Maxsurf News April 2004
In this issue...
New features in Maxsurf 10
Hydromax batch processing options
Tank free surface moments
US Coast Guard Stability Criteria
Additional graphing features
Productivity features in Maxsurf
Body plan sections
Surface edge selection
Additional Toolbar buttons
Workshop stiffener library
User Profile - Damen Shipyards Singapore
Tips & Tricks
Maxsurf Version 10.0 Released
We are pleased to announce the release of version 10 of Maxsurf. It is now nearly 20 years since we first started developing Maxsurf but our program of enhancements and additions is continuing at a rapid pace. We will be sending Maxsurf version 10 to all members of our Maxsurf subscription program over the coming weeks.
Some of the new features to be found in version 10 include more stability criteria and analysis options, user interface improvements, an expanded structural shape library and a new method for resistance prediction. In addition, we have spent considerable effort improving the performance of the underlying algorithms, this together with other improvements to the user interface will increase your productivity with Maxsurf 10.
The batch processing in Hydromax now includes Limiting KG and KN analyses. These analyses are carried out for all damage cases. The Limiting KG analysis includes the option for finding the limiting KG for each criterion individually and performing both Large Angle Stability and Equilibrium analyses at the final VCG. For all analyses, you can also specify that they should be carried out heeling to port or to starboard.
It is now possible to choose the type of free surface moment correction to be applied to slack tanks in Hydromax. The options available are:- maximum upright free surface moment of the tank at all fluid levels;- actual upright free surface moment at the current fluid level;- IMO free surface moment method as specified in the Code on Intact Stability A.749(18) and MSC.75(69); and- a user specified, constant, free surface moment.
Of course it is still possible to simulate the actual shift of the fluid in the tank due to heel and trim using the "Fluid Simulation" approach. This method provides the most accurate hydrostatic analysis.
The US Coast Guard stability criteria are now included in the standard criteria supplied with Hydromax. A total of 61 new individual criteria have been added, as well as a minor change to the parent criteria: the upper limit for finding the value of maximum GZ within a specified heel angle range may now be defined as a specified angle above the angle of equilibrium. This option was specifically incorporated to accommodate some of the damage stability criteria given in the US Coast Guard stability code.
A number of features have been added to all graphs in the Maxsurf suite. Two features that have been in high demand from our users are the ability to print the graph to scale and the ability to directly access the graphed data in numerical form.
We have now added the feature of being able to print the graph to scale. When activated, this option prints the graph to the largest scale that will fit on the selected paper, giving a typical scale of 0.5, 1, 2, or 2.5 cm or inches per grid mark (the choice of cm or inches is determined from the user's currently selected length units). Double clicking in any graph will now display a resizable dialog with a table containing the graphed data in numerical format. This data can easily be copied and pasted into MS Excel or MS Word, etc.
Several useful features have been added to Maxsurf to increase user productivity. These include the following:
For quick navigation through the vessel sections in the body plan view, it is now possible to use the left and right cursor arrows. Simply click in the inset box, then use the right arrow to move to the next station forward or the left arrow to move to the next station aft. This is particularly useful for quickly reviewing the stations when they are closely placed.
For commands such as Bond Edges and Fit Edge to markers, surface edges may be selected by clicking on the edge contour itself rather than a control point on the edge. This is extremely useful for bonding surfaces that only have corner control points.
Toolbar buttons are useful shortcuts for frequently used functions. Maxsurf has a number of additional buttons in the Visibility toolbar that enable users to quickly display a wider range of surface contours. Several buttons have also been added to the Display toolbar. These control Marker and Grid visibility.
Workshop now includes a comprehensive library of marine stiffener sections and appropriate cutouts. These include both rolled and extruded shapes covering typical sections used in steel displacement vessels as well as high-speed aluminium craft.
Workshop's link with ShipConstructor has also been enhanced with the addition of the export of plate meshes to the Structure module of ShipConstructor. See the article on the right for an example of the use of this capability at Damen Shipyards in Singapore.
The Damen Shipyards Group, based in the Netherlands, comprises more than 30 operating companies engaged in shipbuilding, repair and maritime services. The Group has a consolidated turnover of US$ 950M.
In 2000 the Damen Shipyards Group took over Kvaerner Fjellstrand's Singapore Yard to form Damen Shipyards Singapore (DSS). DSS specialise in the construction of high-speed aluminium craft. These include the Damen Fast Ferries (DFF) and the Damen Stan patrol boat.
DSS started using Maxsurf in early 2003 in order to develop an in-house design capability. From Formation Design Systems' (FDS) Maxsurf suite, Maxsurf and Hydromax are used for initial design and hydrostatic analysis. For production design, a combination of FDS' Workshop and Albacore Research Ltd's (ARL) ShipConstructor is used. Karl Nilssen, DSS's Manager Engineering, explains:
"A combination of Maxsurf's user friendly interface and FDS's excellent technical support has enabled us to get up to speed and be productive with the software in a very short period of time."
Workshop is used for the generation of parts that require accurate surface geometry: frames, plates, longitudinal stiffeners etc. Workshop calculates these parts directly from the Maxsurf surface model ensuring that the parts exactly match the surfaces that have been faired in Maxsurf. DSS use Workshop's advanced tools to lay out and fair the longitudinal stiffeners on the hull surfaces. This and other structural data is then exported to the ShipConstructor suite of software for further detailing.
ShipConstructor is the natural down-stream progression from Workshop taking the design through to production. Ship-Constructor allows a single vessel database model to be generated. The model can include structure, piping, outfit and HVAC; ShipConstructor is also able to nest parts and produce NC-code. Built around an SQL Server database, Ship-Constructor offers up to date, accurate production reports at any time.
The main structural elements generated by Workshop form the basis for the Ship-Constructor structural model. Using Ship-Constructor, detail is added to these main parts as necessary and then piping and outfit can be placed into the vessel. DSS have successfully used this combination of software to design and produce their latest catamaran ferry designs the DFF 3007, DFF 3009 and DFF 3810. They also plan to continue using this process on all new projects.
"We have found that the combination of Maxsurf, Hydromax, Workshop and ShipConstructor gives us a cost effective solution for our new developments and our on-going production engineering" says Mr Nilssen.
Further information about the Damen Shipyards Group and Damen Shipyards Singapore can be found on their web site: www.damen.nl
Constrained control point alignment
When designing a vessel in Maxsurf, it is often useful to put control points on exactly the same 3D vector. This is done using the Align to Vector command in the Controls menu: select two points that define the vector then the other point(s) that you wish to place on that vector (use the shift key to add to the selection). You can then use the Align to Vector command to move the points to the 3D vector defined by the first two.
By default, the points are moved to the closest point on the vector. However, in some cases you might not want to change the control points' height, i.e. the align to vector is constrained. This is done by holding down the shift key when selecting the Align to Vector command to display the align to vector constraints dialog.
These constraints are particularly useful if you want to align a bow, but do not want the height of the control points to change:
The constraints for align to plane are very similar to those for align to vector. However, up to two coordinates may be constrained. With either command, if the constraint is impossible to fulfil, the control points will be moved to the closest point on the vector or plane.