Hi Dan, there are a few different things going on there that Shell is sensitive to.

One thing is you've got some really pretty small but tightly curved little surface pieces in there, like here for example:





That does not bode well for shelling, it won't take very much distance for a tiny tight bend like that to start folding over itself.

You'll probably get better results for shelling if you have the solid have sharp edges in those areas instead of rounded edges, and apply any rounding that you need after the shelling by doing fillets rather than putting them in before trying to shell.


The other thing that is probably also causing problems is some areas that are diced up into some small pieces when it would be better if they were larger smooth surfaces, like here for example:



It looks like that little piece there may not be entirely smooth with its surrounding surfaces. Having something that is almost smooth but not actually smooth and instead at a shallow angle will tend to cause difficulties with shelling as well. Part of the shelling process is that surfaces that are not entirely smooth with one another will get extended and then intersected with one another, but the intersection part can get confused when they surfaces meet in some shallow angle like say only a 5 or 10 degree angle instead of being a more distinct sharp edge.

So it would probably help if that side piece was one single long smooth surface instead of split up like that.

To do that you may want to do something like redraw your original profile curves there with one long smooth curve, or you can also do something like fuse a segmented curve into one smooth segment by deleting the control points where joined curve segments are touching each other.

- Michael