> This may be a problem in general with sweeps, or is there a way to fix this?

It's kind of a general problem with any type of operation that moves a distance away from a curve that is going around a tight bend, where the radius of the bend becomes less than the move distance.

Usually the way to fix it is to not do it... :) or you can also build your model more in pieces instead of trying to make it go through a tight bend all in one shot like that.

But you may not have to fix it in certain circumstances - if you are building the model for a quick sketch or rendering purposes then it is ok to have those self-intersecting pieces. But they can cause problems if you want to do further intersections to them later on, or try to manufacture those shapes with a CAM type system...

In this case of a fun quick sketch it seems to be fine not to worry too much about them.

- Michael