Hello,
I have some problems with iges surfaces. I create my models from rhinoceros 5, as you all know we cannot import what we created in rhinoceros, we need to trim some of surfaces in maxsurf then obtain the hydrotatically true model from it. In my iges model, i have skeg, hull surface and appendages (propeler, stern tubes and rudder shaft). When i trim surfaces and create what i desired in maxsurf, i crosscheck my underwater volume both rhinoceros and maxsurf. Rhinoceros gives me a stable result, but in maxsurf i cannot obtain what i expect to obtain. The underwater volume in given draft is always changing. When i untrim the skeg it changes, when i change the surface presicion it changes. Rhino and maxsurf never synchronises. My question is, how can i solve this problem, i need to learn what type of method maxsurf uses to calculate the underwater volume ?
Hi Mehmet,
Is there a reason you are starting your design in Rhino and not MAXSURF? The recommended best practice is to use Rhino for detailing having started with all major surfaces created in MAXSURF.
It is possible to import Rhino files, with or without trimming. File | Import | Rhino .3dm, but as you may have found, moving from a generic modeler that uses static trimming to MAXSURF with dynamic trimming can cause headaches. If you plan on being able to make any adjustments to the model inside MAXSURF, then often it is best to not import the trimming and redo it manually.
Its a bit hard to tell where your problem is without a model, screen grabs or anything visual. MAXSURF calculates volumes by identifying the continuous closed contour around the vessel at each cross section and interpolating along the length.
- You do need to have a single contour that runs around the hull. For example, you need to trim the hull inside the skeg otherwise you will have an overlap.
- Rhino models tend to not use symmetry. Check that your hull is either a half model with symmetry, or if necessary a full model without symmetry.
- Check that your frame of reference is set up correctly. This will affect the values for trim etc.
- Check your curve of areas to see if there are any unexpected bumps or holes.
If you want to test if the problem is with MAXSURF or your model, try exporting a similar MAXSURF sample model to Rhino and calculating the displacement.
Regards,
James
Thanks for your helpful reply dear James,
Main reason i use rhino for hull and detailed appendages that our lines plan is designed in another program which hull can be exported only dxf polylines. I use those curves for hull creation with network command in rhino, that command works very accurate for it. I cannot create 1-1 the same hull charasterictic with maxsurf actually, if its possible let me know i would prefer to use maxsurf for hull creation. I checked all you specify above, all of them is ok. They trimmed well and looks good, no problem in visual. But i have discontinuances in my curve of areas where stern tube and hull intersects and this gives me the displacement problem. To overcome this i created several boxes instead of propeller and rudder with same volume, volume center and surface area. But this was not easy solution for me. What can be cause those discontinuances in my curve of areas ?
MAXSURF has its own tools for fitting surfaces to existing data. Watch these two videos from past Bentley webinars
- https://pages.info.bentley.com/video-details/?video=CO_VID_MXSURF1_WEB_11_16&videoDBID=d47b6431-5d27-464b-8764-aae1026fc7c8
- https://pages.info.bentley.com/video-details/?video=CO_VID_MXSURF2_WEB_12_16&videoDBID=ea905b9c-4a9d-4771-bd0c-02d0e4808e18
You may need to explode the polylines in your CAD package (Rhino) for them to recognized in MAXSURF. It is also possible to import the dxf as markers (File | Import | Markers| DXF) if you would rather work with Markers instead of curves.
There is a really important point to remember when fitting surfaces to markers. You can't do the impossible! Your surface needs to have sufficient flexibility and CPs to be able to fit to the markers you have. Choosing a suitable surface layout and number of CPs can be the tricky bit!
Regarding the glitch in your curve of areas. Make sure you have a suitable number of sections defined (Data | Design Grid), go to body plan view, turn the section contours off. Cycle through the section contours and make sure they all form a continuous section
Answer Verified By: Mehmet A. Baykal