to know the resultant ship displacement and draft we can press Update displacement and draft, taking some time for the computation. We receive following data:

  • Displacement = 37505.5 kg
  • Draft = 0.818664 m

So we are in a unloaded situation, where draft are sightly lower than design draft. Usually lower drafts imply lower ship stability, the draft depends on loading condition, so if we really expect than ship can be operated in this loading condition we can consider implement ballast tanks.

We can also automatically compute ship trim, operation that can take around one minute, retrieving that our ship have 0.95 degrees of trim angle (positive by stern). In this example we will work without trim angle (0 degrees).

Tool request roll angles considered too. In this case we want to know all ship behaviour, so we can set:

  • 0 degrees starting roll angle.
  • 180 degrees ending roll angle.
  • 46 points. One for each 2 degrees. GZ computation can take some time, so take care about the number of points requested.

When we press Accept tool starts the computation. If you run FreeCAD from the terminal you can see work progress. In a couple of seconds we will receive GZ curve.

This tool use pyxplot and ghostscript too. You can see where gz.dat output file has been placed at the report view (View/Views/Report view), and load it with datasheet software (for example libreOffice). Nearby data file several auxiliary files has been created too:

  • gz.dat: Computed GZ curve data.
  • gz.pyxplot: pyxplot layout in order to plot the curve.
  • gz.eps: EPS image version.
  • gz.png: PNG image version.

This files will be overwritten if you executes the tool another time.

Results

Resultant GZ curve.
Resultant GZ curve.
Resultant GZ curve.

GZ maximum value is placed over 30 degrees (45 degrees), getting 0.25 m at 30 degrees (0.2 m is the minimum). Up to 30 degrees the area below GZ curve is 0.065 m·rad, up to 40 degrees we have 0.092 m·rad, being the area between 30 and 40 degrees of 0.027 m·rad. So our ship don't meets the IMO requirements. The solution is place ballast tanks.

At the other hand, the ship in this bad condition has positive GZ values up to 95 degrees roll angle, but has not been enough for IMO stability requirements, showing the hard criteria imposed about this item.

Of course this example is not real (first for all fuel tanks cannot be placed in the double bottom structure, or using hull side as structure), but is a good example in order to learn to use Ship Workbench.

Template:Ship Tools navi/de