Hi wsiew,

> I really don't understand why the sweep is again messy.

It's because you're trying to use 3 rails. There isn't a "3 rail sweep", there is a 2 rail sweep and a 1 rail sweep. If you select more than 2 rails then it will do a one rail sweep along each rail so you can do something like many pipes in one go.

So your case here generates 3 one rail sweeps over top of each other which is why it looks messy, if you drag on it you should be able to see that there are 3 objects on top of each other there.

You could use Network with that curve setup or just Loft through the 3 planar profiles without any rails at all would be better because your rails are not very accurately positioned, there is a gap between them and the profile curve.

- Michael