Problem

Issues with stability calculations.

Solution

1. Tank modelling

Common issues:

• Check each section of your model if the tanks are formed properly.
• Check the volume of each tank if its value is as expected.
• Only compartments and non-buoyant volumes or tanks can overlap with each other. Tanks or compartments of the same type (e.g. two tanks) can not overlap. A tank and a non-buoyant volume are also not allowed to overlap. Stability will first try to form tank sections and then check whether these sections overlap tank sections of adjacent tanks. When two conflicting or overlapping tanks or compartments are detected during the forming process, you will receive an error message. The fixing procedure of overlapping tanks is available in Stability manual p. 70.

2. Loadcase definition

Make sure that at least one loadcase is defined. Loadcases define the loading condition of the vessel. Static weights that make up the vessel lightship are specified here as well as tank filling levels, expressed as either a percentage of the full tank capacity or as a weight.

3. Stability criteria not defined

See Stability Criteria Approach

4. Hull model on the port side

Usually when the model is imported from other software, there is a difference in the coordinate system. As a result, the model is on the port side instead of the starboard side. Before working in Stability, make sure that your surfaces have positive offset values. 

In order to check if your offset values are positive, go to MAXSURF Modeler | Window | Control Points.

More information: Import/Export model - Coordinate system

5. Surfaces with wrong directions

All surfaces should point outwards. The surface direction may be inverted by clicking on the circle at the end of the arrowhead. This is important for rendering, skin thickness direction, and correct interpretation of the design when it is loaded into Stability or Structure.

See Also

Crash Occurs During Analysis

MAXSURF Stability 3: Modeling Compartments and Tanks

MAXSURF Stability 4: Defining Loading Conditions

MAXSURF Stability 5: Stability Analysis, Criteria and Compliance

MAXSURF Stability 6: Damage Definition and Analysis