Watertight Cabin

Though UFX supports non-manifold and open (not watertight) inputs, having a watertight cabin will help to avoid any back and forth between modeling and setup. Once you are comfortable with the model, you can skip certain checks related to watertightness.

1. Extract external surface through a script:
   1. Stamped parts (parts with continuous thickness – doors, hood, cabin floor, and so on)
      • Script identifies one side of thickness surfaces with maximum area
      • After surfaces are extracted, remove unnecessary faces further such that opposite part boundary edges faces each other

        
        
        Figure 1.

   2. Non-stamped parts (mirrors, plastic parts, and so on)
      • Manually extract wetted faces
      • For some complex parts, you might have to trim some surfaces in order to extract clean wetted faces

        
        
        Figure 2.

2. Generate facets/mesh on exterior surfaces:
   • Generate faceted mesh on extracted wetted faces (use rigid body mesher – max size 20 mm, min size 0.1 mm, max deviation 0.1 mm)
   • Rigid body mesher captures all fillets and curvature with optimum number of triads
   • Make sure generated facets are not deviating much from geometry

     
     
     Figure 3.

   • Cabin floor parts can be meshed with constant size of 8 mm
3. Close holes:
   • After facet/mesh generation, fill holes using the Fill Hole/Gap utility
   • Select all components
   • Define maximum width (generally 50 fills up all holes)

     
     
     Figure 4.

4. Fuse gaps:
   • Use fuse tool to connect parts with wetted faces
   • Upper body parts fuse:
     • In the below example, wetted faces are extracted so they have gaps/proximity between them
     • The option “Fuse free edges only” is used
     • Fuse threshold depends on maximum gap between parts. Generally, it varies between 6-12 mm
     • You can select multiple source and target parts for one fuse operation

       
       
       Figure 5.

   • Fuse cabin floor parts:
     • Here parts are either in proximity, overlapping or intersecting

       
       
       Figure 6.

     • Deactivate the “Fuse free edges only” option for such parts
     • Fuse threshold depends on maximum gap between parts. Generally, it varies between 8 - 10 mm
     • Source parts will move to target, so select source and target accordingly
   • After fusing if there are any bad elements, manually fix them at the end
5. Generate apron faces for large openings:
   • If there is a big gap between cabin floor and upper body, create apron faces first
   • Use Fill Hole/Gap tool > Patch fill > Select surrounding nodes and create patch
   • Fuse upper body with cabin floor
6. Perform checks for watertight cabin:
   • Check for free edges, non-manifold edges
   • If free edges are valid, mark the corresponding component with “Baffle” name
   • Check and fix normal of the cabin