Hi David, re: sweep problem,

> The resulting file is attached too, do you know what I did wrong?

It looks like the same problem from this other recent thread here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=6605.5

When you use a scaling rail the scaling rail must cover the entire extent above the rails - just making it touch the profile is not necessarily far enough if your profile is not planar and directly above the rails.

Sometimes it can be easier to construct things like this with more planar pieces like flat rails and then introduce warping later on using the Transform > Deform > Flow command (which is new for the upcoming v3 version), rather than using a lot of 3D warped rail curves from the start.

But anyway your particular sweep here can be fixed by extending the scaling rail in the side view so that it covers the entire area perpendicular above the rails like this:



And you're probably best off making the proflie for the sweep to be positioned perpendicular to the rails rather than having it start out in a slanted position, if you then want to introduce a slant at the end when you're done with the sweep use a boolean or trim to cut off the end with a line rather than trying to build a surface with slanted pieces right in the initial surface construction.

I've attached an example 3DM file here which should work better. Also I aligned the end point and first inside control points on the rails so that the curves are smooth where they touch rather than coming to a sharp angle where they connect.

- Michael