Hi Rainer,
> I have to model an array of lines which have a constant spacing
> between two curves. of course perpendicular....
Well, one problem is that what you are asking for there is actually impossible for the general case, since any 2 random curves do not necessarily even have any perpendicular in common between them.
For example here are 2 curves that have no shared perpendiculars between them:
The case where you do have perpendiculars at every point is when one curve is the offset of the other one, like this:
In a case like that, you can draw in one line and use Transform / Array / Curve to replicate the line at a constant distance along one curve (the distance along the other curve will vary where things bunch together when going around bends, but it will be all perpendicular), like this:
But maybe I don't understand what you are trying to do, could you maybe post the model file with the 2 curves in it that you are trying to work with? That would help to clarify it.
 Michael
