Hi Alex, so like Burr mentions, the problem you're running into there is due to your 2 curves having a different number of segments between them.

You can see the segments by using the Edit > Separate command on the curves - after you do that you can see that some of your straight line pieces on the upper piece are actually made up of a few pieces instead of just 1 line, as shown in Burr's screenshot above.

When you loft between curves that have the same number of segments in them, MoI will match up the curves segment-by-segment. If they have a different number of segments, then the curves are matched just by distance along whole curve and will produce the kind of result that you were seeing.

So if you edit your curve so that you only have single segments in those areas shown above, then your Loft will work with the kind of matching that you want. You can either use the Rebuild command like Burr mentions above, or you can also just delete those pieces and draw in a new line there so that you've got just one segment for those straight pieces instead of multiple sub segments.

I've attached the fixed up 3DM file here - if you use Edit > Separate on the curves in this file you can then select pieces and see that the top one is not broken up into multiple pieces in those areas where your original one was.

See this other recent post for another description of the same kind of thing:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4214.1


Also sometimes to get more specific control over how things are matching up it can be good to do the loft between smaller pieces instead of between long curves too. But you can do it between long curves if you have the segmentation of each curves set up to match each other.

- Michael