Let’s face it: most ships all look the same. This means that in most cases it is possible to take an existing design and, for example by simply resizing it, get reasonably close to a customer’s requirements. In Maxsurf, resizing and/or a simple parametric transformation (eg increasing the displacement) can all be done without touching control points. This means that if you for example have a fair design that was built 30 m long with a displacement of 44 tonnes you can have a 35 m ship with a displacement of for example 54 tonnes in a matter of minutes. And even better: the fairness quality of the surface model will be maintained during the modification.

 Watch a short video that shows you how to resize the trawler sample design and apply a simple parametric transformation on your own MyFirstDesign file: increasing the displacement whilst keeping the draft the same. [Web | Disk]

Resizing

To modify an existing design, you will first need to unlock the relevant surface(s) that you wish to make modifications to. We will return to the sample trawler model as it is a simple single-surface model.

Ø  Close any currently open design by going to File | Close Design.

Ø  Select Open from the File menu.

Ø  Navigate to the Maxsurf program file directory (C:\Program Files\Maxsurf\Sample Designs

Ø  Open the design called Maxsurf Sample_Trawler.msd.

Ø  Display the Sections and the Grid

To modify the design in any way, the applicable surface(s) have to be unlocked. If a surface is locked, its control points cannot be moved and are hidden.

Ø  Go to Surfaces | Locking

Ø  Remove the tick next to the Hull surface by clicking it with the left mouse button.

Note: you can also resize the surfaces using right clicking in the Assembly Pane.

Suppose we wish to resize the trawler from an overall length of approximately 45 m down to 25 m.

Ø  Go to Surfaces | Size Surfaces

When resizing a surface, it is necessary to decide which, if any, of the dimensions should be scaled proportionately. Use this proportional scaling if you have a basis design of which you wish to maintain the beam:depth ratio, length:depth ratio and/or length:beam ratio. To scale two or more dimensions proportionately, place a tick next to the items that should remain in proportion. For example, to maintain length:beam ratio, place a tick in the proportional scaling boxes of length and beam; if you would like to keep all dimensions in proportion, place a tick in all three boxes.

Ø  Place a tick in all three proportional scaling boxes.

Ø  Enter 25m for Length.

Observe how the beam and depth values automatically update to maintain the L/B and L/D ratio.

Ø  Click OK.

Parametric Transformations

Please read the Using Parametric Transformations topic from the Manual (it is only necessary to read up to the Parametric Transformations Restrictions heading. Example exercises do not need to be performed).

Ø  Open your own MyFirstDesign.msd file.

Alternatively, you can open a copy of the file from the C:\Program Files\Maxsurf\Training Samples directory.

Ø  Save the design as MyFirstDesign_transformed.msd

It is generally good practice to save to another filename before doing a parametric transformation or working with the standard sample designs.

Ø   Go to Data | Parametric transformation

Ø  Tick the Displacement and Draft boxes

Ø  Change the displacement to 110% of the current value. Leave all other values as they are.

This will search for an increased displacement by varying the Lwl and Beam, but keeping the Draft the same. If you used the supplied MyFirstDesign.msd from the C:\Program Files\Maxsurf\Training Samples directory, the Scale To box should appear as follows:

Ø  Press Search and wait for the hourglass to disappear

Note that the waterline length and beam have both increased and that the increase in length is reflected in the profile view of the model in the dialog.

Ø  Press OK to accept the new hullshape

Note:

‘Immersed depth’ is equivalent to the draft in the parametric transformation dialog; ‘Lwl’ denotes waterline length and ‘Beam wl’ the waterline beam (the maximum width of the waterplane).

Ø  Go to profile view and do a Ctrl+Z to undo the parametric transformation and a Ctrl+Y to redo it. This quickly gives you an idea of the changes.

Ø  Resave the transformed model.

Continue with the section Other Options to Start a New Design.