Improved stl-file

I have made the stl 'watertight'. I make my stl-files in Rhino. Rhino gives this tip on stl:

1 Join the mesh objects.

Conceptually, this command gets all the triangles into one bag, but it doesn't glue the edges together. (The situation is similar to having surfaces that all fit together but have not been joined into a solid.) 

2) Weld the new mesh object.

3) At the Angle tolerance prompt type 180.

An angle tolerance of 180 tells the Weld command to glue adjacent triangle points together no matter what. 

4) UnifyMeshNormals.

This changes all the triangles so they are oriented the same way, that is, if two triangles share an edge, then they have the same idea of up.

It could be that using a watertight stl improves the mesh quality but I found some holes at the bottom... (You have to click on the picture to enlarge or look at the slice) Rhino reported it changed the normals of a quite lot of cells...

Looks like a perfect mesh: no bumps or holes

The trailing edge is pretty sharp

Oops holes !

A slice through the bumpy zone