Thanks to everyone for the contribution. It is much appreciated.

Michael, your point is well taken. I appreciate that I am dragging MoI and NURBS modelling into an area in which it is not ideally suited. I insist on doing it though because I find Sub-D modelling anything but easy and because I am starting to get things out of MoI that really come close to what I want. I only post about the brick walls I crash into, but fortunately, I also get my way more often than not. What I like about the NURBS approach is the capacity to generate in a split second a huge and complex model made out of a few simple lines, as this is the way engineers created the real world planes and ships in the first place. In my mind, NURBS really HAS to be a better tool than Sub-D to make shapes that were intended to conform to the laws of hydro or aerodynamics.

I appreciate that it is often better to go for smaller components or for bigger pieces than can be trimmed as needed, and I am doing more of that now than in the past. The problem of that approach is to ensure continuity. A viable strategy for the tough cases might be to get as far as I can with MoI and then switch to Modo for the finishing touches. I really like MoI and I want to use it as much as I can to get what I want. So far it has been a journey of discovery and there have been times of huge frustration, but I get better at it, and this tips and findings from this very forum are a big help too. I should probably explain that my purpose is to build models of planes and ships that should be capable of 3D-printing. Overall accuracy of shapes is more important than minute detail and global prettiness. Hence the emphasis on continuity. This being said, it appears that I may have gone a bit overboard about that because the limitations of the 3D-printing process (although already black magic to my bewildered eyes) make it so that a slightly noticeable continuity flaw on my computer screen might be entirely absent in the real world output. As we continue to experiment, I should gain a better appreciation of the limitations. But better safe than sorry. If it is possible to generate reasonably flawless objects with careful planning and advanced NURBS modelling techniques, then let’s go for that.

Planes and ships, especially military ones, tend to be rather complex objects, but they are hard surface things. One should be able to get them modelled with NURBS reasonably accurately. An area that is causing me constant trouble is filleting/blending, hence the theoretical case I submitted to your collective sagacity. A real-world example of this would be the nose of a Lancaster heavy bomber as in the image below, but a submarine hull with protruding sonar would be very similar.


This is a very imperfect example and a rather old one at that. I got much better lately, like for the B-29 front wheel, a component way more suited to MoI's capability, I guess.