Maxsurf stability - Model requirements

Question

Hi Everyone, 
 Please can someone outline the basic requirements of 3d models used for stability and hydrostatics in Maxsurf? 
 It should be NURBs - .IGES with one closed surface? 
 how complex can the model be? 
 can it take other file formats like ,obj or mesh? 
 Sorry if this is a very basic question I am new to the software and have not yet found where these questions are answered in the documentation if you could direct me I would be most grateful. 
 
 Many thanks, 
 
 Ben

pat couser · Answer

hi Ben you need to load the model in Modeler first to set it up for hydrostatics calculations in Stability. There are many file formats that Modeler will accept. You can use NURBS surfaces, mesh surfaces or a combination of the 2. For hysrostatics, any section through the model should form closed, non-intersecting and non-self-intersecting contours. Please refer to the Modeler manual and Stability manual for more details:

pat couser · Answer

Ideally the model is generated in Modeler and then it will work. For hydrostatics NURBS or Mesh surfaces are required. And at any section they must form a closed section. The model you sent had over 20k IGES entities! MAXSURF is not designed to work with a model of that level of complexity. Reduce the model to the surfaces that define the outer watertight envelope of the hull only; delete all the curves since they are not used for hydrostatics. If the vessel is symmetrical then just define the surfaces on the starboard side. 
 your model seems to have many superimposed surfaces, everything appears to be in the model twice?

pat couser · Answer

you really need to clean up and simplify the model - MAXSURF is not going to have any idea of how to interpret this:

pat couser · Answer

yes -- thats what I see in Rhino 6. BTW MAXSURF can read .3rm file also if that's easier than IGES 
 but try to get the model down to < 100 NURBS surfaces 
 Because dynamic / interactive surface trimming is not supported in the IGES format, all surface trimming information is lost when you import IGES to MAXSURF. So you need a model using untrimmed surfaces or you need Modeler to read in the IGES model, trim the surfaces and then send you client a working MAXSURF model file for hydrostatic analysis

pat couser · Answer

I managed to convert you stl to obj - should work but you need to get the model centred and oriented correctly: (and you only need half the model if its symmetrical) 
 x +ve forward; y+ve staboard; y=0 on centreline 
 
 The mesh will work, just get is oriented correctly and half model (unless its as-built and its asymmetric, in which case do the full model)

pat couser · Answer

pat couser · Answer

yes that's left-handed ;-) best to have y+ve staboard and z +ve down with x+ve forward

pat couser · Answer

it becomes slower as the number of triangles increases, 100k is probably upper limit, but for hydrostatics, you probably dont need that level of detail, this model has 69k tris and 36k nodes