Having trouble lofting curves, sections and rails not intersecting

[JasonCSC]

Hi everyone,

I'm trying to loft a sort of sculpted vase shape in Inventor 08 and I am having issues getting the curves to loft.  I keep getting an error messages about the rail curve not intersecting sections.

So I've basically wire framed out the shape with 3 section curves (one at an angle for the top), and 4 rail curves to make up the YZ and XZ planes. 

I've been making the section curves first, placing a point where I want the rail curve to intersect the section, and then projecting the point onto the rail curve sketches.  That isn't working, even though they appear to intersect, they still don't seem to work. 

Is there any way besides projecting those points that will REALLY constrain them together, or definitively associate the point on the section and the intersection curve where they join?

Is there any other approach I should take?

I'm noticing also that if I attempt to loft it as a solid object and I select the 3 section plans first, it appears as if the shape is twisting, and selecting the rails in the YZ plane are failing.  Is there some way to change the direction of the normals or the hooking point on these?

I've attached the file as well.

[rdyson]

Sketch 13 seems to be the problem.

You might want to double check it.

If you take care where you pick the section curve, they will not twist.

Soory, don't have IV '08 anymore.

[JasonCSC]

Yeah, I've rebuilt that sketch numerous times and I've taken care to try and make sure that they are intersecting the mid plane section curve, but it still fails.  I can get it to use the other sketch and get to the stage you are showing in your screen capture too.

Dumb question, but would having EACH individual rail on it's own seperate layer make any differnce in making this loft?  Could it be causing an error because both side rails are on the same sketch?

[JDMather]

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@JasonCSC wrote:

.... would having EACH individual rail on it's own seperate layer make any differnce in making this loft?  Could it be causing an error because both side rails are on the same sketch?

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It does not matter that multiple rails are in a single sketch - but they must be connected to the section profile.
Yours is not connected - I was able to drag the rail away.

First thing I noticed is that your sketches are not constrained - this makes troubleshooting exceedingly difficult and implies to me that other hidden "shortcuts" were taken.  There were also some questionable dimensions (actually missing dimensions).

I would start by reading this document http://home.pct.edu/~jmather/AU2006/MA13-3%20Mather.pdf

If I were doing your part I would start over from the first sketch and fully constrain.  I would probably move the origin.
I would change any line used only for construction to construction linetype.
I would use fewer construction lines by first placing in space and then using midpoint coincident constraint.

I saw a couple of other things I might do differenlty - but they are more of preferences than effect on the outcome of Loft.